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Royal Academy of Nutrition and Health Eating

(101) Nutrition

Vitamin D Deficiency

Vitamin D

vitamine d

What Is Vitamin D?

Vitamin D is called the “sunshine vitamin” because it is made in your body with the help of ultraviolet (UV) rays from sunlight.

In fact, most healthy people can synthesize all the vitamin D they need as long as they receive adequate sun exposure.

People who don’t obtain enough sun exposure must meet their needs through their diets.

Whether from food or sunlight, vitamin D enters your body in an inactive form. The ultraviolet rays of the sun convert a cholesterol-containing compound in your skin to previtamin D, which is then converted to an inactive form of vitamin D in your blood. The vitamin D in your foods is also in this inactive form.

This inactive form travels in your blood to your liver, where it is changed into a circulating form of vitamin D and is released back into your blood. Once in your kidneys, it is converted to an active form of vitamin D.

Functions of Vitamin D

Vitamin D Helps Bone Health by Regulating Calcium and Phosphorus

Once in an active form, vitamin D acts as a hormone and regulates two important bone minerals, calcium and phosphorus.

Vitamin D stimulates the absorption of calcium and phosphorus in the intestinal tract, helping to keep the levels of these minerals within a healthy range in your blood. Because of its role in regulating these minerals, vitamin D helps to build and maintain your bones.

Although phosphorus deficiency is very rare, dietary calcium deficiencies do occur, causing blood levels of calcium to drop. When this happens, vitamin D and parathyroid hormone cause calcium to leave your bones to maintain the necessary levels in your blood. Vitamin D then signals your kidneys to decrease the amount of calcium excreted in the urine.

All of these actions help to regulate the amount of calcium in your blood.

Vitamin D May Prevent Some Cancers and Diabetes

Research studies have shown that breast, colon, and prostate cancers are more prominent in individuals living in sun-poor areas of the world than in those living in sunny regions. Vitamin D helps regulate the growth and differentiation of certain cells. Researchers speculate that an inadequate amount of vitamin D in the body may reduce the proliferation of the healthy cells, and allow cancer cells to flourish.

Vitamin D may also help prevent diabetes mellitus. Many individuals with type 2 diabetes mellitus have low blood levels of vitamin D. One study revealed that insulin resistance, the inability of the cells to effectively use insulin in the blood, was greater among those with low blood levels of vitamin D, suggesting that the vitamin plays a role in insulin sensitivity.

Vitamin D May Help Regulate the Immune System and Blood Pressure

Vitamin D may also reduce the risk of developing certain autoimmune disorders, such as inflammatory bowel syndrome.

Most cells in the immune system have a receptor for vitamin D. The role of vitamin D is still not understood, but some researchers suggest that it may affect the function of the immune system and inhibit the development of autoimmune diseases.

Vitamin D may help reduce high blood pressure by acting on the gene that is involved in regulating blood pressure.

Blood pressure readings tend to be higher during the winter, when people are exposed to less sunlight, than in the summer.

People with mild hypertension may be able to lower their blood pressure by consuming adequate vitamin D.

Daily Needs

Not everyone can rely on the sun to meet their daily vitamin D needs. During the winter months in areas above latitudes of approximately 40 degrees north (Boston, Toronto, Salt Lake City) and below approximately 40 degrees south (Melbourne, Australia), sun exposure isn’t strong enough to synthesize vitamin D in the skin.

Individuals with darker skin, such as African-Americans, have a higher amount of the skin pigment melanin, which reduces vitamin D production from sunlight.

These individuals need a longer period of sun exposure, compared to a person with less melanin, to derive the same amount of vitamin D. The use of sunscreen can also block the body’s ability to synthesize vitamin D by more than 95 percent.

Because of these variables involving sun exposure, your daily vitamin D needs are based on the amount you would need to eat in foods and are not based on the synthesis of vitamin D in your skin from sunlight.

