Multivitamins linked to health

Published 4:00 am Thursday, January 24, 2013

By Anne Aurand / The Bulletin

Multivitamins, on store shelves since the 1940s, are the most common supplement taken by American adults. Sales of vitamin and mineral supplements in the United States totaled $12.4 billion in 2011.

Yet there’s been considerable uncertainty about whether such supplements actually help prevent chronic disease, a top reason people take them.

However, a recent study, conducted in the gold-standard method of scientific research and published in the reputable Journal of the American Medical Association, said that men who took multivitamins daily for more than 10 years had a statistically significant reduction in cancer, a breakthrough finding in the question of whether such supplements serve a purpose.

Multivitamins and cancer rates

In studying 14,600 middle-age male physicians for more than 11 years, researchers found that use of a daily multivitamin-mineral supplement (Centrum Silver was used in the study) was linked to an 8 percent drop in total cancers, compared with those who took a placebo. The reduction reflects significantly fewer cases of leukemia and colorectal, lung and bladder cancers.

Prostate cancers accounted for about half of all the cancer cases. But prostate cancer is not believed to be affected by multivitamins, said Balz Frei, a professor and director of the Linus Pauling Institute at Oregon State University and an international expert on the role of vitamins and micronutrients in promoting health and preventing disease.

“If they removed (prostate cancer cases), the reduction for all other cancers was 12 percent. That’s a pretty significant reduction in cancer risk,” said Frei, who was not involved with the research. “I don’t think there’s any other pill out there that has that large of an effect on cancer.”

Frei said because it was a randomized, placebo-controlled trial done on a large group over a long duration, the results hold some weight. Most studies on vitamins have been observational in nature, which doesn’t show a cause and effect.

“I think this is proof of the concept that multivitamins can prevent cancer,” said Frei.

How vitamins may prevent cancer is not understood in great detail, Frei said. The researchers, from Brigham and Women’s Hospital and Harvard Medical School in Boston, acknowledge this.

“It is difficult to definitively identify any single mechanism of effect through which individual or multiple components of our tested multivitamin may have reduced cancer risk,” the authors wrote. They postulated that the reduction in cancer risk was due to the combination of low-dose vitamins and minerals, rather than an emphasis on a high dose of any one vitamin or mineral.

“It’s probably a little bit of everything that brings the effect,” Frei agreed.

Folic acid, he said, is important in maintaining integrity of the DNA. Antioxidants, selenium, copper and zinc all play a role in normal metabolism and immune functions.

“With respect to cancer, some (vitamins) may be more important, like folate, possibly (vitamin) D, certain minerals like selenium, but, it’s hard to pin it down to a single ingredient. The whole idea behind multivitamins is that you cover all the bases.”

The general population

It’s possible that the physicians who were the subjects in the study have generally healthier lifestyles than the average American. In that case, the impact of multivitamin use in the general population could be even greater than it was in the doctors, Frei said.

Still, federal guidelines and most dieticians don’t outright recommend that most people take a multivitamin.

The federal government’s 2010 Dietary Guidelines for Americans says nutrients should come primarily from foods.

“Sufficient evidence is not available to support a recommendation for or against the use of multivitamin/mineral supplements in the primary prevention of chronic disease for the healthy American population,” according to the national guidelines.

But Frei said he believes most people could benefit from taking a supplement to fill nutritional gaps because most don’t consume all the recommended amounts of vitamins from their diet.

“Everybody is lacking some nutrients unless you eat nine (servings of) fruits and vegetables every day and an otherwise healthy diet,” he said.

“There’s no group or specific population that doesn’t have an inadequacy of something,” Frei said. “To make sure you get all of them, a multivitamin is a no-brainer.”

About 93 percent of Americans don’t get the recommended daily allowance (RDA) of vitamin E, he said. In some black populations, the shortage is higher. Vitamin D inadequacies and deficiencies are common. More than half of Americans don’t get enough magnesium. Deficiencies in vitamins A, C and B6 are common, he said.

