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Vitamin D and Your Health
How Much is Do You Need?

Throughout the year 2009, dozens of articles were published in national health and fitness magazines trumpeting the benefits of Vitamin D. The articles often suggested people take vitamin D in much higher doses than recommended by the United States Department of Agriculture (USDA). So many articles have come out, I decided to see what all the hype was about.

What is vitamin D?

It's a fat-soluble vitamin that's found in very few foods, routinely added as a supplement to others and is available as a dietary supplement. Most people can produce vitamin D when ultraviolet rays from sunlight strike their skin and trigger vitamin D synthesis. Because our bodies can make it by simply being in the sun, it's also called the "sunshine vitamin."

Vitamin D and disease.

If you were a child during the 1920s, the disease known as rickets was widespread. Our bodies require vitamin D to promote calcium absorption in the gut. People that don't get enough vitamin D, can't absorb the calcium their bones need and the bones become thin, brittle or misshapen. That's rickets.

To combat rickets, vitamin D supplements were added to milk in the 1930s and 1940s. Milk consumption rose from 34 gallons of fluid milk per person in 1909 to a peak of 45 gallons per person in 1945. Over that same time, rickets virtually disappeared as a public health concern in America. The problem is what's happened since.

Milk consumption has steady declined since it's peak in 1945. As carbonated beverages increased in popularity and fears of fat and cholesterol from milk began to emerge, milk consumption steadily declined to half that 1945 peak. In 2001, Americans were drinking just under 23 gallons of milk per year.

Over that same time period, concerns about sunburns and skin cancer have prompted more people to avoid the sun and wear sun-blocking clothing. But what's good for preventing skin cancer is bad for vitamin D production.

Even our weight is working against us. In study after study, being obese is recognized as a risk factor for vitamin D deficiency. The reason why isn't understood yet, but it's believed the fat hinders vitamin D absorption from the sun. With more than half of Americans now overweight or obese, vitamin D deficiency is becoming more widely diagnosed.

Noting those trends, supplement companies have started promoting vitamin D using several misleading arguments. Here are the top four myths they're selling you.

Myth 1: Everybody would benefit from taking a vitamin D supplement.

With the decline in so many sources of vitamin D that we mentioned earlier, it would seem logical to assume supplementation would be a good idea for most people. In fact, the Food and Drug Administration (FDA) encourages food producers to fortify dozens of products with vitamin D. The additional supplementation in foods can often make up the difference for what people miss in sunlight exposure. Vitamin D is still added to milk, cheese and butter. But today it's also added to breakfast cereals, grain products, pasta products and even soy milk.

Myth 2: Just sitting in the sun a few minutes every day will give you all the vitamin D you need.

In fact, our bodies ability to produce vitamin D is influenced by several factors. Lighter skin is better at absorbing ultraviolet rays and making vitamin D. Those ultraviolet rays are also stronger along the equator, during summer when the sun is closer, on smog-free and clear sky days. Smoking, certain medications and people with a body mass index over 30 can all reduce our ability to produce vitamin D. If you're dark skinned, it's winter, you live in a northern latitude or in a smoggy city, depending on the sun may not be practical.

Myth 3: Vitamin D reverses osteoporosis and can reduce your risk of cancer.

If only it was true. Current large-scale analysis now show that vitamin D supplementation can actually exacerbate the disease process of osteoporosis. In a meta-analysis released by The Lancet in 2013, researchers found no benefit from vitamin D supplementation for improving bone density. The study authors concluded by saying, "Continuing widespread use of vitamin D for osteoporosis prevention in community-dwelling adults without specific risk factors for vitamin D deficiency seems to be inappropriate."

And those claims vitamin D can reduce cancer? The National Cancer Institute analyzed data for 16,818 subjects over a 12 year period and found no association between the subjects baseline vitamin D status and overall cancer risk in men or women.

Myth 4: Vitamin D supplements are completely safe.

Most people will experience vitamin D toxicity if they take 40,000 IU per day or more. Damage to the kidneys, heart, changes in cardiac rythms or lithiasis are common concerns, as is hypercalcemia.

As of November 30, 2010 the current upper safe limit is considered 2,000 to 4,000 IU daily. Adequate intake is currently defined as 200 IU daily for people up to age 50, 400 IU daily for people age 51-70 and 600 IU daily for anyone over 70.

The American Academy of Pediatrics is currently arguing that these amounts are insufficient and they recommend a minimum of 400 IU daily, even for infants.

Don't rush to start taking Vitamin D supplements just because it sounds like it's the perfect pill for you. Visit your doctor and have a blood test to determine if it's something you really need, not something the supplement companies simply want you to buy.

For more details on Vitamin D, we recommend these two videos by NutritionFacts.org.

Test Caution:

Check your laboratory results. Some labs find people deficient if their levels are 30 ng of vitamin D per milliliter of blood or less, and that level is too high. As of December 2010, the threshold is if you're around 20 nanograms (ng) or lower of vitamin D per milliliter of blood, you're probably deficient.

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1/17/2010
Updated 12/2/2010
Updated 12/3/2010
Updated 8/24/2011
Updated 11/9/2013
Updated 6/30/2016
Updated 7/9/2016