In 1923, the American scientists Burr and Evans discovered that rats deprived of polyunsaturated fatty acids developed symptoms of illness. The idea of essential fatty acids was born. Evans had worked on vitamin A, and called these polyunsaturated fatty acids vitamin F, since they were substances vital for bodily function, but ones the body could not manufacture itself.

A few years later, Burr discovered that a deficiency in linoleic acid could not be corrected by using alpha-linolenic acid, and vice versa. There was thus not a single vitamin F, but really two families of essential fatty acids: omega-3, derived from alpha-linolenic acid, and omega-6, derived from linoleic acid. (The families of fatty acids both have the prefix "lin" after the linseed from which they were extracted.) (Burr and Burr 1929; Burr and Burr 1930).

 

Since then, researchers have shown a growing interest in fatty acids and their findings have multiplied. As an example, there have been over 500 references in the literature since 1930.

The first observations identifying a connection between omega-3 and cardiovascular disease date from the seventies. A Danish epidemiologist pinpointed omega-3 in fish because of the lack of heart problems among the Eskimo (Kromann and Green 1980). In fact, Greenland Eskimos, who eat large quantities of long-chain omega-3 (EPA and DHA) in the form of fish, seal and whale blubber, do not suffer from heart attacks, whereas Eskimos who have emigrated to Copenhagen have the same problems as their Danish neighbours (Bjerregaard and Dyeberg 1988).

There was also a finding from the Seven Country study: the diet in Crete is unusually rich in sources of omega-3 acids and appears to be linked to the island's record life-expectancy. Other data suggested later that the longevity of the Japanese is also due to their higher consumption of rapeseed, soya and fish (Hirai, Terano et al. 1989; Kagawa, Nishizawa et al. 1982).

Burr and Evans had demonstrated the effects of a deficiency in essential fatty acids. But in 1982, the Swedish workers Bergstrom and Samuelsson and the British researcher Vane earned the Nobel Prize for their explanation of the link between a deficiency in essential fatty acids and the symptoms of that deficiency. They showed the central role as cell mediators that eicosanoids, the "hormonal" molecules, played in the body. They include the prostaglandins, prostacyclins, thromboxanes and leukotrienes that regulate immunity, platelet aggregation, inflammation, etc.

All these molecules have one point in common: they are all made from two precursors, the omega-3 and omega-6 unsaturated fatty acids.

The epidemiology supported a hypothesis about omega-3, and clinical trials in the nineties helped confirm it. The research supported omega-3 supplements for populations at risk from heart disease (Burr, Gilbert et al. 1989 (DART); Marchioli, Bomba et al. 1999 (GISSI); de Lorgeril, Salen et al. 1994 and 1999 (Lyon)).

Omega-3 is no longer restricted to use in cardiovascular medicine. Studies using animals were followed by studies of human populations and work on fatty-acid profiles taken from patient blood. They showed that raised levels of omega-3 acids in tissue correlate with a reduced incidence of some mental illnesses such as depression, and of neuro-degenerative diseases such as Alzheimer's. These observations were later confirmed by clinical studies that demonstrated the central role of polyunsaturated fatty acids in human brain function.