Saturday, January 03, 2009

More evidence that antioxidant “dangers” are exaggerated (especially beta-carotene)

More evidence that antioxidant “dangers” are exaggerated (especially beta-carotene) By Neil E. Levin, CCN, DANLA In a study published in 2006, cancer researchers tested daily supplementation of 400 IU of vitamins E as alpha-tocopherol along with 50,000 IU (39 mg) of beta-carotene on 540 head and neck cancer patients for three years after treatment with radiation therapies. Due to safety concerns in previous trials (which I have repeatedly criticized in previous writings, for various reasons), the beta-carotene component was discontinued during the trial. During a median 6 ½ years of follow up, 179 of the patients died. The researchers concluded that high-dose vitamin E supplementation could be harmful to cancer patients, with a 38% increased risk for death. 1 This study has been associated with the hyperbolic warnings against antioxidant use for cancer patients. The same group of researchers published a 2007 study looking at the same group of 540 cancer patients treated by radiation to see if the antioxidant vitamins reduced the toxicity of the treatments. This report investigated the dietary intake, supplementation and plasma levels of beta carotene in the patients to look for correlations in outcomes, specifically acute adverse effects of the radiation therapy and cancer recurrence. A higher beta carotene dietary intake was associated with 39% fewer severe acute adverse effects, and higher plasma levels with 27% fewer severe adverse effects, from the radiation treatments. The researchers reported that, “This study suggests that a higher usual dietary beta carotene intake can reduce the occurrence of severe adverse effects of radiation therapy and decrease local cancer recurrence.” 2 This conclusion is at odds with fears of beta-carotene toxicity that have been massively publicized over the past 14 years. Now, in 2008, we have heard again from this same group of researchers continuing to review the data from the same group of patients. It turns out that the large increase in mortality in the patient group given antioxidants - reported in the 2006 study – was basically limited to those patients who smoked during their radiation treatments. In fact, there was no significant mortality increase in patients who only smoked before or after the course of radiation treatment, or for non-smokers. 3 This new information tells us that the general cautions about antioxidants should be limited to certain narrow conditions or situations, such as active smokers during therapy. This is good information, since we know that 40% of cancer patients actually die of malnutrition; that plasma levels of antioxidants are a far better measure of antioxidant status than supplement intake prescriptions or dietary recall surveys; and that antioxidants are synergistic with inter-related functions and should not be given separately. Now we also can point to numerous benefits of antioxidants in clinical studies that have been far overshadowed by the over-hyped negative conclusions of a relative few prominent-but-flawed studies reported by prestigious institutions, sometimes with NIH funding. I agree with those critics who insist that it should be considered scientifically inappropriate to use the drug model for nutrient research, because the nutrients already exist in the diet and in the body and are clearly impacted by other nutrients; as well as other variables, some of which are quite well known. By contrast, in a drug study a new, foreign chemical is being tested which should not already be present in the diet or the body, making toxicity a bigger issue while eliminating many of the variables that are inappropriately ignored in sensational-but-flawed nutrient studies that get so much media attention and so many undeserved citations in scientific journals. I have previously written about the use of antioxidants for cancer patients, as have others, with the common conclusion that most such warnings are overblown and that much of the published science has been favorable regarding those combinations of factors. REFERENCES

  • Bairati I, Meyer F, Jobin E, Gélinas M, Fortin A, Nabid A, Brochet F, Têtu B. Antioxidant vitamins supplementation and mortality: a randomized trial in head and neck cancer patients. Int J Cancer. 2006 Nov 1;119(9):2221-4. PMID: 16841333
  • Meyer F, Bairati I, Jobin E, Gélinas M, Fortin A, Nabid A, Têtu B. Acute adverse effects of radiation therapy and local recurrence in relation to dietary and plasma beta carotene and alpha tocopherol in head and neck cancer patients. Nutr Cancer. 2007;59(1):29-35. PMID: 17927499
  • Meyer F, Bairati I, Fortin A, Gélinas M, Nabid A, Brochet F, Têtu B. Interaction between antioxidant vitamin supplementation and cigarette smoking during radiation therapy in relation to long-term effects on recurrence and mortality: a randomized trial among head and neck cancer patients. Int J Cancer. 2008 Apr 1;122(7):1679-83. PMID: 18059031

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