A study published mid-July by BMC Medicine written by Marta Guasch-Ferré and colleagues should put to rest any possible suggestion that eating nuts is bad for your health. For unfathomable reasons I still hear of doctors who suggest to their patients that they need to avoid eating too many nuts, suggesting that nuts are too fattening or are bad for your heart. Thirty years ago this was not unreasonable, although there was never any evidence of harm. Back then we lived in a simpler world when it came to dietary advice and it was easier to make sweeping pronouncements. If the data suggested an association between high fat intake (including saturated fats, trans-fats and all the rest under one category), then all fats needed to be avoided.
Humans do like to generalize and seeing foods as good or bad was still a step in the right direction from the American Medical Association’s position that there was no link between diet and disease.
This new study is particularly solid. Let me start with the bottom line for a change.
In a group of about 7, 000 older people, all at high risk for heart disease, eating nuts “… was associated with a significantly reduced risk of all-cause mortality (P for trend <0.05, all). Compared to non-consumers, subjects consuming nuts >3 servings/week ….. had a 39% lower mortality risk …… A similar protective effect against cardiovascular and cancer mortality was observed….. [those participants consuming] >3 servings/week at baseline had the lowest total mortality risk (HR 0.37; 95% CI 0.22 to 0.66).” 
Three one ounce servings of nuts a week doesn’t sound like much but a 63% lower risk of dying does sound like a lot.
This is worth looking at the details.
Data used in this study comes from our often discussed PREDIMED (‘PREvención con DIeta MEDiterránea’) cohort that has been analyzed in several other important papers during the past year. [Those of you who feel like they’ve heard this before can skip the next paragraph or two]
In this particular incarnation of the data, 7,447 older participants (men aged 55 to 80 years and women 60 to 80 years) were assigned to 1 of 3 interventions: a MedDiet enriched with extra-virgin olive oil (EVOO), a Mediterranean Diet supplemented with mixed nuts, or advice on a low-fat diet (control diet). Although participants had no CVD at enrollment, they were at high cardiovascular risk because of the presence of type 2 diabetes or at least three of the following risk factors: current smoking, hypertension, hypercholesterolemia, low high-density lipoprotein (HDL)-cholesterol, overweight or obesity, and family history of premature CVD. Data from participants who reported extremes of total energy intake (>4,000 or <800 kcal per day for men and >3,500 or <500 kcal per day for women) were excluded from analysis. After those subjects (n = 153) and also those with incomplete dietary data (lack of food frequency questionnaire) at baseline (n = 78) had been excluded, 7,216 individuals were left for the present analysis.
Nut consumption was evaluated at baseline using a 137-item semi-quantitative food frequency questionnaire administered in face-to-face interviews by dieticians. Information on self-reported nut intake in general and walnut intake specifically was obtained. Participants reported the frequency and quantity of nuts they consumed and specifically walnuts. Just under an ounce, 28 grams, of nuts was considered a single serving
The outcome measures were simple: total mortality, cardiovascular mortality, and cancer mortality.
During a median follow-up of just under five years, 323 total deaths, 81 cardiovascular deaths and 130 cancer deaths occurred. Nut consumption was associated with a significantly reduced risk of all-cause mortality. Compared to non-consumers, subjects eating more than 3 servings of nuts a week, about one-third of the group had a 39% lower mortality risk . A similar protective effect against cardiovascular and cancer mortality was observed. Participants in group encouraged to follow the Mediterranean diet and who were provided free nuts who ate more than 3 servings per week before the start of the study had the lowest total mortality risk, a 63% reduction.
Let me copy below sections of a commentary written by Rohrman and Faeh , which was published in conjunction with this Guasch-Ferré paper. It sums up as well as I might be able to:
“More than 20 years ago, the first studies were published on possible favorable effects of nut consumption on health in the general population[2,3] . Since then, the effects of nut consumption on health have been examined intensively. Nut consumption improves the body’s lipid profile and may influence inflammatory processes, oxidative stress, vascular reactivity and glycemic control  …..
“The results of this study have shown an effect of any nut consumption on all outcomes . However, although reduced all-cause and cardiovascular disease mortality were observed among consumers of walnuts and other nuts, cancer mortality was only inversely associated with the consumption of walnuts. Nuts are rich in polyunsaturated fatty acids, but also in minerals (calcium, magnesium, potassium) and vitamins. Additionally, they contain a number of phytochemicals such as phenolic acids, polyphenols and phytosterols [3,6]. Compared to other nuts, walnuts have a particularly high content of alpha-linolenic acid, and possibly also a higher bioavailability of the above mentioned phytochemicals : walnuts are usually consumed with the ‘skin’, which has the highest content of phytochemicals, whereas this skin is usually removed from other nuts before consumption. Thus, it has been speculated that walnuts might have stronger health effects than other types of nuts. This is however in contrast to other results, for example, from a meta-analysis showing that different types of nuts had similar effects on blood lipid levels . ” 
[link to full text: http://www.biomedcentral.com/content/pdf/1741-7015-11-165.pdf%5D
The list of benefits associated with nut consumption can be expanded to include reduced risk of type 2 diabetes , CVD  , metabolic syndrome  .
