In general, nuts are healthy foods that would have always been favorites of our hunter-gatherer ancestors because of their high fat concentrations. As was the case with vegetable oils, if you don’t get sufficient long chain omega-3 fatty acids in your diet (0.5 to 1.8 grams of EPA + DHA), nuts have a great potential to give you too much omega-6 fatty acids. Two exceptions to this rule are walnuts with an omega-6/omega-3 ratio of 4.2 and butternuts with an omega-6/omega-3 ratio of 3.9. Otherwise, nuts are a great source of cholesterol-lowering monounsaturated fatty acids and in numerous studies have been shown to reduce the risk for cardiovascular disease. However, because of their high fat content, nuts should not be consumed in unlimited quantity if you are trying to lose weight.
One nut that you should not include in your diet is peanuts. Peanuts are not nuts, but rather are legumes. Here are the reasons why we do not recommend either peanuts or peanut oil. If you look at peanut oil fatty acid composition in the Table of Vegetable Oils, notice that it contains little saturated fat and almost 80% is made up of cholesterol-lowering monounsaturated and polyunsaturated fats. Hence, on the surface, you might think that peanut oil would probably be helpful in preventing the artery clogging process (atherosclerosis) that underlies coronary heart disease. Well, your ideas were not a whole lot different than those of nutritional scientists – that is, until they got around to actually testing peanut oil in laboratory animals. Starting in the 1960s and continuing into the 1980s, scientists unexpectedly found peanut oil to be highly atherogenic, causing arterial plaques to form in rabbits, rats, and primates – only a single study showed otherwise. Peanut oil was found to be so atherogenic that it continues to be routinely fed to rabbits to stimulate atherosclerosis to study the disease itself.
At first, it was not clear how seemingly healthful oil could be so toxic in such a wide variety of animals. Dr. David Kritchevsky and colleagues at the Wistar Institute in Philadelphia were able to show with a series of experiments that peanut oil lectin (PNA) was most likely responsible for its artery clogging properties. See “Lectin may contribute to the atherogenicity of peanut oil.” to learn more about peanut oil and cardiovascular disease.
Lectins are fairly large protein molecules, and most nutritional scientists had assumed that digestive enzymes in the gut would degrade it into its component amino acids. Consequently, it was assumed that the intact lectin molecule would not be able to get into the bloodstream to do its dirty work. But they were wrong. It turned out that lectins were highly resistant to the gut’s protein-shearing enzymes. An experiment conducted by Dr. Wang and colleagues and published in the prestigious medical journal Lancet revealed that PNA got into the bloodstream intact in as little 1-4 hours after subjects ate a handful of roasted, salted peanuts. See “Identification of intact peanut lectin in peripheral venous blood.” for more details.
Even though the concentrations of PNA in the subject’s blood were quite low, they were still at concentrations known to cause atherosclerosis in experimental animals. Lectins are a lot like super glue ö it doesn’t take much. Because these proteins contain carbohydrates, they can bind to a wide variety of cells in the body, including the cells lining the arteries. And indeed, it was found that PNA did its damage to the arteries by binding to a specific sugar receptor. So, the practical point here is to stay away from both peanuts and peanut oil. There are better choices.
In the following tables, we list the fatty acid content of most commercially available nuts. You can use these tables to help you make an informed decision in choosing a nut based upon its fatty acid composition. If you are unfamiliar with fatty acid nomenclature and how the different types of fatty acids impact your health please refer to our fatty acid primer.
Table of Nuts
(grams of fatty acids per 100 grams/nut)