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Vitamin D Deficiency

Unless you have been living under rock, you know that health disparities exist. Health disparities refer to the differences between groups of people.  These differences can affect how frequently a disease affects a group.  I  have always been interested in how vitamin D deficiency in dark skinned people may contribute to disparate rates of illness and disease.

We know that the pigment melanin reduces the skin’s ability to make vitamin D in response to sunlight exposure and studies have shown that older adults with darker skin are at high risk of vitamin D deficiency.  This has made me very interested in how vitamin D deficiency can affect people of all skin colors.  We also know that depending on where you live your exposure to sunlight may be limited and since the body makes vitamin D when skin is exposed to sunlight, people living in areas with minimal sunlight (northern latitudes) may be at risk of deficiency.

The main function of vitamin D is to regulate the absorption of calcium and phosphorus in our bones and aid in cell to cell communication throughout the body. Five forms of vitamin D have been discovered, vitamin D1, D2, D3, D4, D5. The two forms that seem to matter to humans the most are vitamins D2 (ergocalciferol) and D3 (cholecalciferol).  The majority of scientists state that D2 and D3 are equally effective in our bloodstream. However, new research is beginning to suggest that D3 is more effective.  A study published in the The Journal of Clinical Endocrinology & Metabolism, concluded that Vitamin D2 is much less effective than Vitamin D3 in Humans.

Vitamin D is often added to food items, like milk, orange juice, and breakfast cereals.  The FDA has determined the Daily Value (DV) for vitamin D at 400 IU for adults and children age 4 and older.  According to the U.S. Department of Health and Human Services, Vitamin D is essential for:

  • formation, growth, and repair of bones
  • normal calcium absorption and immune function
  • aids the immune system
  • helps maintain healthy body weight
  • reduces symptoms of asthma
  • protects from radiation damage
  • Research suggests that adequate vitamin D levels may reduce the risk of Multiple Sclerosis, Rheumatoid Arthritis, Cancer,  type1 and type 2 diabetes, hypertension, glucose intolerance, and heart attack

Low vitamin D blood levels have been associated with the following:

  • Increased risk of death from cardiovascular disease
  • Cognitive impairment in older adults
  • Severe asthma in children
  • Cancer
  • Preterm birth and low birthweight infants born to mothers with vitamin D deficiency

What causes vitamin D Deficiency?

  • People may not consume the recommended vitamin D levels  (likely if you are a vegetarian since most of the natural sources are animal-based, including fish and fish oils, egg yolks, cheese, fortified milk, and beef liver)
  • Exposure to sunlight is limited
  • Having dark skin

Foods naturally high in vitamin D

  • Oysters
  • Wild-caught mackerel
  • Wild-caught salmon
  • Mushrooms exposed to ultraviolet light
  • Cod liver oil
  • Tuna
  • Sardines
  • Beef liver
  • Egg yolks

SLN's Take Home Message 

For those that want to avoid UV exposure, supplementation with a high quality Vitamin may be a good way to prevent vitamin D deficiency. Here is a product I have used and recommend along with regular exposure (20 mins) of sun everyday.



Michael F Holick. “Sunlight and vitamin D for bone health and prevention of autoimmune diseases, cancers, and cardiovascular disease” Am J Clin Nutr. December 2004 vol. 80 no. 6 1678S-1688S. Accessed October 20th 2013.


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