Vitamin Trials and Cancer: What went Wrong?

Supplementation with Mixed Fruit and Vegetable Juice Concentrates Increased Serum Antioxidants and Folate in Healthy Adults

OBJECTIVE

Epidemiological studies have shown that low plasma levels of antioxidant micronutrients, which are commonly found in fruit and vegetables, are associated with increased risk for diseases such as heart disease, cancer, metabolic disorders and the like. The aim of this study was to monitor the dietary habits of a group of healthy, middle-aged, men and women and to assess the effect of supplementation with a natural phytonutrient preparation from fruits and vegetables, on plasma levels of various antioxidant micronutrients and oxidative stress assessed by measuring 8-oxodGuo (8-oxo-7,8-dihydro-2'-deoxyguanosine) in urine.

METHODS

The study followed a double-blind randomized cross-over design involving 59 healthy men and women (40-60 years of age). The supplement or a placebo was given to two groups for a total period of 14 weeks (crossover week 7). Blood levels of beta-carotene, vitamin C, vitamin E, selenium and folate were measured at 0, 7 and 14 weeks. Fruit and vegetable consumption was monitored by means of a retrospective food frequency questionnaire at week 0, 7 and 14. Urinary 8-oxodGuo was also determined at these time points.

RESULTS

Significant increases in blood nutrient levels after active supplementation were observed for beta-carotene, vitamin C, vitamin E, selenium and folate. Ranges measured, after supplementation, often fell into those associated with a reduced risk for disease. Our data suggests that, although generally health conscious, participants still fell short of the recommended five portions of fruit and vegetables per day. No significant group changes were noted for 8-oxodGuo concentration in urine.

CONCLUSION

Supplementation with mixed fruit and vegetable juice concentrates effectively increased plasma levels of important antioxidant nutrients and folate.

Tobacco-related diseases. Is there a role for antioxidant micronutrient supplementation?

It is clear that smoking causes an increase in free radicals, reactive nitrogen and oxygen species (RNS and ROS, respectively), and that cigarette smoking is associated with increases in the incidence and severity of several diseases including atherosclerosis, cancer, and chronic obstructive lung disease. Although there is still no unequivocal evidence that oxidative stress is a contributor to these diseases or that an increased intake of antioxidant nutrients is beneficial, the observation that smokers have lower circulating levels of some of these nutrients, raises concern. This article discusses the possible links between the observed oxidant-induced damage related to tobacco smoking, effects on cellular mechanisms, and their potential involvement in the causation and enhancement of disease processes.