Sunday, March 15, 2009

Supplements: Vitamins

Image of diet supplements challenged | The Columbia Daily Tribune - Columbia, MO

Image of diet supplements challenged

Nutrition professionals weigh in on vitamins.

In recent years, vitamins, minerals and dietary supplements have sprawled to take over entire sections of supermarkets and drugstores. Nationwide, the industry has ballooned from a niche for health nuts to a mainstream obsession. About half of all adults today use some form of dietary supplement at a national cost of $23 billion a year.

Despite the booming business, the benefits of many supplements are in doubt.

Recently, two local nutrition experts discussed the vitamin phenomenon with a reporter and shared advice on what works, what doesn’t and what science has not yet proved. Pam Hinton and Catherine Peterson both teach at the University of Missouri in the Department of Nutrition and Exercise Physiology. Hinton studies how exercise and nutrition affect bone health, and Peterson’s studies focus on vitamin D.

They discussed six of the 10 most popular categories of vitamins and minerals based on sales calculated by the Nutrition Business Journal.

Multivitamins: The most popular of all supplements, these are the catch-all that allow people to swallow all their recommended daily allowance in an instant. But the two nutrition experts said it’s not the same as getting those same nutrients from food.

“That’s sort of a cop-out,” Hinton said of multivitamins. “If we took the time to actually get the nutrients from foods, then we’d get all the other things in foods that probably improve our health.”

Multivitamins are most important for people who are nutrient deficient, she said. For example, people who don’t eat enough meat need extra iron or zinc in their diet. People who don’t drink enough milk might benefit from the calcium in vitamins.

But many people swear by multivitamins because they offer “mega-doses” — 200 percent or more of the RDA for a given nutrient. The benefits of taking an excessive dose of any nutrient are often negligible, Hinton and Peterson said, because excess vitamins and minerals that are water-soluble will be expelled in urine.

Vitamin B: Hinton and Peterson were mystified by the popularity of this supplement, saying people get plenty by consuming grain, cereal and crackers, which are all Vitamin B-enriched. “It seems silly, very superfluous, in my opinion,” to take extra doses of it, Peterson said. Exceptions to that rule include older people who might be vitamin B-12 deficient.

Vitamin D: This is one vitamin for which science is just uncovering a greater need, Peterson said. Vitamin D is made by skin compounds after exposure to the sun and can be obtained through fortified milk and a few other foods. It was first identified in the 1920s when it was discovered that a vitamin D deficiency caused an abnormal bone growth called rickets. In studies in her laboratory, Peterson found that half the people in her sample had insufficient levels of vitamin D. The numbers were particularly high among people with dark skin.

Peterson said many people in modern society do not get enough sunlight, and experts are just now finding that current RDA levels are too low. “It’s not enough. What you get in milk will prevent rickets,” she said. “But we are now recognizing vitamin D has a role in so many other body functions, everything from the central nervous system to the immune system to the metabolism.”

Calcium: Getting the recommended dose of calcium requires a person to drink three to four glasses of milk each day, a tricky proposition. Women and older people who can be prone to bone weakness should be most attentive to getting the proper amount of calcium. A tablet is a good way to do this, they said.

“If you don’t get it in your diet, it will be mobilized from your bones,” Hinton warned.

Vitamin C: This vitamin is very easy to get from a healthy diet: a half-glass of orange juice or a serving of potatoes should do the trick, Peterson said. Yet people spend lots of money on mega-doses, believing it helps the immune or upper-respiratory systems. There is no evidence to back up that belief, Peterson said. “I worked in an industry where we did focus groups with consumers, and anytime you tell them you’ve got a product with vitamin C, they get excited about it,” Peterson said. But “you really don’t need to be taking 1,000 milligrams a day.”

Fish oil: The American Heart Association recommends two servings of fish per week. Both experts agreed taking fish oil was a safe alternative for people who don’t get two fish servings weekly yet want to get the omega-3 fatty acids that are important for brain and heart function.

The general take-away message from both Hinton and Peterson was “food first.” Don’t use a pill as a crutch for vitamins and minerals that can be consumed through a healthy diet. Nutrients in a pill might not all be absorbed by the body or might even interfere with one another on the way down. That lesson is sometimes hard to get across, they said.

“It’s religion to people, and if they get a benefit from something because they believe that it’s working, I’m not going to burst that bubble,” Hinton said. “So unless people ask my opinion I just try and bite my tongue.”