Natural vegetable oils are a good source of omega-6 fatty acids. [photo: Bigstock]

Time to rethink omega-6 fatty acids?

1 April, 2016

We all know that omega-3s are good and omega-6 are…not so good. Right?

Except it is never that simple and, especially when it comes to fats, – as we have learned from the saturated fats debacle – absolutes often make poor nutritional advice.

Interesting new research at The Ohio State University has found, for example, that th erisk of heart disease and diabetes may be lowered by a diet higher in omega-6 fats.

Specifically the study found that men and women with higher linoleic acid levels tended to have a lower risk of heart disease and diabetes. But the study also had some things to say about how our diets can easily get out of balance.

What you need to know

» Linoleic acid is an omega-6 fatty acid, adequate levels of which are associated with lower risk of heart disease and diabetes and lower weight.

» However, in an attempt to get us to consume higher levels of omega-3, which many of us don’t get enough of, we may be creating yet another imbalance – too little omega-6 in our diets.

» Researchers in the US have found that vegetable oils are changing – often through genetic modification – to have less and less omega-6 and that this may have an impact on our health.

Higher linoleic acid levels also meant lower likelihood of insulin resistance, a precursor to diabetes.

Linoleic acid is an omega-6 fatty acid that is a major component of most vegetable oils. This fatty acid is an essential nutrient and comprising 50% or more of most vegetable oils.

This finding could have obvious implications in preventing diseases of the metabolic syndrome, but also could be important for older adults because higher lean body mass can contribute to a longer life with more independence, said Ohio State’s Martha Belury, a professor of human nutrition and expert in dietary fats, who led the research.

About the study

The study, which appears in the journal Molecular Nutrition & Food Research, used data from two previous studies that focused on stress and included 139 people. In those studies, researchers assessed body composition using DXA scanning, an advanced way of measuring fat and muscle mass.

They tested blood drawn after the men and women fasted for 12 hours, calculating the amount of linoleic acid (found in vegetable foods), oleic acid, (found in olive oil and some other vegetable oils), and long-chain omega-3 fatty acids (found in fatty fish including salmon and tuna) in red blood cells.

They also evaluated the blood for insulin resistance and two markers of inflammation that are connected with disease.

Looking at other oils too

Those with higher levels of linoleic acid tended to have less heart-threatening fat nestled between their vital organs, more lean body mass and less inflammation

Though inflammation decreased as blood levels of other fatty acids rose, higher levels of oleic acid or long-chain omega-3s did not appear to have any relationship to body composition or signs of decreased diabetes risk despite longstanding recommendations that people eat more of these ‘healthy’ fats.

The current study is the first study to examine linoleic acid alongside body composition and other health markers in people who hadn’t been given supplements or prescriptive diets, says Belury.

An unexpected effect of GMOs

But there’s a catch to the apparent food news about omega-6s. Cooking oils rich in linoleic acid are slowly disappearing from grocery shelves, fuelled by industry’s push for oils higher in oleic acid.

In the US, consumption of linoleic acid is declining because of genetic modification of plants for food manufacturers seeking oils higher in oleic acid, Belury said.

There’s been a pronounced shift in the last five years, and it is linked to the push against trans fats. When linoleic acid is made solid (hydrogenated) for processed foods, it is more likely to convert to trans fat than its oleic cousin.

So oils, notably safflower, sunflower and soybean, now routinely contain less linoleic acid – it often makes up less than 20% of the fatty acids in commonly purchased oils, based on food labels and confirmed by testing in her lab, Belury said.

So what now?

The study which only looks at associations can’t explain why linoleic acid helps reduce the risk for heart disease and diabetes. But it does bring up an interesting point about nutritional messaging.

For years we’ve been told that our diets contain too much omega-6 – and this may even have been true.

Too much omega-6 can produce inflammation in the body and as a result many of us have absorbed the message that we should avoid omega-6 in favour of omega-3. In fact, the risk of inflammation seems to be more likely in those who already have health challenges than in healthy people, but this wrinkle in the story has not been well explored. The marketplace has supported this message, as the researchers point out, by producing oils that are lower in omega-6, and as a result a creeping shift in our diets may be taking place.

Previous research found that taking linoleic acid supplements increased lean body mass and lowered fat in the midsection. As little as a teaspoon and a half was all it took, Belury says. Similarly because of research showing cardiovascular benefits of linoleic acid, the American Heart Association recommends that people take in at least 5-10% of their energy in the form of omega-6 fatty acids, which includes linoleic acid.

Finding balance

If you don’t want to eat GM soya or corn oils, grapeseed oil (which is not genetically modified) remains an excellent source of linoleic acid, which constitutes about 80% of its fatty acids. Don’t cook with it – add it to salad dressings and other cold preparations.

Supplementing with borage oil is also a good choice since borage contains high levels of omega-6 gamma linolenic acid (GLA), an essential fatty acid with strong anti-inflammatory properties.

Recent research has also shown that organic dairy products have a much more favourable balance of omega-6 to omega-3 – and balance is what it’s all about.

In fact we all need a range of fats in our diet – including some saturated fats. Anthropological research suggests that our hunter-gatherer ancestors consumed omega-6 and omega-3 fats in a ratio of roughly 1:1. In contrast the modern diet has long been thought to contain 14-25 times more omega-6 fatty acids than omega-3 fatty acids (a ratio you will often see written as 14:1 to 25:1). While there is no hard and fast rule, the omega-6 to -3 ratio should range from 1:1 to 5:1 – and a 2:1 ratio is considered optimal by many experts.

If you’ve been carefully avoiding any omega-6 in favour of ‘healthy’ omega-3 this potentially could create an overbalance of omega-3 in the other direction.

In the end, our fat consumption, like so much else needs to be conscious. Omega-6 is in pure vegetable oils like safflower, sunflower, corn, soya and cottonseed oils and raw nuts, often in a good balance to omega-3. But omega-6 vegetable oils are also key ingredients in processed and convenience foods and so hidden away in things like mayonnaise, margarine, crisp and other pre-prepared and snack foods.