Truth About Carbohydrates & Sugar – Nutrition, Weight Loss, Glycemic Index, Carbs, Psychetruth
Carbohydrates Fuel Your Body Between Meals and Help Spare Protein for Other Uses
As mentioned, both glycogen and fat are important sources of stored fuel that meet your body’s energy needs. These storage forms come in handy between meals when you aren’t eating but your body continues to need fuel. Remember, your red blood cells and your brain, as well as the rest of your nervous system, rely on a steady supply of glucose to function properly. When your blood glucose level dips too low, such as if it has been longer than four hours since your last meal, your body calls upon its glycogen reserves to supply glucose to your blood. The glycogen in your liver is used to maintain your blood glucose level, and your muscle glycogen is used exclusively by the muscles for fuel. During this time, your body will also break down your fat stores to provide the energy for your tissues, such as your muscles. For example, let’s say that your nutrition class is at 8 a.m. and that you overslept and didn’t eat breakfast. The last time you ate was at dinner last night-more than 12 hours ago. As your blood glucose level begins to drop, your pancreas releases another hormone, glucagon, which directs the release of glucose from the stored glycogen in your liver to help raise your blood glucose level. This breakdown of glycogen is called glycogenolysis (lysis = loos-ening).
In addition to directing the breakdown of glycogen, glucagon signals the liver to start gluconeogenesis (gluco = sugar/sweet, neo = new, genesis = origin). This is thecreation of glucose from noncarbohydrate sources, mostly from protein. Gluconeogenesis can only occur in your liver and kidneys, as these are the only organs that have all the enzymes needed. Most of the time, this glucose-generating process occurs in your liver. Gluconeogenesis kicks in from the kidney only after long periods of fasting. In times of deprivation, your body dismantles protein, using specific remnants to generate the glucose that it needs.
If you don’t feed your blood with glucose, your body will attempt to feed it. Thus, consuming adequate amounts of carbohydrates is important to spare protein from being broken down to make glucose. You will learn in Chapter 6 that protein has so many other important functions in your body that you want to preserve it, rather than use it to make glucose. Once your blood glucose returns to normal, glucagon will no longer be released.
In addition to glucagon, other hormones can increase your blood glucose level. Epinephrine, also known as adrenaline, acts on the liver and muscle cells to stimulate glycogenolysis to quickly flood your blood with glucose. Emotional and physical forms of stress, such as fear, excitement, and bleeding, will increase your bodies out-put of epinephrine. For example, if an aggressive dog was chasing you down the street, your body would be pumping out epinephrine to help provide the fuel you need to run. For this reason, epinephrine is also referred to as the “fight-or-flight” hormone.
A low blood glucose level can also trigger the release of epinephrine. In fact, some of the symptoms that you may experience when your blood glucose level dips too low, such as anxiety, rapid heart-beat, turning pale, and shakiness, are caused by the release of epinephrine.
Carbohydrates Fuel Your Body During Fasting and Prevent Ketosis
Skipping breakfast is one thing; fasting, or not eating for long periods of time, is quite another. After about 18 hours of fasting, your liver’s glycogen stores are depleted, so your body must rely solely on fat and protein for fuel. To burn fat thoroughly, you need adequate amounts of glucose. Without it, ketone bodies, by-products of the incomplete breakdown of fat, are created and spill out into your blood. Because most ketone bodies are acids, they can cause your blood to become slightly acidic. After about two days of fasting, the number of ketone bodies in your blood is at least doubled, and you are in a state of ketosis. Individuals who fast or follow strict low-carbohydrate diets are often in ketosis because they consume inadequate amounts of carbohydrates. Although the term ketosis sounds scary, the condition is not necessarily harmful as long as you are otherwise healthy.
As mentioned above, while your body continues to break down fat for fuel, it also uses protein to generate glucose. You can’t store extra protein for this, so protein from your muscles and organs is broken down and some of its parts are used to make glucose. If you continue to fast, your body’s protein reserves will reach a dangerously low level, causing death.
The Take-Home Message
After a meal, when your blood glucose level begins to rise, the hormone insulin is released from the pancreas, directing glucose into your cells to be used for energy. Excess glucose is stored as glycogen or as fat. When your blood glucose drops too low, the hormone glucagon directs the release of glucose from glycogen in your liver to increase the glucose in your blood. Glucagon will also signal the start of gluconeogenesis in the liver, which is the creation of glucose from noncarbohydrate sources, such as protein. Epinephrine also plays a role in increasing your blood glucose level. When you fast, stored fat and ketone bodies become the primary source of energy to fuel your body. This spares your protein-rich tissues by reducing the amount of protein that needs to be broken down to generate glucose. If the fasting continues, death is inevitable.
How Much Carbohydrate Do You Need and What Are the Best Food Sources?
Although your body has mechanisms in place to provide the energy it needs on demand, you have to feed it the proper fuel to keep it running efficiently. Consequently, the question of how much carbohydrate you should consume daily has two answers.
The first refers to the minimum amount of carbohydrates that you should eat to provide adequate fuel for your body, specifically your brain, to function efficiently. The longer, and more challenging, answer relates to the best type and source of carbohydrates that you should eat daily for long-term health. First, let’s look at the amount of carbohydrates that you should eat daily.
You Need a Minimum Amount of Carbohydrates Daily
The latest Dietary Reference Intakes (DRIs) for carbohydrates recommend that adults and children consume a minimum of 130 grams daily. This is based on the estimated minimum amount of glucose your brain needs to function efficiently. This may sound like a lot, but 130 grams is less than the amount you would consume by eating the minimum recommended daily servings for each food group in MyPyramid, that is, 6 servings from the grain group, 3 servings each from the vegetable and dairy groups, and 2 servings from the fruit group.
