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Dark days of winter short on vitamin D

November 29th, 2005

Michael Woods / Toledo Blade

These are the D days — vitamin D days.

It’s the time of year when people get less exposure to sunlight, which the body needs to make vitamin D. Blame winter’s short days and the cold, stormy weather that keeps people indoors.

On the one hand, research shows that vitamin D is important for strong bones and protecting people against cancer and other diseases. On the other hand, study after study shows that most Americans — especially older people — don’t get enough of this key vitamin.

Vitamin D is an odd nutrient. People get very little of it from food. Even the best of diets — with dairy products fortified with the vitamin — supplies only about 10 percent of the vitamin D that the body uses each day.

Sunlight provides the other 90 percent. Sunlight orchestrates a chemical reaction in the skin that makes vitamin D and supplies it to the rest of the body. Natural production of vitamin D dwindles on short, dim days.

The body needs vitamin D to absorb calcium. Without it, calcium will pass out of the body without doing any good.

Some studies hint that ample vitamin D is more important in preventing the bone-weakening disorder osteoporosis than taking calcium supplements.

The recommended daily allowance for the vitamin is 200 International Units up to age 50, 400 IUs for ages 50-70, and 600 IUs for people older than 70.

One of the richest and most affordable sources, fortified milk, contains barely 100 IUs per cup. Other good sources are salmon (360 IUs per serving), mackerel (345), sardines (250) and tuna (200). For those with cast-iron taste buds, a tablespoon of cod liver oil has 1,360 IUs.

Multivitamin tablets for older adults, calcium-with-vitamin D tablets, and plain vitamin D tablets usually contain 400 IUs.

But don’t go overboard with vitamin D supplements. Unlike some other vitamins, too much D can be toxic. The safe upper limit is about 2,000 IUs daily, according to the Institute of Medicine.

Source: detnews.com

Entry Filed under: Nutrition News

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