Antioxidant Status of Irish Vegetarians

In my continuing review of the literature of the glutathione and antioxidant status of vegetarians, today’s episode is a 2007 cross-sectional study from Ireland (1).

The study included 31 vegetarians (including 6 vegans) and 58 omnivores. The results were adjusted for age, gender, and body mass index (which did not significantly differ between the two groups). Antioxidant supplements were allowed and results were examined both for the entire group and for non-supplement users.

There were no significant differences between the groups for glutathione or any antioxidant enzymes. The only differences between the two groups of note were:

• Vegetarians had higher levels of carotenoids, associated with a higher vegetable intake.

• Among those not taking antioxidant supplements, the omnivores had a higher total antioxidant status (known as FRAP). This was due to higher uric acid levels (which is an antioxidant) in the omnivores, which was probably due to meat intake.

The authors say, “The results of this study indicate that there were no differences between vegetarians and omnivores in the level of cellular endogenous antioxidants…and in the plasma levels [of] antioxidant nutrients (vitamin C, retinol and a-tocopherol) despite the increased dietary intakes of these antioxidants by the vegetarian group. The reason for the lack of difference in the antioxidant vitamin status between the two groups might partly be due to homeostasis…” In other words, once you have reached a certain threshold of antioxidants in your system, adding more might not do much.

Regarding the uric acid and total antioxidant capacity, this study was interesting, and could possibly indicate that lacto-ovo vegetarians are at a disadvantage. As we saw from my recent post Higher Uric Acid Levels in Vegans, vegans would not be at a disadvantage.

In terms of glutathione levels, we now have a cross-sectional study (1) and a clinical trial (2) indicating that vegetarians have similar glutathione levels as omnivores.

As an aside, one other measure of interest was that plasma zinc levels did not differ between the two groups.

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1. Haldar S, Rowland IR, Barnett YA, Bradbury I, Robson PJ, Powell J, Fletcher J. Influence of habitual diet on antioxidant status: a study in a population of vegetarians and omnivores. Eur J Clin Nutr. 2007 Aug;61(8):1011-22. | link

2. Kahleova H, Matoulek M, Malinska H, Oliyarnik O, Kazdova L, Neskudla T, Skoch A, Hajek M, Hill M, Kahle M, Pelikanova T. Vegetarian diet improves insulin resistance and oxidative stress markers more than conventional diet in subjects with Type 2 diabetes. Diabet Med. 2011 May;28(5):549-59. | Link

2 Responses to “Antioxidant Status of Irish Vegetarians”

  1. Ren Says:

    Looks like there’s been some bad news about antioxidants lately. How does this fit in with the context of antioxidants being a good thing?

    Thanks very much!

  2. Jack Norris RD Says:


    The comment on that article by Harold L Evans from Oct 18 2015 summarizes my view as well and in a concise way.

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