At the moment, there is no evidence either way as researchers aren’t exploring these questions.

Saturated fat to the rescue The current received wisdom accepts that fat intake is associated with obesity, heart disease and cancer. But the data are far from unequivocal. As one review of the evidence into dietary fat and heart health concluded: 'Despite decades of effort and many thousands of people randomised, there is still only limited and inconclusive evidence of the effects of modification of total, saturated, monosaturated or polyunsaturated fats on cardiovascular morbidity and mortality' (BMJ, 2001; 322: 757-63).

In fact, evidence continues to show that saturated fats are not the poisons we think they are. All fats - with the exception of man-made trans fats - have something positive to offer the body. The current trend is toward a moderate intake of saturated fats rather than its wholesale elimination from the diet.

We now know, for instance, that fatty acids such as those found in butter are more easily metabolised for energy. The body also needs saturated fats to absorb EFAs, to take up calcium in the bones, to stimulate the immune system, and to add (along with cholesterol) structure and stability to cell walls.

Saturated fats are also more stable than polyunsaturates. They don’t turn rancid as quickly and are more stable when heated (making them more suitable for cooking). This means they are less likely to produce heart-damaging and cancer-causing free radicals.

Polyunsaturated fatty acids have been associated with a range of adverse effects on the thyroid, resulting in hypothyroid-like symptoms. Saturated fats, on the other hand, increase tissue sensitivity to thyroid hormone T3 (J Biol Chem, 1986; 261: 13997-4004).

While we associate tropical oils, such as coconut and palm oils, with poor health, they have evidence of as yet unexplored promise. For example, lauric acid, prominent in coconut oil, has potent antiviral, antibacterial, and antiprotozoal properties (J Gen Virol, 1994; 75: 353-61). Until recently, no one in the mainstream nutrition community has made the link between this and the treatment of many serious viral infections, yet the potential is there.

Tropical oils may also benefit heart health. A review of the literature on coconut oil’s effect on cholesterol and atherogenesis concluded that 'coconut oil is a neutral fat in terms of atherogenicity' (J Philippine Med Assoc, 1989; 65: 144-52).

Other studies comparing the effect of coconut and soy oils in healthy young men found that coconut oil increased (good) HDL cholesterol while soy oil reduced it (Br J Nutr, 1990; 63: 547-52). Where intake of tropical oils is traditionally high, heart disease is rare. But when these people moved to places where the typical Western diet is consumed, their total and (bad) LDL cholesterol increased while HDL cholesterol was decreased (Am J Clin Nutr, 1981; 34: 1552-61).

Good, bad and ugly? These days, we make what we believe are subtle distinctions between different types of fats. They can, for instance, be good fats - like the monounsaturates found in olive and canola oils, cashews, peanuts, macadamia nuts, almonds and avocados, and the polyunsaturates found in salmon, mackerel, herring, sardines, hemp, sunflowerseeds and flaxseeds, and flax, corn, safflower, sunflower, soybean and sesame oils.

Fats can also be bad, like the saturated fats in meat, butter, cheese, egg yolks, whole milk, and coconut and palm oils.