The Health Benefits of Vitamin D

The Health Benefits of Vitamin D

Introduction & Biological Role

Vitamin D is a fat soluble vitamin that has the unique property of being synthesized by the human body. It plays an important role in electrolyte metabolism and balance in our bodies and I will attempt to summarize that for you here.

Dietary vitamin D is absorbed in the small intestine, then transferred to the liver where the body modifies it for use. The kidneys also play a role in maintaining appropriate levels. Vitamin D has different names based on where in the body it is currently being metabolized; eg cholecalciferol, ergocalciferol and calcitriol. For most people, the type of vitamin D called ‘cholecalciferol’ is the one you want to supplement with. If you have kidney or liver disease, talk to your doctor to make sure you’re taking the appropriate form of the vitamin.

The function of vitamin D is to regulate calcium and phosphorus levels in the body. When blood levels of calcium are low, the body ramps up the activity of vitamin D to increase calcium absorption in the gut and calcium retention in the kidneys. Parathyroid hormone is a parallel factor in this regulatory process.

Vitamin D Supplements

The following are benefits and protective effects of Vitamin D

  1. Depression: deficiency in vitamin D has been associated with an increased risk of depression, therapeutic levels appear to reduce that risk.

  2. Multiple Sclerosis: May have a protective effect against Multiple Sclerosis, the development of which is closely linked to sun exposure and distance from the equator.

  3. Alzheimer’s Disease: Vitamin D levels in the normal range appear to reduce the risk of developing the disease.

  4. Parkinson’s Disease: Vitamin D levels in the normal range appear to reduce the risk of developing the disease.

  5. Sleep quality: Deficiency may impact quality of sleep, although this has not been consistently proven in studies.

  6. Overall mortality: Vitamin D supplementation is associated with an overall reduced risk of death. This is especially true in persons over the age of 60.

  7. Cancer: There is an inverse correlation between breast cancer and vitamin D deficiency. That is to say that the risk of developing breast cancer goes up as your bodies vitamin D stores decrease. This also appears to be true with colon, prostate, pancreatic, and ovarian cancer as well.

  8. Heart Health: Therapeutic levels of vitamin D may help control blood pressure, reduced hypertrophy (excess growth) of cardiac tissue and reduced atherosclerosis.

  9. Lung health: Individuals with normal vitamin D levels appear to have reduced incidence of asthma and respiratory disease. It may be protective against the effects of smoking.

  10. Diabetes: Deficiency appears to increase the risk of developing insulin resistance and diabetes.

  11. Testosterone: Increases in vitamin D are associated with increased testosterone

Exercise and Performance Enhancement

Individuals with a deficiency will benefit from supplementation to correct it. Supplementation may improve athletic performance as noted in one study. Vitamin D deficiency was associated with an increased risk of illness and injury among athletes, especially fractures.

Bone and Joint health

Because of vitamin D’s regulation of calcium and phosphate, it plays an important role in bone density and overall health of joints. Having appropriate levels of vitamin D is associated in a reduced risk of fractures in both the young and the old. It may also reduce the risk of falls in the elderly.


Potential causes of vitamin D deficiency include insufficient sunlight exposure and synthesis in the skin, inadequate dietary intake, malabsorption syndromes (eg, cystic fibrosis or crohn’s disease), liver disease, and kidney disease. Ultimately, a chronic deficiency in vitamin D causes low serum calcium. This deficiency may contribute to the development of osteoporosis and an increased risk of fractures and falls in the elderly.

Severe cases can lead to rickets in children or osteomalacia in adults. It’s worth noting that your bodies vitamin D stores decline with age. Levels of vitamin D can also decrease during winter months where sun exposure often decreases, especially in more temperate climates.


Vitamin D toxicity is most likely to occur from individuals who consume so-called megadoses or supplement their diet with too much of the vitamin. The toxic levels subsequently cause hypercalcemia, or too much calcium in the blood. The level at which vitamin D becomes toxic is not well understood.

Dietary Sources

Vitamin D is synthesized in the skin when exposed to sunlight and also absorbed in the GI tract from dietary intake. Dietary sources of vitamin D include fortified milk, fish, eggs, fortified cereal, and some cheese. In the US, fortified milk is the primary source.

There are many factors that increase vitamin D synthesis in sun exposure. However, there are two important factors. First is latitude; the closer to the equator you live, the more you will synthesize. The second is skin tone; the darker your skin the slower you absorb and synthesize the ultraviolet light.


Because of the importance of calcium, especially in growing children and older adults at risk of osteoporosis, many professional organizations recommend supplementing vitamin D intake. It’s worth noting that the darker your skin, the more sun exposure you need to generate adequate levels of vitamin D. For example, a caucasian individual of northern European descent generates more vitamin D than an african american individual in the same amount of time.

Below are the recommended daily allowances. Please consult your primary care physician to make sure you have appropriate levels of vitamin D. In the US, vitamin D levels can safely be consumed up to 2000 IU/day.

Recommended Daily Allowance (RDA, in international units [IU])

  • Infants (0 to 12 months) - 400 IU/day
  • Children (1 to 18 years) - 600 IU/day
  • Adults (19 to 70 years) - 600 IU/day
  • Adults (>70 years) - 800 IU/day

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