Evidence on Nut Consumption and Human Health
In the whole food plant based food community, there is a tempest in the teapot and it’s a pretty nutty tempest. By no means am I an expert on nuts—the foods, that is. My views on this topic are entirely based on the scientific research evidence, after professionally being in the field of nutrition for more than a half century.
So let’s start with the evidence on nut consumption and human health. It’s easy for me. I suggest reading Michael Greger’s summary of the evidence in his new book, How Not To Die (2015). It’s the best recent review, in my opinion. Greger summarizes several studies of recent years that now suggest nuts are beneficial in reducing cardiovascular and other diseases. For women who are at high risk for heart disease, one study showed that those who ate either nuts or a tablespoon of peanut butter 5 or more days a week cut their risk of a heart attack nearly in half compared to those eating 1 serving or less per week (p. 345). Another long term study of over 7000 men and women at high risk for cardiovascular disease found that one group who doubled their intake of nuts to about an ounce (a handful) of nuts every day cut their risk of stroke in half. And in general, those in the study who ate more nuts every day “had a significantly lower risk of dying prematurely overall.” (p.344-345). Walnuts seem to have extra health benefits – those who ate more than 3 servings of walnuts a week cut their risk of dying from cancer in half (p. 345).
Nuts are one of the most nutrient dense of all plant-based foods. I recall many years ago teaching nutrition and pointing out that nuts are an especially good source of the fat soluble antioxidant, vitamin E. I imagined that this made sense because the purpose of nuts (and seeds) is to store the nutrients necessary for startup growth of the new tree offspring. My thought process at that time (probably not original) was that nuts might have to remain viable for long periods of times until conditions become suitable for the nut to sprout new growth. This needs a good source of energy and what better nutrient than fat, the most concentrated source. But, as I thought more about it, fats stored for many years might become rancid through oxidation of the fat, especially the more susceptible polyunsaturated fats. Nature resolved this potential problem by adding a rich source of the antioxidant vitamin E (a group of antioxidant tocopherols and related isomers). And, it chose the fat soluble vitamin E, instead of the many water soluble antioxidants found in other parts of the plant.
A second condition to be met for new growth is the inclusion of a rich supply of many other nutrients—vitamins and trace minerals. So, without belaboring the point, fat soluble antioxidants such as vitamin E and unsaturated fats go together. So, too, do they work together in our bodies as well and when we eat nuts, we are getting a good deal, including the addition of some interesting nut flavors to our culinary toolkit.
I know well the position of my colleague Dr. Caldwell Esselstyn and his enormously impressive accomplishments with his heart patients. He counsels these patients against the consumption of fatty foods, even those containing fats in their natural form, as in nuts and avocados. I have always felt it would be interesting some day to do a clinical trial, to see if the same, or even more beneficial results could be obtained with a whole foods, plant-based diet containing modest amounts of natural fats. But I understand the cautionary stance of Dr. Esselstyn. It is true that many nuts are sold in bags, already shelled, making them easy to over consume. Eating too much of any rich food, even if in whole form, may not be a good idea for people with heart disease. Esselstyn’s impressive results were obtained without nuts.
But fat content aside, I am impressed with the findings now showing health benefits for most nuts. And when we judge a food by one nutrient, in this case judging nuts only because of their fat content, we may be falling into the same trap that has caused so much past misinformation.
Investigating nutrients in isolation, i.e., reductionism, is fine when we are exploring the mechanisms by which they work. But, for an understanding of a food’s nutritional properties, we must seek and understand context, i.e., wholism. I am distressed with too much unnecessary confusion in this field called nutrition, most of which comes from interpretations based solely on reductionist research findings, a practice great for pharmaceutical firms and other financial interests.
We should remember that the dairy industry argued for years that we should consume milk and cheese because these products contain calcium, and calcium is important to bone health. This is a reductionist argument focused narrowly on consumption of calcium. As it turns out, foods high in animal protein such as cheese and milk cause a net calcium loss by causing a condition in the body called “acidosis,” which results in a leaching of calcium from the bones. So whatever calcium you consume when consuming milk or cheese is likely to be more than offset by the loss of calcium from the bones, excreted through the urine.
When we argue that nuts and avocados are unhealthy, we are using the same reductionist logic used by those promoting dairy consumption. And if we eliminate a whole category of foods abundantly available in most natural settings in temperate to tropical climates, a kind of food our ancestors would undoubtedly have found flavorful, then we are undermining the very rationale for a whole foods plant-based diet, which is rooted in Nature and in our evolution over eons of time. Even some of our primate cousins use stone tools to crack nuts, which they seem to relish. This is a story with long roots.
I would never suggest people eat nuts and other fatty plant foods to excess, because these foods are not available in Nature in excessive amounts. These foods should be consumed in moderation, and if eaten this way, I believe they provide important beneficial health effects.
- Greger, M. How Not To Die. 562 pp. (Flatiron Books, Inc., 2015).
- Campbell, TC. Whole: Rethinking the Science of Nutrition. 352 pp. (Benbella Books, 2014).
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