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Blood pressure news
Mercury fears are no reason to stop eating fish
Researchers have found that mercury in fish and shellfish could raise blood pressure levels by very small amounts. However, the study's authors encourage everyone to keep eating fish because the benefits far outweigh the concerns.
Oily fish contain high levels of omega-3 oils that have been shown to reduce the risk of heart attacks, strokes and heart disease. It is recommended that everyone should eat at least two fish meals a week – one of which should be an oily fish (such as salmon, trout, herring, tuna or sardines).
This Canadian research looked at mercury and blood pressure levels in native inuit communities in Quebec. These people's diets tend to be rich in fish, whale and seal meat and are they known to eat greater amounts of mercury than other populations because of this.
It is also known that mercury can affect the lining of the blood vessels, making it more difficult for them to relax and open out.
In total, 732 adult inuits were studied. They had an average blood mercury level that was roughly 12.5 times that of an average American (50 nmol/l of mercury compared with just 4 nmol/l).
After allowing for other blood-pressure raising factors, such as lifestyle issues and age, it was found that mercury does raise blood pressure. However, the effect is very small – a 10 per cent rise in mercury levels only produces a 0.2mmHg rise in blood pressure. So, if your blood pressure is 120/80, then eating 10 per cent more mercury will only raise your blood pressure to 120.2/80.
The study's authors note that the benefits of eating omega-3 fish oils far outweigh the negative effects of mercury and have encouraged everyone to continue to eat fish at least twice a week to protect their hearts.
The best approach appears to be to continue to eat fish, but to eat those that contain the highest levels of omega-3 oils, while avoiding the ones that contain the most mercury:
- fish that are high in omega 3 – try to eat these: salmon, trout, herring, sardines
- fish that are highest in mercury – try to avoid these: swordfish, marlin, shark and king mackerel.
Valera B, Dewailly Éric and Poirier P. Environmental Mercury Exposure and Blood Pressure Among Nunavik Inuit Adults. Hypertension Published online before print October 5, 2009, doi: 10.1161/HYPERTENSIONAHA.109.135046
Topics: Lifestyle, High blood pressure