This week, the Daily Mail and the Express reported on the benefits of nuts and seeds, stating that snacking on them could halve the risk of premature death.
This comes following a study published in the American Journal of Clinical Nutrition into omega-6 fatty acid linoleic acid, for which nuts and seeds are a good source.
Study background and findings
The study was carried out following debate about the health effects of linoleic acid.
On the one hand, there was the view that it can reduce cholesterol levels and can increase the production of anti-inflammatory compounds, therefore helping reduce disease.
On the other hand, there was speculation that it may actually cause inflammation when it gets converted in the body into arachindonic acid, thereby increasing the risk of several chronic diseases.
The research aimed to clarify matters…
- 2,480 men aged between 42 and 62 years were followed for 22 years.
- Blood levels of the linoleic acid were taken during the study. These levels are determined by your diet.
- By the end of the study, 1,143 deaths due to disease had occurred.
- When grouped according to blood linoleic acid levels, the risk of premature death was 43% lower in the group with the highest linoleic acid levels, compared to the group with the lowest level. There was also a lower risk of death due to cardiovascular diseases, as well as for death due to reasons other than cardiovascular diseases or cancer.
- No specific association between omega-6 levels and death due to cancer was found.
- The researchers support the current dietary recommendations to increase linoleic acid intake for cardiovascular disease prevention.
Behind the headlines: the Nutrilicious dietetic view
Was it a valuable study?
The study had a few weaknesses:
- Only a single baseline fatty acid measurement was taken for all men. Dietary habits can change during such a long follow up period and this could alter the results.
- Higher levels of blood linoleic acid were associated with a more healthy lifestyle and diet. This could influence the results, meaning we cannot be absolutely sure it is just the levels of linoleic acid causing the effects.
- Only white middle-aged and older men were included in the study. We don’t know whether the findings would be the same for women and other races/ethnicities.
However, it also has considerable strengths:
- Large sample size
- No participants dropped out
- The researchers used an objective biomarker – blood levels of linoleic acid – rather than using dietary recall or assessment measures, which are not very reliable.
Translating the findings into practical guidance
To help prevent cardiovascular disease, current guidelines are that we should be limiting our intakes of saturated fats to 20g per day for women and 30g per day for men.
They should be replaced with unsaturated fats including monounsaturated and polyunsaturated fats, which provide essential fatty acids and fat-soluble vitamins.
Linoleic acid is the most common type of polyunsaturated omega-6 fatty acid, so we’d recommend unsalted nuts as a daily snack. Indeed, HEART UK state: “Nuts are packed full of heart-healthy nutrients such as protein, soluble fibres, plant sterols, vitamin E, magnesium, potassium, zinc and copper. Because they are also naturally rich in unsaturated fats and low in saturated fat they can help lower cholesterol as part of a diet low in saturated fats.”
A portion of nuts would be considered around 30-35g, which is about one handful (about 175-200 calories).
Nuts are quite high in calories, so those watching their weight may need to consider how and where this fits into a calorie controlled eating plan.
Remember the full picture
While the headlines focus on nuts and seeds, vegetable oils and plant-based spreads are also good sources of linoleic acid.
The shift from saturated to unsaturated fats should form part of an overall healthy diet, such as DASH (Dietary Approaches to Stop Hypertension) or the Mediterranean diet.
More detailed advice into dietary fats can be found from: