(92) Nutrition
What Happens If You Eat Too Much or Too Little Protein?
While protein is essential to health and normal body function, eating too much or too little can be unhealthy. Let’s look at what happens to the human body when it gets too much or too little protein.
Eating Too Much Protein Can Mean Too Much Heart-Unhealthy Fat and Weaker Bones
As you read in the beginning of our texts, Melissa, the college student, had switched to a high-protein diet to help her slim down. Unfortunately, her steady diet of low-fiber, fat-rich cheeses, hamburgers, and fried foods was affecting her health. The lack of fiber-rich whole grains, fruits, and vegetables was causing her to become extremely constipated and giving her bellyaches. A diet high in saturated fat can raise the LDL (“bad”) cholesterol level in the blood. Before Melissa switched to a high-protein diet, her LDL cholesterol was in the healthy range. But her steady diet of fatty foods caused her LDL cholesterol to climb into the dangerously high range. Her doctor sent her to a registered dietitian (RD), who advised her to trim the fatty foods from her diet and add back the fiber-rich whole grains, fruits, and vegetables. Melissa’s cholesterol dropped to a healthy level within months, and the high-fiber foods helped to “keep things moving” in her intestinal tract and eliminate constipation. The RD also recommended that Melissa walks on campus between classes daily to help her better manage her weight.
Although consuming protein is a key to good health, eating more is clearly not necessarily eating better. In fact, a diet that is too high in protein is associated with the following risks:
Heart disease. A high-protein diet may increase your risk for heart disease and die prematurely from heart disease. Many foods rich in protein are also rich in heart-unhealthy saturated fats. Although lean meats and skinless poultry contain less saturated fat than some other cuts of meat, they are not completely free of saturated fat. Hence, a high protein intake can make a low saturated fat intake a challenge. Lowering the saturated fat in your diet is important in lowering your risk for heart disease.
Kidney stones. A high-protein diet may also increase your risk for kidney stones, which commonly contain calcium. More than 10 percent of Americans will likely suffer from a kidney stone at least once in their lives.
Osteoporosis. A high-protein diet may also increase your risk of osteoporosis (poor bone density). Although still a controversial issue, numerous research studies have shown that bones lose calcium when a person’s diet is too high in protein. The loss seems to occur because calcium is taken from bone to act as a buffer, offsetting the acid generated when specific amino acids are broken down. Other research has attempted to determine if calcium loss leads to osteoporosis when there is an adequate amount of calcium in a high-protein diet. If a higher dietary protein intake is coming from foods such as low-fat milk, yogurt, and cheese, it can add calcium to the diet. Unfortunately, many American adults are falling short of their recommended calcium intake. If their diets are also high in protein, this isn’t a healthy combination for their bones.
Cancer. A high-protein diet may increase your risk for cancer; however, this relationship is also less than clear. While large amounts of meat, especially red and processed meats, may increase the risk for colon cancer, research doesn’t necessarily support a connection between high amounts of total protein and increased colon cancer risk.
One final health concern surrounding a high-protein diet is the displacement of other foods. If your diet is overloaded with protein-rich foods, such as meat, fish, and poultry, they will likely crowd out another nutrient- and fiber-rich foods. As you know, a diet that contains high fiber and a wide variety of nutrient-dense foods can help you reduce your risk for several chronic diseases, such as cancer, heart disease, diabetes, and stroke. If you fill up on meat and milk at meals, you might be shortchanging yourself on foods, such as whole grains, fruits, and vegetables that contain disease-fighting compounds.
While many individuals have the luxury of worrying about consuming too much protein, others are desperately trying to meet their daily needs. Let’s look at the serious health implications of chronically eating too little dietary protein.
Eating Too Little Protein Can Lead to Poor Bone Health and Malnutrition
Eating too little protein can lead to many health problems, including compromised bone health. In fact, eating too little protein has been shown to lead to loss of bone mass. A study of more than 500 women over age 55 showed that higher dietary protein consumption was associated with more dense bone. Another study of more than 2,000 males and females ranging in age from 50 to 89 showed that those under the age of 70 who had a diet higher in protein had 65 percent fewer hip fractures compared with those with the lowest protein intake. When it comes to our bones, too much protein or too little can both be unhealthy.
Protein-Energy Malnutrition
Every day, almost 17,000 children around the world approximately 6 million annually-die because they don’t have access to enough food. These children’s diets are inadequate in either protein or calories or both, a condition is known as protein-energy malnutrition (PEM).When calories and protein are inadequate, dietary protein is used for energy rather than reserved for its numerous other roles in the body.
Moreover, other important nutrients, such as vitamins and minerals, also tend to be in short supply, which further compounds PEM. Many factors can lead to PEM, including poverty, poor food quality, insufficient food intake, unsanitary living conditions, ignorance regarding the proper feeding of children, and stopping lactation (nursing) too early. Because they are growing, infants and children have higher nutritional needs for their size than adults. They are also dependent on others to provide them with food. For these reasons, PEM is more frequently seen in infants and children than in adults.
Because protein is needed for so many functions in the body, it isn’t surprising that a chronic protein deficiency can lead to many health problems. For example, without adequate dietary protein, the cells in the lining of the gastrointestinal tract aren’t adequately replaced when they are routinely sloughed off. The inability to regenerate these cells inhibits their function. Absorption of the little amount of food that may be available is reduced, and bacteria that normally stay in the intestines can get into the blood and poison it, causing septicemia. Malnourished individuals frequently have a compromised immune system, which can make fighting even a minor infection, such as a respiratory infection or diarrhea, impossible. Malnourished children have died after exposure to measles as well as after bouts of diarrhea.
