What is the Role of Vitamin D in Good Nutrition?



Vitamin D differs from other vitamins in that our bodies can make it upon exposure to sunlight. It is also found in foods of animal origin.

In its active form, it is considered to be a hormone. It has hormone-like effects on mineral absorption, bone mineralization and some secretions.

What are the Key Functions of Vitamin D?

What are the Food Sources of D Vitamin?

Who would benefit from D Vitamin supplementation?

How much D Vitamin is usually taken?

When should D Vitamin supplementation be used?

What are the side effects of using D Vitamins?



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What are the Key Functions of Vitamin D?


  • It is crucial for the development of healthy bones and teeth. Without it, the body cannot build or maintain strong bones.
  • As a fat-soluble vitamin it plays a role in controlling calcium absorption, which affects bone development and is also essential for blood clotting.
  • When it is in short supply in the body, less calcium is absorbed from food, and blood calcium levels have to be maintained by taking calcium from the bones.

D-Vitamin’s most important role is maintaining blood levels of calcium, which it accomplishes by increasing absorption of calcium from food and reducing urinary calcium loss. Both effects keep calcium in the body and therefore spare the calcium that is stored in bones.

When necessary, D vitamin transfers calcium from the bone into the bloodstream, which does not benefit bones. Although the overall effect on the bones is complicated, some D-vitamin is necessary for healthy bones and teeth.

D-Vitamin plays a role in immunity and blood cell formation and also helps cells “differentiate” - a process that may reduce the risk of cancer.

From studies, is has been hypothesized that D-vitamin may protect people from multiple sclerosis, autoimmune arthritis, and diabetes.

D-Vitamin is also needed for adequate blood levels of insulin. D-Vitamin receptors have been found in the pancreas where insulin is made, and preliminary evidence suggests that supplementation may increase insulin secretion for some people with adult-onset diabetes.

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What are the Food Sources of D Vitamin?



Cod liver oil, herring, mackerel, sardines, salmon, margarine, tuna, and cheddar cheese


Cod liver oilSardinesMargarine
Cod liver oil capsulesSardinesMargarine
TunaCheddar cheese
TunaCheese


Here are potential amounts of Vitamin d available when consuming the following:

  • Cod Liver Oil: 1 tablespoon = 1360 IU
  • Salmon: 3 ounces = 425 IU
  • Herring: 3 ounces = 765 IU
  • Sardines: Canned, 3 ounces = 255 IU

Cod liver oil is an excellent dietary source, as are D-vitamin fortified foods. Traces are also found in egg yolks and butter.

However, the majority of D-vitamin in the body is created during a chemical reaction that starts with sunlight exposure to the skin.

Cholecalciferol (D3-vitamin) is the animal form of this vitamin.

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Who would benefit from D Vitamin supplementation?



In a study involving 150 children and adults with unexplained muscle and bone pain, almost all were found to be vitamin d deficient; many were severely deficient with extremely low levels of D-vitamin in their bodies.

"The message here is that unexplained pain may very well be linked to a vit-D deficiency," Gregory A. Plotnikoff, MD, of the University of Minnesota Medical School tells WebMD.

Michael Holick, MD runs the D-Vitamin Research Lab at Boston University Medical Center and he claims there is a strong epidemiological case linking vitamin d deficiency with a host of cancers including those of the prostate, colon, and breast; and he also says D-vitamin may help protect against heart disease, autoimmune diseases, and even type 1 diabetes.

In adults, D-vitamin deficiency may result in a softening of the bones known as osteomalacia. This condition is treated with D-vitamin, sometimes in combination with calcium supplements.

In people of any age, deficiency causes abnormal bone formation. It happens more commonly following winter, owing to restricted sunlight exposure during that season.

D-Vitamin deficiency commonly exists in strict vegetarians (who avoid vitamin d-fortified dairy foods), dark-skinned people, alcoholics, and people with liver or kidney disease. People with liver and kidney disease can make vitamin d but cannot activate it.

D-Vitamin deficiency is common in people suffering from intestinal mal-absorption, which may have occurred following previous intestinal surgeries, or from celiac disease.

People with cystic fibrosis tend to also be deficient in vitamin-D. Deficiency is common in individuals with Graves' disease, particularly women.

In children, deficiency is called rickets and causes a bowing of bones not seen in adults with vitamin d deficiency.

In a study of people with mild hyperparathyroidism, a condition in which the parathyroid gland is overactive, D-vitamin levels were below normal in 7% of them and suboptimal in 53% of them.

Men with advanced prostate cancer also show D-Vitamin deficiency.

Another study showed one in seven adults to be deficient in D-vitamin.

Deficiency is particularly common among the elderly. Age-related decline in D-vitamin status may be due to reduced absorption, transport, or liver metabolism of vitamin d.

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When should D Vitamin supplementation be used?



D-Vitamin has been used in connection with the following conditions:

Alcohol withdrawal support Amenorrhea (calcium for preventing bone loss)
Breast cancer (reduces risk) Cardiac arrhythmia
Celiac disease (for deficiency only) Colon cancer (reduces risk)
Crohn’s disease Cystic fibrosis
Depression Diabetes
Hypertension (for deficiency only) Migraine headaches
Multiple sclerosis Osteoporosis
Parkinson’s disease Rickets/osteomalacia

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How much Vitamin D (RDA) is usually taken?



People who get plenty of sun exposure do not require supplemental D-vitamin, since sunlight increases D-vitamin synthesis when it strikes bare skin.

Although the recommended dietary allowance for D-vitamin is 200 IU per day for adults, there is some evidence that elderly people need 800 to 1,000 IU per day for maximum effects on preserving bone density and preventing fractures. Sun-deprived people should take no less than 600 IU per day and ideally around 1,000 IU per day.

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What are the side effects of using Vitamin D?



People with hyperparathyroidism should not take D-vitamins without consulting a physician.

People with sarcoidosis should not supplement with D-vitamin, unless a doctor has determined that their calcium levels are not elevated.

Too much D-vitamin taken for long periods of time may lead to headaches, weight loss, and kidney stones.

Although rarely, excessive D-vitamin may even lead to deafness, blindness, increased thirst, increased urination, diarrhea, irritability, children’s failure to gain weight, or death.

Remember the total daily intake of D-vitamin includes vitamin d from fortified milk and other fortified foods, cod liver oil, supplements that contain vitamin d, and sunlight. People who receive adequate sunlight exposure do not need as much D-vitamin in their diet as do people who receive minimal sunlight exposure.

D-Vitamin increases both calcium and phosphorus absorption and has also been reported to increase absorption of aluminum. Increased blood levels of calcium (which may be a marker for D-vitamin status) have been linked to heart disease.

Some, but not all, research suggests that D-vitamin may slightly raise blood levels of cholesterol in humans.

Take note:

You or someone in the family should not take D-Vitamin supplements without consulting a physician or doctor.

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