It may not be surprising to hear that the human diet has evolved significantly over time and that the modern diet varies drastically across geographic regions. As well, not surprising, is the fact that the incidence of many diseases follow similar patterns. The question that has plagued nutrition researchers for decades is whether or not these two phenomena are related. Although they have successfully shown that many diseases, including heart disease and diabetes, are attributable to an unhealthy diet and sedentary lifestyle, many mysteries still remain.
Of great confusion to the world of science is the staggering increase in allergic disease over the past thirty years. For example, one disease that has developed into epidemic proportions in the industrialized world is asthma. In Canada, in the late 1970’s, the rate of childhood asthma was about 2.5% and rose to 11.2% by 1995. A similar trend occurred in countries such as England and Australia, and as many countries adopt the Western way of living, the worldwide rate of asthma continues to increase.
This evidence makes one wonder what has changed about the way we live during the last thirty years. Among the many ideas proposed, a theory popular within the nutrition community is that this mysterious increase in asthma prevalence is due to a corresponding decrease of omega-3 and an increase in omega-6 fats in the diet. The modern, or Western, diet differs from more traditional diets in the respect that it includes more processed, synthetic foods and less fruits, vegetables and fresh fish. An increased emphasis on cardiovascular health led to the replacement of animal and dairy fats, which are rich in saturated fats, with vegetable oils, which are rich in omega-6 fats. As a result, the consumption of omega-6 fats in the modern Western diet has greatly increased, while consumption of omega-3 fats has decreased. When we used to consume about five times more omega-6 fats than omega-3, we are now eating closer to 15-25 times more.
Not only has the relationship between omega-3 and asthma been investigated, but also the relationships between omega-3 and inflammatory bowel disease, attention deficit disorder, depression, cystic fibrosis, heart disease, stroke, rheumatoid arthritis and many others. Although there have been some promising results in these studies, there is no scientifically confirmed consensus on the role of omega-6 and omega-3 in the increasing prevalence of asthma and other disease. The relationship between the imbalance of omega-3 and disease makes sense biologically, but the lack of conclusive results from research makes it difficult to prove.
What are Omega-6 and Omega-3 fats?
Omega 6 and omega-3 fats can be found in different forms in different places in the food system. Omega-6 fats are found in their simplest form in plants where they exist as a molecule called linoleic acid (LA). Plant oils that are rich in this omega-6 fat include corn, soy, safflower and sunflower. Once we have eaten them, they can be converted to their slightly longer molecule, arachadonic acid (AA). This happens in our body, as well as within other mammals. So, when we eat animals that eat omega-6 from plants, we are eating arachadonic acid.
Omega-3 fats are also found in their simplest form in plants as a molecule called α-linolenic acid (alpha-linolenic acid: ALA). Plants that contain ALA include canola, flax, walnuts, and leafy greens. Within our body, ALA is converted to DHA and EPA, the active forms of omega-3 fats. Similarly to arachadonic acid, we can eat DHA and EPA by eating animals, such as cold-water fish. Omega-3’s can also be found in poultry and eggs, depending what the chickens eat.
For example, if a chicken eats corn, which is high in omega-6, its meat and eggs will also be high in omega-6. If the chicken eats flax seed, which is high in omega-3, its meat and eggs will be high in omega-3.
Omega-6 and omega-3 fats are essential to human beings, as they are to all mammals. Most other fats can be made within our bodies from proteins and carbohydrates, but these fats must be eaten in our diet. The amounts of these fats that we eat directly reflect the amounts that are stored in our bodies. Most of them are used to make up our cell membranes, the layer around each cell that holds the cells contents inside. They are stored in the membranes and used by our cells as needed.
Omega-3 and omega-6 have different functions than each other. One function of omega-6 fats is to promote inflammation (a process crucial to allergic response), while omega-3’s can act to prevent inflammation.
Changing Our Diet
If you are convinced by the omega-3 theory, there are changes that can be made in your diet. It seems to be a common misconception that to benefit from health effects omega-3’s, we must eat fish. This way of thinking could possibly have negative consequences on the environment, as it has been suggested that over-fishing has pushed global fisheries into a state of crisis. Taking fish oil, or DHA/EPA capsules, can be expensive and adds unnecessary calories (since they are fat, after all) to your diet. Also, the suggested problems related to omega-3 consumption are not just a low number of omega-3 fats in the diet, but also an excessively high amount of omega-6. Therefore, perhaps the most effective way to restore the balance between these two essential fats is to eat less omega-6, as well as more omega-3 fats. This can be achieved by replacing omega-6 rich oils in the diet with oils and foods rich in omega-3, or oils that are low in omega-6.
Unfortunately, it is difficult to avoid omega-6 rich foods in our current food system. Corn and soy oil, which are high in omega-6 fats, are produced in large quantities causing them to appear in all kinds of processed and pre-packaged foods. Therefore, it may take a little extra work and foresight to make a change in your diet.
Hemp seeds (left) and flax meal (right) — two excellent sources of omega-3.
1) Don’t buy salad dressings; make your own (or check the labels). Use oils such as canola and flax, which are rich in omega-3, or olive oil, which is low in omega-6.
2) Check labels. Many processed and pre-packaged foods are made with omega-6 rich oils, such as sunflower, soy, corn and safflower.
3) Use butter in baking, or canola-based margarines.
4) Add flax-seed to your baking and breakfasts. You must make sure it is ground, since our body cannot digest the whole seeds. Also, ground flax must be kept in the fridge or freezer, as it turns rancid quickly. Ground flax blends nicely into smoothies and can be sprinkled onto yogurt or cereal, which adds a pleasant, nutty flavor. When baking, replace some of the flour with ground flax. It doesn’t change the taste a lot, but adds extra omega-3, as well as fiber, another dietary necessity.
5) There are vegetarian EPA and DHA supplements available on the market: microalgae. This is where fish get their omega-3’s from.
Food sources of omega-6 and omega-3:
|Food high in omega-6 (eat less)||Foods high in omega-3 (eat more)||Foods low in omega-6 (eat more)|
|Corn oilSoy oilSafflower oilSunflower oilGrapeseed oil||Flax seed, flax oilCanola oilWalnuts, walnut oilHemp seed, hemp oilchia seeds||Olive oilAnimal and dairy fat (sparingly)|
Written by: Deanna Ibbitson, M.Sc., CPT