From the Guidelines
Linoleic acid (LA) is a crucial omega-6 fatty acid that plays a significant role in human health, particularly in lowering LDL-cholesterol and triglyceride-rich lipoproteins, raising HDL-cholesterol, and exhibiting anti-inflammatory and insulin-sensitizing effects. According to a comprehensive review published in Circulation in 2016 1, LA consumption has been shown to have numerous health benefits, including reducing the risk of cardiovascular disease and type 2 diabetes. The study highlights that LA is an essential fatty acid that must be consumed in the diet, as humans cannot synthesize it.
Some of the key benefits of LA include:
- Lowering LDL-cholesterol and triglyceride-rich lipoproteins
- Raising HDL-cholesterol
- Exhibiting anti-inflammatory and insulin-sensitizing effects
- Reducing hepatic steatosis and systemic inflammation
- Increasing lean muscle mass
- Reducing the risk of coronary heart disease (CHD)
It is essential to note that while some studies have suggested that LA may have pro-inflammatory effects, the evidence from human studies is limited, and the majority of the evidence suggests that LA has anti-inflammatory effects 1. Additionally, the study found that higher biomarker levels of arachidonic acid, a metabolite of LA, are linked to significantly lower risk of CHD.
In terms of dietary recommendations, the study suggests that consuming LA-rich vegetable oils in place of animal fats can reduce CHD events 1. However, it is crucial to maintain a balanced ratio between omega-6 and omega-3 fatty acids, ideally between 4:1 to 1:1, to optimize health benefits. Overall, the evidence suggests that LA is a vital component of a healthy diet, and its consumption should be encouraged as part of a balanced dietary pattern.
From the Research
Role of Linoleic Acid in Human Health
- Linoleic acid (LA) is the most abundant polyunsaturated fatty acid in human nutrition, with an average daily intake of about 14 g in the US diet 2.
- LA is a direct precursor of the bioactive oxidized linoleic acid metabolites and arachidonic acid, which produces pro-inflammatory eicosanoids and endocannabinoids 2.
- A majority of studies on LA and its derivatives show a direct/indirect link with inflammation and metabolic diseases, with many authors claiming that high LA intake may promote inflammation in humans 2.
Cardiovascular Effects
- The cardioprotective effect of n-3 fatty acids, particularly in the secondary prevention of sudden cardiac death due to arrhythmias, is well-established, but the role of LA is more complex 3.
- Some studies suggest that a high intake of LA may be associated with improved cardiovascular risk, including a better plasma lipid profile, long-term glycaemic control, and insulin resistance 4.
- Observational data show that elevated dietary intake or tissue levels of LA are associated with a reduced incidence of cardiovascular diseases, particularly coronary artery diseases, and new onset metabolic syndrome or type 2 diabetes 4.
Inflammation and Metabolic Diseases
- The interaction between omega-3 and omega-6 fatty acids and their lipid mediators in the context of inflammation is complex and not fully understood 5.
- While some studies suggest that LA may increase inflammation, others have found that increased intake of LA does not increase inflammatory markers, and may even be linked to reduced inflammation 5.
- A high omega-6 fatty acid diet may inhibit the anti-inflammatory and inflammation-resolving effect of omega-3 fatty acids, highlighting the need for further research on the balance between these fatty acids 5, 6.
Dietary Sources and Metabolism
- LA and alpha-linolenic acid (ALA) are essential fatty acids that cannot be synthesized by humans and are mostly obtained from the diet, with food sources including vegetable oils, cereals, and walnuts 3, 6.
- LA is metabolized into arachidonic acid, which gives rise to pro-inflammatory eicosanoids, whereas ALA is metabolized into eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which give rise to anti-inflammatory eicosanoids 6.