Oxidative Stress in Vegetarian Diets: Take Two
This is the second part to yesterday’s Vegetarian Diet, Glutathione and Oxidative Stress.
A 2012 study from Korea compared the antioxidant status of 45 vegetarians (10 vegans and 35 lacto-ovo vegetarians) to 30 omnivores (1). The vegetarians had to have been vegetarian for at least 10 years and they were mostly Seventh-day Adventists. The vegetarians consumed animal products only occasionally. They had to be without chronic disease and not taking antioxidant supplements, could not be smokers, and could not drink one or more alcoholic beverages per week.
The vegetarians ate a diet of 66% carbohydrate, 19% protein, and 15% fat (versus 60%, 17%, and 25%, respectively, for omnivores). The vegetarians ate about the same amount of calories as omnivores (1,832 vs. 1,790). There was no iron-deficiency anemia. The groups were similar in weight, height, body mass index, and blood pressure but the vegetarians had a lower body fat percentage. Vegetarians had average cholesterol levels of 174 mg/dl, compared to 193 mg/dl for omnivores.
Antioxidant status findings: Vegetarians had significantly lower amounts of diacron reactive oxygen metabolites, which is a reflection of oxidative stress. From what I can tell, by “oxidative stress” they mean “oxidative damage.”
Despite the difference in oxidative stress, both groups had the same levels of biological antioxidant potential. They measured a number of other antioxidant enzymes, including glutathione peroxidase, and found them to be the same in both groups. The authors suggest that the reason for the lack of differences in antioxidant capacity between diet groups could be a tendency to maintain homeostasis.
Body fat, total cholesterol, and LDL cholesterol were significantly and positively associated with reactive oxygen metabolites level.
In this study, vegetarians suffered less oxidative stress (or damage). So far, Kiefer appears to be 0 for 2.
Reference
1. Kim MK, Cho SW, Park YK. Long-term vegetarians have low oxidative stress, body fat, and cholesterol levels. Nutr Res Pract. 2012 Apr;6(2):155-61. Epub 2012 Apr 30. | link
February 15th, 2013 at 5:35 pm
So I guess the broader question in my mind is: should we even care about the antioxidant potential of our diets. This relates to James Watson’s (of DNA fame) recent article about high levels of antioxidants in our diets (primarily from supplements I assume, but he doesn’t really make that distinction when he refers to blueberries) increasing cancer risk. I thought it was interesting that in your recent excellent interviews posted on Animal Voices (link can be found a few posts below) the interviewer read out a long excerpt from a commentary on Watson’s article but didn’t actually ask you to comment on this issue. Do you have any thoughts on a) whether dietary antioxidants would even be powerful enough to make a difference relative to the body’s own antioxidant defence system and b) the more radical notion that dietary antioxidants might actually be doing us harm – and that fruit and veg etc are therefore health promoting because of other phytonutrients, not necesssarily because of their antioxidant effects. Sorry for the long question.
February 15th, 2013 at 5:45 pm
kate,
No issues on the question length!
I think Erin, of Animal Voices, injected that reading of Watson’s article after we’d already done the interview and so that’s why she didn’t ask me about it. 🙂 As for your questions:
a) I don’t feel too confident, but I would put my money on the idea that antioxidants make a difference in extremely antioxidant-poor diets. In other words, I don’t think that without any antioxidants in the diet, someone would be at full antioxidant capacity, but it might not take much to get them there.
b) I doubt they’re doing us harm at the levels involved without supplementation.