What are multivitamins made of?

Although there are more than 100 healthful compounds in fruits and vegetables, your average multivitamin bottle usually contains only 12-25 nutrients. The number depends on the brand and if the formula also includes minerals like iron and zinc.

The ingredients may look like a pharmacist’s shelf because the specific technical names of vitamins are listed. For example, what we know as vitamin C may be listed as ascorbic acid. Vitamins are classes or groups of related compounds that do the same things in the body. There can be minor differences in their chemical structure and these differences can be important in, for example, absorption or how well a form is used in the body. This is another reason why a specific form is on the label.

Common Nutrients

The most common nutrients in multivitamins are:

  • Vitamins A, C, D, E, B6
  • Thiamin
  • Riboflavin
  • Niacin
  • Folic acid
  • Panothetic acid
  • Biotin
  • Vitamins B12, K  

Many multivitamins also contain minerals. Here is a list of the most common:

  • Iron
  • Phosphorus
  • Magnesium
  • Zinc
  • Potassium
  • Selenium
  • Copper
  • Manganese  
  • You may also find iodine, boron, nickel, silicon and vanadium in very small amounts. 

IU, mg, mcg???

We are all familiar with cups, teaspoons and tablespoons for measuring food in the kitchen. In a similar way, IU, mg and mcg are abbreviations for measuring the amount of a nutrient in your pill.

IU is International Unit. It is based on the biological activity of a substance. Not all nutrients use IUs to express their amounts (vitamins A, D and E are the most common). Some vitamins, like A, can be listed with an IU or mcg (micrograms).

Mg is a milligram, one-thousandth of a gram. One ounce is 28349.5 milligrams.

Mcg is a microgram. This is one-millionth of a gram. One ounce is 28349523.1 micrograms.

What does “bioavailability” mean?

You might have heard people talk about the bioavailability of multivitamins and wondered what it means. To be available means to be present or ready to use. We like to measure how much of something is available for us to use. For example, we have gauges to see how much gas is available in our car. But cars can use different amounts of gas in town vs. on the highway. Different forms of nutrients are the same way. Some are more available for us to use in our bodies than others. The “bio” refers to biological or having to do with living organisms.

What’s up with calcium?

Most multivitamins don’t have much calcium. Calcium is needed in much bigger amounts by our bodies than other nutrients, at least 1000 mg or 1 gram a day for most healthy adults. Adding this much calcium to one pill would make it too big to swallow. Also, our bodies can only process about 500 mg (0.5 g) calcium at a time from a supplement. Calcium can interfere with the absorption of other nutrients, making them less “bioavailable.” That’s why most multivitamins don’t have a lot of calcium. Try to get your needed calcium from food sources, in addition to taking a multivitamin.

Watch out for A

It is possible to get too much of a good thing. When it comes to multivitamins, it is possible to get too much vitamin A. This might increase your risk of having a baby with a birth defect. Some research indicates that too much vitamin A in supplements might not be good for your bones either. So don’t take more than 5,000 IU of vitamin A daily. At least 20 percent should come from beta carotene (indicated on the label). Fifty percent is even better!

The “orange” factor

Ok…you know what we mean. You took your vitamin at breakfast and then, a few hours later, you notice that orange color when using the restroom. Don’t worry. Although it may seem strange, it’s harmless. Manufacturers put some colors in the pills in order to standardize the shade. If they didn’t, each batch would look a little different so consumers might wonder if it is good or not. A little orange doesn’t mean anything is wrong.

Revised: May 30, 2011

This web site is designed for informational use only; it is not designed to give advice, diagnose, cure or treat any medical condition you may have. If you have any questions about your health, please contact your health care provider.