Which multivitamin? (page 1 of 2)

While many studies suggest multivitamin supplementation can reduce the risk of various chronic diseases, other studies indicate that supplementation may be toxic at higher levels. How much should you take and what should you look for in a quality multivitamin?

The "how much" is a difficult question to answer. For example, in the United States consumers are aware of the United States Recommended Daily Allowance (USRDA) and strive to achieve 100% of this value in their supplement. There are many flaws to this approach, however. For example, RDAs should not be confused with nutritional requirements. Requirements differ from individual to individual due to many factors from genetics and environment to intensity of training and stress levels. Most agree that it's not harmful to consume two to three times the recommended levels of most vitamins and minerals. Many people regularly do this through a combination of foods and supplements. Some vitamins, such as Vitamins A and D, are exceptions to this as they are known to be toxic at higher intakes.

While it's impossible to quantify all of the possible nutrients that may appear in a multivitamin, we can estimate the quality by using a few reference ingredients.
To come up with our comparison, we started with the USRDA for our sample nutrients. This is really the bare minimum needed for survival. For example, the USRDA for Vitamin C was established based on the lowest amount with a reasonable margin of error that would prevent scurvy. Obviously, Vitamin C has many more uses than the prevention of scurvy, but this is the key factor in determining the RDA guidelines! In addition to the RDA, however, another guideline has been established for most nutrients by the Food and Nutrition Board (FNB - a U.S. organization established in 1940 to study issues pertaining to the safety and adequacy of the food supply.) This is the "tolerable upper limit" which establishes the safe upper limit of intake. As you will see, there is a considerable gap between the recommended daily allowance and the tolerable upper limit. So where in this range should your intake fall?

Again, this is a matter of debate. Nutrition science is constantly changing, and we discover new information about vitamins, minerals, and other nutrients every day. We based our guidelines on a book by Lyle McDonald called, "The Comparative Guide to Nutritional Supplements." In this book, he surveyed several doctors known to specialize in nutrition and obtained their recommendations for daily vitamin supplementation. He then averaged these recommendations to create a weighted standard. The USRDA, suggested intake, and tolerable upper limits for some key vitamins and a sample mineral are listed below:



As you can see, there is quite a variance between the RDA, upper limit, and suggested amounts. These are by no means the total list of nutrients that should be found in a multivitamin, but a sample reference for comparing different products.

Before we start shopping for a multivitamin, the next thing to be aware of is the quality of ingredients. Laws in different countries differ with respect to how vitamins may be manufactured and distributed. In the United States, for example, supplement manufacturers are not required to adhere to a pharmaceutical level of testing. This means sometimes bottles are produced where the actual ingredients do not match the label claims. There are several consumer groups that regularly test and rate vitamins to help determine which adhere to the label claims.