Overall, Pritsos was critical of the study and its design. "I was disappointed by ... how they [failed to] control for their subjects' differences" on measures relevant to oxidative stress. Of particular concern to him was that the researchers did not take possible confounders, such as prior diets, prior training, and most importantly, smoking into account. "Smoking has a major impact on oxidative stress, and all of these are potential confounders."
Pritsos also has concerns that the investigators report no attempt to ensure the Marines were actually taking the placebo supplement. In studies of this nature, he says, "You need some kind of compliance measure," he says. Another weakness in the study was that the investigators failed to spell out pre- and post-measurements of oxidative stress, which Pritsos argues are critical for assessing the benefits and possible harms of the supplements.
Joy E. Swanson, PhD, also raises red flags about the study. "I think it is difficult to make any conclusion here about what looks like a lack of response" in the study, says Swanson. "One glaring error is that they did not even measure the response to diet. ... The military fortifies a heck of a lot of its food." Swanson is a research associate in nutrition sciences at Cornell University in Ithaca, N.Y.
Both Pritsos and Swanson worry that this study might be reviewed uncritically and misguide patients and physicians. Based on a slew of high-quality research, both question whether the study was simply not powered enough to evaluate the benefits of the specific supplements. And both researchers say that for patients undergoing chemotherapy or radiation therapy, antioxidants could prove helpful because those treatments produce an excess of oxygen radicals.
The study was supported by Ross Products of Abbott Laboratories, DataChem Laboratories, and the U.S. Naval Research Center.
- A new study shows a modest benefit for taking antioxidants while participating in strenuous exercise at moderate elevations.
- Antioxidants work by helping the body neutralize potentially damaging free radicals.
- Some experts criticized the study for its design, but agree that antioxidants are helpful for people under oxidative stress, which can be caused by high altitudes.