While deficiencies of both calories and protein often occur simultaneously, sometimes one condition may be more prevalent than the other. A severe deficiency of protein is called kwashiorkor, whereas a severe deficiency of calories is called marasmus. A condition that is caused by a chronic deficiency of both calories and protein is called marasmic kwashiorkor.
Kwashiorkor
Kwashiorkor was first observed in the 1930s in tribes in West Africa: often the firstborn child became sick when a new sibling became part of the family. Typically, the newborn displaced the first child, usually around 18 months of age, from his or her lactating mother and her nutritionally balanced breast milk. The first child was then relegated to an inadequate and unbalanced diet high in carbohydrate-rich grains but severely deficient in protein. This sets the stage for serious medical complications.
A classic symptom of severe kwashiorkor is edema in the legs, feet, and stomach. As we discussed earlier, protein plays an important role in maintaining fluid balance in the blood and around the cells. With protein deficiency, fluid accumulates in the spaces surrounding the cells, causing swelling. The body wastes away as the muscle proteins are broken down to generate the amino acids needed to synthesize other proteins. Consequently, muscle tone and strength diminish. Those with kwashiorkor often have skin that is dry and peeling. Rashes or lesions can also develop. Their hair is often brittle and can be easily pulled out. These children often appear pale, have facial expressions that display sadness and apathy, and cry easily. They are prone to infections, rapid heartbeats, excess fluid in the lungs, pneumonia, septicemia, and water and electrolyte imbalances-all of which can be deadly.
Marasmus and Marasmic Kwashiorkor
The bloating seen in kwashiorkor is the opposite of the frail, emaciated appearance of marasmus. Because they are not consuming enough calories, marasmic individuals are starving. They are often not even at 60 percent of their desirable body weight.Marasmic children’s bodies use all available calories to stay alive; thus, growth is interrupted. These children are weakened and appear apathetic. Many can’t stand without support. They look old beyond their years, as the loss of fat in the face one of the last places that the body loses fat during starvation causes the disappearance of a robust childlike appearance. Their hair is thin and dry and lacks the sheen seen in the hair of healthy children. Their body temperature and blood pressure are both low, and they are prone to dehydration, infections, and unnecessary blood clotting.
Individuals with marasmic kwashiorkor have the worst of both conditions. They often have edema in their legs and arms, yet have a “skin and bones” appearance in other parts of the body. When these individuals are provided with medical and nutritional treatment, such as receiving adequate protein, the edema subsides and their clinical symptoms more closely resemble that of a person with marasmus.
Appropriate medical care and treatment can dramatically reduce the 20 to 30 percent mortality rate seen among children with severe PEM worldwide. The treatment for PEM should be carefully and slowly implemented using a three-step approach. The first step addresses the life-threatening factors, such as severe dehydration and fluid and nutrient imbalances. The second step is to restore the individual’s depleted tissues by gradually providing nutritionally dense calories and high-quality protein. The third step involves transitioning the person to foods and introducing the physical activity. The only successful way to cure PEM is to eradicate it.
Message
A high-protein diet may play a role in increasing the risk of heart disease, kidney problems, and calcium loss from bone. Consuming too much protein from animal sources can increase the amount of heart-unhealthy saturated fat in your diet. Too many protein-rich foods in the diet can displace whole grains, fruits, and vegetables, which have been shown to help reduce many chronic diseases. A low-protein diet has also been shown to lead to loss of bone mass. PEM is caused by an inadequate amount of protein and/or calories in the diet. A severe deficiency of protein is called kwashiorkor; a deficiency of calories is called marasmus.
These conditions can be improved with proper food and treatment.
Figs are a sweet way to get some calcium. Five large figs provide more than 10 percent of many adults’ daily calcium needs.
Where’s the Protein and Saturated Fat in Your Foods?
While many foods, in particular, dairy foods and meats, can provide a hefty amount of protein, they can also provide a large amount of saturated fat. Choose nonfat and low-fat dairy foods and lean sources of meats and skinless poultry to enjoy your protein without consuming too much-saturated fat.
Terms:
Protein-energy malnutrition (PEM) - A lack of sufficient dietary protein and/or calories.
Kwashiorkor - A state of PEM where there is a severe deficiency of dietary protein.
Marasmus - A state of PEM where there is a severe deficiency of calories that perpetuates wasting; also called starvation.
(93) Nutrition
What If The World Went Vegetarian?
Vegetarian Food
How Do Vegetarians Meet Their Protein Needs?
What do spaghetti topped with marinara sauce, cheese pizza, and macaroni and cheese all have in common? These common, classic vegetarian meals all lack meat. For many people, being a vegetarian is a lifestyle choice made for a particular reason. While some vegetarians avoid foods from animal sources for ethical, religious, or environmental reasons, others choose a vegetarian lifestyle because they believe it’s better for their health. An estimated 3 percent of American adults, or about 6 million people, follow a vegetarian diet.
Because vegetarians avoid meat, which is high in protein, they need to be sure to get adequate protein from other food sources. Vegetarians can meet their daily protein needs by consuming a varied plant-based diet that contains protein-rich meat alternatives such as soy, dried beans and other legumes, and nuts. Some vegetarians include protein-rich eggs, dairy foods, and fish as part of their diet. There are several types of vegetarians and associated ranges of acceptable foods.
In the United States, the vegetarian food market has grown to be a $1.1 billion-plus industry as manufacturers accommodate growing consumer demand with an array of new vegetarian products each year. More than 70 percent of sit-down restaurants offer a vegetarian entrée on their menus, and even some fast-food restaurants now offer veggie burgers. University food services are increasingly making vegetarian options available to meet growing student demand.
