Of course you think you're being virtuous when you take a multivitamin and eat nutrient-fortified foods, like 100 percent-daily-value-of-everything breakfast cereals. And you are, for the most part—but there's a caveat. A new study published by the Environmental Working Group found that children can actually overdose on certain nutrients—and, Lisa Young, R.D., Ph.D., author of The Portion Teller Plan, says adults can, too.
For the study, researchers from the Environmental Working Group reviewed fortified foods on the market today and found that young children are at risk of consuming too much of three nutrients in particular: zinc, vitamin A, and niacin. The main culprit? Fortified breakfast cereals. That's because the recommended daily amount listed on these cereals is meant for adults—but kids eat the stuff, too.
Now, here's the thing: While this study focused on children, Young says the results can also apply to adults. There's a crucial difference between you and a six-year-old, though. Since adults are just bigger—obviously—they need more nutrients, so the overdose risk lies primarily in taking a multivitamin in addition to eating nutrient-fortified foods. "What people don't realize is that if you're already taking a multivitamin, that's enough added nutrients for the day," says Young. "You don't need to eat more nutrient-fortified foods."
In fact, if you do, you could end up overdoing it on certain nutrients—but luckily, it's not too likely. "To overdose on nutrients, you'd have to have an excessive amount," says Young. "'Excessive amount' is tricky to define because it varies depending on the nutrient, but for certain nutrients, having 10 times the recommended amount could cause toxic symptoms and be harmful to your body." For example, too much vitamin A can lead to liver damage, peeling skin, hair loss, and skeletal abnormalities; too much zinc can cause impaired immune function; too much niacin can lead to nausea, rashes, and vomiting.
So how can you guarantee that you're not ingesting too many vitamins? For starters, skip the foods that offer 100 percent of your recommended daily intake of any vitamins. "Those are unnecessary in every way because real foods have nutrients, too," says Young. "So if you have highly fortified foods, you're automatically taking in far more daily nutrients than you need."
The better plan: Focus on your multivitamin intake. If you take a multi every day, try to skip the processed, vitamin-fortified stuff entirely, and opt for simple, healthy, natural foods instead. Your body actually absorbs the nutrients from foods better, so you get more out of them that way, says Young. And if you do end up eating some nutrient-fortified foods, try to go for only the ones that offer 10 to 15 percent of your daily value, suggests Young.
If you don't take a multivitamin every day, that's fine, too. In that case, though, it's OK to choose foods with a slightly higher nutrient content. "Anything that offers 20 to 25 percent of your daily value should be fine as long as you eat natural, nutrient-rich foods to get the rest of your daily value," says Young.