Doctor's Review: Medicine on the Move

August 20, 2017

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Later for you, antioxidants

Have you noticed a recent change in the language used to describe phytochemicals in our food? Why are we now talking about bioactive compounds rather than antioxidants?

The original evidence that phytochemicals were associated with better health came from observational studies. A 2010 study reported that consuming tea was linked to a reduced risk of death from coronary heart disease.1 In the past, this was believed to be due to the antioxidant effect of flavonoids tea, but recent research proposes a new mechanism of action: the flavonoids act by increasing nitric-oxide status and therefore the function of the cells lining the blood vessels.2 Other studies suggest that in vitro, the polyphenols in black tea inhibit tumor proteasome activity.3

Phytochemicals in foods have also been linked to a reduction of diabetes and treatments for type 2 diabetes mellitus (T2DM). Looking at 16 different traditional foods used in the treatment of T2DM, researchers at China Pharmaceutical University found that garlic in vitro and in animals lowered serum blood glucose levels. Interestingly, different mechanisms of actions have been proposed. One is the enhanced serum insulin levels combine with compounds like cysteine, which reduce insulin inactivation. The other is that garlic acts as an anti-diabetic agent by increasing the secretion of insulin from the beta cells of the pancreas or by increasing the liberation of bound insulin.4

This new information has led the USDA to remove the table of the antioxidant capacity of foods (ORAC values) from its website citing the following reason: “There is no evidence that the beneficial effects of polyphenol-rich foods can be attributed to the antioxidant properties of these foods. The data for antioxidant capacity of foods generated by in vitro (test-tube) methods cannot be extrapolated to in vivo (human) effects and the clinical trials to test benefits of dietary antioxidants have produced mixed results.”5

For its part, the European Food Safety Authority stated: “No evidence has been provided to establish that having antioxidant activity/content and/or antioxidant properties is a beneficial physiological effect.”6

Do we have to change our message to our patients? In part. We now can say that consuming phytochemicals is associated with better health outcomes, though we have not yet determined their mechanism of actions. That said, eating seven to 10 portions of vegetables and fruits, drinking tea and red wine as well as adding spices to foods is still the golden rule.

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  1. On August 21, 2012, Christine said:
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