Based on the important roles that vitamin D plays in your body, it is currently recommended that adults ages 19 to 70 consume 15 micrograms, or 600 IU, of vitamin D daily. This is a significant increase from previously recommended daily amounts. Also based on revised Dietary Reference Intakes, adults over the age of 70 should incorporate 20 micrograms, or 800 IU, into their daily consumption.

When you are reading labels to assess the amount of vitamin D in your foods, keep in mind that the Daily Value (DV) on the Nutrition Facts panel is set at 400 IU, twice the current amount recommended for many adults.

Food Sources

One of the easiest ways to get your vitamin D from food is to drink fortified milk, which provides 100 IU, or 21⁄2 micrograms, of vitamin D per cup. Other than fatty fish (such as sardines and salmon) and fortified milk, breakfast cereals, juice, and yogurt, very few foods provide ample amounts of vitamin D. With this scarcity of naturally occurring vitamin D–rich sources, it isn’t surprising that many Americans are not meeting their daily dietary vitamin D needs.34

Too Much or Too Little

Consuming too much vitamin D can cause loss of appetite, nausea, vomiting, and constipation. The upper level for vitamin D has been set at 2,000 IU (50 micrograms), which is three to ten times higher than recommended daily.

As with the other fat-soluble vitamins, excess amounts of vitamin D are stored in the fat cells, and an accumulation can reach toxic levels, causing hypervitaminosis D. This condition causes over absorption of calcium from the intestines as well as calcium loss from bones. When both of these symptoms occur, blood calcium levels can become dangerously high.

A chronically high amount of calcium in the blood, or hypercalcemia (hyper = over, calc = calcium, emia = blood), can cause damaging calcium deposits in the tissues of your kidneys, lungs, blood vessels, and heart. Excess vitamin D can also affect your nervous system and cause severe depression.

The good news is that it is highly unlikely that you will get hypervitaminosis D from foods, even fortified foods. The only exception is fish oils, specifically cod-liver oil, which provides 1,360 IU of vitamin D per tablespoon. Luckily, the less-than pleasant taste of this oil is a safeguard against overconsumption. A more likely culprit behind hypervitaminosis D is the overuse of vitamin D supplements.

Sun worshippers don’t have to worry about getting hypervitaminosis D from the sun (although they should be concerned about the risk of skin cancer). Overexposing the skin to UV rays will eventually destroy the inactive form of vitamin D in the skin, causing the body to shut down production of vitamin D.

Rickets on the Rise

Rickets is a vitamin D deficiency disease that occurs in children. The bones of children with rickets aren’t adequately mineralized with calcium and phosphorus, and this causes them to weaken. Because of their “soft bones,” these children develop bowed legs, as they are unable to hold up their own body weight when they are standing upright. Since milk became fortified with vitamin D in the 1930s, rickets has been considered a rare disease among children in the United States. However, the disease has once again become a public health concern. In the late 1990s, a review of hospital records in Georgia suggested that as many as five out of every 1 million children between 6 months and 5 years of age were hospitalized with rickets associated with a vitamin D deficiency. This probably underestimates the prevalence of rickets in the state, as only hospitalized children were investigated. Similarly, more than 20 percent of more than 300 adolescents at a Boston-based hospital clinic were recently found to be deficient in vitamin D.

Changes in the diets and lifestyles of children provide clues as to why rickets is on the rise in America. One factor may be the increased consumption of soft drinks.

A U.S. Department of Agriculture (USDA) report found that the number of children, who drank soft drinks, in and outside of school, has more than doubled over a 20-year period. This displacement of milk (a good source of vitamin D) with soft drinks (a poor source) is causing many children to come up short in their vitamin D intake.

Increased concern over skin cancer may be another factor. Skin cancer is the most common form of cancer in the United States, and childhood sun exposure appears to increase the risk of skin cancer in later years. Because of this, organizations such as the Centers for Disease Control and the American Cancer Society have run campaigns that recommend limiting exposure to ultraviolet light.

