Worldwide, there are numerous studies - epidemiological, clinical and laboratory - showing that increased nut consumption improves our health, particularly our cardiovascular health, and growing research shows nuts outperform many common medications with no negative side effects. Nutrients found in nuts include vitamins A, B complex, C, D and E, zinc, calcium, copper, folic acid, magnesium, selenium, potassium, and protein. Nuts are rich sources of fibre, prebiotics, healthy fats, antioxidants, phytosterols and other phyto (plant) nutrients.
The mechanism for the health benefits of nuts probably lies in the synergistic interaction of the many bioactive constituents of nuts, which may all favourably influence human biochemistry and physiology. Consistently, just one serve of nuts a day dramatically reduces the risk of CVD. Numerous studies have demonstrated that nuts favourably affect serum lipids (fats including cholesterol), improve weight management, insulin sensitivity, have favourable endothelial (artery wall) effects, as well as having anti-inflammatory properties (chronic disease). Incorporating nuts into the diets of more people is likely to lead to a variety of cardiovascular benefits, including longer life.
More Nuts, Less Heart Disease
A pooled analysis of these studies shows that subjects in the highest intake group for nut consumption had a 37% reduction in risk of fatal chronic heart disease (4). The Nurses' Study, which followed participants for 14 years, found frequent nut consumption was inversely related to the risk of coronary heart disease, despite differences in participants' dietary and lifestyle habits (5). A study of 31,208 Seventh Day Adventists found that subjects who consumed nuts more than four times per week had 52% fewer fatal coronary heart disease events and 49% fewer non-fatal heart attacks (myocardial infarction) when compared to those who consumed less than one serving of nuts per week. This was independent of blood pressure, relative weight and other foods. Similarly, in a study of 41,837 post-menopausal women, coronary mortality was inversely associated with nut intake in these women - a relative risk of 43% in women consuming nuts two to four times per week (6,7).
It is now well established that CVD is an inflammatory condition, not cholesterol. Not surprisingly, studies have consistently shown a reduction of inflammation markers associated with nut consumption, which supports the increasing evidence that frequent consumption of nuts is cardio-protective. In an analysis of data from nearly 6,000 participants, consumption of nuts and seeds was inversely associated with levels of inflammatory markers, C-reactive protein (CRP), interleukin-6 (IL-6) and fibrinogen (8). These inflammatory markers are very good indicators of nearly all forms of chronic illness, from cancer to cardiovascular disease. A study of 987 diabetic women (9) and a study of 772 older subjects at high risk (10) showed similar results.
Although cholesterol is only a marker and not the illness, studies of all types of nuts have consistently shown LDL cholesterol reductions ranging from four percent to 11% versus comparative diets, confirming the cholesterol-lowering efficacy of various nut types. A meta-analysis of 13 clinical trials involving 365 participants who supplemented with walnuts found a significantly greater decrease in total and LDL cholesterol concentrations (11). The overall result indicated that the walnut diets compared with the control diets were associated with a 6.7% greater decrease in LDL cholesterol concentration and only positive side effects.
In a study of 20 healthy women and 20 healthy men, subjects were randomly assigned to one of two groups. One group was fed a "normal" healthy diet, while the other was fed a diet rich in walnuts (with 12.5% of the energy derived from 44-58 grams of walnuts per day). The total cholesterol and serum apolipoprotein B concentrations were significantly lower in men and women fed the walnut diet, as was the ratio of LDL cholesterol to HDL cholesterol. Women (10.6%) showed a greater reduction in LDL cholesterol levels than men (8.9%) when both followed the walnut diet. Total cholesterol was lowered by 3.8% in men and 4.9% in women. The researchers also found a significant elevation of alpha-linolenic acid in women (76%) and men (107%). The study reconfirms a growing body of research that walnuts improve blood lipid levels and help reduce risk of heart disease. Walnuts are the only nuts that contain substantial amounts of ALA (alpha-linolenic acid, omega 3), which is described as one of the more anti-inflammatory fatty acids.
Benefits of walnuts and almonds
Studies consistently show that people who eat roughly one handful of almonds a day significantly reduced total and LDL cholesterol and have fast and noticeable results, thus confirming that nuts will benefit our health within a short period of time (12). A study of heart patients revealed a reduction in LDL cholesterol levels after eating two handfuls of raw almonds each day for a month, together with a healthy diet. A nine week study of men who consumed peanuts in the first three weeks of the trial, then almonds for the next three weeks, followed by walnuts for the final three weeks, found a significant reduction in LDL and total cholesterol after consumption of almonds and walnuts (13). These results show how rapidly nuts can benefit the human body, as does a Canadian study in which the participants' lowdensity lipoprotein cholesterol was lowered by 35% within two weeks by eating a wholesome diet including almonds.
