Health Off The Shelf
by Cate House

Working at Weaver Street Market, a whole-foods grocery store in Carrboro, Skye Murray talks to people every day who come in looking for diet supplements that will help them feel better. They want to ease their arthritis pain, boost their energy, lift their moods, ward off their colds, alleviate their stress.

“Most of our customers already know what they want to take,” Murray says. “They’ve either read somewhere or been told about a supplement that will help with their problem. For instance, many people have read about the benefits of echinacea for boosting the immune system or about garlic for preventing heart disease.”

But once in the store, customers face many choices. So Murray starts asking questions. She asks what they want to take, why they want to take it, and in what form. She also asks what they’ve taken before and if they had any side effects. “A lot of people, for example, can’t take supplements in gel form either because it’s an animal source or because they are allergic to it,” she says.

Murray’s customers are among the group of Americans who spent $12 billion on diet supplements in 1998. That’s up from $6.5 billion in 1996. But as the numbers climb, researchers are working to find out just how effective these diet supplements are—and whether they’re safe.

When nutritional supplements are taken with another drug or at doses higher than someone would normally be exposed to in a daily diet, they can cause illness or death. “Just because something is natural does not mean it’s safe,” says Steven Zeisel, chair of nutrition.

Zeisel points out that some plants, for instance, contain a wide variety of toxic chemicals that help them fight off bacteria, insects, and herbivores. In small doses, these chemicals may not have any negative consequences, but in greater amounts they may cause serious side effects.

Yet there are many people who believe that taking more of a substance increases their chances of preventing illnesses such as heart disease or cancer. In some cases, this may be true, but in others it could cause major problems.

That’s one of the reasons why the National Institutes of Health have helped Carolina establish a Clinical Nutrition Research Unit—to help determine at what levels supplements are still safe and if they’re effective in preventing and treating diseases. Started in October 1999, the unit is one of only eight in the country that provide core research facilities, including molecular biology tools, assistance in conducting population-based studies, and multimedia resources for educating the public about issues in nutrition.

As it is now, nutritional supplements are unregulated by the federal government. That means it’s not certain whether a particular supplement has been tested for safety or effectiveness. If a company wants to make a claim on the product’s label that it has been shown to cure a disease, then the claim has to be approved by the Food and Drug Administration (FDA). That means lots of research. Because many companies don’t have the facilities to conduct the necessary research, they often turn to research universities to help them test their supplements for safety and effectiveness.

One of the supplements Zeisel and his team of researchers are studying is genistein, a component of soybeans known as an isoflavone, that may be beneficial as an anticancer agent for prostate and breast cancers. In Asian countries, where people eat diets high in soy, the rate of these cancers is considerably less than in the United States. Previous studies have also shown genistein to inhibit cancer in rats and to suppress human tumor cells from growing in test tubes.

The National Cancer Institute (NCI) wants to conduct a national study on cancer prevention using genistein pills and has asked UNC-CH to look into the effects of soy isoflavones on humans. To do that, researchers first tested genistein on healthy volunteers to make sure it’s still safe—that it’s not toxic—when given in amounts greater than can be found in food. Another thing researchers checked was the pharmacokinetic data, which tells them how the body absorbs, metabolizes, and excretes the supplement. Knowing this information helps researchers determine how often the supplement should be administered. “You want to make sure that steady levels are achieved that don’t rise or fall sharply during the day,” says LeAnne Tyndall, associate project director of the study.

To decide how much genistein to start with, researchers looked at the amount Asians typically consume in their daily diets—somewhere between 20 and 80 milligrams (mg). They started around 70 to 80 mg, depending on the participant’s weight, then, gradually, went up to 1,300 mg. “It’s virtually impossible to get these levels from diet alone,” Tyndall says. “That’s why you have to test for safety.”

The genistein used in the study is a purified form, which is not the same as the genistein found in food, where it is bound to a sugar molecule. This means that in order for the genistein from food to be absorbed and carry out its function, the bacteria in our bodies have to remove the sugar unit before it becomes active. “In our test compound, the sugar group has been removed, so the body does not have to work as hard to absorb it,” Tyndall says.

At each stage Tyndall and other members of the research team conducted a variety of tests, including blood and urine samples, chest x-rays, electrocardiograms, and physical examinations. They also asked each subject if he or she was experiencing any side effects.

After testing separate groups of healthy males and females for 30 days, and finding no adverse indications, the team is now ready to move on to patients with prostate cancer, which is the second part of the study supported by NCI.

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