Find out which nutrients can cause problems and how to avoid getting too much of them.
Can You Get Too Many Vitamins?
A lot of people take vitamin supplements just to make sure that they are getting the recommended amount of nutrients. (See also my episode on “Are Fruits and Vegetables Getting Less Nutritious?”) But people taking supplements often end up getting significantly more than the recommended amount of some nutrients, and more is not always better.
Vitamin A: How Much is Too Much?
Vitamin A is a good example. Vitamin A helps you see in the dark, fight off infections, and make red blood cells. The recommended amount is 3000 IU for healthy adult men and a little less for adult women. But many vitamin supplements—especially high-potency formulations—can contain as much as 5,000 IU.
If you take a couple of different supplements, such as a multi-vitamin plus an immune-booster, you could easily go over the safe upper limit of 10,000 IU. Signs of vitamin A overload include headaches, bone and joint pain, and itchy, peeling skin. Eventually, it can lead to liver damage.
Vitamin A is not hard to get from foods. It’s found in eggs, milk, butter, and fortified breakfast cereals. Your body also makes vitamin A from beta-carotene, which is found in, yes, carrots, but all kinds of other fruits and vegetables, as well. Beta-carotene is only converted into vitamin A as needed, by the way, so supplements or foods that contain beta-carotene won’t contribute to vitamin A overload.
My advice is to check the label on any and all supplements that you take on a regular basis and make sure that the total amount of pre-formed Vitamin A, or retinol, doesn’t exceed 2,500 IU per day.
Folic Acid: How Much is Too Much?
Folic acid helps you metabolize protein and synthesize DNA, protects against cancer and heart disease, and prevents serious birth defects. Although it’s important to get enough folic acid, more is not necessarily better. The main problem with getting too much folic acid is that it can mask B12 deficiency—and it’s really important to diagnose and correct B12 deficiencies because they can lead to neurological damage.
Recently, there’s been some buzz about folic acid and colon cancer. Suffice it to say that folic acid doesn’t cause colon cancer—in fact, it protects against it. But if you already have colon cancer, high doses of folic acid can feed tumor growth, which is another good reason not to go overboard with the supplements.
Healthy adults need about 400mcg a day and women need extra during pregnancy. Leafy greens like spinach and kale are a good source of folate, as are lentils and other legumes—and there’s really no danger of getting too much folate from foods. The real concern is with supplements. Now, if you’re pregnant, your doctor has probably given you a pre-natal vitamin that contains plenty of folic acid. That’s because it’s so important to be sure that you’re getting enough folic acid when you’re pregnant.
My advice for everyone else is to eat lots of folate-rich foods but not to get more than 400 mcg of folic acid from supplements. If you have any history of colon cancer in your family, you’ll want to be particularly careful about supplements; check with your doctor. And, of course, everyone over 50 needs to be screened for colon cancer annually.