Enjoying a handful of nuts every day can reduce your risk of developing cardiovascular disease by more than 20% and coronary heart disease by nearly 30% [1]. And if you have heart disease, eating nuts can reduce your risk of dying from it [1].
Regularly eating nuts can also significantly reduce total cholesterol, LDL (bad) cholesterol and improve the ratio of bad to good cholesterol, which are all risk factors for heart disease [2].

How do nuts support heart health?

  • Nuts have a high proportion of healthy, mono- and polyunsaturated fats, and lower unhealthy saturated fats. A diet high in saturated and trans-fat is associated with higher cholesterol levels [3].
  • Nuts contain phytosterols, which help reduce cholesterol in the blood by reducing the amount that the body absorbs, and removing it from the body instead [4, 5].
  • Arginine, an essential amino acid, helps blood vessels remain flexible and prevent blood clots [6]. 
  • Vitamin E, riboflavin, selenium, manganese, copper, zinc and polyphenols are all found in nuts. These act as antioxidants, which help protect your body’s cells from damage caused by oxidation [7-9]. 
  • The fibre and soluble fibre found in nuts helps reduce blood cholesterol by lowering cholesterol re-absorption from the intestine [10].

Many studies have investigated how many nuts you should eat, with the majority suggesting that 30g (about one handful) of nuts 2-5 times a week will support heart health.

Studies have been conducted on many different tree nuts, with most suggesting all nuts have a similar effect on heart health. However, we know Australians eat too much salt (which can increase blood pressure), so it’s best to enjoy raw or roasted, unsalted nuts as your everyday choice, saving salted nuts for special occasions.

What the research says

The body of evidence for the benefits of nuts for heart health has been established by decades of research. Four large prospective cohort studies (the Adventist Health Study [11], the Iowa Women Health Study [12], the Nurses’ Health Study [13], the Physicians’ Health Study [14]) examined the relation between nut consumption and the risk of coronary heart disease (CHD) and all found an inverse association.  

Since then, the evidence has continued to support these findings.  Evidence from a systematic literature review and meta-analysis of 20 prospective cohort studies shows that nuts are associated with a 24% reduced relative risk of CHD and a 19% reduced relative risk of cardiovascular disease (CVD) [1]. In the dose response meta-analysis, there was a 29% and 21% reduction in the relative risk of CHD and CVD respectively, for a one serving per day increase in nut intake.  

Finally, an extensive systemic literature review on nuts and heart health was conducted by researchers from the University of Wollongong in 2015 [15] and in 2018 [2] which found a causal relationship between nut intake and heart health indicators (total cholesterol, LDL cholesterol, and LDL:HDL ratio) and reduced mortality from CVD.  

Risk of disease [1]

  • Risk of coronary heart disease: For a 28g/day increase in nut intake, there was a 29% reduction in the relative risk of CHD (RR 0.71, 95% CI)  
  • Risk of cardiovascular disease: For a 28g/day increase in nut intake, there was a 21% reduction in the relative risk of CVD (RR 0.79, 95% CI).

Mortality and morbidity [2]

Observational studies reported moderate to high consistent associations between nut consumption and reduced risk of total incidence of and mortality from CVD and CHD. 

Heart health indicators [2]

Total of 136 analyses on cardiovascular outcomes were assessed:

  • Decrease in total cholesterolunweighted mean change: -3.28%
  • Decrease in LDL cholesterolunweighted mean change:4.03%
  • LDL: HDL cholesterol ratiounweighted mean change: -7.38%
  • Triglycerides, HDL and BPlack of any consistent favourable effects

How many nuts and for how long?

  • Findings were based on 1 oz servings/day (i.e. 28g or around a handful) [1]. 
  • Doses ranged from 10-100g per day, however observational evidence continues to suggest beneficial outcomes with 1 oz (28g) per day, which also aligns with serving recommendations from the Australian Dietary Guidelines, which state a serve of nuts as being 30g [2]. 
  • It has also been found that favourable effects of nut intake are sustained over long periods of time – around 30 years [16]. 

Potential mechanisms of action

There are several ways that nuts are thought to reduce heart disease risk and reduce heart health indicators.

