Eating oily fish — such as salmon, sardines and mackerel — may help to protect the brain against the toxic damage of air pollution, a study has suggested.
Experts from the US studied the diet, pollution exposure and brain volumes of 1,315 senior women to see if omega-3 fatty acids might shield against air pollution.
The team found that the women who ate more than one or two servings of omega-3 rich fish a week had a larger hippocampus and white matter volume.
Furthermore, higher levels of omega-3 were found to be associated with smaller reductions in white matter volume when exposed to higher levels of air pollution.
Eating oily fish — such as salmon, sardines and mackerel, pictured — may help to protect the brain against the toxic damage of air pollution, a study has suggested
‘Fish are an excellent source of omega-3 fatty acids and easy to add to the diet,’ said paper author and epidemiologist Ka Kahe of New York’s Columbia University.
‘Omega-3 fatty acids have been shown to fight inflammation and maintain brain structure in ageing brains.’
‘They have also been found to reduce brain damage caused by neurotoxins like lead and mercury.’
‘So, we explored if omega-3 fatty acids have a protective effect against another neurotoxin — the fine particulate matter found in air pollution.’
Dr Kahe and colleagues found that people who lived on busy roads and had the lowest levels of omega-3 in their blood typically had fewer neurons than those who consumed more of the fatty acids.
Once controversial, the notion that dirty air damages the brain has gained popularity — along with mounting evidence in support of the theory.
It has been known since the 1970s that air pollution can increases the risk of heart and lung diseases.
More recently, high levels of air pollution have been linked to both poor cognitive abilities in children and an increased risk of cognitive decline — and possibly also depression — among adults.
‘Fish are an excellent source of omega-3 fatty acids and easy to add to the diet,’ said paper author and epidemiologist Ka Kahe of New York’s Columbia University. ‘Omega-3 fatty acids have been shown to fight inflammation and maintain brain structure in ageing brains’
In their study, the team polled 1,315 women — whose average age was 70 and who did not have dementia — about their diet, physical activity and medical history.
The researchers calculated how much fish each woman typically consumed per week — including broiled or baked fish, canned tuna, tuna salad, tuna casserole and non-fried shellfish.
Fried fish was not included in these calculations, as past research has shown that deep frying damages omega-3 fatty acids.
The team then performed blood tests on each participant to measure the levels of omega-3 fatty acids in the women’s red blood cells.
Dr Kahe and colleagues also used each participant’s home address to work out their three-year average exposure to air pollution.
Dr Kahe and colleagues found that people who lived on busy roads and had the lowest levels of omega-3 in their blood typically had fewer neurons than those who consumed more of the fatty acids. Pictured, sardines — one fish known to be rich in omega-3 fatty acids
Finally, the participants underwent magnetic resonance imaging — or MRI — scans to measure various areas of their brains.
These included the white matter, composed of nerve fibres that send signals throughout the brain, and the hippocampus — the part associated with memory.
The researchers found that those with the most omega-3 fatty acids had more white matter than those with the least — specifically, 410 cubic centimetres compared to just 403 (or 25, rather than 24.6, cubic inches).
Furthermore, the team noted that for each 25 per cent increase in air pollution the women experienced, their average volume of white matter was 11.52 cubic centimetres (0.7 cubic inches) smaller if they had low levels of omega-3 fatty acids.
This was compared with a decrease of just 0.12 cubic centimetres (0.007 cubic centimetres) among those with higher levels of omega-3 in their blood.
The participants who had the highest levels of omega-3 fatty acids were also seen to typically have a larger hippocampus.
This was so even after taking into account other factors that could affect brain shrinkage — including age, education and history of smoking.
‘Our findings suggest higher levels of omega-3 fatty acids in the blood from fish consumption may preserve brain volume as women age and possibly protect against the potential toxic effects of air pollution,’ said Dr Kahe.
‘It’s important to note our study only found an association between brain volume and eating fish. It does not prove that eating fish preserves brain volume.’ he added.
‘Since separate studies have found some species of fish may contain environmental toxins, it’s important to talk to a doctor about what types of fish to eat before adding more fish to your diet.’
The full findings of the study were published in the journal Neurology.
THE HEALTH CLAIMS SURROUNDING FISH OIL
Most of the health claims surrounding fish oil involve the essential fatty acid omega-3.
Omega-3 is thought to have a positive, anti-inflammatory effect, which can benefit a number of heath conditions and protect people from disease.
It is found in rich quantities in the flesh of oily fish including salmon and trout.
These acids are important because the body cannot make them itself, so they much be provided by diet or supplements.
Previous research has indicated that fish oil is most effective in supporting heart and brain health as well as reducing joint pain.