If your diet is well balanced, feeding your brain should be a no-brainer. In the
The AMDR for carbohydrates is 45 to 65 percent of your total daily calories. Adults in the
Because few people know the exact number of calories they consume daily, the recommendations for fiber are categorized by both age and gender so that your estimated needs can be determined. Unfortunately, most Americans fall short of this goal and consume approximately 15 grams of fiber a day, on average.
The Best Carbohydrates Are Found in These Foods
Now let’s turn to the second part of our answer and look at the best type and source of carbohydrates to choose for long-term health. As with other nutrients, not all carbohydrate-laden foods are created equal. For example, eating high-sugar foods containing lots of calories and saturated fat, but few other nutrients, can lead to weight gain and promote heart disease. It’s best to choose carbohydrates from a variety of nutrient-dense, low-saturated-fat foods whenever possible. In general, the best strategy for long-term health is to eat a diet with fewer (low to moderate amounts of) simple carbohydrates and more complex carbohydrates.
Whole Grains Can Help Meet Starch and Fiber Needs
Starch is the primary complex carbohydrate found in refined grains, while fiber is found in whole grains. Select whole-grain breads and cereals that have at least 2 to 3 grams of total fiber per serving, such as quinoa, whole-wheat bread, bulgur, brown rice, and whole-wheat pasta.
Fruits and Vegetables Provide Simple Sugars, Starch, and Fiber
Whole fruits, 100-percent fruit juices, and vegetables are naturally good sources of simple carbohydrates. The flesh of fruit, for example, is rich in simple sugars, including fructose and glucose. Though you can also get simple sugars from processed foods and sweets, the higher calorie and lower nutrient levels in these foods make them a less healthy option (you’ll learn more about the pros and cons of natural and added sugars in the next section). The skins of many fruits contain cellulose (a type of insoluble fiber), so eat unpeeled (but cleaned and scrubbed) fruit more often. Another type of fiber, pectin, is found in the flesh of fruit, and makes up about 15 percent to 30 percent of the fiber in fruit. Fruit over-all contains about 2 grams of dietary fiber per serving. When selecting fruit, choose fresh or frozen versions over canned, but if canned is your only option, choose fruit packed in fruit juice rather than heavy syrup, to cut down on added sugar.
Vegetables contain abundant amounts of complex carbohydrates, including starch and fiber. A serving of vegetables contains approximately 2 grams of fiber. In general, starchy vegetables, such as corn and potatoes, contain more carbohydrate per serving than no starchy vegetables like green beans or carrots.
Legumes, Nuts, and Seeds Are Excellent Sources of Carbohydrates and Fiber
Legumes, such as kidney beans and chickpeas, are rich sources of both carbohydrates and fiber. Nuts and seeds are also good sources of fiber, providing over 2 grams in an ounce or small handful. An ounce of nuts is about 30 peanuts, 14 walnut halves, or 49 shelled pistachios
Low-Fat and Fat-Free Dairy Products Provide Some Simple Sugars
Milk and milk products, including cheese and yogurt, contain 1 to 17 grams of lactose per serving. Choose low-fat or fat-free dairy products whenever possible, for the sake of your heart health. The lactose content is the same regardless of the fat content.
Terms:
Glucagon – The hormone that directs glycogenolysis and gluconeogenesis to increase glucose in the blood. Glucagon is produced in and released from the pancreas.
Gluconeogenesis – The creation of glucose from noncarbohydrate sources, predominantly protein ketosis The condition of increased ketone bodies in the blood.
Ketone bodies – The by-products of the incomplete breakdown of fat.
Food Sources of Carbohydrates
You need to eat at least 130 grams of carbohydrates daily. Eating the minimum recommended servings from the grains, vegetables, fruits, and dairy groups will meet this need.
*Based on a 2,000-calorie diet.
Food Sources of Fiber
Adults need to consume about 20 to 38 grams of fiber daily. Foods are a combination of soluble and insoluble fiber.
An orange has four times the fiber of six ounces of orange juice.
High Five! Five Ways to Increase Fiber Daily
Choose only whole-grain cereals for breakfast.
Eat two pieces of whole fruit daily as snacks.
Use only 100% whole-wheat bread for your lunchtime sandwich.
Layer lettuce, tomatoes, or other vegetables on your sandwich.
Eat a large salad topped with chickpeas with dinner nightly.
Packaged Foods Can Also Provide Carbohydrates
Processed foods, such as ready-to-eat cereals, crackers, and savory snacks, can be good sources of carbohydrate, but can also contain fair amounts of added sugar, salt, and fat. When selecting these packaged foods, choose products that contain at least 2 grams of dietary fiber per serving and be aware of the amounts of added sugar, salt, fat, and total calories. Choose whole-grain cereals with lower amounts of added sugar, whole-grain crackers, and baked rather than fried snacks.
The Nutrition Facts panel and ingredients listings on the product can help you to choose healthier packaged foods.
The Take-Home Message
You need to consume a minimum of 130 grams of carbohydrates daily to provide adequate glucose for your brain. It is recommended that 45 to 65 percent of your daily calories come from carbohydrates. You should consume 14 grams of fiber for every 1,000 calories you eat. Whole grains, whole fruits and vegetables, legumes, and lean dairy products are the best food sources of simple carbohydrates and starch.
Whole grains, fruits, vegetables, legumes, nuts, and seeds are excellent sources of fiber. Packaged foods can be good sources of carbohydrate, but the added sugars, fat, and total calories in such foods should be monitored.
