What dementia research is teaching us about diet, exercise and stress

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In a segment on ABC TV’s 7.30 program this week dementia was described as ‘the tsunami that’s bearing down upon us’. So what are we learning from prevention trials?

As the segment pointed out, dementia affects 400,000 Australians and that number is expected to soar over coming decades.

Prevention trials are investigating brain training, nutrition and exercise and the combination of all three.

Amy Reichelt is a young British neuroscientist working in Canada. She’s interested in how diet, exercise and stress affect the brain, which means she spends a lot of time in a lab with rats and mice since that’s where most brain research starts.

Her work shows that high sugar diets reduce the capacity for decision-making and behaviour control. At least in rodents. Eating sugar makes them want to keep eating it, and if possible they do.

But human studies are backing that up. Research at Macquarie Uni found that people who regularly eat high-fat, high-sugar foods are more likely to crave snack foods even when they’re not hungry.

The same people also performed worse on memory tests after just four days of eating a high-fat, high-sugar breakfast.

Along the same lines, a Sydney Uni study showed that people who joined an I Quit Sugar diet program had better memories by the end of the program.

Sugar consumption — or maybe it’s sugar + fat consumption — appears to have a negative impact on the function of the hippocampus, the part of our brain that regulates motivation, emotion, learning and memory. It also enables us to build an internal map of our surroundings, so we know where we are.

The Mediterranean diet is a key feature of studies on nutrition and dementia prevention. One theory argues that excess dietary sugar promotes inflammation in the hippocampus, impairing its function. The Mediterranean diet, with its seafood, olive oil and vegetables, is anti-inflammatory.

The woman featured in the 7.30 story was shown playing table tennis. She said that the more oxygen she got into her brain through exercise the more normal she felt.

Rats and mice who run on wheels show more growth factors in their brains. Growth factors are chemicals that stimulate new cell growth, increase the formation of synapses, and help grow new blood vessels. More blood vessels mean more blood flow and oxygen delivery to the brain.

This new growth also improves learning capacity and protects against mental decline. It’s what we’re referring to when we talk about ‘neuroplasticity’.

People who exercise regularly are said to have a bigger hippocampus, suggesting they have more of this new cell growth and supposedly, better memory.

Normally, growth of new brain cells slows with age and very low levels go hand-in-hand with dementia, so it’s argued that staying active can help to maintain our brains as we get older.

The good news is that about half an hour of moderate activity such as walking, swimming or even housework most days of the week is enough to provide this stimulus for the growth of new cells. As a rule, exercise that’s good for our heart is good for our brain.

The 7.30 segment also discussed drug trials aimed at lowering the stress hormone cortisol. High cortisol levels destroy cells in the hippocampus and may be a factor in increasing the risk of dementia. It has the opposite effect of exercise. But a useful benefit of exercise is that for many people it also relieves stress.

The upshot so far? Keep doing your cryptic crossword but if you want to keep a healthy brain in the future, skip the sugary food, manage your stress and get into a regular exercise habit.

Photo source: Bigstock

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