People are encouraged to use sunscreen, wear protective clothing when outdoors, and minimize activities in the sun. The American Association of Pediatricians also recommends that infants younger than 6 months not be exposed to direct sunlight and that children use sunscreen before going outside. With less exposure to UV light, many children aren’t able to synthesize vitamin D in adequate amounts to meet their needs, thereby increasing their risk of developing rickets.

The increased use of child day-care facilities, which may limit outdoor activities during the day, may also play a role in this increased prevalence of rickets.

Finally, air pollution reduces the ultraviolet rays of the sun by as much as 60 percent-another factor limiting the production of vitamin D in the skin. In fact, children living in an industrial, polluted region of India were shown to have less vitamin D in their blood than children living in a less polluted area of the country.

Other Vitamin D Deficiency Disorders

Osteomalacia is the adult equivalent of rickets and can cause muscle and bone weakness and pain. The bones can’t mineralize properly because there isn’t enough calcium and phosphorus available in the blood. Although there may be adequate amounts of these minerals in the diet, the deficiency of vitamin D hampers their absorption.

Vitamin D deficiency and its subsequent effect on decreased calcium absorption can lead to osteoporosis, a condition in which the bones can mineralize properly, but there isn’t enough calcium in the diet to maximize the bone density, or mass.

Table Tips

Dynamite Ways to Get Vitamin D

Use low-fat milk, not cream, in your hot or iced coffee.

Buy vitamin-D–fortified yogurts and have one daily as a snack. Top it with a vitamin-D–fortified cereal for another boost of “D.”

Start your morning with cereal, and douse it with plenty of low-fat or skim milk.

Flake canned salmon over your lunchtime salad.

Make instant hot cocoa with hot milk rather than water.


(102) Nutrition

Vitamin B vs. Vitamin C


The B Vitamins and Vitamin C Are Water Soluble

There are nine water-soluble vitamins, and eight of them belong to the vitamin B complex. When initially discovered in the early 1900s, the “water-soluble B” was thought to be one vitamin. After years of research, it became apparent that this was not a single substance but rather many vitamins-thiamin, riboflavin, niacin, vitamin B6, folate, vitamin B12, pantothenic acid, and biotin-known collectively as the B vitamins.

The ninth water-soluble vitamin is vitamin C.

Water-soluble vitamins are different from fat-soluble vitamins in that they dissolve in water, are generally not stored in the body, and are often excreted through the urine. Consumers who take large amounts of water-soluble vitamins in an attempt to “beef up” their vitamin stores literally end up flushing their vitamins, and their money, down the toilet. Because excess amounts are not stored, most water-soluble vitamins are not toxic. However, routine intakes of excessive amounts can be harmful.

In fact, Brendan’s illness, described at the beginning of the chapter, wasn’t due to a vitamin deficiency but to overconsumption of the water-soluble vitamin C.

Under consuming the water-soluble vitamins can lead to deficiency symptoms, and because many B vitamins are found in similar food sources, an individual experiencing a deficiency of one B vitamin is likely also deficient in others.

Water-soluble vitamins serve numerous similar functions in the body. The B vitamins share a common role as coenzymes, helping numerous enzymes produce reactions in your cells. Although vitamins don’t provide calories and thus aren’t sources of energy, you need many of the B vitamins to use the three energy-yielding nutrients (carbohydrates, proteins, and fat). The roles of the B vitamins don’t end here. Each vitamin has other important functions in your body. Vitamin C plays important roles in the immune system and in bone health, in addition to its other functions. Take the Self-Assessment to see if you are consuming foods that are rich in the B vitamins and vitamin C.

Are You Getting Enough Water-Soluble Vitamins in Your Diet?

Take this brief self-assessment to see if your diet is rich in the water-soluble B vitamins and vitamin C.

