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Nutrition and supplements (DHEA, Ginkgo Biloba, Omega-3): separating myth from fact

How can nutrition influence brain functions?

Assorted Fruits & VegetablesFirst of all, the brain consumes considerable amount of glucose. One of the earliest sign of dementia is a decrease in the ability of the brain to use glucose efficiently. As such a dysfunction is at the core of diabetes, some neuroscientists refer to Alzheimer’s Disease as Type 3 diabetes.

The brain is also a fatty organ. Fats are present in the neurons’ membranes to keep them flexible. These fats are the omega 3 and omega 6 fatty acids molecules. Our brain is dependent on dietary fat intake to get enough fatty acids. Omega-3 fatty acids can be found in cold-water fish (such as mackerel, herring, salmon, and tuna), kiwi, and walnuts. Docosahexaenoic acid, or DHA, is the most abundant omega-3 fatty acid in cell membranes in the brain.

In general, the brain is highly susceptible to oxidative damage. This is why antioxidant food has become popular for their positive effects on brain function. Antioxidants are found in a variety of food: Alpha lipoic is found in spinach, broccoli and potatoes; Vitamin E is found in vegetable oils, nuts, green leafy vegetables; Vitamin C is found in citrus fruit and several plants and vegetables. Berries are well known for their antioxidant capacity but it is not clear which of their many components has an effect on cognition.

Based on these observations, Dr. Larry McCleary (whose interview you will find at the end of this Chapter) recommend a diet containing fatty fish, vegetables and salads, non-starchy fruits (like berries) – that are high in free radical fighting compounds – and nuts.

As most people you probably have bought or thought of buying nutrition complements. Indeed it is hard to get all the good nutrients in one’s diet. The most common consumer purchase is herbal and vitamin supplements purported to improve memory. Table 2 shows you the most recent findings associated with well-known supplements such as Ginkgo biloba.

However one has to be cautious. One negative aspect of self-medication with herbal supplements is the fact that some products have been shown to counteract the effects of prescription and over-the-counter medications. For example, in 2001, Dr. Piscitelli from the National Institute of Health (NIH) showed a significant drug interaction between St. John’s wort (hypericum perforatum), an herbal product sold as a dietary supplement, and Indinavir, a protease inhibitor used to treat HIV infection. The herb has also caused negative interactions with cancer chemotherapeutic drugs and with birth control drugs.

Experts usually recommend a balanced diet, that is getting healthy nutrients (Omega-3, antioxidants, etc.) from the food you eat, rather than ingesting supplements. Few studies so far have shown that supplements are beneficial to brain health. More importantly the best dosage of these supplements is not known.

Supplement

Recent Evidence

DHEA

A steroid precursor to testosterone and estrogen purported to fight aging.

The conclusion of a two year study at the Mayo Clinic in Minnesota and University of Padua in Italy showed that DHEA did not improve strength, physical performance, or other measures of health. The study’s lead author, Dr. Nair (2006) said, “No beneficial effects on quality of life were observed. There’s no evidence based on this study that DHEA has an anti-aging effect.”
Ginkgo biloba

An over-the-counter “memory-enhancing” supplement.

In 2002 Dr. Paul Solomon from Williams College found that “when taken following the manufacturer’s instructions, ginkgo provides no measurable benefit in memory or related cognitive function to adults with healthy cognitive function.”

Dr. Burns (2006) from the University of Adelaide, Australia found longer-term memory improved in healthy fifty-five to seventy-nine year olds, but no other cognitive measure improved for younger participants.

Dr. Elsabagh (2005) from King’s College London found that ginkgo initially improved attention and memory. However, there were no benefits after 6 weeks, suggesting that a tolerance develops quickly.

A recent randomized trial (DeKosky et al., 2008), conducted in 5 academic medical centers in the United States and including 2587 volunteers aged 75 years or older with normal cognition, showed that G biloba at 120 mg twice a day was not effective in reducing the overall incidence rate of dementia.

Omega-3 fatty acids

Components of neurons’ membranes.

Dr. Fontani’s work at the University of Siena in Italy associated omega-3 supplementation with improved attentional and physiological functions, particularly those involving complex cortical processing.

Table 2. Summary of recent findings on supposedly brain-enhancing dietary supplements.

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This new online resource is based on the content from the book The SharpBrains Guide to Brain Fitness (May 2009, $19.95), by Alvaro Fernandez and Dr. Elkhonon Goldberg.

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