The fatty acids profile of body fat can vary greatly as a direct consequence of differing contents of saturated, monounsaturated, and essential fatty acids (EFAs) in different diets. The percentages of linoleic acid (LA, 18:2w6) and alpha-linolenic acid (LNA, 18:3w3) found in fat tissues of various groups of people varies.
Three interesting points emerge from this information.
- In both tissue samples from people living in hot, sunny, dry climates (New Zealand, Africa), low-fat tissue levels of LA and LNA are found, in keeping with low LA and LNA content in their food supply. Neither Maoris nor Hottentots are especially prone to degenerative diseases but, on the other hand, neither are known for longevity, either.
- In temperate areas, obese people have levels of less than 10% LA in their adipose tissue, and ‘normal’ adult Americans (remember that 68% of these ‘normal’ people die from degenerative conditions) generally have only about 10% LA in their fat tissues.
- People in temperate regions with the lowest incidence of degenerative diseases (Japanese, British vegans) have higher than average levels of LA and LNA in their fatty tissues.
The evidence does not support the opinion of writers who warn against high levels of polyunsaturates (PUFAs) because of fear of cancer. If the PUFAs are fried, oxidized by light or air, hydrogenated, or processed at high temperatures – in other words, if EFAs in the oils are altered – they may indeed increase cancer incidence. If antioxidants (vitamin E and carotene) are removed from PUFA (w6) oils by refining, these oils also increase cancer incidence.
If the diet also lacks vitamin C, selenium, and sulphur, PUFAs that peroxidize within our tissues may cause damage and increase cancer. It is important to distinguish between health-destroying kinds of PUFAs and EFA-containing oils in their natural (unrefined) state, which are health-enhancing.