The body of evidence about nuts and heart health continues to grow, with new local and international research papers regularly published.

Large population studies

All found inverse associations between nut consumption and the risk of coronary heart disease.

Key studies: systematic literature reviews and meta-analyses

Effect of Tree Nuts Consumption on Serum Lipid Profile in Hyperlipidemic Individuals: A Systematic Review (2020).
Altamimi M. et al. This new systematic review, of 29 intervention studies, offers more evidence that tree nut consumption can improve serum lipid levels – this time, in adults with hyperlipidaemia. It found different nuts favourably impact different lipid parameters. But across the board, all nuts effectively raised HDL-cholesterol levels. Study intervention periods varied from three weeks to 12 months, and nut ‘doses’ ranged from 15 to 126g a day.

Does nut consumption reduce mortality and/or risk of cardiometabolic disease? An updated review based on meta-analyses. (2019).
Nut consumption appears to exert a protective effect on cardiometabolic disease, possibly through improved concentrations of fasting glucose, total cholesterol, and LDL-C.

Nut consumption and incidence of cardiovascular diseases and cardiovascular disease mortality: a meta-analysis of prospective cohort studies. (2019).
A systematic review and meta-analysis of all published studies concludes that the consumption of nuts helps reduce the risk of incidence of cardiovascular disease and mortality.

Almond consumption and risk factors for cardiovascular disease: A systematic review and meta-analysis of randomized controlled trials. (2019).
A systematic review and meta-analysis of RCTs showed that almonds significantly reduce total cholesterol, LDL cholesterol, body weight and apolipoprotein B.

Portfolio dietary pattern and cardiovascular disease: A systematic review and meta-analysis of controlled trials. (2018).
Dietary portfolio is a plant based dietary pattern, as a ‘portfolio’ of 4 cholesterol lowering foods, incl 42g nuts (tree nuts or peanuts). Study revealed significantly lowered LDL cholesterol by 17%, which is beyond that which is seen with the NCEP Step II diet alone.

Effect of nut consumption on vascular endothelial function: A systematic review and meta-analysis of randomized controlled trials. (2018).
Nut consumption significantly improved endothelial function. However, the beneficial effect was limited to walnuts. More studies examining the effect of other nuts on endothelial function are needed in the future.

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. (2016).
Nut consumption may reduce the risk of coronary heart disease, stroke, cardiovascular disease, total cancer, and all-cause mortality, and possibly mortality from diabetes, respiratory disease, and infectious disease. In the dose–response analysis there was a 29% reduction in the relative risk of CHD and a 21% reduction in the relative risk of CVD for a one serving per day increase in nut intake (one serving = 28 grams).

The effect of nut consumption on markers of inflammation and endothelial function: a systematic review and meta-analysis of randomised controlled trials. (2017).
This paper suggests that nut consumption, particularly walnuts, has favourable effects on flow-mediated dilation – a measure of endothelial function that may be an important predictor of cardiovascular risk – but that nuts did not affect markers of inflammation.

A systematic review and meta-analysis of nut consumption and incident risk of CVD and all-cause mortality. (2016).
In conclusion, we found that higher nut consumption is associated with a lower risk of all-cause mortality, total CVD, CVD mortality, total CHD, CHD mortality and sudden cardiac death.

Nut consumption on all-cause, cardiovascular, and cancer mortality risk: a systematic review and meta-analysis of epidemiologic studies. (2015).
Nut consumption is associated with lower risk of all-cause, CVD, and cancer mortality, but the presence of confounding factors should be taken into account when considering such findings.

Relationship of tree nut, peanut and peanut butter intake with total and cause-specific mortality: a cohort study and meta-analysis. (2015).
Total nut intake was related to lower overall and cause-specific mortality (cancer, diabetes, cardiovascular, respiratory, neurodegenerative diseases, other causes) in men and women. Nut intake was related to lower overall and cause-specific mortality, with evidence for nonlinear dose-response relationships. Peanut butter was not related to mortality.

Nut consumption and risk of type 2 diabetes, cardiovascular disease, and all-cause mortality: a systematic review and meta-analysis. (2014).
Our meta-analysis indicates that nut intake is inversely associated with IHD, overall CVD, and all-cause mortality but not significantly associated with diabetes and stroke. The inverse association between the consumption of nuts and diabetes was attenuated after adjustment for body mass index. These findings support recommendations to include nuts as part of a healthy dietary pattern for the prevention of chronic diseases.

