Taking Too Much Vitamin D?

Recent studies show the risks of high doses of vitamin D 

The health benefits of taking proper doses of Vitamin D supplements are well established, such as stronger bones and teeth; lowered risk of developing diabetes, heart disease, and some cancers; and improved resistance to multiple sclerosis. Studies also show that Vitamin D may have protective benefits against cognitive decline in older adults.

Recent research, however, such as a study published last year in The Journal of the American Medical Association (JAMA) Internal Medicine, suggests that high monthly doses of Vitamin D do not improve lower extremity functioning and muscle strength in adults over age 70. Furthermore, high doses of Vitamin D also may lead to an increased risk of falling in seniors.

Vitamin D is best known as the vitamin we get from sun exposure. Some foods are sources of Vitamin D (although often in relatively small amounts):

  • cod liver oil
  • tuna
  • salmon
  • sardines
  • milk or yogurt fortified with vitamin D
  • beef or calf liver
  • egg yolks
  • cheese

But, as people age, their skin converts less sunlight into Vitamin D. For example, the body of a 70-year-old will make about 25 percent less Vitamin D than a 20-year-old will make given equal exposure to sunlight, says the anti-aging organization Life Extension. Older adults also have a lowered ability to absorb Vitamin D from food sources.

The Food and Nutrition Board (FNB) at the Institute of Medicine of The National Academies establishes the Recommended Dietary Allowances (RDA) for vitamin D and other nutrients. The RDA for vitamin D rises for people over age 70 for several reasons: their decreased ability to efficiently synthesize vitamin D, they are likely to spend more time indoors, and they may not be taking adequate doses of vitamin D supplements.

At age 70 the recommended minimum daily International Units (IU) of Vitamin D is 800 IU per day, says the National Institutes of Health’s Office of Dietary Supplements. These requirements can vary from person to person, depending on a variety of factors.

Will taking higher doses of vitamin D supplements increase the vitamin’s health benefits? Not necessarily.

The Vitamin D Council warns that, although most people take Vitamin D supplements with no problems, it is possible to take too much, which can bring on a condition called Vitamin D toxicity. These harmful levels of Vitamin D can happen if you take 4,000 IU (or more) for three months or longer, or if you take a very large one-time dose (more than 300,000 IU within 24 hours). For some people, harmful levels might occur at even lower doses.

Are you getting enough Vitamin D? Too little? Too much? The only way to know is through a 25(OH)D blood test. Ask your doctor for this specific test. The results will show whether you’re getting healthy amounts of Vitamin D. You can then talk with your doctor about taking proper levels of Vitamin D supplements, how much sun exposure is beneficial, and dietary changes you should consider.