Vitamin D – The New Miracle Cure?

"If something sounds too good to be true," the saying goes, "then it probably is." That has certainly been the case for one supposed "natural remedy" after another. For example, Vitamin C does not really prevent cancer, Gingko Biloba does not prevent Alzheimer's disease, Glucosamine has no proven benefit over placebo in arthritis, and Fish oil (despite its ability to lower triglyceride level) has never been shown to prevent heart attacks. Some vitamins (vitamin E) may even increase your chance of cancer. And the list goes on and on. That's the difference between hype and hard science. And it is the job of the National Institute of Health, and other scientific associations, to differentiate fact from fiction on these matters.

The latest "big deal" on the vitamin scene are the many reported benefits of vitamin D supplementation. It has certainly been known for many years that severe vitamin D deficiency can cause "weak bones" – rickets in children and osteomalacia in adults. There are many other reported problems associated with vitamin D deficiency: an increase in over-all death rate, risk of falls, fractures, muscle weakness, pain and arthritis in the elderly, psoriasis, infections, poor oral health, cardiovascular disease, diabetes, multiple sclerosis, and cancers. Some people also believe that vitamin D deficiency can aggravate depression and dementia. The findings regarding these non-skeletal issues are based mostly on observational studies, however, and some people question the validity of these results.

Not everyone agrees that using vitamin D in large doses is good for your health. "The Washington Post" and the "Journal of the American Medical Association" recently ran editorials saying the advantages of large doses of vitamin D are greatly exaggerated, and may be potentially dangerous. They quoted Drs Manson and Bassuk, of the Division of Preventive Medicine at Brigham and Women's Hospital in Boston, who said "clinical enthusiasm for supplemental vitamin D has outpaced available evidence on its effectiveness."

Vitamin D compounds are derived from dietary ergocalciferol (Vit D2, from plants) or cholecalciferol (vit D3, from animals) or by conversion of pre-Vit D to VitD3 in the skin on exposure to sunlight or other uV light. The kidneys then convert this to the active form of vitamin D, and in the presence of chronic kidney disease vitamin D deficiency is almost always a problem.

The Institute of Medicine (IOM) says the recommended daily allowance (RDA) for vitamin D for individuals between the ages of 1 and 70 years is 600 IU per day and is 800 IU per day for people over the age of 70. This amount is felt to be the amount needed to avoid deficiency in 97% of Americans from a bone health perspective (which requires a vitamin D blood level over 20 ng/ml). There is some controversy regarding the ideal vitamin D levels, however. The American Association of Clinical Endocrinologists (AACE) and the National Osteoporosis Foundation (NAF) recommend somewhat higher target vitamin levels between 30 and 60 ng/mL, and some experts are now recommending levels of 50 to 100. Vitamin D levels that are too low (for a variety of reasons) are extremely common, and are an easy way to potentially improve several health problems. While low vitamin D levels are common, the opposite issue (high vitamin D levels) are uncommon. Excess vitamin D could theoretically cause kidney stones, soft tissue calcification, and cardiovascular disease. Blood levels under 10 are regarded severe deficiency, 10-19 mild to moderate deficiency, 20-50 are regarded by some as optimal, between 50 and 100 are upper normal, and levels over 100 are potentially toxic.

The amount of vitamin D that a doctor recommends should be based on the clinical problem and your vitamin D blood level. Most of the time the standard 800 IU per day recommendation is given to older adults, with higher doses recommended if there is a specific problem or documented deficiency. If there is a severe deficiency, don't be surprised if the doctor recommends a three month loading dose up to 50,000 units twice weekly for 3 weeks, followed by later dose (depending on vitamin D blood levels) in the 2000 to 5000 unit per day range.

In the recent JAMA report they acknowledged that vitamin D intake under 10,000 IU per day has not been associated with increased side effects. They nonetheless said the upper limit for vitamin D replacement should be 4,000 IU per day. This level reflects concern about potential side effects in people who have chronically elevated vitamin D levels.

Since treatment guidelines greatly depend on what your vitamin D blood level is, you would think that this test would be done routinely – but it isn't. Medicare and most insurance companies do not pay for the test unless you have a "deficiency." My frustration is this: How can a doctor tell if you have a deficiency unless you test for it? Be that as it may, most authorities do not currently recommend routine testing for this nutrient. [P.S. I test it anyway.]

So is there a controversy? I believe the weight of evidence is definitely in favor of taking larger amounts of vitamin than is currently being recommended. But there are several very large studies that are currently underway to clarify this issue. Those final results won't be available until 2018. In the meantime you should follow the RDA guidelines: 600 IU per day for younger people and 800 IU per day if you are over the age of 70. A daily intake of 3-4 servings each day of fortified foods such as milk, yogurt, soy beverages, orange juice, or cereal will help. You should also eat fatty fish twice a week. Exposure to sunlight is also useful. If you can't reach those goals, then you should just take a supplement. And for many people that means taking a "prescribed amount" above the RDA, based on your blood level and your health care provider's recommendations.