Getting to Know Nutraceuticals

Claims for some of these food-based dietary supplements stand up to scientific scrutiny, but others falter

But when her research team analyzed blood lycopene levels of participants in a large cancer study, including 692 men who had developed prostate cancer and 844 randomly selected men who had not, they found no association between the antioxidant and the malignancy. Even more troubling, her study found a link between high blood levels of lycopene's chemical cousin, beta-carotene, and an increased risk of aggressive prostate cancer--not enough to justify avoiding carrots and other food sources of beta-carotene but an ominous sign that not all food-derived compounds are necessarily benign when taken at higher doses.

The results were very disappointing, Peters says. It would be great to have such an inexpensive way to lower prostate cancer risk, but our study dampens that possibility. Unfortunately, it often happens that health claims get out in front of scientific evidence.

Whether that has also been the case with another, much more popular supplement is still unclear. Glucosamine, a simple amino sugar, is well known to biochemists as the precursor for a wide range of important structural components of the body, including the protein collagen in tough connective tissues such as tendons and ligaments. Collagen is also a major component of the cartilage that makes up the smooth layer that protects and lubricates the bones in joints. Early observational studies suggested that glucosamine could be helpful in combating the pain and cartilage destruction of osteoarthritis, and it is widely available as a supplement derived from shellfish, often in combination with the biochemicals chondroitin sulfate, which helps to make collagen spongy, and methylsulfonylmethane (MSM), a potential anti-inflammatory agent.

Consumer sales reached an estimated 818 million for glucosamine and chondroitin sulfate in 2006, according to the Nutrition Business Journal. Observational studies, while sometimes contradictory, have suggested that arthritis sufferers do indeed benefit from using the supplements. That possibility led to a large NIH-funded clinical trial of the supplements involving patients with knee osteoarthritis. For 24 weeks, 1,583 participants in the aptly named GAIT (Glucosamine/chondroitin Arthritis Intervention Trial) were given one of the following treatments: glucosamine, chondroitin sulfate, both in combination, a placebo, or the COX-2 inhibitor Celebrex (celecoxib) as a control. (COX-2 inhibitors have since been linked to negative cardiovascular side effects.)

The results, published in 2006, were underwhelming. True, almost 67 percent of the patients taking glucosamine plus chondroitin sulfate reported a significant decrease in knee pain--but so did fully 60 percent of those taking the placebo. Only in patients with moderate or severe knee pain at the outset did the supplements show a significant advantage over the placebo, with almost 80 percent of that group reporting a significant improvement, compared with 54.3 percent who took the inert pills. That favorable result is nothing to sneeze at--nor, for that matter, is a placebo effect of 60 percent--but it's far from warranting a blanket recommendation.

Simple Foods aren't so Simple

Even if ketchup is one day recognized as a nutritional powerhouse, it's not likely to topple tofu from its shimmering, gelatinous perch atop the health food heap. High in protein and low in sugars and unhealthy fats, soybeans and the bean curd produced from them have long been lauded as a sound substitute for animal proteins. But they are also loaded with bioactive compounds, and the science is not yet in on whether consuming them at nutraceutical doses is a good or bad thing. The most investigated of those are a group of hormonelike polyphenols called isoflavones, which seem to have effects on everything from kidney and cardiovascular disease and various cancers to hot flashes, bone calcium loss and other symptoms of menopause.

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