The Potential Benefits and Risks of a Vegetarian Diet
A plant-based diet can be rich in high-fiber whole grains, vegetables, fruits, legumes, and nuts and thus naturally lower in saturated fat and cholesterol.
This type of diet contains the fundamentals for reducing the risk of the following diseases:
Heart disease. Vegetarian food staples, such as soy, nuts, and soluble fiber–rich foods, such as beans and oats, have been shown to reduce blood cholesterol levels. Numerous studies have shown that the rates of deaths from heart disease are about 25 percent lower among vegetarians than among nonvegetarians.
High blood pressure. Vegetarians tend to have lower blood pressure than meat eaters. The incidence of high blood pressure has been shown to be more than two times higher in nonvegetarians. High blood pressure is a risk factor not only for heart disease but also for stroke.
Type 2 diabetes. A plant-based diet can help reduce the risk for type 2 diabetes, so it shouldn’t surprise you that vegetarians tend to have a lower risk for diabetes. Diabetes is also a risk for heart disease.
For people with diabetes, consuming foods rich in fiber and low in saturated fat and cholesterol makes eating a vegetarian diet an attractive strategy to better manage this disease.
Certain types of cancer. Vegetarian diets have been shown to reduce the risk for both prostate and colon cancer. Respected health organizations, such as the American Institute for Cancer Research and the American Cancer Society, advocate a plant-based diet to reduce the risk for cancer.
Obesity. A plant-based diet containing mostly fiber-rich whole grains and low calorie, nutrient-rich vegetables and fruits tend to “fill you up before it fills you out,” making you more likely to eat fewer calories overall. Hence, the plant based foods of a vegetarian diet can be a healthy, satisfying strategy for those fighting the battle against obesity.
In addition to diet, other lifestyle habits such as not smoking, abstaining from alcohol and recreational drugs, and enjoying the daily physical activity, which is all common among vegetarians, may also contribute to their lower risk of the above conditions. The biggest risk of a vegetarian diet is in not consuming enough of the nutrients, such as protein and vitamin B12 that are found in abundance in animal foods. Strictly avoiding meat, fish, poultry, and foods derived from animal sources can be unhealthy if you don’t replace these foods with healthy, nutrient-dense, nonmeat alternatives. Also, vegetarian meals may not always be low in saturated fat if full-fat dairy products are heavily used. Planning is needed to be a healthy vegetarian.
How You Can Be a Healthy Vegetarian
To avoid nutrient deficiencies, vegetarians must consume adequate amounts of all nutrients by eating a wide variety of foods. Some nutrients found in abundance in animal foods, including protein, iron, zinc, calcium, vitamin D, riboflavin (a B vitamin), vitamin B12, vitamin A, and omega-3 fatty acids, are particularly important to monitor solely from plant foods. Comparing these nutrient profiles may surprise you! Finally, when following a vegetarian diet, a vitamin and mineral supplement may be necessary.
Athletes Can Follow a Vegetarian Diet
Sports dietitians agree that athletes consuming a vegetarian diet can keep their competitive edge-with careful planning. Soy products, eggs, yogurt, cow’s milk, cheese, and protein shakes can help a vegetarian athlete get needed amounts of protein, vitamin B12, calcium, and vitamin D. Iron is a critical nutrient for athletes because it carries oxygen to working muscles. Zinc is important to help tissues recover from the stress of training. Fortified foods can help increase the level of these minerals in a vegetarian diet, and a daily multivitamin/mineral supplement can provide added insurance.
For athletes who don’t consume fish, soy products, walnuts, flaxseeds, soybean oil, and canola oil provide omega-3 fatty acids. Vegetarian athletes should consult a registered dietitian to plan a nutritionally complete diet.
Message
Vegetarian diets can be a healthy eating style that may help reduce the risk of some chronic diseases. Some vegetarians abstain from all animal foods, while others may eat animal foods (such as eggs and dairy products) in limited amounts. All vegetarians must take care in planning a varied diet that meets their nutrient needs, especially for protein, iron, zinc, calcium, vitamin D, riboflavin (a B vitamin), vitamin B12, vitamin A, and omega-3 fatty acids.
Vegetarian Food Guide Pyramid
Vegetarians should eat a variety of foods from each food group, especially legumes, nuts, and oils, to obtain essential fatty acids, and adequate protein, calcium, and vitamin B12.
Source: Reprinted from Journal of the American Dietetic Association. Vol. 103, Issue 6, Messina et al., “A new food guide for North American vegetarians,” pp. 771–775. © 2003, with permission from Elsevier. www.sciencedirect.com/science/journal
Term:
Vegetarian - A person who doesn’t eat meat, fish, or poultry or (sometimes) foods made from these animal sources
(94) Nutrition
Is Soy Bad For You, or Good? The Shocking Truth
The Joy of Soy
Soy has been used as a dietary staple for centuries in Asia. Soy consumption in the United States, in foods ranging from soy milk to soy bars, has been increasing since the early1990s. From 1992 to 2008, the market for soy products has grown from $300 million to $4 billion. According to a survey conducted by the United Soybean Board, 84 percent of U.S. consumers perceive soy foods as being healthy and one-third of consumers intentionally seek out soy products on a regular basis.
The popularity of soy foods is increasing among many age groups and ethnic groups, including baby boomers, who are more interested in good health and longevity than their parents’ generation was; Asian populations in the United States looking for traditional soy-based foods; and young adults with an increasing interest in vegetarian diets.
Soy is a high-quality protein source that is low in saturated fat and that contains isoflavones, which are naturally occurring phytoestrogens (phyto = plant).
