Precious Yet Perilous
Written by Chris Masterjohn Phd
How Essential Are the Essential Fatty Acids ? A More Detailed Look
The requirement for essential fatty acids is, under most conditions, exceedingly small. This should not be surprising; after all, if we require omega-6 fatty acids because we need enough arachidonic acid to allow our body to convert into signaling compounds as it needs them, then arachidonic acid fills a role similar to that of vitamins A and D. We require several hundred micrograms per day of vitamin D and several milligrams per day of vitamin A. To put this in perspective, we consume proteins, carbohydrates and fats in gram amounts. A microgram is one millionth of a gram and a milligram is one thousandth of a gram. We should therefore expect the requirement for essential fatty acids to constitute an extremely small percentage of our total energy intake.
Researchers who attempted to quantify the essential fatty acid requirement using purified fatty acids showed that just over two percent of calories as linoleic acid was needed to prevent deficiency in growing rats while less than 0.7 percent of calories as arachidonic acid was needed.10 Lower amounts of arachidonic acid may have proven effective had the researchers tested them. The Burrs did not use this approach. They used purified fatty acids to prove the point that the fatty acids themselves were curative, but used whole foods to quantify the requirement. “All workers,” they wrote, “recognize the fact that the acids isolated by the bromination method may not have exactly the same structure that they had in the natural oil.”8 The Burrs showed that the requirement was only 0.4 percent of calories when they used lard to cure the disease in growing rats and that the requirement was only 0.1 percent of calories when they used liver to cure it.7 Liver probably proved more effective than lard both because it is much richer in arachidonic acid and because it is rich in vitamin B6, which greatly enhances the conversion of linoleic acid to arachidonic acid.19
The essential fatty acid requirement seems to be similar in humans. Butter supplying 1.3 percent of calories as PUFA prevented poor growth, scaly skin and increased susceptibility to infections in human infants consuming a formula made partly from skim milk and mostly from corn syrup, but the investigators did not try using smaller amounts.28 The same authors reported that both 1.3 percent and 2.0 percent of calories as purified linoleic acid incorporated into a synthetic fat molecule cured eczema in infants fed the same type of formula.29 The requirement for purified linoleic acid in human infants fed a diet composed mostly of refined sugar is thus similar to the requirement in young, growing rats fed a similarly atrocious diet, which suggests that the essential fatty acid requirement in infants and growing children can be met by a diet providing less than 0.5 percent of calories as PUFA from animal fat, and much less than this if the fat is provided by liver.
One naturally wonders what the essential fatty acid requirement might be in people who are not consuming most of their calories as refined sucrose or corn syrup. In the 1960s, researchers compared the effect of starch-based and sucrose-based diets on PUFA metabolism. Both diets were deficient in essential fatty acids. The starch-based diet contained only 0.003 percent more calories as linoleic acid than the sucrose-based diet, but the rats fed starch had 50 percent more arachidonic acid and 80 percent more linoleic acid in their livers than the rats fed sucrose.18
Similarly, in essential fatty acid-deficient infants fed 80 percent corn oil, replacement of half the corn oil with hydrogenated coconut oil, which is completely devoid of PUFAs, substantially improved their eczema. High-sucrose diets increase lipid peroxidation in rats,30 a process that causes the destruction of essential fatty acids. Reducing refined sugar in the diet is therefore likely to sharply reduce the essential fatty acid requirement. A number of other factors may reduce this requirement as well, including biotin, vitamin B6, calcium, magnesium, avoidance of rancid vegetable oil, sufficient intake of protein and total energy, and a diet rich in fresh, whole foods abundant in natural antioxidants.31