The information from this current study comes as no surprise; it only confirms earlier reports. We have been sending you newsletters about the benefits of nuts for almost that long. You should have gotten the idea by now. So why are we taking the time to discuss this new study?
We are doing so because, to our continual surprise, we come across both medical and naturopathic doctors advising patients to avoid eating nuts to reduce CVD risk. For these doctors to provide such advice ignores twenty years of solid science.
It is easier to understand when medical doctors make such inaccurate pronouncements; it is easy to remind ourselves how little training or interest they may have in diet in nutrition; they are simply dinosaurs [late adopters] who have not kept up with the science. There is also a tendency I am afraid to report that I have observed in some medical doctors, to consider the information they learned in medical school to be gospel, some sort of truth that will not change over time.
It is far more troubling to discover members of our own naturopathic profession who, when advocating for a particular dietary philosophy, advise patients not to consume nuts; these dear colleagues of ours should know better. We are a profession that prides itself with keeping up with the latest developments in nutrition research and strive to adapt to current scientific knowledge as it evolves. If we let belief and faith in our understanding trump good science, then perhaps it is time for some of to apply for tax-exempt status as a religion as what they are doing is no longer the practice of naturopathic medicine.
1. Guasch-Ferré M, Bulló M, Martínez-González MA, Ros E, Corella D, Estruch R, Fitó M, Arós F, Julia Wärnberg J, Fiol M, Lapetra J et al, on behalf of the PREDIMED study group. Frequency of nut consumption and mortality risk in the PREDIMED nutrition intervention trial. BMC Medicine 2013, 11:
2. Fraser GE, Sabate J, Beeson WL, Strahan TM: A possible protective effect of nut consumption on risk of coronary heart disease. The Adventist Health Study. Arch Intern Med 1992, 152(7):1416–1424.
3. Sabate J, Fraser GE, Burke K, Knutsen SF, Bennett H, Lindsted KD: Effects of walnuts on serum lipid levels and blood pressure in normal men. N Engl J Med 1993, 328(9):603–607.
4. Ros E: Health benefits of nut consumption. Nutrients 2010, 2(7):652–682.
5. Guasch-Ferré M, Bulló M, Martínez-González MÁ, Ros E, Corella D, Estruch
R, Fitó M, Arós F, Wärnberg J, Fiol M, et al: Frequency of nut consumption
and mortality risk in the PREDIMED nutrition intervention trial. BMC Medicine 2013, 11:164.
6. King JC, Blumberg J, Ingwersen L, Jenab M, Tucker KL: Tree nuts and peanuts as components of a healthy diet. J Nutr 2008, 138(9):1736S–1740S.
7. Vinson JA, Cai Y: Nuts, especially walnuts, have both antioxidant quantity and efficacy and exhibit significant potential health benefits. Food Funct 2012, 3(2):134–140.
8. Sabate J, Oda K, Ros E: Nut consumption and blood lipid levels: a pooled analysis of 25 intervention trials. Arch Intern Med 2010, 170(9):821–827.
9. Rohrman S and Faeh D, Should we go nuts about nuts? BMC Medicine 2013, 11:165
10. Estruch R, Ros E, Salas-Salvadó J, Covas MI, Corella D, Arós F, Gómez-Gracia E, Ruiz-Gutiérrez V, Fiol M, Lapetra J, Lamuela-Raventos RM, Serra-Majem L, Pintó X, Basora J, Muñoz MA, Sorlí JV, Martínez JA, Martínez-González MA; PREDIMED Study Investigators. Primary prevention of cardiovascular disease with a Mediterranean diet. N Engl J Med. 2013 Apr 4;368(14):1279-90.
11. Salas-Salvadó J, Fernández-Ballart J, Ros E, Martínez-González MA, Fitó M, Estruch R, Corella D, Fiol M, Gómez-Gracia E, Arós F, Flores G, Lapetra J, Lamuela-Raventós R, Ruiz-Gutiérrez V, Bulló M, Basora J, Covas MI; PREDIMED Study Investigators. Effect of a Mediterranean diet supplemented with nuts on metabolicsyndrome status: one-year results of the PREDIMED randomized trial. Arch Intern Med. 2008 Dec 8;168(22):2449-58.