Can You Get Too Many Vitamins?
Find out which nutrients can cause problems and how to avoid getting too much of them.
Can You Get Too Many Vitamins?
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.
Zinc: How Much is Too Much?
Zinc is a critically important mineral, needed for thousands of cellular transactions in the body. Healthy adults need around 10 mg of zinc a day to meet their requirements and it turns out that that’s about what people get from their diet, on average. But zinc is also a popular ingredient in dietary supplements. In addition to your multivitamins, you’ll often find zinc in immune boosting formulas, cold remedies, and men’s health and prostate health formulas too. If you’re taking one or more of these on a daily basis, you could easily go over the recommended upper limit of 40mg per day.
One problem with taking too much zinc is that it interferes with your ability to absorb copper, another important nutrient. Copper deficiency can make you anemic as well as more susceptible to infection, which is, obviously, Not Good.
It’s also possible to exceed the upper limit by eating oysters, which are very high in zinc. But, unless you eat oysters every day, you don’t need to worry about that. It takes several weeks of daily zinc overload to cause copper deficiency.
My advice—which of course is not intended to replace medical advice from your own doctor—is to add up the zinc in any supplements you take and make sure it doesn’t add up to more than 40 mg per day.
Do Zinc Lozenges Prevent Colds?
During cold and flu season, zinc lozenges are a popular item; they’re said to reduce the severity or duration of a cold. When used as directed, you’ll be getting a lot more than the recommended amount of zinc. That’s OK for a short period of time; but I don’t recommend using them for more than a week. I also don’t recommend sucking on zinc-charged cough drops all winter long. Not only is it unlikely to keep you from getting sick, but it could cause a copper deficiency.
(See also my show on How to Prevent a Cold.)
Selenium: How Much is Too Much?
Let me offer selenium as one last example. Like all the others, selenium is an essential nutrient with important roles to play in your health. It’s an antioxidant that helps make other antioxidants more potent, it helps protect against cancer, and it bolsters the immune system. Seafood, poultry, and meat, are all good sources of selenium. Vegans get selenium from whole grains and nuts, especially Brazil nuts, which are super high in selenium.
The recommended intake for healthy adults is 55 mcg per day and the average person gets about 100mcg from their diet, which is perfectly safe. But you don’t want to go nuts here. Overdoing the selenium can eventually make your nails brittle and your hair fall out. The safe upper limit for selenium is 400 mcg per day, and if you’re taking more than one vitamin supplement, you could easily be going over the limit.
In fact, you can exceed the upper limit for selenium with a single serving of Brazil nuts. One ounce provides up to 550mcg of selenium, depending on where they’re grown. Going over the limit occasionally won’t cause your hair to fall out. But you might not want to eat Brazil nuts every single day.
My advice is to add up the selenium in any supplements you take on a daily basis and make sure you’re not getting more than 250mcg of selenium per day. And of course, watch your consumption of Brazil nuts.
Get Your Nutrition From Foods, Not Pills
So, my quick and dirty tip this week is not to overdo it with the vitamin supplements, and to be particularly alert when you start combining several formulations so you can be sure that you’re not exceeding the safe limits. If you want to be excessively well-nourished, go for it, but with foods, not pills!
Related Tips
Getting More Nutrition From Vegetables
Nutrition for Breastfeeding Moms
Keep the Vitamins in Your Veggies
Resources
Micronutrient Information Center (Oregon State University)
Vitamin and Mineral Supplement Fact Sheets (National Institute of Health)
Nutrient Content of Foods (NutritionData.com)
Nutrition Information for Vegetarians (Vegetarian Resource Group)
Vitamins image courtesy of Shutterstock
About the Author
Monica Reinagel is a board-certified licensed nutritionist, author, and the creator of one of iTunes’ most highly ranked health and fitness podcasts. Her advice is regularly featured on the TODAY show, Dr. Oz, NPR, and in the nation’s leading newspapers, magazines, and websites. Do you have a nutrition question? Call the Nutrition Diva listener line at 443-961-6206. Your question could be featured on the show.