Fatty acid profileThe fatty acid profile of nuts, namely their high proportion of monounsaturated fat and/or polyunsaturated fat (depending on nut type) relative to saturated fat may in part explain their favourable effects on lipid profiles [17].
Nuts are rich sources of phytosterols, which are associated with reductions in cholesterol levels, mediated by decreased cholesterol absorption and increased faecal cholesterol excretion [4, 5].
Amino acids Nuts contain arginine, an essential amino acid which is involved in the synthesis of nitric oxide. Nitric oxide causes the blood vessels to dilate and remain elastic – maintaining endothelial function. It is also involved in the prevention of blood clots. [6]. 
Phytochemicals Nuts contain a variety of phytochemicals with antioxidant potential such as vitamin E, riboflavin, selenium, manganese, copper, zinc and polyphenols. It is this antioxidant action that is thought to have positive effects on lipid oxidation, oxidative stress and platelet function [7-9].
Fibre Nuts contain fibre and soluble fibre assists in reducing blood cholesterol by lowering cholesterol re-absorption from the intestine [10]. 

References

  1. Aune, D., et al., Nut consumption and risk of cardiovascular disease, total cancer, all-cause and cause-specific mortality: a systematic review and dose-response meta-analysis of prospective studies. BMC Med, 2016. 14(1): p. 207.
  2. Neale, E., et al., The effect of nut consumption on heart health: an updated systematic review of the literature. 2018. Nuts for Life, unpublished.
  3. Mensink, R., Effects of saturated fatty acids on serum lipids and lipoproteins: a systematic review and regression analysis. Geneva: World Health Organization. 2016.
  4. Racette, S.B., et al., Dose effects of dietary phytosterols on cholesterol metabolism: a controlled feeding study. The American Journal of Clinical Nutrition, 2010. 91(1): p. 32-38.
  5. Rocha, M., et al., A review on the role of phytosterols: new insights into cardiovascular risk. Current Pharmaceutical Design, 2011. 17(36): p. 4061-4075.
  6. Neale, E.P., et al., The effect of nut consumption on markers of inflammation and endothelial function: a systematic review and meta-analysis of randomised controlled trials. BMJ Open, 2017. 7(11): p. e016863.
  7. Lopez-Uriarte, P., et al., Nuts and oxidation: a systematic review. Nutr Rev, 2009. 67(9): p. 497-508.
  8. Olas, B. and B. Wachowicz, Resveratrol, a phenolic antioxidant with effects on blood platelet functions. Platelets, 2005. 16(5): p. 251-60.
  9. Bullo, M., R. Lamuela-Raventos, and J. Salas-Salvado, Mediterranean diet and oxidation: nuts and olive oil as important sources of fat and antioxidants. Curr Top Med Chem, 2011. 11(14): p. 1797-810.
  10. Surampudi, P., et al., Lipid Lowering with Soluble Dietary Fiber. Curr Atheroscler Rep, 2016. 18(12): p. 75.
  11. Fraser, G.E., et al., A possible protective effect of nut consumption on risk of coronary heart disease. The Adventist Health Study. Arch Intern Med, 1992. 152(7): p. 1416-24.
  12. Ellsworth, J.L., L.H. Kushi, and A.R. Folsom, Frequent nut intake and risk of death from coronary heart disease and all causes in postmenopausal women: the Iowa Women's Health Study. Nutr Metab Cardiovasc Dis, 2001. 11(6): p. 372-7.
  13. Hu, F.B., et al., Frequent nut consumption and risk of coronary heart disease in women: prospective cohort study. BMJ, 1998. 317(7169): p. 1341-5.
  14. Albert, C.M., et al., Nut consumption and decreased risk of sudden cardiac death in the Physicians' Health Study. Arch Intern Med, 2002. 162(12): p. 1382-7.
  15. Neale, E., D. Nolan-Clark, and L. Tapsell, The effect of nut consumption on heart health: a systematic literature review. 2015. Nuts for Life, unpublished.
  16. Guasch-Ferre, M., et al., Nut Consumption and Risk of Cardiovascular Disease. J Am Coll Cardiol, 2017. 70(20): p. 2519-2532.
  17. Ros, E., Health Benefits of Nut Consumption. Nutrients, 2010. 2(7): p. 652-682.
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