The Vitamin D Toxicity Myth

Naturally Savvy
Naturally Savvy

The Myth

One of the universal truths (or myths) we were all taught in medical school 30 or more years ago was that fat-soluble vitamins like vitamin D were toxic at certain levels. It was said that daily vitamin D doses of over 2,000 IU would elevate blood levels of calcium, damage the kidneys irreversibly, and lead to generalized atherosclerosis (hardening of the arteries).

To this day, I still hear conventional medical doctors regurgitating these same fears to their patients. Some companies, such as AOR (Advanced Orthomolecular Research), have been forced to stop selling supplements with 5,000 IU per capsule. Biotics Research used to have a supplement containing 2,000 IU per drop, which was similarly terminated in 2008.

Doesn’t it seem odd to you that whenever research indicates a benefit from a certain food supplement, then that same food supplement suddenly experiences a great deal of opposition from the drug czars? Millions of people in this country and in most of North America are vitamin D deficient. In my opinion, restricting access to supplemental vitamin D is a big mistake.

Don’t Be Afraid

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According to the world research authorities on vitamin D, the Vitamin D Council, fears of high dose vitamin D are irrational.

From the Vitamin D Council website:

“The single most important fact anyone needs to know about vitamin D is how much nature supplies if we behave naturally, e.g., go into the sun. Humans make at least 10,000 units of vitamin D within 30 minutes of full body exposure to the sun—what is called a minimal erythemal dose. Vitamin D production in the skin occurs within minutes and is already maximized before your skin turns pink.”

The Liver Truth

Does vitamin D supplementation cause liver toxicity? Does it cause fatty liver? After all, fish and many other animals store vitamin D in the liver.

The truth is that vitamin D deficiency can lead to liver failure. Supplementing vitamin D up to normal levels reverses liver disease.

In people with non-alcoholic fatty liver disease (NAFLD), a growing problem in North America thought to be caused by insulin resistance, the levels of vitamin D are usually quite low. The liver dysfunction can be brought back to normal with adequate vitamin D supplementation. A 2007 study concludes that vitamin D3 may play a role in both the development and progression of NAFLD.

Vitamin D Can Help Statin Damage

What if you take drugs that affect the liver like the statins that are used for lowering cholesterol? Statins like Lipitor, Pravachol, Mevacor, Zocor, and Crestor all can potentially cause liver toxicity.

Statins also deplete coenzyme Q10 levels. These drugs all work by inhibiting enzymes (HMG CoEnzyme A reductase) in the liver that manufacture cholesterol. This class of drugs gradually reduces Coenzyme Q10 by at least 40% over a period of a year creating such unwanted symptoms such as:

  • fatigue
  • weak and tired muscles
  • lethargy
  • a general sense of low energy

A deficiency of coenzyme Q10 can result in high blood pressure. Thus, statins can theoretically increase your risk of having a heart attack or stroke.

Coenzyme Q10 is the most important nutrient for ideal heart function. It is used by the energy producing cell organelles known as the mitochondria and is vitally important for a normal cardiac output. Studies indicate that supplementing with Coenzyme Q10 improves every measurement of cardiac function.

Three months of Coenzyme Q10 supplementation can lower blood pressure in at least half the people who take it who have elevated blood pressure. It has also been shown to be important in cancer treatment, especially in breast cancer, Parkinson’s disease and periodontal disease.

Interestingly enough, one study done in 2009 indicates that 92% of people who developed muscle damage from statins (myositis-myalgia) were able to reverse this side effect with vitamin D supplementation. In other words, taking a supplement of vitamin D may help correct liver damage caused by statins. Perhaps other drug side effects can be helped by vitamin D but that remains to be seen.

The take-away message here is that, if you are on a statin, take a Coenzyme Q10 supplement, but also get your vitamin D blood levels checked.

Vitamin D deficiency leads to as much as a 60% increase in cancer rates. Some oncologists, however, have been telling all my cancer patients that they should take no supplemental vitamins when receiving radiation or chemotherapy. The reasons for this seem to me to have no basis in scientific fact.

How Much Vitamin D Should You Take?

In June 2007, in a flurry of generosity, even the highly conservative Canadian Cancer Society recommended that we all supplement with 1,000 IU daily of vitamin D. Unfortunately, a daily dose of 1,000 IU will do nothing to correct a deficiency. According to Dr. Reinhold Vieth PhD, researcher at the University of Toronto, blood levels don’t even measurably rise until 4,000 IU (100 mcg) is consumed. Real toxicity (hypercalcemia and rampant atherosclerosis) begins at 40,000 IU (1000 mcg or 1 mg) only after many weeks of use.

My advice—and it’s quite conservative—is for all North Americans living in northern latitudes to supplement with a bare minimum of 4,000 IU of vitamin D3 daily during the winter months. This is especially true for pregnant women who have a family history of MS or cancer—just to name a couple of diseases that can be prevented by vitamin D supplements.

Most individuals will some benefit with vitamin D supplements within three or four months. But since there is a great genetic variation in terms of vitamin D metabolism from individual to individual, the changes may be evident either earlier or much later. The best way to monitor the safety and effectiveness of supplements as well as how much you may need at any given time is with periodic blood tests.

In the summer, provided you get adequate sunshine (at least half an hour a day), you may not need supplements and no monitoring is really necessary because the body monitors and adjust blood levels of vitamin D automatically.

For example, if you are out in the sun for over five hours, you could theoretically be making 100,000 units of vitamin D under your exposed skin. Despite this, the blood levels will be adjusted such that the vitamin D levels remain stable. If you then stay out of the sun for many days, the skin reserves of vitamin D will slowly be moved into your bloodstream to normalize levels there. This sort of thing will not happen with oral supplements. If you happen to supplement at doses much higher than 4,000 IU daily, the potential for toxicity is there.

So, as a general rule, if you supplement at very high doses for any length of time, get regular blood testing for 25-hydroxy-vitamin D done at least every three months.

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Dr. Zoltan P. Rona is a graduate of McGill University Medical School (1977) and has a Master’s Degree in Biochemistry and Clinical Nutrition from the University of Bridgeport in Connecticut (1984). He is past president of The Canadian Holistic Medical Association (1987-88) and is the author of three Canadian bestsellers: The Joy of Health (1991), Return to the Joy of Health (1995) and Childhood Illness and The Allergy Connection (1997). He is co-author with Jeanne Marie Martin of The Complete Candida Yeast Guidebook (1996) and is the medical editor of the Benjamin Franklin Award winning Encyclopedia of Natural Healing (1998). He has had a private medical practice in Toronto for the past 35 years, has appeared on radio and TV as well as lectured extensively in Canada and the U.S. Dr. Rona currently writes regular articles for Reader’s Digest, Alive, Vitality magazine and for several web sites. His latest book “Vitamin D, the Sunshine Vitamin” was published in 2010. In 2011, Dr. Rona was named Chief Medical Advisor for NAKA Herbs and Vitamins and has developed a line of nutritional supplements (TriStar Naturals) which are sold in health food stores across Canada. He can be found at