Vitamin D

The U.S. population currently has the highest per capita intake of calcium in the world. Paradoxically, we also have the highest rates of osteoporosis in the world.

You may have heard that “you can get all the vitamins and minerals you need from a well-balanced diet”, and that you don’t need to supplement.  If that is the case, then what foods naturally contain vitamin D?  Oily fish such as mackerel, sardines, and salmon are the only foods where you’ll find vitamin D naturally occurring in any appreciable amount.  Milk in the United States has also had vitamin D added, but the amounts are notoriously unreliable.

Let the Sun Shine

The way most people get their vitamin D is from the sun.  When sunlight hits the skin, it converts 7-dehydrocholesterol, a molecule similar to cholesterol, into vitamin D.  The vitamin D then travels throughout the body to where it’s needed.  When humans originally migrated from Africa to northern Europe, they encountered a climate with much less sunlight, especially in the winter months.  Over time these early Europeans lost pigmentation in their skin, enabling them to produce adequate levels of vitamin D.

Today most of us have jobs that keep us inside most of the day, we wear clothes that cover most of our bodies when we’re outside, and we put sunscreen on anything left showing.  As a result, undiagnosed vitamin D deficiency is rampant.  Over one third of all adults examined in one recent study were found to be deficient.  Rates of deficiency in dark-skinned individuals were found to be as high as 84%.

Health Benefits

Optimal vitamin D levels are essential for optimal bone strength.  Without adequate vitamin D, your body will not even absorb the calcium that you do ingest.  Rickets is the classic vitamin D deficiency disease found in children, while adults with low vitamin D levels are likely to have osteomalacia (softening of the bones) or osteoporosis (in which the bones become brittle). Vitamin D is also a powerful inhibitor of cancer cell growth, and studies have shown that inadequate levels of this molecule contribute to the development of over 16 cancers, including those of the breast, prostate, colon, and ovaries.  Vitamin D also plays a role in preventing various autoimmune disorders, including type 1 diabetes, rheumatoid arthritis, and multiple sclerosis.  People with insulin resistance and metabolic syndrome are more likely to have low levels of vitamin D.

The Food and Nutrition Board has declared adequate intakes of vitamin D to be 200 IU/day for adults up to age 50, 400 IU for those 51-70, and 600 IU for those over 70 years old.  However, recent research indicates that our bodies use approximately 4000 IU of vitamin D every day.  To get this amount from milk alone would require the consumption of approximately 40 cups per day.

Here in sunny Colorado we are currently taking a supplement of 300 IU per day, in addition to eating fish about three times per week.  In the winter months (which are also pretty sunny) we switch our fish oil supplement to cod liver oil, which adds an additional 500 IU per day of vitamin D.  If you live in a climate with less sun, or purposefully avoid sun for other reasons, you may want to strongly consider increasing your supplementation level to 1200 IU per day.  This would be especially important in the winter months.  (A recent study estimated that 734,000 hip fractures would be avoided in the U.S. each year if that amount of vitamin D was supplemented each day by those over age 65).

Your doctor, who is likely woefully uninformed about nutrition, may caution you about the toxicity of vitamin D, and recommend lower amounts.  Because it is fat soluble, toxic amounts can accumulate in your body.  Fortunately, your body quits producing vitamin D when your levels are high enough, and supplementing with 1200 IU per day is perfectly safe, though at this time I would not recommend exceeding 2000 IU on a continuous daily basis without medical supervision.

Go Long,

Wiley