Of all the components of a healthy Mediterranean diet, which are associated with a longer lifespan?
Does just reducing one’s intake of meat, dairy, and eggs significantly reduce mortality?
How might adding a few nuts to one’s daily diet–in this case about four walnuts, almonds and hazelnuts–cut one’s stroke risk nearly in half? Well, olives and nuts are plant foods, and as such, packed with antioxidants, raising the antioxidant level of our bloodstream, resulting in lower fat oxidation and free radical DNA damage. But what’s happening inside people’s arteries?
Researchers measured the amount of atherosclerotic plaque in the neck arteries going to the brain in folks who for years were eating the added nuts, or added extra virgin olive oil, or neither to their daily diets. In the control group, the plaque got worse, which is what happens when one continues to eat an artery-clogging diet, but there were no significant changes in the added extra virgin olive oil group, and the plaque in the added nut group appeared to get better. The nuts appeared to induce a regression of the disease, or at least a significant delay in the progression. Now the nut group was still suffering strokes, but only half as many, perhaps because the reduction in plaque height within the arteries on extra nuts was indicating a stabilization of the plaque rendering them less likely to rupture.
Adding nuts to our diet may also improve endothelial function, boosting the ability of our arteries to dilate naturally by about 30%. If you look at the baseline adherence to Mediterranean diet principles, and control for things like smoking and exercise, there were only two factors significantly associated with reduced heart attack and stroke risk: more vegetables and more nuts. No significant association with the olive oil or the wine or the fish, or cutting back on soda and cookies. Among the individual Mediterranean diet components, only increased consumption of vegetables and nuts were related to reduced cardiovascular events.
On the one hand, cutting stroke risk in half just by eating a handful of nuts a day is pretty amazing, but those in the added nut group didn’t appear to live any longer overall. And other studies have suggested that frequent nut consumption may indeed extend life–for example, the Harvard Health Professionals studies, involving a whopping three million person-years of follow-up over decades, found nut consumption associated with fewer deaths from cancer, heart disease, respiratory disease, and most importantly, fewer deaths overall, confirmed by all the other big major prospective studies, as of 2014, with a new one just published: 17,000 people followed for five years, and those who ate nuts had less than half the risk of dying.
Maybe this is just because people may eat nuts instead of meat, eggs, and dairy, and that’s why they live longer? No, since vegetarians who frequently eat nuts also have a dramatically reduced risk compared to those who don’t.
So what’s going on here with the PREDIMED study showing no longevity benefit from nuts? Did they just not wait long enough? Well, just because people were randomized to the nut group doesn't mean they actually ate more nuts, and those randomized to the other groups didn’t necessarily stay away from nuts. If you re-analyze the data comparing the death rates of those who actually ate more nuts to those who actually didn’t, nut consumption was indeed associated with significantly reduced risk of death. If you do the same kind of post-hoc analysis with olive oil, even with the extra virgin, there is no benefit in terms of living longer. This is consistent with how Ancel Keys, the so-called father of the Mediterranean diet, viewed olive oil. He thought of its benefit more as a way of just replacing the animal fat–anything to get people to eat less lard and butter.
What are the best kinds of nut? The greatest benefits were attributed to walnuts–particularly it seems, for preventing cancer deaths. Those eating more than three servings of walnuts a week appeared to cut their risk of dying from cancer in half.
Now it’s just a matter of communicating the research to the public. All the major cancer groups emphasize a more plant-based diet, remarkably consistent with the World Health Organization guidelines for healthy eating. The far-reaching positive effects of a plant-based diet–including walnuts–may be the most critical message for the public.
To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is just an approximation of the audio contributed by Katie Schloer.
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I Sari, Y Baltaci, C Bagci, V Davutoglu, O Erel, H Celik, O Ozer, N Aksoy, M Aksoy. Effect of pistachio diet on lipid parameters, endothelial function, inflammation, and oxidative status: a prospective study. Nutrition. 2010 Apr;26(4):399-404.
R Estruch, E Ros, J Salas=Salvado, M I Covas, D Coreela, F Aros, E Gomez-Gracia, V Ruiz-Gutierrez,M Fiol, J Lapetra, R M Lamuela-Raventos, L Serra-Majem, X Pinto, J Basora, M A Munoz, J V Sorli, J A Martinez, M A Martinez-Gonzalez, PREMIDED Study Investigators. Primary prevention of cardiovascular disease with a Mediterranean diet. N Engl J Med. 2013 Apr 4;368(14):1279-90.
M T Mitiavila, M Fandos, J Salas-Salvado, M I Covas, S Borrego, R Estruch, R Lamuela-Raventos, D Corella, M A Martinez-Gonzalez, J M Sanchez, M Bullo, M Fito, C TOrnos, C Cerda, R Casillas, J J Moreno, A Iradi, C Zaragoza, J Chaves, G T Saez. The Mediterranean diet improves the systemic lipid and DNA oxidative damage in metabolic syndrome individuals. A randomized, controlled, trial. Clin Nutr. 2013 Apr;32(2):172-8.
A Fernandez-Montero, M Bes-Rastrollo, M T Barrio-Lopez, L Cuente-Arrillage Cde, J Salas-Salvado, L Moreno-Galarraga, M A Martinez-Gonzalez. Nut consumption and 5-y all-cause mortality in a Mediterranean cohort: the SUN project. Nutrition. 2014 Sep;30(9):1022-7.
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This is the fourth of a six-part video series on the Mediterranean diet. Here are the first three in case you missed them:
And then there were two:
Think the effects of adding a few nuts to one’s daily diet are too good to believe? Check out my video Four Nuts Once a Month. For more on Walnuts and Artery Function check out the video, and for more on nuts and cancer prevention, see Which Nut Fights Cancer Better?
Nuts May Help Prevent Death and so may beans; see Increased Lifespan from Beans. What about Fruits and Longevity: How Many Minutes per Mouthful?
More on protecting ourselves from “brain attacks” in Preventing Strokes with Diet.
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A randomized controlled trial found that a Mediterranean-type diet can dramatically lower the risk of subsequent heart attacks. How does it compare with plant-based diet data?
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