Can You Get Too Many Vitamins?
Find out which nutrients can cause problems and how to avoid getting too much of them.
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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!
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)