Rancid Fats

This post by Holly Hickman takes issue with the idea that phytic acid in nuts is bad news. I posted very recently about this issue and came to the opposite conclusion. Perhaps it is because my site is oriented towards people eating paleo to help autoimmune conditions. Holly is right that every plant food contains some sort of "don't eat me" chemical. You can be sensitive to many of these...or none of them. There are plenty of people who gobble down Planter's Mixed Nuts without a problem, but I'm not one of them. I can eat a few fresh nuts, but something like almond-flour crackers would make me sick for days. If your gut has problems, it's worth it to examine your intake of plant foods and figure out which ones are making your problems worse. 

It's also worth remembering that nuts were seasonal and eaten in small amounts by paleolithic people. When we buy shell nuts we forget how tough they are to crack! Shelled nuts might also be a bad idea because the fats in nuts can go rancid easily. Rancid fats might sound gross, but actually some rancid fats do not have a detectable taste or smell. 

That's bad news, because according to Oxidized Fat in the Diet by Jeffrey S. Cohn is a review article summarizing several research studies, 

Consumption of lower levels of oxidized fat on repeated occasions may pose a more chronic threat to health, however, particularly because low-level oxidation of meat, milk, poultry and cereal products during storage and processing is virtually unavoidable [4]. More extreme oxidation of fat can also occur when oils are used for cooking.

He mentions that the natural oxidation of cholesterol produces at least 30 different compounds that are biologically active and are particularly prevalent in the milk and egg powders used in processed foods. Compounds such of these are shown in experiments to absorb quite easily into the intestinal wall. In animal studies, oxidized fat led to higher incidence of atherosclerosis. In studies of healthy adults, the consumption of these fats led to impaired arterial function. These effects were not seen following low-fat meals or meals of less oxidized fats.

Comparative Nutritional Value of Diets Containing Rancid Fat, Neutral Fat, and No Fat by Dorothy Whipple is an old one and describes the diet of lab animals. Lab rats fed slightly rancid fats slowly developed horrible symptoms like swelling, hair loss, and neurological degeneration...and eventually died prematurely. Animals fed no fats developed the typical dry-skin symptoms and lived somewhat longer. Animals fed fresh fats were the healthiest and lived the longest. The researcher concluded that in terms of her experimental animals, it was better to feed no fat than oxidized fat, though neither was optimal.

Nuts are probably not the worst source of rancid fats. If you are eating paleo, you are avoiding most of the worst sources like cereals, milk powders, egg powders, and other trash. But I still think it's worth seeking out the best freshest nuts if you are going to eat them. This nut-growing website notes that "Levels of vitamin E are reduced by around 30% after three months of refrigerated storage."....most walnuts aren't even refrigerated. The best chefs contract with growers and buy fresh nuts which they freeze. 

I'm definitely thinking of contacting a NY farmer and doing a nut CSA here. Right now there isn't one, which is too bad.