Taking Too Many Vitamins? Side Effects of Vitamin Overdosing
Nowadays, everything from bottled water to orange juice has elevated levels of vitamins and minerals.
This may sound like a way to help cover your nutritional bases, especially if your diet isn’t stellar. But a regular overabundance of vitamins and minerals can harm you. Too much vitamin C or zinc can cause nausea, diarrhea, and stomach cramps. Too much selenium can lead to hair loss, gastrointestinal upset, fatigue, and mild nerve damage.
Supplements: check the dose
Chances are, the unfortified foods you eat aren’t the problem. “It’s very hard to go overboard on food,” says Joanna Dwyer, MD, senior scientist at the National Institutes of Health’s Office of Dietary Supplements.
“Most people don’t realize that there’s no real benefit to taking more vitamins and minerals than recommended, and they don’t realize that there can be downsides,” says Dwyer.
“If you’re taking a supplement, stick to one that doesn’t exceed your daily allowance,” says Dwyer. (Daily value is the amount of a vitamin or nutrient a person should be getting for optimal health.)
Talk to your doctor about any supplements you take, including vitamins and minerals, and the doses you take. Therefore, your doctor can help you keep your doses within a safe range.
“If you’re taking a basic multivitamin, don’t be afraid to take too much,” says Andrew Shao, Ph.D., senior vice president of scientific and regulatory affairs at the Council for Responsible Nutrition, a trade group for the supplement industry.
“Most multivitamins have such a large margin of safety that even if you combine them with fortified foods, it still won’t make you break down,” says Shao.
Subtle Signs You’re Getting Too Much
“I haven’t seen anyone on the street taking toxic doses of vitamin A or D — it’s very unusual,” says David Katz, MD, director of the Yale University Prevention Research Center in New Haven, Connecticut, whose medical practice specializes in on food. “I’m more likely to see a person with a supplement dosage level that is higher than optimal.”
Scientists don’t yet know if taking too many vitamins or minerals on a regular basis (as opposed to megadoses) is a problem, says Katz.
“There may be hints of anxiety, but these will be very subtle signs,” he says.
These fairly mild symptoms may include trouble sleeping or concentrating, nerve problems such as numbness or tingling, or feeling more irritable, depending on the nutrient that’s going overboard.
Most worrying, according to Katz, is that we are “beautifying food supplies with over-enrichment.”
He says manufacturers have shifted their focus from what they’ve removed from food, such as fat, sugar or salt, to what they’ve added, whether it’s vitamin D, probiotics, or omega-3 fats. – any nutrient in vogue.
“As more and more products improve, consumers become unable to know how much they are getting during the day,” says Katz. “Physicians need to understand that because of this practice, we can introduce new dietary imbalances.”
Three nutrients to look out for
Dwyer says vitamin D, calcium, and folic acid are three nutrients you can get in excess, especially with supplements.
Adults who regularly go well over 4,000 international units (IU) of the daily safe upper limit for vitamin D may experience serious heart problems.
Folic acid is added to fortified grains—white flour, pasta, rice, bread, and cereals—to help prevent birth defects in children due to folic acid deficiency in pregnant women. While folic acid fortification reduced birth defects by 25-50%, it could create other health problems in people who get too much.
It’s easy to get more than 1,000 micrograms of folic acid per day (the safe upper limit for adults) from fortified foods and supplements on a regular basis. It can hide signs of vitamin B12 deficiency in the elderly. Vitamin B12 deficiency can sometimes lead to permanent nerve damage if left untreated.
“Most people can now get enough folic acid without relying on supplements,” says Dwyer.
In fact, she says, “most people don’t have problems [with getting too many vitamins or minerals] if they start with food, which is the healthiest and safest way to get them.”