Natural antioxidants found in fruits and vegetables, like polyphenols, provide protective effects for the brain through a variety of biological actions. Polyphenols are plant metabolites; the most common dietary polyphenols, and probably most thoroughly investigated, are the flavonols quercetin and catechin as well as the recently popular non-flavanoid resveratrol. Resveratrol is present in red wine and the skin of grapes. Plants use resveratrol to defend itself from fungus. Resveratrol is the focus of many current clinical trials and is believed to be responsible for the “French Paradox.” Quercetin is found in apples, tea, capers, and onions. Polyphenols are everywhere in nature! More than 50 different plant species and over 8000 such compounds have been identified in plant extracts. Obviously, investigating the multiple health benefits of these natural chemicals poses an enormous challenge.
Green tea polyphenols are believed to be strong antioxidants. Tea contains a number of bioactive chemicals and is particularly rich in flavonoids. In neurodegenerative diseases, administration of green tea extracts reduced the production of mutant proteins and may prevent neuron cell death in Alzheimer’s disease. Although tea is not a cure for Alzheimer’s disease, its use is certainly justified given its safety and potential for long term benefits. Similar chemicals extracted from grape seeds may offer similar benefits.
Baicalin, an ancient Chinese herbal medicine extracted from the root of the Scutellaria genus of plants, is a flavonoid that has been shown to inhibit the aggregation mutant proteins in the brains of patients with Alzheimer’s disease. Curcumin, derived from spice turmeric, the powdered rhizome of the medicinal plant Curcuma longa Linn, has been used for many centuries throughout Asia and India as a food additive and a traditional herbal remedy. I have published studies showing that curcumin has potent anti-oxidative and anti-inflammatory proclivities that may be beneficial for patients with either Alzheimer’s or Parkinson’s disease.
Interventional studies of patients with either Alzheimer’s or Parkinson’s disease using synthetic compounds have proven difficult to perform due to their toxicity, tendency to cause cancer or difficulty of administration. Therefore, treatments with natural anti-oxidants and anti-inflammatories via the diet or dietary supplements are becoming attractive alternatives. Unfortunately, very few clinical trials using polyphenol supplementation in humans have been performed. Also, we do not know how well many of these chemicals are absorbed after ingestion, how they interact with other components of the diet, their metabolic fate in the liver, or how well the brain is able to absorb them. In spite our current ignorance about the specific actions of these plant extracts, the epidemiological and preclinical data strongly indicate that they are much more beneficial than eating anything from a cow.
© Gary L. Wenk, Ph.D. Author of Your Brain on Food (Oxford University Press)