Is There Too Much Copper In Your Multivitamin?

A new report investigates

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Multivitamins are supposed to do a body good. In one little capsule, they contain every nutrient your body needs to function—a "complete" pill you need to take just once a day. But there is new concern that some multis may contain harmful levels of metals that are linked to a wide variety of cognitive problems later in life, says Neal D. Barnard, MD, president of the Physicians Committee for Responsible Medicine and adjunct associate professor of medicine at George Washington School of Medicine.

Dr. Barnard recently authored a report sounding the alarm on copper and iron in dietary supplements. His group analyzed levels of those metals in multivitamins and found that the majority contained double the recommended amounts of copper and iron, much more than most people need. While both metals do provide health benefits—copper helps your body metabolize iron, boosts your immune system, and keeps your nerves and blood vessels healthy; iron carries oxygen to red blood cells and to muscles—too much can affect brain health, says Dr. Barnard.

How? For one, the metals are increasingly being flagged as Alzheimer's disease triggers. In fact, the authors of an August 2013 study published in the Proceedings of the National Academy of Sciences concluded that copper appears to be one of the main environmental factors behind Alzheimer's disease. The researchers exposed mice then human brain cells to low levels of copper commonly seen in the average diet, and found that the metal interferes with the way the brain rids itself of the plaques that cause Alzheimer's disease. They also found that in mice already plagued with Alzheimer's, copper can pass the blood-brain barrier and accelerate the formation of plaques.

Prior studies have come to similar conclusions. In a 2010 review of the science on copper toxicity, published in Chemical Research in Toxicology, George Brewer, MD, professor emeritus of internal medicine and human genetics at the University of Michigan Medical School, wrote that research has linked both excess copper and iron to Alzheimer's disease, heart disease, diabetes, Parkinson's disease, and a few other neurological disorders.

More from Prevention: Is This Metal Messing With Your Brain? 

Dr. Barnard refers to one study in which researchers analyzed copper levels in the blood of a large sample of healthy adults over a six-year period, and those with the highest levels of copper lost cognition three times faster than adults with normal copper levels. Iron is suspected of causing similar damage, he writes, because both metals can introduce too much oxygen into the brain, causing "oxidative stress" that damages neurons. That same study noted that the people with the highest levels of copper and iron in their systems took multivitamins. A separate study, published in the 2008 Journal of Nutrition, Health and Aging, found that in a group of 1,450 people, those who performed highest on cognition tests also had the lowest levels of copper and iron in their bloodstreams.

"Alzheimer's disease is an epidemic that is growing rapidly," says Dr. Barnard. "But up until now, most people had no idea they could do anything about it."

While there's no silver bullet, there are a number of ways you can reduce your intake of copper and iron so you aren't taking in too much.

Eat lots of vegetables. All meats and vegetables contain copper, Dr. Barnard says, but red meat contains forms of both copper and iron that are easily absorbed by your body, making it easy for the metals to accumulate over time. Copper and iron in vegetables, on the other hand, are available in forms that are more easily regulated by your body—if you need more of either metal, your body takes what it needs from these plant sources and excretes the rest. Plus, eating less red meat will benefit your health—and the environment—in other ways. (For more foods that are good for your long-term brain health, read The Happiness Diet).

Eat a variety of foods. Dr. Barnard says that most people who follow a diet of whole foods—lots of fruits, vegetables, and whole grains—probably don't need multivitamins. The only vitamins you might consider taking, he says, are vitamins B12 and D, which are both uncommon in foods. If your doctor does tell you to take a multivitamin, he adds, read labels to make sure you're taking on that's free of copper and iron, since you are likely getting enough from other sources, including meats and vegetables and other fortified foods.

Buy a water filter. Eighty percent of homes in the U.S. have copper water pipes, and copper could be leaching from them. According to the National Sanitation Foundation, carbon filters, reverse osmosis systems, and distillers will remove copper from your water, so be sure to buy a filter that's NSF-certified to do just that.

More from Prevention: You Can Prevent Alzheimer's Disease

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