These plant estrogens have a chemical structure similar to human estrogen. While they are considered weak estrogens (they have less than a thousandth of the potential activity of estrogen), they may interfere with or mimic some of estrogen’s activities in certain cells in the body. Although isoflavones can also be found in other plant foods, such as grains, vegetables, and legumes, soybeans contain the largest amount found in food.
Soy and Your Health
Epidemiological studies, which look at health and disease in populations, have suggested that isoflavones may reduce the risk of chronic diseases, including heart disease and certain cancers. Some other studies suggest that isoflavones may help relieve menopausal symptoms. At the same time, because isoflavones act as weak estrogens in the body, some concern exists that they may be harmful for diseases such as breast cancer.
Eating soy protein as part of a heart healthy diet may reduce the risk of heart disease by lowering cholesterol levels. A review of more than 35 research studies showed that soy protein lowered the “bad” LDL cholesterol by about 10 percent. However, recent findings suggest that the lowering effect may be a more modest 3 percent.
Interest in soy as a cancer fighter was sparked after researchers observed that Asian countries had lower rates of breast cancer than Western countries, including the United States. Numerous studies suggest that the isoflavones in soy may help reduce the risk of cancer, as these weak estrogens may have anticancer functions in the body. One of the functions of isoflavones is that they compete with the hormone estrogen for its binding site on specific cells. The isoflavone latches onto the cell and blocks the binding of the hormone. Because estrogen may increase the risk of breast cancer, inhibiting or blocking the actions of estrogen may help reduce the risk.
Timing may be an important part in the preventive role that soy plays in breast cancer. A study of Chinese women found that those who ate the most soy during their adolescent years had a reduced risk of breast cancer in adulthood. The early exposure to soy foods may be protective by stimulating the growth of cells in the breast, enhancing the rate at which the glands mature, and altering the tissues in a beneficial way. The anticancer role of isoflavones may also be a detriment. There is some concern that once the isoflavones are bound to the estrogen receptors, they can initiate the production of cancer cells, which can raise the risk of breast cancer. A review of more than 200 research studies supports the safety of soy isoflavones when consumed as soy and soy products. However, this issue of potentially increasing the risk of breast cancer, especially for those who are at high risk of developing it or who presently have breast cancer, isn’t resolved as yet. According to the American Cancer Society, women with breast cancer should consume a healthy, plant-based diet with only moderate amounts of soy foods and should avoid soy-containing pills, powders, and supplements with high levels of isoflavones.
Soy can be an inexpensive, heart healthy protein source that may also help modestly lower your blood cholesterol. While soy may help lower the risk of certain cancers, it is currently unclear if it is beneficial or harmful for individuals at high risk of developing breast cancer.
Tofu
Cooked, puréed soybeans that are processed into a silken, soft, or firm texture; has a neutral flavor, which allows it to blend well
Use the silken version in dips, soups, and cream pies. Use the firm variety in stir-fries or on salads, or marinate it and then bake or grill it.
Edamame
Tender young soybeans; can be purchased fresh, frozen, or canned
Use in salads, grain dishes, stir-fries, and casseroles.
Soy Flour
Made from ground, roasted soybeans
Use it in baked goods such as pancakes, muffins, and cookies.
It can also substitute for eggs in baked goods:
Use 1 tbs soy flour combined with 1 tbs of water for each whole egg.
Soy Milk
A soy beverage made from a mixture of ground soybeans and water
Use it in place of cow’s milk. Combine soy milk with ice and fruit in a blender for a soy shake.
Tempeh
Made from cooked whole soybeans that are condensed into a solid block
Can be seasoned and used as a meat substitute.
Miso
A flavorful paste of fermented soybeans used to season foods
Use in soups, stews, and sauces.
Soy Meat Analogs
Products such as hot dogs, sausages, burgers, cold cuts, yogurts, and cheese that are made using soy
Use as a meat substitute at meals and snacks.
Textured Soy Protein
Created from defatted soy flour that has been compressed and dehydrated
Use it as a meat substitute in foods such as meatballs, meatloaf, chili, tacos, and spaghetti sauce.
(95) Nutrition
What is a Protein? Learn about the 3D shape and function of macromolecules
Protein
What Are Proteins?
Proteins are the predominant structural and functional materials in every cell in your body. Proteins are made up of amino acids.
As with carbohydrates and fats, amino acids are made up of carbon, hydrogen, and oxygen atoms. Unlike carbohydrates and fats, amino acid molecules also contain nitrogen.
The atoms that make up every amino acid molecule are clustered into three groups. The acid group contains carbon, hydrogen, and oxygen atoms (COOH), which is why it is called an amino “acid.” The amine group (NH2) contains the nitrogen. These two groups are the same for every amino acid. The third group, a unique side chain, varies from amino acid to amino acid and gives each its distinguishing qualities.
There are 20 different amino acids, nine of which are essential and 11 of which are nonessential. Essential amino acids are not made in the body and need to be obtained through foods. Nonessential amino acids are synthesized in the body.
Peptide Bonds Link Amino Acids into Protein Chains
Amino acids are joined to each other by peptide bonds to build proteins. Two amino acids joined together form a dipeptide. Three amino acids joined together form a tripeptide. And a polypeptide consists of many amino acids joined together.
Shapes of Proteins Are Altered by Denaturation
The shape of a protein determines its function. The weak bonds between the side chains on the amino acids can be denatured, or broken apart, by temperature change or acids, bases, or salts. Although denaturation doesn’t alter the sequence of amino acids in the protein strand, changing the protein’s shape can alter its function, sometimes permanently.
Functions of Protein
Proteins provide structural and mechanical support and help maintain body tissues.
Proteins build enzymes and hormones.
Proteins help maintain acid-base balance.
Proteins transport substances throughout the body and act as channels in membranes.
