A number of nutrients from commonly eaten foods have important in vivo antioxidant activity in humans. Antioxidant nutrients are of interest because there appears to be a link between the aetiology of certain diseases and free radicals. Obesity is one condition that is increasingly being associated with chronic low grade inflammation and a subsequent generation of high levels of oxidative stress that result in depletion of plasma antioxidants. The oxidative stress in obesity is though to derive primarily from macrophage infiltration of adipose tissue. This results in the secretion of a number of inflammatory cytokines including tumour necrosis factor alpha (TNF-α) and interleukin-6 (IL-6), as well as inhibition of the metabolic regulatory cytokine, adiponectin. Although oxidative stress is not the cause of the obesity, it is recognised that the high amounts of free radicals are involved in the development of many of the diseases associated with obesity.
Because the low grade chronic inflammation produced in obesity in associated with disease development, researchers1 have investigated the effects of synergistic antioxidant nutrient supplementation on the metabolic and oxidative stress associated with being overweight. The supplement contained resveratrol, green tea, α-tocopherol, vitamin C, n-3 polyunsaturated fatty acids and tomato extract and was administered for 5 weeks to 36 overweight but healthy men. The results showed that plasma levels of adiponectin increased by 7% in the treatment group compared to the control. Adiponectin is negatively associated with obesity and individuals with cardiovascular disease and diabetes have suppressed levels. Adiponectin is known to increase activity of acetyl-CoA carboxylase with subsequent increases in mitochondrial β-oxidation. Supplementation with the antioxidant nutrients did not however alter plasma levels of the systemic marker of inflammation, C-reactive protein.
The researchers also detected a number of subtle changes in inflammatory markers that suggested that the antioxidant nutrient mix was effective at reducing oxidative stress. The number of pro-inflammatory eicosanoid precursors was reduced and at the same time anti-inflammatory eicosanoid precursors increased. In addition, favourable changes in expression of a number of genes associated with anti-inflammatory actions and favourable changes in cytokine ratios were observed. Beneficial changes in aggregation and coagulation markers were also detected. Concentrations of some markers of oxidative stress were also reduced. Interestingly, the supplemental antioxidant regimen caused plasma concentrations of total, HDL and LDL cholesterol to increase, and triglyceride levels to decrease. Taken as a whole these result show that even short term supplementation (5 weeks) with antioxidant nutrients found in food, reduces some markers of oxidative stress in humans.