Oxidative stress is a cellular or physiological condition involving elevated concentrations of free radicals (reactive oxygen species) that cause molecular damage to vital structures and functions, which has been associated with the development of several disorders including atherosclerosis, cardiovascular disease, cancer, diabetes complications, macular degeneration and arthritis.
To limit the harmful effects of reactive oxygen species, a high-performance antioxidant system consisting of enzymes, proteins, vitamins (A, C and E), carotenoids, trace elements, and other small molecules may interact with the free radicals and regulate their production down to the physiological range. If these antioxidant defences are overwhelmed by excessive free radical production, or not sufficiently provided by diet or supplements, oxidative stress may consequently take place in the body.
Several factors influence the susceptibility to oxidative stress by affecting the antioxidant status or free oxygen radical generation. Regular exercise and carbohydrate-rich diets seem to increase the resistance to oxidative stress. Air pollution, alcohol, cigarette smoke, non-ionizing radiation and psychological stress seem to increase oxidative stress. Alcohol in lower doses may act as an antioxidant on low density lipoproteins and thereby have an anti-atherosclerotic property.
The ELAN (Etude Liègeoise sur les Antioxydants) cohort study, performed in the province of Liège, Belgium, in 2006, was the first large-scale trial investigating the relationship between oxidative stress status and the lifestyle of 897 people aged 40–60 years (1). For this purpose, information on the participants’ age, occupation, height, weight, blood pressure, smoking habits, alcohol and drugs consumption, waist circumference and physical activity was collected. In the same time, all participants completed a food questionnaire at home in order to evaluate their daily intake of fruit and vegetables. According to tables of diet composition, a score reflecting the daily consumption of both vitamin C and beta-carotene was established. In addition, plasma concentrations of the antioxidants were measured in blood samples.
These values were compared with the critical antioxidant plasma concentrations defined by the WHO-MONICA study (2): plasma concentrations for vitamin C below 50–60 micromole/l (8.8–10.5 micrograms/ml) and beta-carotene concentrations below 0.4–0.5 micromole/l (0.21–0.27 micrograms/ml) have been associated with an increased risk of developing cancer and cardiovascular disease.
- Men had a lower antioxidant status than women (in agreement with the French SUIVMAX study).
- 6% of the population were classified as clearly vitamin C deficient (plasma levels below 3.5 micrograms/ml), and another 10.3% were identified to be sub-deficient (levels below 6.2 micrograms/ml).
- For beta-carotene the results were significantly worse: almost one in two individuals (46.6%) was found to be beta-carotene deficient (levels below 0.22 micrograms/ml).
- The plasma concentrations of vitamin C and beta-carotene were clearly regulated by lifestyle factors such as physical activity, intake of fruit, smoking, oral contraception, and obesity.
A statistical model allows predictions to be made about how bad lifestyle behaviors increase the chance of getting plasma concentrations below values of 6 micrograms/ml vitamin C and 0.22 micrograms/ml beta-carotene (see also image).