Proteins are needed for antibodies and the immune response.
Proteins can provide energy.
Daily Needs
If you are 14 to 18 years old, you need 0.85 gram of protein per kilogram of body weight (g/kg) per day. If you are 19 years of age or older, you need 0.80 gram per kilogram daily.
Not all proteins are created equal. Protein quality is determined by two factors: your body’s ability to digest the protein, which is unique to each person, and the types of amino acids (essential, nonessential, or both) that the protein contains.
Proteins that are more easily digested and that contain both essential and nonessential amino acids are of higher quality.
Food Sources
Protein is particularly abundant in meat, fish, poultry, and meat alternatives such as peanut butter and soy. A 3-ounce serving of cooked meat, poultry, or fish provides approximately 21 to 25 grams of protein, or about 7 grams per ounce. Dried beans are not only a good source of protein, but also of fiber. Dairy foods are excellent protein sources and grains and vegetables can also add to your daily protein intake.
Too Much or Too Little
A diet that is too high in protein has been linked to health problems such as cardio-vascular disease, kidney stones, osteoporosis, and some types of cancer. Eating too little protein can also lead to compromised bone health.
Diets that are inadequate in protein, calories, or both lead to protein-energy malnutrition (PEM). Two forms of PEM are kwashiorkor and marasmus. Kwashiorkor occurs when a person consumes sufficient calories but not sufficient protein. A classic symptom of severe kwashiorkor is edema in the legs, feet, and stomach. Other symptoms include dry and peeling skin, rashes or lesions, and brittle hair that can be easily pulled out. Marasmus is a disease caused by insufficient intake of energy.
Marasmic individuals are starving and are often not even at 60 percent of their desirable body weight for their height. Although protein is an important nutrient in your diet, you don’t want to consume protein-rich sources at the expense of your heart. Your best bet is to choose leaner protein foods, as they contain less heart-unhealthy saturated fat.
Here are some typical protein rich foods made over and made nutritionally better!
Are Protein Shakes and Supplements Beneficial? As you’ve learned in this text, our bodies need protein to build muscle, among other functions. But in addition to the protein we get from food, extra protein, in the form of powders and shakes, is frequently touted as a means to build muscle, lose weight, or help the body recover after exercise, especially among athletes and bodybuilders.
Does the average person need these types of specially formulated products? Is more protein always better? Read the arguments for and against and draw your own conclusions
Yes
• Older adults, who may have limited appetites and be less likely to consume adequate nutrients in foods, as well as people suffering from fatigue or certain other physical ailments, can benefit from a liquid protein supplement.
• High-level strength and endurance athletes can require twice as much protein as nonathletes to repair muscle tissue after bouts of strenuous exercise. Although most can get enough protein through their diet, some may need supplements.
• A supplement containing carbohydrates and a small amount of protein has proven effective, immediately after exercise, in improving muscle protein synthesis, which helps athletes, as well as anyone who exercises, recover faster post workout and build muscle.
NO
The average American already consumes enough protein to build muscle. Excess calories from additional protein will be stored in the body as fat.
• The claims made on supplement labels, and the purity of the supplements themselves, are not regulated by the FDA.
• Consuming too much protein, such as from shakes or supplements, can lead to loss of appetite, diarrhea, dehydration, and undue stress on the kidneys.
• Excess protein can also lead to a loss of calcium through the urine. Chronic calcium loss can increase the risk of osteoporosis, especially in women.
• While replacing certain meals with protein shakes may help reduce daily calories, thus helping you lose weight, you would miss out on the nutritional benefits of whole foods.
• Protein supplements tend to be expensive. Recall from the chapter that the average bar will cost about $1–3 each, and the average shake about $1.50, while a just-as-effective peanut butter sandwich costs about $0.22.
1. Do you think most people would benefit from consuming protein bars or shakes? Why or why not?
2. Are there any benefits of protein supplements that cannot be achieved by consuming protein-rich foods? If yes, what are they?
3. What role does marketing play in promoting protein shakes and supplements?
The Top Ten Points to Remember
1. Proteins are made of amino acids, which contain an acid group, an amine group, and a unique side chain. Each group is made of carbon, hydrogen, oxygen, and, in the case of the amine group, nitrogen. There are 20 unique side chains and therefore 20 unique amino acids. Amino acids are joined together by peptide bonds to form proteins.
2. The interactions between the amino acids cause individual proteins to fold into precise three-dimensional shapes. The shape of a protein determines its function. Heat, acids, bases, and salts denature these bonds and disrupt the shape and function of a protein.
3. Of the 20 amino acids, 9 are essential, so you need to obtain them through your diet. Your body can synthesize the remaining 11 amino acids, so they are nonessential.
4. With the help of stomach juices and enzymes, your body digests and breaks down proteins into amino acids to make them available for use. A limited amount of amino acids exists in pools in your body. The DNA in your cells directs the synthesis of proteins. Excess amino acids are also broken down and either stored in another form or used as energy, depending on your needs. The nitrogen is converted to the waste product urea and excreted in your urine.
5. Proteins play many roles in your body. They provide structural and mechanical support, supply materials for ongoing maintenance, form enzymes and hormones, maintain acid base and fluid balance, transport nutrients, and aid your immune system. Proteins can provide energy, be used to make glucose, and increase satiety at meals. Calories from excess protein will be stored as fat.
6. Healthy adults are usually in a state of nitrogen balance, which means they excrete as much nitrogen as they consume. Pregnant and lactating women and growing children are in a state of positive nitrogen balance because they use additional nitrogen to grow new tissues. People who are malnourished or experiencing medical trauma may be in negative nitrogen balance.
