Around 400 BC, the celebrated Greek physician Hippocrates offered some advice about diet and health. He declared, "Let food be thy medicine and medicine be thy food." The growing number of Americans who turn to supplements to make up for a poor diet ought to pay attention to those words of wisdom.

Each day, millions of adults in the United States take high doses of vitamins and minerals with hopes of feeling better, getting sick less often, and living longer. For years, physicians told consumers that, at worst, they were just wasting their money. But now, the word is to be careful—because high doses of certain vitamins and minerals may actually increase the risk of disease.

Dietary Supplements 101

As you probably already know, we need vitamins—by far the most popular choice of supplement—to live (that is, they are ‘vital’ to our survival). But the body cannot make them on its own, so we must get vitamins from our diet. Similarly, we need minerals like iron and calcium to function, and must rely on outside sources to meet our requirements. (Other supplements, such as herbs, are a whole other story.)

Although supplements are a good idea in certain cases (such as for pregnant women, the elderly, and vegetarians), experts agree the best way for you to get the nutrients you need is by eating a well-balanced, healthful diet.

Too Much of a Good Thing

One hundred years ago, scientists began to identify the nutrients in foods that we need to avoid getting deficiency diseases like beriberi and rickets. With attention being given to the benefits of vitamins and minerals, it’s no wonder that many of us choose to take supplements. Problems arise, however, when people take individual vitamins or minerals in excessive amounts, rather than eat a nutritious diet.

Use the following chart as a guide:

The Bottom Line

While it may be promising, the evidence so far linking supplements with a reduced risk of chronic disease is much less convincing than most people realize. What is clear is just how easy it is to overdose on certain supplements. Therefore, your best bet is to get most of the nutrients you need from the foods you eat. For a healthful diet, be sure to include lots of fruits and vegetables, whole grains (like whole wheat bread and brown rice), unsaturated fats (found in nuts, avocados, and oils), and low-fat dairy products.

If you do take supplements, keep the following in mind:

• A multivitamin cannot provide adequate calcium, and for this reason many people could benefit from a separate calcium supplement.
• Be wary of unfounded medical claims for dietary supplements.
• Talk to your doctor about all supplements you take, including concentrations and amounts.
• Keep supplements out of the reach of children.