Transfats cause nutritional deficiencies
This page was updated and greatly expanded in November 2005.
What are omega-3 and omega-6?
Most people know that if you want to stay healthy, your diet has to include sufficient amounts of vitamins and minerals, but few people know that two special fats are also essential for human health. They are the polyunsaturated fatty acids omega-3 and omega-6. Our bodies need them to make both cell membranes and signalling molecules such as hormones, but unlike other forms of fat they can't be manufactured inside the body and must come from our diet. Because every cell in our body needs them, most of the bad effects of eating trans fats stem from the ways they disrupt our bodies' use of these essential fatty acids (EFAs).
Modern Western diets are deficient in omega-3
While omega-6 (linoleic acid) is plentiful in the modern Western diet because it is found in most vegetable oils, omega-3 has become very scarce in the food we eat. Small amounts are found in leafy green vegetables, walnuts, flaxseeds and wheat germ, but this is short-chain omega-3 (alpha-linolenic acid) and not the long-chain forms our brains and nerve cells require for healthy functioning (docosahexaenoic acid or DHA and eicosapentaenoic acid or EPA).
The best source of these long-chain omega-3s is cold-water oily fish, such as herring and mackerel, but we are eating much less of this than in the past. It used to be assumed that most people's bodies could build the long-chain forms given an adequate intake of short-chain omega-3, but we now know that without sufficient quantities of other vitamins and minerals (also deficient in many people's diets) this conversion cannot take place. Other factors, such as old age or the stress so common in modern life, can also hinder this process.
Trans fats make this deficiency worse
On top of all this, consumption of trans fats throws a further spanner into the works as our bodies attempt to build long-chain omega-3. We know that trans fats hinder the work of the delta-6 desaturase enzyme, which together with elongation enzymes converts short-chain omega-3s into long-chain omega-3s.
The other ways in which they interfere with the metabolism of omega-3 are not as well understood. However, our cells need both short- and long-chain omega-3s to build their membranes and some of the molecules which they use to signal each other. The body has no way of distinguishing between trans and natural forms of omega-3, so if you eat trans fats, you will end up with twisted molecules in your cell walls and hormones. So they are not likely to work as well as they should, just as a shed built from warped timber will not keep out the rain as effectively as one built with straight boards.
Omega-3 deficiency linked to many diseases
So it may well be the case that even if you eat enough omega-3 (dining on oily fish twice a week, say), but also consume trans fats, you will be deficient in properly-formed long-chain omega-3. The health consequences of this can be seen in almost every chronic disease that afflicts modern society.
Low levels of EPA and DHA are a major factor in heart disease and strokes, but they also worsen inflammatory conditions such as arthritis and allergies. They are also known to promote insulin resistance, which leads to diabetes, and to accelerate the development of cancer. And as if that weren't bad enough, we are increasingly discovering that lack of omega-3 (particularly of EPA) plays a major role in the development of mental illnesses, such as clinical depression, including post-natal depression, and hyperactivity in children.
Ratio of omega-3 to omega-6 is also crucial
The foods eaten by human beings prior to agriculture (and by our pre-human ancestors), such as wild game, leafy green vegetables and fruit, contained relatively high amounts of omega-3 and low amounts of omega-6, so that our ancestors consumed equal amounts of both essential fatty acids, in other words, a ratio of 1:1. This is the ratio that our bodies have evolved to expect.
When humans started growing cereal grains, which are high in omega-6, our diet began to shift away from that fundamental ratio, yet people in many pre-modern societies enjoyed good health and freedom from degenerative diseases because they continued to eat many foods high in omega-3, such as meat from grazing animals, wild fish and wholemeal bread.
But when it was discovered that wheat could be milled by high-speed rollers in such a way that all the bran and germ could be stripped out, leaving only starch, and then that cattle and other animals could be fattened cheaply on a diet of grain, and finally that chemicals and industrial processes could be used to extract oils from seeds such as cotton and soy, human diets changed far more profoundly.
White bread lacked any essential fatty acids as well as most other nutrients (a few of these are now put back into flour but not the EFAs). Meat-and dairy products as well-became high in omega-6. The new oils were cheap but almost all were also very high in omega-6. So now the typical modern Western diet, instead of having equal amounts of the two essential fatty acids, has 20 to 25 times more omega-6 than omega-3.
While not all experts agree that we must return to the ancient ratio of 1:1 (some believe that humans can enjoy long-term good health on a ratio of omega-6 to omega-3 as high as 4:1), the consensus is that we are eating far too much omega-6 compared to omega-3 and that this by itself, quite apart from trans fats, is causing serious harm to our health. However, most trans fats are made from the high-omega-6 seed oils, so if you are scrupulous about cutting out all trans fats from your diet, you will already have gone a long way towards redressing the balance, and as Dr Artemis Simopoulos has pointed out,
"a diet such as the traditional Greek diet balanced in omega-6 and omega-3 fatty acids and rich in vitamins C and E (fruits and vegetables) is associated with decreased rates of heart disease and cancer more so than any other diet or drug intervention." (Simopoulos, p.427, emphasis mine)
Food and Behaviour Research. See also www.fabresearch.org. The website of this charity gives authoritative and up-to-date information on the latest discoveries about mental health and nutrition. It includes pages on recognizing and treating probable omega-3 deficiency and is especially useful for parents of children with dyslexia, dyspraxia, and ADHD.
Kummerow, Fred A. et al.. "Trans fatty acids in hydrogenated fat inhibited the synthesis of the polyunsaturated fatty acids in the phospholipid of arterial cells", Life Sciences 74 (2004), pp.2707-23. This paper describes an experiment in which seven-week-old piglets whose mothers had been fed a diet containing trans fats before they were born were shown to have insufficient quantities of long-chain omega-6 in the cells of their arteries and early signs of heart disease. Without enough long-chain omega-6 in their membranes, the cells of their arteries let in too much calcium, causing plaques to begin building up on their artery walls.
Mafouz, M. M. et al. "Effects of dietary fats on desaturase activities and the biosynthesis of fatty acids in rat liver microsomes", Lipids 19 (1984), pp.214-22. This paper describes in detail how trans fats prevent the construction of long-chain omega-3 by inhibiting the action of the delta-6 desaturase enzyme even when sufficient amounts of short-chain omega-3 are present.
Simopoulos, A.. "Evolutionary aspects of omega-3 fatty acids in the food supply". Prostagladins, Leukotrienes and Essential Fatty Acids 60:5&6 (1999), pp.421-29. This paper contrasts the modern Western diet with the diet of our Palaeolithic ancestors, focusing especially on changes in the levels and ratios of omega-3 and omega-6. The author argues that the traditional diet of Crete best reflects the levels of nutrients and especially essential fatty acids that evolution requires us to eat for lifelong good health.
Stoll, A. L.. The omega-3 connection: the groundbreaking omega-3 antidepression diet and brain program. Simon & Schuster, New York 2001. This book, by the scientist who discovered that fish oil dramatically benefited patients suffering from bipolar disorder, is a good introduction for the general reader on how and why omega-3 can be used to treat a range of mental illnesses.