1. Do you eat at least 1 cup of a ready-to-eat cereal or hot cereal every day? Yes _ No _

2. Do you enjoy a citrus fruit or fruit juice, such as an orange, a grapefruit, or orange juice, every day? Yes _ No _

3. Do you have at least one slice of bread, a bagel, or a muffin daily? Yes _ No _

4. Do you have at least a cup of vegetables throughout your day? Yes _ No _

5. Do you consume at least 1⁄2 cup of pasta daily? Yes _ No _


Yes answers to all of these questions, make you a vitamin superstar! Rice, pasta, cereals, and bread and bread products are all excellent sources of B vitamins. Citrus fruits are a ringer for vitamin C. In fact, all vegetables can contribute to meeting your daily vitamin C needs. If you answered no more than yes, read on to learn how to add more Bs and C to your diet.


Coenzymes - Substances needed by enzymes to perform many chemical reactions in your body. Many vitamins act as coenzymes.


(103) Nutrition

Find a Vitamin or Supplement THIAMINE (VITAMIN B1)

Thiamine (Vitamin B1)

Vitamin B1  Thiamine  1

Thiamin (B1)

What Is Thiamin?

Thiamin, or vitamin B1, was the first B vitamin to be discovered. The path to its discovery began in the 1890s in East Asia. A Dutch doctor, Christiann Eijkman, noticed that chickens and pigeons that ate polished rice (rice with the nutrient and thiamin-rich outer layer and germ stripped away) developed polyneuritis (poly = many, neur = nerves, itis = inflammation).

This debilitating nerve condition resulted in the birds not being able to fly or stand up. Eijkman noted that polyneuritis was also a symptom of beriberi, a similar disease that had been observed in humans.

When Eijkman changed the birds’ diet to unpolished rice, with the outer layer and germ intact, the birds were cured.

Though Eijkman realized that the unpolished rice eliminated the symptoms, he didn’t know why. Finally, in 1911, Casimir Funk identified thiamin as the curative factor in the unpolished rice.

Functions of Thiamin

Thiamin Is Needed for Nerve

Function and Energy Metabolism Thiamin plays a role in the transmission of nerve impulses and so helps keep nerves healthy and functioning properly.

You also need thiamin for the metabolism of carbohydrates and certain amino acids. Thiamin also plays a role in breaking down alcohol in the body.

Daily Needs

The RDA for thiamin for adults is 1.1 milligrams for women and 1.2 milligrams for men. Currently, adult American men consume close to 2 milligrams of thiamin daily, whereas women, on average, at approximately 1.2 milligrams daily, so both groups are meeting their daily needs.

Food Sources

Enriched and whole-grain foods, such as bread and bread products, ready-to-eat cereals, pasta, and rice, and combined foods, such as sandwiches, are the biggest contributors of thiamin in the American diet. A medium-sized bowl of ready-to-eat cereal in the morning and a sandwich at lunch will just about meet your daily thiamin requirement.

Pork is the richest source of naturally occurring thiamin.

Too Much or Too Little

There are no known toxicity symptoms from consuming too much thiamin from food or supplements, so no upper level has been set.

The disease that occurs in humans who are deficient in thiamin is beriberi.

There are two types of beriberi. Wet beriberi affects the cardiovascular system, so symptoms often include a rapid heartbeat, shortness of breath, and oedema (swelling) in a person’s calves and feet. Dry beriberi affects the nervous system, so symptoms may include difficulty in walking, tingling in the hands and feet.


(104) Nutrition

The Many Names And Faces Of Vitamin B3



Niacin (B3)

What Is Niacin?

Niacin, or vitamin B3, is the generic term for nicotinic acid and nicotinamide, which are the two active forms of niacin that are derived from foods.

Functions of Niacin

Niacin Is Needed to Use the Energy in Your Food

Niacin is another nutrient your body needs in order to use carbohydrates, proteins, and fats. Without niacin, you wouldn’t be able to create energy from the foods that you eat. Niacin is also needed to synthesize fat and cholesterol.

