A high intake of alpha linolenic acid (ALA) – found mainly in nuts, seeds, and plant oils – is associated with a lower risk of death from all causes, and specifically from diseases of the heart and blood vessels, according to a study published by The BMJ.
ALA is a type of omega-3 polyunsaturated fatty acid found in plants, such as soybean, nuts, canola oils and flaxseed. Higher ALA intake was, however, associated with a slightly higher risk of death from cancer.
An international team of researchers analysed the results of 41 studies published between 1991 and 2021 on the associations between ALA and risk of death from all causes, cardiovascular disease and cancer. These studies involved around 120,000 participants aged between 18 and 98 years, who were monitored for between two and 32 years, accounting for factors such as age, weight, smoking status, alcohol consumption, and physical activity.
After thoroughly assessing each study for bias, the researchers found that a high intake of ALA was associated with a 10%, 8%, and 11% lower risk of mortality from cardiovascular disease, and coronary heart disease, respectively.
A dose-response effect was found for dietary ALA intake and cardiovascular disease mortality, such that a 1 g per day increase in ALA intake (equivalent to one tablespoon of canola oil or 0.5 ounces of walnut oil) was associated with a 5% lower risk of cardiovascular disease mortality. Higher blood levels of ALA were also associated with lower risks of mortality.
Due to the observational design of included studies, causality cannot be established, nor can the researchers rule out the possibility that other unknown factors or measurement errors of food and nutrient intakes might have affected their results. Nevertheless, use of stringent study inclusion criteria together with rigorous and systematic evaluation of study quality suggests their conclusions are robust.
“Further studies should examine the association between ALA and a wider range of causes of death to provide a more comprehensive assessment of the potential health effects of ALA as well as to examine whether specific foods rich in ALA are differentially associated with mortality from cancer and other causes,” the researchers noted.
Despite the beneficial effects of omega-3 fatty acids, the research team noted that intake recommendations should be made cautiously because ALA might slightly increase the risk of cancer mortality. Further studies are, however, needed to examine this increased risk.
The full article can be read here: https://www.bmj.com/content/375/bmj.n2213