Australian Aborigines develop high frequencies of diabetes and cardiovascular diseases when they make the transition to an urban lifestyle. The composition of the traditional diet, particularly its lipid components, is a most important aspect of the hunter-gatherer lifestyle that would bear on the risk of these diseases. We have examined the fat content and fatty acid composition of a variety of animal foods eaten traditionally by Aborigines from different regions of Australia. The muscle samples of the wild animals from all over Australia were uniformly low in fat (less than 2.6% wet weight) with a high proportion of polyunsaturated fatty acids (greater than or equal to 20% PUFA). Liver samples had a higher range of fat content (5-10% wet weight) but were also rich in PUFA (33-42%). Depot fat samples varied widely in their PUFA content (5-40%). In terms of their PUFA composition the foods tended to fall into three groups: (i) those rich in both n-3 and n-6 PUFA, which included land-based, coastal and freshwater animals; (ii) those rich in n-3 PUFA, i.e., marine species; (iii) those rich in n-6 PUFA, mainly land-based species. The results of these analyses suggest that even when the traditional Aboriginal diet contained a high proportion of animal foods it would have been low in fat with a high proportion of PUFA and thereby could have protected Aborigines against cardiovascular diseases and related conditions through a combination of factors: low energy density, low saturated fat and relatively high PUFA content.

The fatty acid composition of 10 species of fish caught off the northwest coast of Australia (latitude 17 degrees S) was examined. All species contained high levels of omega 6 fatty acids (9.6-23.1% of total fatty acids) with arachidonic acid being the major omega 6 fatty acid (5.9-14.8% of fatty acids). Docosatetraenoic and docosapentaenoic acids of the omega 6 series accounted for 3-8% of the total fatty acids. The ratio of omega 6 to omega 3 fatty acids in these fish varied from 0.38 to 0.93, compared with an average ratio of 0.16 for fish from the northern hemisphere (latitude greater than 30 degrees N). The present data and figures from the literature indicate that the marine food chain in the southern hemisphere contains significant quantities of omega 6 fatty acids.

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