New Australian research shows most of us are missing out on the significant health benefits of eating a handful of…
Nuts and heart health
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 , the Iowa Women Health Study , the Nurses’ Health Study , the Physicians’ Health Study ) 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) . 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  and in 2018  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 
- 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 
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 
Total of 136 analyses on cardiovascular outcomes were assessed:
- Decrease in total cholesterol – unweighted mean change: -3.28%
- Decrease in LDL cholesterol – unweighted mean change: –4.03%
- LDL: HDL cholesterol ratio – unweighted mean change: -7.38%
- Triglycerides, HDL and BP – lack 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) .
- 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 .
- It has also been found that favourable effects of nut intake are sustained over long periods of time – around 30 years .
Potential mechanisms of action:
There are several ways that nuts are thought to reduce heart disease risk and reduce heart health indicators:
Fatty acid profile
the 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 .
Nuts are rich sources of phytosterols, which are associated with reductions in cholesterol levels, mediated by decreased cholesterol absorption and increased faecal cholesterol excretion [10, 11].
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. .
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 [13-15].
Nuts contain fibre and soluble fibre assists in reducing blood cholesterol by lowering cholesterol re-absorption from the intestine .
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- Neale, E., et al., The effect of nut consumption on heart health: an updated systematic review of the literature. 2018. Nuts for Life, unpublished.
- Guasch-Ferre, M., et al., Nut Consumption and Risk of Cardiovascular Disease. J Am Coll Cardiol, 2017. 70(20): p. 2519-2532.
- Ros, E., Health Benefits of Nut Consumption. Nutrients, 2010. 2(7): p. 652-682.
- 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.
- 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.
- 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.
- Lopez-Uriarte, P., et al., Nuts and oxidation: a systematic review. Nutr Rev, 2009. 67(9): p. 497-508.
- Olas, B. and B. Wachowicz, Resveratrol, a phenolic antioxidant with effects on blood platelet functions. Platelets, 2005. 16(5): p. 251-60.
- 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.
- Surampudi, P., et al., Lipid Lowering with Soluble Dietary Fiber. Curr Atheroscler Rep, 2016. 18(12): p. 75.