Another clinical trial found that women and men who ate about one handful of almonds each day lowered their LDL cholesterol by 4.4% from baseline and if they ate two handfuls there was a 9.4% drop in LDL cholesterol. The researchers also found that all of the people in the study maintained their weight. The researchers reported that the almonds reduced coronary heart disease risk factors in a dose-dependent manner, that is, the more almonds they ate the lower the risk of CVD. There are antioxidant compounds in almond skin - in addition to its naturally occurring form of vitamin E - that may provide positive health effects when eaten with the meal of the almond. In a Japanese study investigating the effects of a walnutcontaining diet, researchers found that serum LDL cholesterol to HDL cholesterol ratio and serum apo B concentrations were lowered in both men and women when walnuts were consumed (4353 grams per day) in place of other dietary fat (14).
In a controlled metabolic clinical study of the health benefits of pecans, researchers discovered that a heart-healthy diet that incorporates pecans can significantly lower blood cholesterol levels (15). Although both diets, the pecan and the low fat diet, lowered total and LDL cholesterol levels, the pecan diet, which contained 11% more fat than the traditional heart-healthy diet, lowered cholesterol levels twice as much. The response to the pecan diet was equivalent to what some people experience with cholesterol-lowering drugs. In addition, even on the higher fat pecan diet, study participants did not gain weight.
In a study of 15 men with high cholesterol aged 48+/-8 years fed hazelnuts, compared with the baseline, the hazelnut-enriched diet decreased the concentrations of VLDL cholesterol, triacylglycerol, apolipoprotein B by 29.5%, 31.8%, and 9.2%, respectively, while increasing HDL cholesterol concentrations by 12.6%. This study demonstrated that a high-fat hazelnut diet was superior to a low-fat control diet because of favourable changes in blood lipid levels (16). Studies have also shown similar results for pistachios (17), macadamias (18), and peanuts (although not real nuts) (19).
Eating as little as one handful of nuts once per week has been shown to keep the arteries in both the heart and eyes healthy (20) and in the case of the eyes reduced macular degeneration by 40%. The risk of type 2 diabetes is also reduced (21). In a study of walnut intake and incident type 2 diabetes in two large cohort studies, the consumption of total nuts and other tree nuts was inversely associated with risk of type 2 diabetes, and the associations were largely explained by Body Mass Index (BMI) - that is, the nut eaters had a healthier weight. These results suggest that higher walnut consumption is associated with a significantly lower risk of type 2 diabetes in women and weight gain (22).
While nuts are rich in nutrients, the antioxidants are located in the pellicle or outer soft shell but 50% or more of them are lost when the skin is removed (23) and oxidation of the fats can occur when the nuts are ground into powder and left to stand. Bleaching of nuts when the hard shells are cracked, as it occurs naturally in pistachios, also destroys most of the antioxidants (24).
So everyone (with the exception of people with nut allergies) should be consuming more nuts. A handful of nuts keeps the doctor - and heart attack - away.
DISCLAIMER: Dr Peter Dingle is a researcher, educator and public health advocate. He has a PhD in the field of environmental toxicology and is not a medical doctor.
REFERENCESSingh et al. 1992; Singh et al. 1992 bOrnish et al. 1999Kelly and Sabaté, 2006Hu et al. 1998Fraser et al. 1992 Prineas 1993 Jiang et al 2006;Mantzoros 2006;Salas-Salvadó et al 2008;Banel, Hu, 2009;Jenkins, 2008Abbey et al. 1994Masako et al. 2000). Journal of Nutrition September 2001Mercanligil et al 2007 MGebauer et al 2008Griel et al 2008Lokko 2007McVeigh 2004Rui et al. 2006J. Nutr. April 1, 2013 vol. 143 no. 4 512-518).Blomhoff et al 2006Seeram et al 2006.
Dr Peter Dingle (PhD) has spent the past 30 years as a researcher, educator, author and advocate for a common sense approach to health and wellbeing. He has a PhD in the field of environmental toxicology and is not a medical doctor. He is Australia’s leading motivational health speaker and has 14 books in publication.