Eating fish may protect our brains against air pollution

• The benefits of omega-3 fatty acids, found naturally in many fish, are plentiful
• A new study looked at how fish consumption may reduce the effects of air pollution on the brain
• Eating just one to two servings of fish a week can provide striking benefits

Fish is a phenomenal source of protein and healthy omega-3 fats. Omega-3s are essential fatty acids that our bodies can’t produce, and must, therefore, come from our diet.

Among their benefits are: helping to control mood and cognition, preventing brain conditions such as Alzheimer’s, and anti-inflammatory properties. This means they can protect against heart disease, notes Women’s Health. And to add to this list is a new discovery: eating one to two servings a week of baked or broiled fish or shellfish may counteract the effects of air pollution on the brain.

This is according to a study published in the online issue of Neurology, the medical journal of the American Academy of Neurology. The study results were based on the assessment of 1 315 older women who lived in areas with high air pollution and ate more than one to two servings a week of fish or shellfish per week.

Fried fish excluded

Some fish are healthier and more sustainable than others as a result of contamination and overfishing, for example, and the link between nutrition levels and the way the fish is cooked is also vital. For the purposes of this study, fried fish was therefore excluded, as research indicates that deep-frying damages omega-3 fatty acids.

This 2010 study, for instance, found that cooking and microwave heating tuna better retain the health benefits of its fatty acids, compared to frying and canning. Another study published in the Natural Medicine Journal found that eating fried fish one or more times per week was associated with a 48% increase in risk of heart failure.

"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," said study author Ka He, M.D., Sc.D., of Columbia University. 

Taking a deeper look

The women included in the study were on average 70 years old, and were reported not to have dementia at the start of the study. All participants completed questionnaires about their diet, physical activity, and medical history.

The diet questionnaires were used to calculate the average amount of fish each woman consumed each week, which included the following: broiled or baked fish, canned tuna, tuna salad, tuna casserole and non-fried shellfish.

This was followed by blood tests, which the researchers used to measure the amount of omega-3 fatty acids in the women's red blood cells. They were then divided into four groups based on the amount of omega-3 fatty acids in their blood.

White matter: findings

Participants’ home addresses were used in order to determine their three-year average exposure to air pollution; they then underwent brain scans with magnetic resonance imaging (MRI) to measure various areas of the brain. These included white matter (tissue in the brain composed of nerve fibres) and the hippocampus (associated with memory).

After adjusting for age, education, smoking and other factors that could affect brain shrinkage, the research team found the following:

• Women who had the highest levels of omega-3 fatty acids in their blood had greater volumes of white matter than those with the lowest levels. 
• Those in the highest group had 410 cubic centimetres (cm³) white matter, compared to 403 cm³ for those in the lowest group. 
• For each quartile increase in air pollution levels, the average white matter volume was 11.52 cm³ smaller among people with lower levels of omega-3 fatty acids and 0.12 cm³ smaller among those with higher levels.

Another interesting finding was that women with the highest levels of omega-3 fatty acids in their blood also had greater hippocampus volumes.

No proof that fish consumption preserves brain volume

"Our findings suggest that 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," He said, adding:

"It's important to note that our study only found an association between brain volume and eating fish. It does not prove that eating fish preserves brain volume.”

He also explained that separate studies have found some species of fish may contain environmental toxins, so it’s important that one talks to one's doctor about what types of fish to eat before adding more fish to one's diet.

Things to consider

As with most studies, this study also has its limitations in that the majority of the participants were older white women. As a result, the team cautioned that their findings won't necessarily apply to other groups.

More than this, they noted that they were only able to assess exposures to later-life air pollution and therefore encouraged further studies to look at early or mid-life exposures to air pollution.

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