Fish only offers protection against heart attacks if you eat walnuts too
The omega-3 fatty acids in fish and fish oil capsules offer noticeably better protection against heart attacks in combination with alpha-linolenic acid - the omega-3 fatty acid found in walnuts, linseed and soya. Epidemiologists at the National University of Singapore write about it in the Journal of Nutrition.
The researchers used data gathered for the Singapore Chinese Health Study, in which 63,257 Chinese people aged 45-74 were followed from 1993 to 2010.
The researchers knew how much ALA, EPA and DHA the participants had in their blood, and divided the participants on the basis of this into four equal-sized groups - called quartiles. The participants in quartile 1 [Q1] had the lowest concentrations of fatty acid in their blood; those in quartile 4 [Q4] had the highest.
The more EPA, DHA and ALA the participants had in their blood, the lower the chance of them having a heart attack. DHA in particular was an important factor. The effect of ALA was somewhat less.
EPA and DHA improved cholesterol balance and lowered glyceride concentration. ALA had the same effect, and also lowered blood pressure. [Table]
The researchers discovered that the participants who had relatively large amounts of EPA and DHA in their blood only had good protection if there were also high amounts of ALA in their blood.
When there were only low amounts of ALA in their blood, EPA and DHA reduced the chance of a heart attack by 18 percent, according to the figure above. At a high ALA concentration, the reduction was as high as 49 percent.
"These results suggest that higher fish consumption can contribute to a substantial reduction in the incidence of acute myocardial infarction," the researchers wrote.
"We did not observe a linear association between plasma alpha-linolenic acid and risk of acute myocardial infarction, and the dose-response relation and possible underlying mechanisms require further research."
"Our results suggest that higher plasma alpha-linolenic acid concentrations may be beneficial even in persons with high plasma concentrations of long-chain omega-3 polyunsaturated fatty acids."
J Nutr. 2016 Feb;146(2):275-82.
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