Other Functions of Niacin

Niacin is needed to keep your skin cells healthy and your digestive system functioning properly.

Niacin has been shown to lower the total amount of cholesterol in the blood and the “bad” LDL cholesterol carrier. It can also lower high levels of fat (triglycerides) in the blood and simultaneously raise the level of the “good” HDL cholesterol carrier. The nicotinic acid form of niacin is sometimes prescribed by physicians for patients with high blood cholesterol levels. When niacin is used to treat high blood cholesterol, it is considered a drug. The amount prescribed by a physician is often more than 40 times the upper level for niacin. Note that you should never consume high amounts of niacin unless a physician is monitoring you.

Daily Needs

The recommended daily amount for adults is 14 milligrams for women and 16 milligrams for men, an amount set to prevent the deficiency disease pellagra. American adults, on average, far exceed their daily niacin needs. Niacin is found in many foods, but it can also be synthesized in the body from the amino acid tryptophan. For this reason, your daily niacin needs are measured in niacin equivalents (NE). It is estimated that 60 milligrams of tryptophan can be converted to 1 milligram of niacin or 1 milligram NE.

Food Sources

Niacin is found in meat, fish, poultry, enriched whole-grain bread and bread products, and fortified cereals. Protein-rich foods, particularly animal foods such as meat, are good sources of tryptophan and thus of niacin. However, if you are falling short of both your dietary protein and niacin, tryptophan will first be used to make protein in your body, at the expense of your niacin needs. As with thiamin, your niacin needs are probably met after you eat your breakfast and lunch, especially since similar foods contain both vitamins.

Too Much or Too Little

As with most water-soluble vitamins, there isn’t any known danger from consuming too much niacin from foods such as meat and enriched grains. 


(105) Nutrition

Vitamin B6 Benefits, Deficiency & Sources

Vitamin B6 - Mayo Clinic

Vitamin B6


Vitamin B6

What Is Vitamin B6?

Vitamin B6 is a collective name for several related compounds, including pyridoxine, the major form found in plant foods and the form used in supplements and fortified foods. Two other forms, pyridoxal and pyridoxamine, are found in animal food sources such as chicken and meat.

Functions of Vitamin B6

Vitamin B6 Is an Active Coenzyme Vitamin B6 acts as a coenzyme with more than 100 enzymes involved in the metabolism of proteins. It is needed to create nonessential amino acids and to convert the amino acid tryptophan to niacin. Vitamin B6 also helps your body metabolize fats and carbohydrates and break down glycogen, the storage form of glucose.

Other Functions of B6

Vitamin B6 is needed to make the oxygen-carrying hemoglobin in your red blood cells and to keep your immune and nervous systems healthy.

Finally, recent research indicates that vitamin B6, along with two other watersoluble vitamins, folate and vitamin B12, may help reduce the risk of heart disease.

Daily Needs

Adult women need 1.3 to 1.5 milligrams and men need 1.3 to 1.7 milligrams of vitamin B6 daily, depending on their age.

Food Sources

Because vitamin B6 is found in so many foods, including ready-to-eat cereals, meat, fish, poultry, many vegetables and fruits, nuts, peanut butter, and other legumes, Americans on average easily meet their daily needs.

Too Much or Too Little

To protect against potential nerve damage, the upper level for vitamin B6 is set at 100 milligrams daily for adults over the age of 19. Luckily, it would be extremely difficult to take in a dangerous level of vitamin B6 from food alone.

However, taking vitamin B6 in supplement form can be harmful. Over the years, vitamin B6 has been touted to aid a variety of ailments, including carpal tunnel syndrome and premenstrual syndrome (PMS). But research studies have failed to show any significant clinical benefit of taking vitamin B6 supplements for either of these syndromes.



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