July 23, 2021
The Daily Mail reports that “consuming oily fish on a regular basis can reduce life expectancy more than smoking”. We look behind the headlines and give the BHF’s point of view.
A recent study suggests that low levels of omega-3 fatty acids in the blood can shorten your life just as much as smoking.
Omega-3s (the kind found in oily fish like salmon, sardines, and mackerel) can help keep your heart healthy, which is why we all recommend eating one serving of oily fish a week. Omega-3 fatty acids are said to help keep blood vessels healthy and lower blood pressure.
The researchers tried to find out whether the level of fatty acids in the blood could predict the risk of early death in the same way as other risk factors related to heart disease such as age, gender, smoking, and diabetes. This could help identify people at early risk of death and ensure they are receiving the right treatment to reduce their risk.
The study, published in the American Journal of Clinical Nutrition, tracked 2,240 people over an 11-year period. The researchers took blood samples from the participants to measure the levels of various fatty acids in their blood.
The researchers found that omega-3 levels were a useful predictor of life expectancy and compared well with established risk factors for accuracy.
On average, people with the lowest omega-3 levels lived 4.7 years less than those with the highest. Smoking had the same impact – 4.7 years of life lost compared to non-smokers.
The researchers found that life expectancy in Japan, where people eat more fatty fish and have higher levels of omega-3s, is five years longer than the United States.
The study’s authors conclude that there is a “strong link” between omega-3 levels and mortality, and that “the eating habits that alter omega-3s” [levels] can extend life. “
The study also looked at the levels of nine other fatty acids and found three that were related to life expectancy. People with higher myristic and behenic acid levels were more likely to live longer, while those with higher palmitoleic acid levels lived shorter. These fatty acids are less directly related to diet than omega-3s, although the authors suggest that myristic acid levels may be linked to dairy consumption, which has been linked to some health benefits.
The researchers said that while they expected an association between omega-3s and life expectancy, the other fatty acids were not necessarily what they would have expected. And unlike omega-3, there is no clear link between diet and levels of the other fatty acids in the blood.
They said their research suggests consuming more omega-3s (in fatty fish or in supplements) and not smoking are the biggest changes people can make to increase their life expectancy.
How good was the research?
One of the study’s strengths is that it looked at large numbers of people over a long period of time.
One weakness of the study is that it examines the risk of death in an elderly population, with a mean age of 65 at the start of the study and 76 years at the end of the study, so its results do not apply to the entire population. More studies are needed to see if these results are the same in other age groups. The study compared the accuracy of fatty acids in predicting risk of death with existing measurements (such as blood pressure, cholesterol levels, whether you smoke, and whether you have diabetes). The researchers point out that the existing metrics were developed from research on people who mean age 49, so they may not be equally accurate in older age groups. Risk factors can affect the life expectancy of an older person differently than that of a younger person.
It can also be difficult to compare the effects of omega-3 levels with smoking, especially since omega-3 levels can fluctuate. The study measured omega-3 levels, but not how much people smoked – just whether they smoked or not.
The BHF view
Senior Nutritionist Victoria Taylor says, “The inclusion of fish as part of a healthy, balanced diet has long been a recommendation in the UK and also a feature of the Mediterranean diet that has been linked to cardiovascular health benefits.
“But on average we eat far less than the recommended serving of fatty fish per week.
“Salmon, sardines or mackerel are all good and easy to get – try them in fish cakes, pasta or in a salad.”
How accurate was the media coverage?
The story has been featured in the Daily Mail, The Telegraph, and the Daily Express.
The Daily Mail says that “a lack of omega-3s in the diet can shorten life even more than smoking”. Research doesn’t say that. The main finding from research is that omega-3 levels could be used to predict the risk of death, as is the case with smoking. It found that smoking was associated with the same difference in life length as the lowest omega-3 levels compared to the highest. The Mail article suggests helpful ways to reduce risk, including diet and reducing tobacco and alcohol use.
The Telegraph reports: “A diet low in omega-3s can shorten life expectancy like smoking”. It’s important to remember that research like this can only point to a link, not cause and effect.
The Daily Express headline reads “How to Live Longer: One Food You Should Never Skip – It Can Shorten Your Life Expectancy” While the headline understandably seeks to make this research relevant to people’s lives, omega-3 is not a food, and the article does not further explain what “never skip” means in practice. The study only looked at blood omega-3 levels, not the amount of fatty fish or supplements you would need to consume to get the highest levels of omega-3s. It tells us that this is the case with “older adults”, although it would be even more useful to highlight the ages of the people involved.
None of the reports mention that research has found other fatty acids related to life expectancy, not just omega-3s.