The world of dietary fats is a complicated alphabet soup of names and numbers, and our understanding of how each type of fat works in the body - for good or ill - is far from complete.
To aid our understanding, we tend to reduce the issue to its most basic equation. For a long time, this has translated into ‘fat is bad’. The official advice from medical circles - both conventional and alternative - has been to cut out all ‘unnecessary’ fat from your diet.
Nevertheless, fats are important in nutrition. They provide a concentrated source of energy for the body, constitute a form of insulation for body tissues, and aid the absorption of the fat-soluble vitamins A, D, E and K.
They are also important in food preparation, enhancing its flavour and its ‘feel’ in the mouth. Fats tenderise meat products, and conduct heat during cooking. Some nutritionists even believe that fats are important for feelings of satiety. So, in slavishly following a low-fat diet, we could be condemning ourselves to life-long feelings of hunger as well as a range of debilitating diseases.
The question is: how much fat do we need? This question is particularly pertinent to the essential fatty acids (EFAs) known as omega-6 and omega-3. The body cannot make these fats and must obtain them from dietary sources. Yet, no single authority can agree on the quantities we need or the correct proportions of these important dietary fats in relation to each other. Even the recommendations of ‘experts’ are mostly guesswork pieced together from information on traditional diets and the official guidelines of various authorities.
Inuits (Eskimos) eating a traditional diet may consume approximately 5 g of omega-3 fatty acids daily, equivalent to the EFAs in about a pound of salmon. But most of us don’t need this much to benefit from the omega-3s.
Researchers in Sweden tell us that fish has a ‘dose-dependent’ effect - that is, the more fish in your diet, the healthier your heart (BMJ, 1986; 293: 426). In one study, men who included as little as half a pound of fatty fish in their diet every week had healthier cardiovascular systems than non-fish eaters (N Engl J Med, 1985; 312: 1205).
Nutritionists do not know the optimal intake of omega-6 fatty acids. It is generally believed that, to prevent a deficiency in adults, about 2 per cent of daily calories should be derived from omega-6 fatty acids. This is equivalent to approximately 4.5 g of omega-6 fatty acids per day.
The ideal intake of omega-3s is also unknown, though some researchers recommend a general daily intake of 3 g (Arch Intern Med, 1993; 153: 1429-38; Arthritis Rheum, 1994; 37: 824-9).
Taking these recommendations on board means that the average person would be getting a ratio of 1.5:1 of omega-6 to omega-3.
Yet, this ratio is not reflected in official recommendations and is certainly not reflected in our normal eating habits. The current dietary omega-6 to omega-3 ratio in the West ranges from about 10:1 to 25:1, indicating that the typical diet is very low in omega-3 fatty acids compared with the Paleolithic diet on which humans evolved (Am J Clin Nutr, 1991; 54: 438-63).
After ignoring the problem for years, the US Institute of Medicine finally set recommended daily intakes for omega-6 and omega-3 at a ratio of around 10:1 (IOM, National Academy of Sciences Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein and Amino Acids, National Academy Press, 2002).