Monday, September 21, 2009

Vitamin D - not just for bones - Part I

As September comes to a close, many folks are still playing, relaxing, working or just plain sweating in the summer sun. But it won’t be long before fall and winter arrive, and the reversed slant of the Earth’s axis inhibits our ability to synthesize vitamin D from ultraviolet rays.

Why do we need vitamin D?

Vitamin D is a fat-soluble vitamin that works with calcium to maintain a healthy skeletal system. When the body has sufficient D stores, absorption of calcium from food can range from 30 to 80%. When D levels are insufficient, that number lowers to a maximum of 15%.

The prevalent problem of rickets (called osteomalacia in adults) around the turn of the 20th century was mostly eradicated by the fortification of cow’s milk with vitamin D.

But bone health isn’t the only area where D is important. Studies have shown that adequate levels of vitamin D may ward off colon, prostate and breast cancers. Promising studies also show evidence that D may also be used to prevent and treat conditions like Type I and II diabetes, hypertension and multiple sclerosis. Deficiency in this nutrient is also now being linked to depression.

Who’s at risk for vitamin D deficiency?

The American Family Physician states that vitamin D deficiency is more widespread than you might think. About 50% of homebound adults and 80% of elderly African American women are D deficient. Levels drop to 20% for other demographics.

The elderly have a profoundly decreased capacity to absorb D than their younger counterparts – up to 75% less.

Darker skinned people require more sun exposure than lighter skinned people.

Where you live will play a large role in the likelihood of a deficiency. California residents need not worry – they are able to synthesize D the entire year. However, those who live on the same latitude as Massachusetts will produce considerably less – or no – vitamin D for the months of December and January. If you move up higher to central Canada, your months without D will be from November through February. Notoriously fair Scandinavians have limited D production from October all the way through March.

It should also be noted that sunscreen will inhibit vitamin D absorption. Responsible sun exposure is encouraged. 15 to 30 minutes of sunlight for the average person will be beneficial. Darker skinned people need more, and very fair people should certainly avoid overexposure and sunburn.

A rather interesting calculator for personalized D production based on personal characteristics and location can be found here.

In Part II, we’ll explore the ways to ensure a healthy level of vitamin D in our bodies.

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