Exercise, Nutrition and the Brain

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July 23, 2013

This weekend, I attended a conference in DC that I’ve been looking forward to for months – Nutrition and the Brain. While most medical conferences have some ‘exciting’ aspects when new research is revealed, here almost every speaker discussed something that can personally affect all our readers and patients.

The talks covered many aspects of dementia – new concepts about causes and genetic predisposition; dietary factors including antioxidants and metals; and the effects of sleep — or lack thereof. There were talks on Parkinson’s, migraines, and … drumroll please … the effect of exercise on brain structures and function. In my next entry, I’ll mention some of the other highlights, but there’s enough remarkable research ongoing about using exercise to alter our cognitive future that I feel compelled to gush. The speaker, Kirk Erickson, PhD from the University of Pittsburgh, started with a quote by Mark Twain:

When I was younger, I could remember anything whether it had happened or not; but my faculties are decaying now and soon I shall be so I cannot remember anything but the things that never happened. It is sad to go to pieces like this but we all have to do it.

Fortunately, dementia is NOT inevitable. I hope to remember things that actually did happen into a happy, healthy, old age – but let me tell you this before I forget. The hippocampus is the part of the brain that is responsible for memory. In those over 50 years old, this area declines at a rate of 1-2% per year. In people with dementia, the average loss is 3-5% per year. This deterioration predicts conversion to Alzheimer’s. So, what does this have to do with exercise, you might ask. Physical inactivity has been shown to be a risk factor for dementia in humans — couch potatoes lose more of their hippocampus year by year than active people do.

Over 20 years ago, the molecular pathways that change with exercise were identified in rodents; we haven’t reached that level of knowledge in humans. For obvious reasons, it’s easier to look at rodent brains under a microscope than it is to look at ours. We know that in rodents, exercise causes changes mainly in the hippocampus, the memory area of the brain. New blood vessels and nerve connections form, and the rodents’ ability to learn is improved. For them, this means being able to find their food in a maze faster. We would hope for more sophisticated benefits.

In humans, studies have shown that 6 months of exercise improves executive function (such as switching tasks or organizing projects) as well as spatial memory and speed in problem solving. Ten years ago, it was shown that more physical activity was associated with a reduced risk of dementia. Following a 6 month exercise study, MRI studies showed that the hippocampus area increased by 2% in 1 year as opposed to the normal 2% decline during that year. That’s a big difference, especially if benefits continue to accrue year after year. Even if we can use exercise to just maintain hippocampal volume, we would be way ahead of those declining by 2% yearly – if volume and brain function go hand in hand. Stay tuned for more research on that.

Other studies have shown that a chemical called brain-derived neurotrophic factor (BDNF), which is concentrated in the hippocampus, increases with exercise. In rodents, this chemical protects the brain from damage resulting from strokes and trauma. Research is ongoing to see if this chemical, and others like it, are responsible for the benefits of exercise on brain function in humans. If so, could we use it in patients to avoid brain damage after similar insults?

With many of the studies described, I gained an appreciation for just how difficult these clinical studies are — you have to control for all the other factors so you know that the benefit subjects derive is truly just from the difference in exercise routines.

Some very basic points that are clear. Exercise can change the hippocampus volume by MRI. How this translates to improved function still is under investigation. But significantly, it shows that the brain can change — that it remains ‘plastic’ — and can adapt over time, even in older adults. This is a new concept. When I was in medical school, it was believed that once a brain cell died, you had one less brain cell — forever! Realize that the medications we use to treat dementia can NOT induce the same amount of change as 6 months of exercise can. In children, similar changes are seen in the hippocampus with exercise; it is not yet known how that affects brain maturation and development. This is definitely exciting territory for future research.

Why doesn’t exercise have the same effect on everyone? There’s the “Big Mac effect” – i.e., what one does outside of the training session — like eat a Big Mac and fries on the way home from exercising. Then there are multiple known genes that affect cognition. The most researched one is the ApoE4 allele, a gene variant that causes Alzheimer’s disease (AD). Although it is only responsible for a few percent of people with AD, having 2 copies of this gene is a sure path to dementia. I was pleasantly surprised to see that exercise could even overcome the effect of this ‘bad’ gene. As the saying goes, you can’t choose your parents, but perhaps we’ll see that people with a strong family history of AD can change their future by exercising and following a healthy diet (see below)

  • Many statistics about exercise and Alzheimer’s were discussed. Some of the most impressive were:
  • as much as 20% of AD in the US could be attributed to physical inactivity
  • only 6 months of exercise is enough to make a difference, even if the person has been sedentary for most of their life
  • there’s slower progression of AD in those with physical activity at least 3 times per week. The term ‘physical activity’ can include bowling, gardening, etc – not necessarily going to the gym.
  • And here are some more factoids from the nutrition talks:
  • intake of green leafy vegetables has the strongest correlation with positive cognitive changes, moreso than fruits;
  • Vitamin E intake is helpful in food, in terms of decreasing risk of AD. Higher doses are associated with increased risk of prostate cancer.
  • Vegan and vegetarian diets are associated with a trend toward better cognition (not a significant difference, statistically speaking). These diets are also associated with a decrease in death rate, especially in males, perhaps by as much as 14%. There was a decrease in deaths from heart disease and kidney disease, which in turn were probably related to a decreased incidence of diabetes in vegetarians.

I’m always pleased to share positive lifestyle changes that are good for you now and will continue to pay off later. In the next article, I’ll go over some other odds and ends from the conference, including the effect of sleep on the brain, but I had to share the exercise info first!

If you’re interested in learning more about a plant-based diet, you can go to the website of the conference organizer, Physicians Committee for Responsible Medicine: www.pcrm.org

For well-researched, organized info on food products without a commercial bias, and a supply of excellent recipes, go to the Center for Science in the Public Interest: www.cspinet.org. I highly recommend subscribing to their newsletter Nutrition Action.

Think of healthy food and frequent exercise as Tender Loving Care for your brain — treat it well and enjoy the ride!