Finding Good Vitamins

Few consumer items are as mind-boggling as nutritional supplements. Store shelves featuring endless bottles of vitamins, minerals, herbs and essential oils can leave the potential buyer thoroughly confused. How to choose?

Fortunately, Dr. Weil has spent a lifetime researching nutrition and health, including which forms of nutrients are the most bioactive; that is, have the greatest potential to provide benefits. In every case, the form he recommends is the form he specified for the products sold online via the Vitamin Advisor. (Dr. Weil donates all of his after-tax profits from royalties from sales of Vitamin Advisor products and Weil Nutritional Supplements directly to the Weil Foundation, an organization dedicated to sustaining the vision of integrative medicine.)

Here are examples of his chief insights among the major supplement classes:

  • Vitamin A: Some forms of supplemental vitamin A, when taken in even moderate daily doses, can be toxic. Dr. Weil specifies the use of mixed carotenoids – these are substances that the body converts to vitamin A, avoiding toxicity potential and maximizing effectiveness.
  • Vitamin D: Inexpensive vitamins tend to contain vitamin D2 (ergocalciferol), the kind synthesized by plants. But when humans eat plant-derived D2, it needs to be converted by the body to D3 (choleciferol), the form most readily used by the human body and which skin makes when exposed to ultraviolet light. Although vitamin D2 will contribute to adequate daily intakes, Dr. Weil specifies D3 in his supplements, as this form has been shown to have greater biological activity in human tissue.
  • Vitamin E: In nature, this vitamin is found as a combination of eight different active compounds – four tocopherols, and four tocotrienols. Many manufacturers use inexpensive, synthetic versions of one or only a few of those eight forms. In his supplements, Dr. Weil specifies a complete, naturally derived tocopherol/tocotrienol complex that more closely mirrors the natural vitamin E found in foods.
  • Calcium: Manufacturers make calcium supplements in many forms, including calcium carbonate (the main constituent of chalk, and the most common supplement type), calcium lactate and calcium aspartate. Dr. Weil specifies calcium citrate because it is more easily absorbed, especially by older people who may have less stomach acid. Although more expensive, calcium citrate is more than twice as bioavailable as calcium carbonate.
  • Fish Oils: Oils derived from the fat of cold-water fish are an excellent source of essential omega-3 fatty acids. Unless carefully sourced, however, these otherwise natural compounds can be contaminated with toxic heavy metals. Dr. Weil suggests seeking out products derived from fresh catches and waterways with minimal pollution, and recommends those that have received the highest rating for purity – five out of five stars – from the International Fish Oil Standards program.

“Vitamins and supplements are much like anything else – you generally get what you pay for,” says Dr. Weil. “But even very expensive vitamins sometimes miss the mark.” He says that one reason he co-directs the Annual Conference on Nutrition and Health; State of the Science & Clinical Applications, which unites the world’s leading nutrition researchers, is that it allows him to get the latest news on the best forms of supplements directly from the researchers who investigate them.


Updated by: Andrew Weil, M.D., and Brian Becker, M.D., on February 24th, 2014.

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