7. Protein quality is determined by the protein digestibility corrected amino acid score (PDCAAS), which is based on the protein’s digestibility and its amino acid profile. Protein from animal foods is more easily digested than protein from plant foods. Proteins from animal foods and soy are typically complete proteins and provide all of the essential amino acids along with some nonessential amino acids. Plant proteins are typically incomplete, as they are missing one or more essential amino acids.
8. Adults should consume 0.8 gram of protein for each kilogram of body weight. A varied diet provides most Americans with far more protein than they need. Consuming too much protein from animal sources can increase the amount of heart-unhealthy saturated fat in your diet. A high-protein diet has been associated with the loss of calcium from the body and the development of kidney stones. An excess of protein-rich foods in the diet can displace whole grains, fruits, and vegetables.
9. Protein-energy malnutrition (PEM) is caused by an inadequate amount of protein and/or calories in the diet. Kwashiorkor is a severe deficiency of protein; marasmus is a severe deficiency of calories. A deficiency of both calories and protein is known as marasmic kwashiorkor.
10. Healthy vegetarian diets can reduce the risk of certain chronic diseases. Some vegetarians abstain from all animal foods, while others may eat a limited amount. All vegetarians must take care to eat a varied diet that meets all of their nutrient needs. Answers to Myths and Misperceptions
1. True. If you make the correct food choices, your body can extract all the building materials it needs to create all of the proteins that it needs.
2. True. Protein also plays other important roles in your body.
3. True. There are thousands of unique enzymes in your body, and the majority are made of protein.
4. True. However, burning proteins, rather than carbohydrates or fat, for energy is an inefficient way to use this precious nutrient.
5. False. Growing children are in a state of positive nitrogen balance, which means that more nitrogen is being retained by the body (to be incorporated into new body proteins) than is excreted in the urine.
6. False. Although both pasta and chicken can contribute to your daily protein needs, the protein in poultry is more easily digested than the protein found in grains.
7. False. Proteins do play a vital role in your body, but a little can go a long way. For most healthy adults, less than one fifth of their daily calories should come from dietary protein.
8. False. Even an extremely active person or competitive athlete can easily meet his or her protein needs through a well-balanced diet.
9. True. A high-protein diet that contains artery-clogging saturated fat and low amounts of whole grains, fruits, and vegetables is not heart friendly and may raise your blood cholesterol
10. True. Soy foods are excellent sources of protein, and they help fight certain chronic diseases.
(96) Nutrition
VITAMINS
While vitamins (vita = vital) have always been in foods, they remained nameless and undiscovered substances as recently as 100 years ago. If you were to flash back to the early part of the twentieth century, you would find scientists hard at work searching for substances to cure diseases such as beriberi, scurvy, and rickets. These may sound like the names of rock bands to you, but they’re actually the devastating diseases caused by deficiencies of thiamin (for beriberi), vitamin C (for scurvy), and vitamin D (for rickets). Throughout the twentieth century, scientists received Nobel Prizes for their discoveries of the vitamins that cured these and other diseases. By the 1940s, the U.S. government mandated that specific vitamins be added to grains and milk to improve the nation’s health by improving people’s diet.
Now flash forward to the latter part of the twentieth century, when an improved diet meant that vitamin deficiencies became less of an issue for most Americans. Scientists shifted their focus from using vitamins to cure disease to using them to prevent disease. Today, research is being done to find out how vitamins affect and prevent everything from birth defects to heart disease and cancer.
What Are Vitamins?
Vitamins are tasteless organic compounds that you need in small amounts for growth, reproduction, and overall good health. Although they don’t provide energy (calories) for your body, they are essential nutrients for your well-being. A deficiency of any one will cause physiological symptoms. There are 13 vitamins, and you get most of them by eating a variety of foods from each of the MyPyramid food groups, though the vitamins D, K, niacin, and biotin can also be synthesized in your body or by microorganisms in the intestinal tract.
A chronic deficiency of any of the essential vitamins can cause a cascade of symptoms from scaly skin to blindness. However, consuming too much of some vitamins can also cause adverse effects that can be as damaging as consuming too little. Balance is always your best bet when it comes to meeting your vitamin needs.
Vitamins Are Either Fat Soluble or Water Soluble
A vitamin is either fat soluble or water soluble, depending on how it is absorbed and handled in your body. Fat-soluble vitamins need dietary fat to be properly absorbed, whereas water-soluble vitamins are absorbed with water. Vitamins A, D, E, and K are fat soluble; the B vitamins and vitamin C are water soluble.
The fat-soluble vitamins are absorbed at the beginning of your small intestine. They are packaged with fatty acids and bile in micelles, small transport carriers that shuttle them close to the intestinal wall. Once there, the fat-soluble vitamins travel through the cells in the intestinal wall and are packaged with fat and other lipids in chylomicrons. The vitamins then travel through your lymph system before they enter your bloodstream. Fat-soluble vitamins are stored in your body and used as needed when your dietary intake falls short. Your liver is the main storage depot for vitamin A and to a lesser extent vitamins K and E, whereas vitamin D is mainly stored in your fat and muscle tissues. Because they are stored in the body, large quantities of some of the fat-soluble vitamins, particularly A and D, can build up to the point of toxicity, causing harmful symptoms and conditions.
Water-soluble vitamins are absorbed with water and enter your bloodstream directly. Most water-soluble vitamins are absorbed in the upper portion of your small intestine, although vitamin B12 is absorbed in the lower part of your small intestine. Water-soluble vitamins are typically not stored in your body, and excess amounts are excreted, so it’s important to consume adequate amounts of them every day. Note that even though most water-soluble vitamins aren’t stored, dietary excesses can still be harmful.
