How much of a vitamin or mineral supplement should you take? Are your daily multivitamins enough, or should you worry about vitamin deficiency? Could you already be taking too much? It can be hard to tell -- especially with so many nutritional terms, abbreviations, and numbers out there. Here’s what you need to know.
What the Numbers Mean
To help people better understand the minimum and maximum doses for supplements, the Institute of Medicine has established some guidelines.
The RDA (Recommended Dietary Allowance) and the AI (Adequate Intake) are the amounts of a vitamin or mineral you need to stay healthy and avoid nutritional deficiencies. They are tailored to women, men, and specific age groups.
The UL (Tolerable Upper Intake Level) is the maximum amount of daily vitamins and minerals that you can safely take without risking an overdose or serious side effects. For certain nutrients, the higher you go above the UL, the greater the chance of having problems.
Separate from the RDA and the UL, the FDA uses a different measurement of nutritional intake.
The DV (Daily Value) is the only measurement you’ll find on food and supplement labels. That’s because space is limited, and there’s a need for one single reference number. That number is the amount of a vitamin or nutrient that a person should get for optimum health from a 2,000 calories-a-day diet. The DV is sometimes the same as the RDA and sometimes not.
Although the details may be different, just remember that the RDA and DV are both designed to help us get the nutrients we need to prevent disease and avoid problems caused by malnutrition.
But many people take higher doses of specific supplements in the hopes of gaining other health benefits, like added protection against or treatment of disease.
Is taking doses higher than the RDA or DV safe? For many vitamins and minerals, yes. In some cases, doctors even recommend it. Take vitamin D, for instance. The RDA of vitamin D for a 60-year-old is 600 international units (IU). But for bone health, the National Osteoporosis Foundation recommends 800-1,000 IU for that age group.
How Much Is Too Much?
Because high doses of some supplements can have risks, how do you know when it’s OK to take more than the RDA or DV and when it isn’t?
One way is to look for the UL (tolerable upper intake level) of a nutrient. The Institute of Medicine sets the UL after reviewing studies of that nutrient.
With many vitamins and minerals, you can safely take a dose much higher than the RDA or DV without coming close to the UL. For instance, the average person can take more than 50 times the RDA of vitamin B6 without reaching the upper limit. However, some people develop neuropathy symptoms with these higher levels of B6. So you should always be cautious. Here are some things to keep in mind.