Adults don’t absorb B12 as well as they get older, added Julie Hood Gonsalves, a registered dietician and associate professor at Central Oregon Community College

And, Gonsalves said, people who avoid any particular food group, such as dairy, are probably missing nutrients from that food group.

Considerations

But Gonsalves stops short of suggesting most people take a multivitamin.

“In general, a multivitamin isn’t a problem,” she said.

But, she said, “sources are saying there may be no benefit, a small benefit or even a small risk of harm by taking multiple vitamins.”

For example, one study on women suggested health risks associated with regular use of supplements.

The observational study was published in the Archives of Internal Medicine in 2011. It assessed vitamin and mineral supplementation on 38,772 women with a mean age of 62. Researchers suggested, based on the outcomes, that commonly used dietary vitamin and mineral supplements “may be associated with increased total mortality risk.” The association was strongest with supplemental iron.

Frei dismissed this study, known as the Iowa Health Study, as “an outlier,” an exception to the bulk of studies. But, he said, he does suggest older adults take supplements without iron.

Gonsalves also noted that this study was exclusively done on women, just as the cancer benefit study was just on men. Neither outcome should be extrapolated to the general population. There are differences between how men’s and women’s bodies handle drugs, but the exact differences are generally unknown, Gonsalves said.

Multivitamins are generally safe when taken in “physiological doses” as opposed to “pharmacological or clinical doses,” Gonsalves said. Physiological doses are the amount in which the vitamin could be consumed from food. Pharmacological doses are isolated and concentrated amounts of a vitamin. Used therapeutically, these high doses can come with side effects.

Read the label on any multivitamin bottle and make sure individual vitamins are in doses of 100 percent of the RDA or less, she insisted.

No standard or regulatory definition defines what nutrients a multivitamin-mineral supplement should contain. Manufacturers decide types and levels of the ingredients.

Sometimes, in the interest of marketing, an individual vitamin will be as high as 3,000 percent of the RDA, with exceptional health claims for fighting cancer, for example, she said.

It’s also worth considering what other fortified foods you’re consuming, she said. Fortified foods such as cereals and snack bars may add to one’s vitamin intake, and push certain levels too high.

Some studies, Gonsalves said, have shown long-term supplementation with high levels of vitamin A or beta carotene is associated with increased risk of some cancers. Vitamin A at two or three times the RDA in pregnant women can cause birth defects, she said. And, too much vitamin A can thin the bones and lead to osteoporosis, she said.

“Those things, if you take multivitamins and eat fortified cereals and extra fortified foods, could be a big deal,” she said.

Gonsalves generally discourages high-dose supplements such as Emergen-C or Airborne, although she said “usually people take them short-term and it’s not a big deal.” These supplements, which dissolve into a glass of water, are marketed as energy and immune boosters that improve health.

“It’s a marketing thing not backed by science. People can make a lot of money on supplements. But they’re not multivitamins,” she said. These products include a selection of vitamins in high doses. Emergen-C, for example, contains more than 1,600 percent of the RDA of vitamin C and 500 percent of the RDA of B6. Airborne is similar with more than 1,600 percent of RDA for vitamin C, and 150 percent of RDA for manganese.

Overloading your body with vitamin C, for example, could create gastrointestinal upset and, potentially, kidney stones, she said. Vitamin D in excessive doses can also lead to kidney stones. But these things take a long time to develop. Niacin, in pharmacological doses, can spark an immediate hot flush and over time, can cause liver damage, Gonsalves said.

Heart disease

The same research that resulted in findings about reduced cancer from long-term, daily multivitamin use also showed that taking a multivitamin regularly did not lower the risk of major cardiovascular events — heart attacks, strokes and death from heart disease.

The physicians on which the research was conducted, Frei said, are more likely to “self-medicate” with baby aspirin or statin medications that lower rates of heart disease. Physicians tend to have a lower rate of heart disease than the general population. Therefore, he said, they might not need the multivitamin as much as the general population. In the doctors, he said, “you probably wouldn’t see an additional (lowering of heart disease) from the multivitamin.”