Link Between Dietary Intake of Plant-based Essential Fatty Acids and Death Risk

Alpha-linolenic acid (ALA) is a type of omega-3 polyunsaturated fatty acid present in nuts, seeds, and plant oils that decrease death risk from all causes, especially from heart and blood vessel diseases.

Highlights:

Though alpha-linolenic acid(ALA) is associated with a lower risk of heart disease, its role in mortality has been inconclusive
To address this uncertainty, a meta-analysis of studies published based on this association was conducted
The analysis found that higher blood levels of ALA were also associated with lower death risk from all causes except cancer.

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, finds a study published in the journal The BMJ.

Adherence to a healthy diet can delay the onset of chronic diseases and improve longevity. Fatty acids are the major components of a healthy diet.

Low consumption of saturated fatty acids and trans fatty acids and high consumption of foods rich in polyunsaturated fatty acids, particularly omega 3 fatty acids has been a cornerstone of worldwide dietary guidelines.

However, the findings on the association between essential fatty acids and the risk of death have been inconsistent. In this article, the available findings are summarized.

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‘Higher blood levels of alpha-linolenic acid (ALA) were associated with a lower risk of cardiovascular disease mortality.’
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Alpha linolenic acid (ALA)

Alpha-linolenic acid (ALA) available in plant sources. Essential fatty acid means that it cannot be produced in the body. So, it must be obtained from the foods we consume.

This fatty acid is readily available in soybean, nuts, canola oils, flaxseed, and other plant food sources. ALA might have a preventive effect against heart disease and some cancers through its anti-inflammatory properties.

A recent meta-analysis concluded that a higher intake of ALA is associated with a lower risk of fatal heart disease, but findings from another meta-analysis indicated a positive association between dietary intake of ALA and prostate cancer risk.

Although some meta-analyses are available on the link between ALA and the risk of chronic diseases, no study has examined the association between ALA and death risk from all causes.

New Health Benefit

To overcome these shortcomings, a systematic review of studies with findings on the association between ALA and the risk of death from all causes by considering both dietary intake and tissue biomarkers of ALA was conducted.

An international team of researchers analyzed the results of 41 studies published between 1991 and 2021 that involved around 120,000 participants aged between 18 and 98 years who were monitored for between two and 32 years.

They also accounted 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 all causes, cardiovascular disease, and coronary heart disease, respectively.

This is equivalent to 113 fewer deaths per 10,000 person-years for all causes, 33 fewer cardiovascular disease deaths, and 23 fewer coronary heart disease deaths.

A higher intake of ALA was associated with a slightly higher risk of cancer mortality, equivalent to 63 extra cancer deaths for the highest compared with the lowest levels of ALA intake. This finding suggests that recommendations for ALA intake should be made cautiously.

A dose-response effect was found for dietary ALA intake and cardiovascular disease mortality, such that a 1g 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.

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, the use of stringent study inclusion criteria together with rigorous and systematic evaluation of study quality suggests their conclusions are robust. This adds to evidence of the potential health benefits of polyunsaturated fatty acids.

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.

Whether specific foods rich in ALA are differentially associated with death risk from cancer and other causes, need to be examined in the future.

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Alpha-linolenic acid- How to Take It

The recommended adequate intake of alpha-linolenic acid in the diet is listed below:

It's recommended that adult females consume 1.1 grams daily, and adult males consume 1.6 grams daily to maintain adequate nutrition.
When pregnant, 1.4 grams should be consumed daily, and when breastfeeding, 1.3 grams should be consumed daily.
Recommended amounts for children depend on age.
Speak with a healthcare provider to find out what dose might be best for a specific condition.

Amounts of alpha-linolenic acid in oils and foods:

Flaxseed has about 2.2 g per tbsp
Canola oil, 1.3 g per tbsp
Flaxseed oil, 8.5 g per tbsp
English walnuts, .7 g per tbsp

Dietary supplements should be taken only under the supervision of a knowledgeable healthcare provider.

References:

Dietary intake and biomarkers of alpha linolenic acid and risk of all cause, cardiovascular, and cancer mortality: systematic review and dose-response meta-analysis of cohort studies - (https://www.bmj.com/content/375/bmj.n2213)
Alpha-linolenic acid - (https://www.mountsinai.org/health-library/supplement/alpha-linolenic-acid)
Alpha-Linolenic Acid: An Omega-3 Fatty Acid with Neuroprotective Properties—Ready for Use in the Stroke Clinic? - (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4350958/)

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