Some Vitamins Function as Antioxidants
Antioxidants (anti = against; oxidants = oxygen-containing substances) are a group of compounds that includes vitamins E and C, the mineral selenium, and certain phytochemicals. Just as their name implies, antioxidants counteract oxidation, a harmful chemical reaction that takes place in your cells. During oxidation, oxygen-containing molecules called free radicals can damage cell structure, cell proteins, and even DNA. Like prowling thieves, the unstable free radicals steal electrons from other molecules in order to stabilize themselves. The robbed molecule then itself becomes a free radical, and looks for another molecule to attack. This chain reaction, if not stopped, can significantly damage cells.
Free radicals are normal by-products of your body’s metabolic reactions, which release energy from food. They can also result from exposure to chemicals in the environment (such as cigarette smoke and air pollution) and from the damaging effects of the sun’s ultraviolet rays on unprotected skin.
Antioxidants are part of your body’s natural defense system to harness free radicals and stop them from damaging cells. If free radicals accumulate faster than your body can neutralize them (a condition known as oxidative stress), their effects can contribute to various health problems, including heart disease, cancer, type 2 diabetes, arthritis, and Alzheimer’s disease.
Free radicals can also damage your eyes by contributing to age-related macular degeneration (AMD) and cataracts. Age-related macular degeneration (AMD) results from damage to the macula, a tiny area of the retina that is needed for central vision (the ability to see things that are directly in front of you). AMD can make activities such as reading, driving, and watching television impossible. It is usually the culprit when Americans 60 years of age or older experience blindness. A study conducted by the National Eye Institute (NEI) discovered that supplements containing large amounts of antioxidants (vitamin C, vitamin E, and beta-carotene),with the minerals zinc and copper, are effective in reducing the risk for AMD, as well as the extent of vision loss.
A cataract is a disorder in which the lens of the eye becomes cloudy, resulting in blurred vision. More than half of all Americans have experienced cataracts by the time they reach 80 years of age, and many undergo surgery to remove them. The NEI recommends consuming antioxidant- and carotenoid-rich fruits and vegetables, such as citrus fruits, broccoli, and leafy dark green vegetables, for the health of your eyes.
There is no question that diets high in antioxidant-rich fruits, vegetables, and whole grains are associated with a lower incidence of some diseases. However, these foods contain other compounds that may work with antioxidants to provide protection. For example, phytochemicals (phyto = plant), naturally occurring plant compounds that give fruits and vegetables their vibrant colors, have many beneficial functions in the body, such as acting as antioxidants, stimulating the immune system, and interacting with hormones that may help prevent certain cancers
The big question that remains is if antioxidant supplements provide the same health protection as antioxidants consumed in foods. As you will soon read, too much of vitamins C and E, as well as beta-carotene supplements-all of which are antioxidants-can cause health problems. At this time, the American Heart Association, National Cancer Institute, and United States Preventive Services Task Force do not advocate taking supplements to reduce the risk of specific diseases, but encourage eating a phytochemical- and antioxidant-rich, well-balanced diet. Filling your plate with a colorful variety of plant-based foods is currently one of the best-known strategies to fight chronic diseases.
Vitamins Differ in Bioavailability
Not all of the vitamins consumed in foods are available to be used in the body. In other words, they are not 100 percent bioavailable. The bioavailability of individual vitamins varies according to several factors, including the amount of the vitamin in the food; whether the food is cooked, raw, or refined; how efficiently the food is digested and absorbed; the individual’s nutritional status; and whether or not the vitamin is natural or synthetic. In general, if the body needs more vitamins, a greater percentage will be absorbed. For example, a young child or pregnant woman will absorb more ingested vitamins than will a nonpregnant adult.
The bioavailability of fat-soluble vitamins is usually less than that of water-soluble vitamins because fat-soluble vitamins require bile salts and the formation of a micelle to be absorbed. Vitamins in plant foods are typically less bioavailable than those in animal foods because plant fiber can trap vitamins.
Vitamins Can Be Destroyed by Air, Water, or Heat
Water-soluble vitamins can be destroyed by exposure to air, water, or heat. In fact, vegetables and fruits begin to lose their vitamins almost immediately after being harvested, and some preparation and storage methods can accelerate vitamin loss. Although the fat-soluble vitamins tend to be more stable than water-soluble vitamins, some food preparation techniques can cause the loss of these vitamins as well.
Don’t Expose Your Produce to Air
Air (oxygen) exposure can destroy the water-soluble vitamins and the fat-soluble vitamins A, E, and K. For this reason, fresh vegetables and fruits should be stored in airtight, covered containers and used soon after being purchased. Cutting vegetables and fruits increases the amount of surface exposed to air, so cut your produce close to the cooking and serving time to minimize vitamin loss.
A Little Water Is Enough
When you toss out the water that cooks your vegetables, you are also tossing out some water-soluble vitamins. Soaking foods will cause water-soluble vitamins to leach out of the food and into the liquid. To reduce vitamin loss, cook vegetables in a minimal amount of liquid-just enough to prevent the pot from scorching and to keep your vegetables crisp. Although cooking rice in water doesn’t diminish its nutrient content (because the water is absorbed by the grain rather than discarded), washing rice before cooking it will wash away the B vitamins that were sprayed on during the enrichment process.
Reduce Cooking Time
Heat, especially prolonged heat from cooking, will also destroy water-soluble vitamins, especially vitamin C. Because they are exposed to less heat, vegetables cooked by microwaving, steaming, or stir-frying can have approximately 11⁄2 times more vitamin C after cooking than if they were boiled, which involves longer heat exposure. The first three cooking methods are faster than boiling, reducing the length of time the food is in direct contact with the heat, and they all use less added water. (Stir-frying typically uses only oil.) Cooking vegetables until “just tender” is best, as it reduces the cooking time and heat exposure and preserves the vitamins. If you find yourself with a plate full of limp and soggy vegetables, this is a sure sign that vitamins have been lost.
Keep Your Food Cool
Whereas heat causes foods to lose vitamins, cooler temperatures help preserve them. For this reason, produce should be stored in your refrigerator rather than on a counter or in a pantry. A package of fresh spinach left at room temperature will loses more than half of its folate, a B vitamin, after four days. Keeping the spinach in the refrigerator delays that loss until eight days.12 See the Table Tips for ways to preserve the vitamins in your foods.
Overconsumption of Some Vitamins Can Be Toxic
Vitamin toxicity, or hypervitaminosis, is very rare. This condition results from ingesting more of the vitamin than the body needs, to the point where tissues become saturated. The excess vitamin can damage cells, sometimes permanently. Vitamin toxicity does not occur by eating a normal balanced diet. It can result when individuals consume mega dose levels of vitamin supplements, usually in the mistaken belief that “more is better.”Many individuals, for example, overload on vitamin C tablets to ward off a cold, despite the fact that there is no evidence showing that vitamin C prevents the common cold, and despite the fact that too much vitamin C in the body can lead to unpleasant side effects.
To prevent excessive intake, the Dietary Reference Intakes include a tolerable upper intake level for most vitamins. Even though some vitamins lack sufficient evidence to establish a UL, there still may be risks in taking them in mega dose amounts.
Provitamins Can Be Converted to Vitamins by the Body
Provitamins are substances found in foods that are not in a form directly usable by the body, but that can be converted into an active form once they are absorbed. The best-known example of this is beta-carotene, which is split into two molecules of vitamin A in the small intestinal cell wall or in the liver cells. Vitamins found in foods that are already in the active form, called preformed vitamins, do not undergo conversion.
Now that we’ve discussed the general characteristics of vitamins, let’s review them individually. Before we begin our discussion of the fat-soluble vitamins, take the Self-Assessment to see if your diet is rich in foods containing these important nutrients.
Message
Vitamins are essential nutrients needed in small amounts for growth, reproduction, and overall good health. All vitamins are either fat soluble or water soluble. The fat-soluble vitamins, A, D, E, and K, require fat for absorption and are stored in your body. For this reason, chronic dietary excesses of some fat-soluble vitamins can be toxic. The water-soluble B and C vitamins are absorbed with water. Excess water-soluble vitamins are excreted from your body, and surplus amounts generally aren’t stored. Some vitamins, such as vitamins E and C, as well as the mineral selenium, flavonoids, and carotenoids, act as antioxidants because they help counteract the damaging effects of oxygen-containing molecules called free radicals. If free radicals accumulate faster than your body can neutralize them, their damaging effects can contribute to chronic diseases and conditions. Fruits, vegetables, and whole grains are robust sources of antioxidants. Many vitamins in foods can be destroyed or lost by exposure to air, water, and heat. The overconsumption of some vitamins can be toxic. Provitamins can be converted to vitamins in the body.
Vitamins Found Widely in MyPyramid
Eating a wide variety of foods from all food groups will ensure that you meet your vitamin
needs.
Categorizing the Vitamins:
Fat Soluble and Water Soluble
Fat-soluble vitamins need dietary fat to be properly absorbed, whereas water-soluble vitamins are absorbed with water.
Digesting and Absorbing Vitamins
(a) Once in the small intestine, the fat-soluble vitamins are packaged with fatty acids and bile in micelles that transport them to the intestinal wall. The fat-soluble vitamins travel through the cells in the intestinal wall and are packaged with fat and other lipids in chylomicrons. The chylomicrons travel through the lymph system and into the bloodstream. (b) The water-soluble vitamins are absorbed directly into the bloodstream from the small intestine.
Terms:
Vitamins - Essential nutrients that your body needs in small amounts to grow, reproduce, and maintain good health.
Antioxidants - Substances that neutralize free radicals. Vitamins A, C, and E and beta-carotene are antioxidants
Oxidation - The process during which oxygen combines with other molecules.
Free radicals - Unstable oxygen containing molecules that can damage the cells of the body and possibly contribute to the increased risk of chronic diseases
Age-related macular degeneration (AMD) - A disease that affects the macula of the retina, causing blurry vision.
Cataract - A common eye disorder that occurs when the lens of the eye becomes cloudy.
Phytochemicals - Naturally occurring substances in fruits, vegetables, and whole grains that protect against certain chronic diseases.
Bioavailability - The degree to which a nutrient is absorbed from foods and used in the body.
Toxicity - The accumulation of a substance to the level of being poisonous.
Mega dose - A very large dose or amount.
Provitamins - Substances found in foods that can be converted into an active form once they are absorbed.
Preformed vitamins - Substances that are found in active form in foods.
Vitamins were originally called vitamines. Casimir Funk, a chemist and early vitamin researcher, believed that vitamins were vital to life (he was correct) and were probably also a nitrogen-containing amine (he was incorrect). When later discoveries found that an amine wasn’t present, the e was dropped from the word.
Preserve Your Vitamins!
Cook your vegetables in a small amount of water. If you have to boil vegetables, use the leftover cooking liquid as a soup or gravy base.
Don’t rinse rice before cooking it or pasta after cooking it. You’ll wash away water soluble vitamins.
Steam, microwave, or stir-fry vegetables instead of boiling them to reduce the amount of time they are exposed to heat and therefore the amount of vitamins that are lost.
Store produce in a refrigerator and eat it soon after purchase.
Cut vegetables and fruits close to the time that they are going to be cooked and/or served.
