Looking again at coenzyme Q-10

Coenzyme Q-10 (CoQ-10), which we last looked at in 1996, is one of the most popular dietary supplements—not just in this country, but around the world, especially in Japan. It's claimed that CoQ-10 prevents and/or combats many disorders, including heart disease, cancer, AIDS, lung disease, hypertension, gum disease, obesity, impaired immunity, chronic fatigue syndrome, asthma, Alzheimer's, allergies, and aging itself. In recent years much research on CoQ-10 has confirmed that it is indeed a very important substance. But even so, the clinical research is still in its infancy—and thus the marketing claims remain overblown.

CoQ-10 is necessary for generating energy in all human cells—as well as in all living organisms. First isolated in 1957, it was named ubiquinone because it belongs to a class of compounds called quinones, and because it's ubiquitous. It also acts as a powerful antioxidant, meaning that it helps prevent the cellular damage caused by free radicals in the body. CoQ-10 is manufactured by the liver; it is also found in many foods, but is most concentrated in meat and fish. CoQ-10 is one of many substances (including DHEA and melatonin) in the body that tend to decline as people age and/or develop certain diseases (such as various cardiac conditions and Parkinson's). But that doesn't mean that the lower levels of CoQ-10 cause aging or disease, or that supplemental CoQ-10 will combat or reverse the effects of aging or disease.

What the studies show

Interest in CoQ-10 began after early research in Texas showed that CoQ-10 supplements can help treat otherwise unresponsive congestive heart failure and certain other heart problems. Studies since then have had inconsistent results. Further clinical trials are underway.

An international conference on CoQ-10, held in 1998 in Boston but only recently published, included three dozen studies and reports. Among the findings: CoQ-10 may work even better than vitamin E against two kinds of free radicals. But, unfortunately, it can also "auto-oxidize"—that is, it can become a free radical itself under some circumstances. Vitamin E can prevent this, however. Indeed, studies suggested that these two substances work synergistically, as do many other antioxidants—such as vitamins C and E, beta carotene, and alpha-lipoic acid.

Another study found that the more CoQ-10 there is in LDL ("bad") cholesterol, the less susceptible it is to oxidation. It's theorized that the oxidation of LDL increases plaque development in artery walls. Vitamin E also helps reduce the oxidation of LDL, thus reducing the risk of heart attack. Other researchers at the conference reported that the cholesterol-lowering drugs known as "statins" (which include lovastatin and the dietary supplement Cholestin) reduce the body's synthesis of CoQ-10, but the health effects of this are unknown.

Most of these studies and presentations were highly theoretical and/or preliminary, merely suggesting potential benefits of CoQ-10 supplements.

Keep in mind: There's still no solid clinical evidence that CoQ-10 supplements benefit healthy people. So why not take them just to be safe? There doesn't seem to be any danger, but no one knows what the long-term effects are. CoQ-10 costs about $15 to $30 a month for typical doses. The large doses of high-potency capsules some advocates are recommending for heart patients cost as much as $6 a day.

If you have heart disease, talk to your cardiologist about CoQ-10. If you're taking CoQ-10 on your own, make sure your doctor knows. Make sure you also take vitamins E and C. And don't think that CoQ-10 can take the place of proven, reliable treatments.

UC Berkeley Wellness