Alzheimer’s and other forms of dementia are not an inevitable part of ageing, and it’s not a mainly genetic disease.
Professor David Smith, Oxford University
The number of New Zealanders living with dementia is expected to triple by the year 2050, from 50,000 to 150,000, according to Alzheimer’s New Zealand.
But Oxford University emeritus professor David Smith says memory loss and cognitive impairments are not a normal part of ageing but a preventable lifestyle disease.
Professor Smith is in New Zealand this month to meet colleagues at Brain Research New Zealand, a Centre of Research Excellence that brings together brain scientists from 67 research groups throughout New Zealand.
He says relatively simple dietary changes could prevent or slow down the loss of brain cells and neural connections seen during the early stages of Alzheimer’s disease.
There is a big difference between the brain of somebody who suffers from Alzheimer’s disease and a normal brain, he says, with 30 or 40 per cent of brain tissue lost as the condition progresses.
We can’t cure it. Once you’ve got it, you’re not going to be able to put back the nerve cells and connections that have gone, and even if you could, you wouldn’t recover the memories that have been lost. But there are ways of slowing down the shrinkage of the brain.
In a trial of 250 people with mild cognitive impairment, his team showed that the rate of brain atrophy can be slowed down by more than half by adding vitamins from the B complex to the diet.
“We are looking at some of the B vitamins – folic acid, Vitamin B12 and Vitamin B6 - because they control the level of an amino acid in the blood called homocysteine, which seems to be toxic for the brain,” he says.
“People with higher levels of homocysteine in the blood show a faster rate of shrinkage of the brain than people with low or normal levels.”
Professor Smith says raised homocysteine levels in the blood are one of the leading causes of Alzheimer’s disease, “probably because it’s got many different ways of damaging the brain”.
In the original study, people with mild cognitive impairment were given the vitamin and those with high levels of homocysteine showed markedly slow rates of brain shrinkage, by as much as 53 per cent. But Professor Smith says the team also uncovered another connection.
“Omega-3 fatty acids could also play a role and have a protective effect. We measured blood levels of omega-3 fatty acids at start and the end of the two-year trial and showed that if B vitamins were present, omega-3 was as a protective agent.
“The higher the level of omega-3 fatty acids in your blood the better the B vitamins work at slowing the brain shrinkage.”
Both omega-3 fatty acids and B vitamins can be taken up as part of a healthy diet, but in older people the normal absorption may not be working sufficiently well. Professor Smith’s recommendation is that people who develop memory problems have their homocysteine levels measured and if they are high, they should take high-dose supplements of Vitamin B12 and folic acid.
He says the trial results also show that Alzheimer’s and other forms of dementia are not an inevitable part of ageing but a lifestyle disease “in the sense that our diet is no longer sufficient to keep our brains healthy”.
“There are genetic elements which increase the risk but the genes that cause it are extremely rare. What we need to do it to identify the risk factors that we can modify … and if we can persuade people to develop a better lifestyle we could reduce the incidence of dementia by half.