Applied nutritional investigationEffects of a long-term vegetarian diet on biomarkers of antioxidant status and cardiovascular disease risk☆
Introduction
Diets rich in fruit and vegetables protect against chronic, degenerative disease. These beneficial effects are believed to be due to plant-based antioxidant compounds, such as ascorbic acid, carotenoids, and flavonoids, that may protect key biological sites, such as lipoproteins, membranes, and DNA, from oxidative damage.1, 2 Evidence of benefit is so strong that the World Cancer Research Fund recommends five or more servings of fruit and vegetables each day,3 and the recommended daily intake of vitamin C in the United States was recently revised upward to 75 mg/d for women and 90 mg/d for men.4 Although the identity of the protective component or components in fruit and vegetables is not yet clear, evidence exists that intakes and plasma concentrations of vitamin C (ascorbic acid) correlate inversely with all-cause mortality rate and may act as biomarkers of health status.5 In addition, the lipophilic antioxidant vitamin E (mainly α-tocopherol) is an antiatherogenic and anti-inflammatory agent.6, 7 Increased antioxidant status, therefore, may account for at least part of the benefit of plant-based diets. One cross-sectional study has suggested that vegetarians are healthier than non-vegetarians,8 and we were interested in determining whether vegetarians exhibit a more favorable profile in terms of antioxidant status and risk of chronic disease than do omnivores of similar age. Therefore, we compared biomarkers of antioxidant status, oxidative stress, inflammation, and coronary heart disease (CHD) risk in a group of long-term vegetarians with those of age- and sex-matched omnivores.
Section snippets
Materials and methods
Thirty vegetarians (27 women and 3 men; mean age ± standard deviation: 44.2 ± 9.0 y) were recruited with their informed consent. These subjects had been vegetarian for 5 to 55 y (21.8 ± 12.2 y). They ate no meat or fish owing to their religious (Taoist) beliefs, but some occasionally consumed eggs and milk in small amounts. The control group comprised 30 non-Taoist adults (27 women and 3 men, 44.0 ± 9.2 y) matched by age- and sex-stratified sampling from a pool of participants in a
Results
As shown in Table I, plasma ascorbic acid concentrations were significantly higher in the vegetarians than in the omnivores (P < 0.0001). Malondialdehyde concentrations were slightly but non-significantly lower in the vegetarians. No significant difference in the total antioxidant capacity of plasma (as the FRAP value) was seen; however, the contribution of ascorbic acid to the FRAP value of the vegetarian subjects was 50% higher than that in the omnivores (averaging 16.6% and 11.8% for
Discussion
Individuals who eat a diet rich in fruit and vegetables or who have high plasma concentrations of antioxidant micronutrients have a low risk of cardiovascular disease and stroke.13, 14, 15, 16 This observational evidence has led to the recommendation that high-risk individuals or populations with a high incidence of CHD and stroke should substantially increase their intakes of dietary antioxidants. It has been shown that plasma concentrations of antioxidants, such as α- and β-carotenoids and
Acknowledgements
The authors thank the anonymous reviewers who provided valuable, constructive, and expert comment.
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This study was funded by The Hong Kong Polytechnic University.