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Why Don’t Vitamin D Supplements Work as Expected?

Vitamin D supplements are extremely popular. Millions swallow little golden pills daily. But why are clinical trials producing such disappointing results?
Why Don’t Vitamin D Supplements Work as Expected?

If you are taking big doses of vitamin D in the hopes of staving off all sorts of health problems, you may be disappointed. Most research has not demonstrated that taking high doses of vitamin D supplements will improve health. Why Not?

The Fascinating Vitamin D story:

Vitamin D leads a double life. In addition to being a crucial vitamin, it is also a hormone that affects every cell in the body.

For years, health professionals thought that this nutrient was responsible primarily for building strong bones. When there was a deficiency in vitamin D, children developed rickets. In this condition, bones are fragile and can become deformed, resulting in bowed legs and thickened wrists.

Over the last several decades, scientists have discovered that there are vitamin D receptors throughout the body. People who are deficient in vitamin D are more susceptible to a wide range of disorders, from arthritis and heart disease to diabetes and cancer. Researchers report that when circulating levels of vitamin D are low, people are more susceptible to respiratory infections and more likely to die prematurely (Circulation Journal, April 20, 2017).

Health Problems Linked to Low Vitamin D Levels:

  • Asthma in children
  • Autoimmune disorders such as multiple sclerosis
  • Cancer
  • Cardiovascular disease (heart attacks, etc)
  • Cognitive impairment (Alzheimer’s disease, dementia)
  • Diabetes
  • Erectile dysfunction
  • Fractures, osteopenia, osteoporosis
  • High blood pressure
  • Infections (pneumonia, colds, etc)
  • Mental illness (depression, schizophrenia)
  • Psoriatic arthritis

Vitamin D Supplements: A Puzzling Paradox

What has scientists confused is why vitamin D supplements haven’t prevented some, or all, of these serious health conditions. Why aren’t vitamin D supplements working as expected?


a bright sun

cc0 from https://pixabay.com/en/sun-bright-yellow-sunset-sky-1953052/

Vitamin D and the Sun:

For thousands of years, humans have gotten their vitamin D through sun exposure. When ultraviolet rays hit the skin a precursor of the hormone (cholecalciferol) is formed and absorbed. The kidney converts it into the active form of vitamin D.

There is tremendous variability in the amount of vitamin D the skin will make. It depends in part on the intensity of the sun, the time of day and skin type. Your body can make between 10,000 and 25,000 international units of vitamin D in less time than it takes to develop a sunburn. Sunscreen blocks the natural formation of vitamin D from the sun.

The body carefully regulates its production of vitamin D. You can’t overdose on vitamin D through sun exposure (Institute of Medicine, 2011).

Researchers have noticed the problems associated with low levels of vitamin D. They have conducted many experiments to see how well supplements of vitamin D can treat the disorders connected to vitamin D deficiency.

Vitamin D Supplements and Disappointing Results:

A study in the European Heart Journal, May 12, 2017 reported that vitamin D supplements “did not reduce mortality in patients with advanced HF [heart failure].”

Research published in BMJ Open (online, Oct. 23, 2013) found that vitamin D supplements did not help patients with a severe autoimmune condition called sarcoidosis.

High use of vitamin D supplements did not lower the risk of early menopause Nurses’ Health Study II). This was published in the American Journal of Clinical Nutrition (May 10, 2017). When these women got their vitamin D from food, however, there was a modest reduction in early symptoms of menopause.

High-dose vitamin D supplements were not beneficial for overweight, vitamin D deficient patients who were diagnosed with type 2 diabetes (American Journal of Clinical Nutrition, May 10, 2017). The authors concluded that it would be unlikely that vitamin D supplements

“would be an effective strategy for reducing diabetes risk even in vitamin D-deficient populations.”

Other studies have also yielded disappointing results. A recent example is a study published in The Lancet Diabetes & Endocrinology (April 28, 2017).

The investigators recruited more than 5,000 volunteers in Auckland, New Zealand, for a placebo-controlled trial. Half of them were given cholecalciferol (vitamin D3) at a dose of 100,000 IU once a month. The other half got a placebo once a month. All of the participants kept track of any falls or fractures they experienced during the three-plus years the study continued.

The investigators didn’t find any differences between the two groups, whether in falls, fractures or death. They concluded that this form of supplementation was ineffective. To give them credit, however, they noted: “Further research is needed to ascertain the effects of daily vitamin D dosing, with or without calcium.”

Daily Dosing: How Important?

We too would like to see more studies with daily vitamin D dosing. We suspect that one reason so many studies that use enormous doses once a month or even once every few months haven’t shown benefit is that the scientists are taking the wrong view of this vitamin.

They are treating it as if it were a drug. But a hormone that is intimately involved in so many processes in the body might not behave like a drug at all. The body may not respond normally to such a high dose. In nature, the body gets a smaller amount every day. And the body regulates that natural vitamin D quite effectively. It may also be that the vitamin D (and its derivatives) made by the body from sun exposure work differently in the body than the oral vitamin D supplements so many people take.

To learn more about this crucial hormone, you may wish to read our Guide to Vitamin D Deficiency. It can be downloaded from our website.

Anyone who would like a printed copy, please send $3 in check or money order with a long (no. 10) stamped (70 cents), self-addressed envelope to:

  • Graedons’ People’s Pharmacy, No. D-23
  • P. O. Box 52027
  • Durham, NC 27717-2027.

Share your own experience with vitamin D supplements in the comment section below. If you found this information of interest, please vote at the top of the article.

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About the Author
Joe Graedon is a pharmacologist who has dedicated his career to making drug information understandable to consumers. His best-selling book, The People’s Pharmacy, was published in 1976 and led to a syndicated newspaper column, syndicated public radio show and web site. In 2006, Long Island University awarded him an honorary doctorate as “one of the country's leading drug experts for the consumer.” .
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