Dietary fats can be grouped into one of three main categories based on their structure. There are saturated fatty acids (SFA), monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA).
Any food that contains fat (nuts, seeds, whole grains, milk, beef, eggs etc.) will contain all three categories of fat, just in different amounts or ratios. This is just how fat is naturally stored in different foods.
As a nutrient, fat helps the body to absorb certain nutrients such as vitamins A, D, E and K and any number of carotenoids, pigments found in plants, like beta-carotene for example. Fat also enhances the pleasure of eating and is a source of energy for the body.
Of the three categories of dietary fat, two types of PUFAs, linoleic acid or LA (omega-6) and alpha-linolenic acid or ALA (omega-3) are considered essential because the body cannot make them on its own so the diet must provide them (1).
Omega-6 LA is found in grain and seed oils like corn, soybean, grapeseed, sunflower seed, and cottonseed, nuts and seeds, and animal foods like chicken and eggs. Omega-3 ALA is found in plant foods such as walnuts, flaxseeds, chia seeds, canola oil, and hemp to name a few (2).
Both the omega-6 fatty acid LA and the omega-3 fatty acid ALA are metabolized by the body into different derivatives (or metabolites) that support overall health.
FUN FACT: when referring to the ratio of omega-6 to omega-3, it’s the ratio of those fats in the total diet, the amount eaten over the course of days and weeks and not the ratio in a single food or serving. Remember to keep your eye on the big picture!
To further tease out the role of ALA, some of it is converted into two other forms of omega-3 fats: EPA and DHA. If you’ve ever heard about the health benefits of omega-3 fats such as supporting brain and eye health, mood regulation, reducing inflammation, supporting cardiovascular health, and more, it’s specifically the EPA and DHA form of omega-3s that are responsible.
The problem, however, humans don’t convert the ALA from walnuts, hemp, canola oil, etc., into EPA and DHA very well; in fact, the conversion rate is abysmal. Under ideal conditions, a mere 4 to 8% of the amount of ALA consumed makes its way to EPA and even less to DHA.
To make matters worse, research has shown that the vast majority of Canadians aren’t getting the recommended intake of the omega-3 fatty acids EPA and DHA either; an estimated 140 mg per day versus the recommended 250 – 500 mg per day.
Because of this, health experts recommend that Canadians regularly eat foods rich in EPA and DHA such as fish and seafood or omega-3 fortified foods like eggs, as well as, supplements if needed.
Omega-6 to Omega-3 Ratio
Despite the importance of these essential fats, getting too much of either one can interfere with how the other one functions. It’s estimated that ancestral/primitive diets provided omega-6s to omega-3s in a ratio closer to 1:1 to 4:1 (2). This is because, before industrialization, the human diet didn’t contain an imbalance of either one.
Over the past 100 years or so, there was a substantial shift in the North American diet where PUFAs are concerned.
Traditional animal fats were slowly substituted with vegetable oils and vegetable oil-based products such as shortening, margarine, salad dressings, used to make baked goods (everything from muffins to crackers, cereal bars, prepared and convenience foods), as well as, for frying.
This led to a significant increase in omega-6 consumption from about 13 g to 37 g/day. Omega-6 LA accounts for about 21% of our total fat intake (3). The resulting omega-6 to omega-3 ratio is now in the neighbourhood of 10:1 to 20:1 (2).
Imbalanced omegas – does it matter?
You might be wondering what the big deal is? Omega-6 and omega-3 fats carry out essential tasks in the body. They are involved in metabolic pathways that produce compounds that have hormone-like activity in the body.
This includes balancing both pro-inflammatory and anti-inflammatory actions. Neither is inherently bad; both are needed to be healthy and to thrive but the key is that they need to be in balance (4).
There is robust research showing that excess consumption of omega-6 LA can increase inflammation, promote chronic disease and aggravate existing chronic disease (5, 6).
Bringing back balance
Health experts agree that we would all benefit from bringing the ratio of omega-6 to omega-3 in the total diet closer to what it was before industrialization and the introduction and use of grain and seeds oils and products made with them.
The best way to do this to reduce the amount of grain and seed oils used in food preparation.
Also, reduce your intake of foods made with these oils (that involves reading ingredient lists). Include more EPA and DHA omega-3 rich foods such as fish and seafood.
Coldwater fish such as sardines, salmon, trout, mackerel, and herring have more EPA and DHA per serving. If you’re worried about the messaging around fish and mercury, don’t be. That only applies to a certain segment of the population AND fish and seafood that also contains selenium, offers protection against any trace amounts of mercury in those nutritious foods.
The majority of mercury exposure comes from the atmosphere from coal-burning plants
Also, include more fortified foods like eggs and if needed, consider a supplement (fish, calamari, algal oil if you want a vegan option or seal oil which also has a decent amount of the omega 3 fat DPA) to get your omega-6 to omega-3 ratio back in balance.
For more info:
Oregon State University – Linus Pauling Institute
Doug Cook RDN is a Toronto based integrative and functional nutritionist and dietitian with a focus on digestive, gut, and mental health. Follow me on Facebook, Instagram and Twitter.