Other evidence

A pilot study on the effects of nut consumption on cardiovascular biomarkers. (2020).
The US-based research found that eating a handful of nuts daily, over just four weeks, drastically improved the blood markers that are linked with heart disease. The researchers asked 11 study participants, with an average age of 52 years and who all had undesirable blood lipid levels, to eat a combination of three almonds, three hazelnuts and three walnuts each morning for four weeks. This led to a positive shift in all five markers they measured. That is, higher HDL (good) cholesterol; lower total cholesterol; lower total cholesterol: HDL cholesterol ratio; lower LDL (bad) cholesterol; lower triglycerides.

Mediterranean diet and atherothrombosis biomarkers: A randomised controlled trial. (2020).
This study assessed whether following a Mediterranean diet (MedDiet) improved atherothrombosis biomarkers in high cardiovascular risk individuals. In 358 random volunteers from the PREvención con DIeta MEDiterránea trial, the authors assessed the one-year effects on atherothrombosis markers of an intervention with MedDiet, enriched with virgin olive oil (MedDiet-VOO; n = 120) or nuts (MedDiet-Nuts; n = 119), compared with a low-fat control diet (n = 119). Increases in nut, fruit, vegetable, and fatty fish consumption, and decreases in processed meat intake, were linked to beneficial changes in atherothrombosis biomarkers. The researchers concluded that following a MedDiet improved atherothrombosis biomarkers in high cardiovascular risk individuals.

Association Between Plant and Animal Protein Intake and Overall and Cause-Specific Mortality (2020).
Huang J. et al. Those who ate more plant-based protein reduced their overall risk for death when compared to those who ate less plant-based protein, including a reduced risk of death from heart disease by up to 12%.

Association of Nut Intake with Risk Factors, Cardiovascular Disease, and Mortality in 16 Countries From 5 Continents: Analysis from the Prospective Urban and Rural Epidemiology (PURE) Study. (2020).
de Souza R. et al.
Higher nut intake was associated with lower mortality risk from both cardiovascular and non-cardiovascular causes in low-, middle-, and high-income countries.

Association Between Healthy Eating Patterns and Risk of Cardiovascular Disease. (2020).
Shan Z. et al.
In 3 large prospective cohorts with up to 32 years of follow-up, greater adherence to various healthy eating patterns was consistently associated with lower risk of CVD. These findings support the recommendations of the 2015-2020 Dietary Guidelines for Americans, emphasising diets rich in wholegrains, fruits and vegetables, nuts and legumes.

Daily almond consumption in cardiovascular disease prevention via LDL-C change in the U.S. population: a cost-effectiveness analysis. (2020)
Wang J. et al.
This study assessed the cost-effectiveness of almond consumption in the short term and up to 10 years for CVD prevention. The authors found that consuming almonds may be a cost-effective solution for the primary prevention of CVD in both the short and long term.

Effects of a Healthy Diet Enriched or Not With Pecan Nuts or Extra-Virgin Olive Oil on the Lipid Profile of Patients With Stable Coronary Artery Disease: A Randomised Clinical Trial. (2020)
Campos VP. Et al.
This trial investigated changes in the lipid profiles of patients with coronary artery disease, randomised to a control group (healthy diet); pecan group (healthy diet plus 30g pecans/day) or olive oil group (health diet plus 30ml olive oil/day). Whilst no differences were observed for LDL or HDL cholesterol, LDL: HDL cholesterol ratio, or the HDL: triglyceride ratio between groups, the pecan group exhibited significant reductions in other lipid parameters.

Effect of a 12-Week Almond-Enriched Diet on Biomarkers of Cognitive Performance, Mood, and Cardiometabolic Health in Older Overweight Adults. (2020)
Coates A. et al
This study examined supplementing habitual diets with almonds or carbohydrate-rich snack foods (providing 15% energy) on biomarkers of cardiovascular and metabolic health, mood and cognitive performance. The inclusion of almonds in the diet improves aspects of cardiometabolic health without affecting cognitive performance or mood in overweight/obese adults.

Snacking on whole almonds for 6 weeks improves endothelial function and lowers LDL cholesterol but does not affect liver fat and other cardiometabolic risk factors in healthy adults: the ATTIS study, a randomised controlled trial. (2020)
Dikariyanto V. et al.
Whole almonds consumed as snacks markedly improve endothelial function, in addition to lowering LDL cholesterol, in adults with above-average risk of CVD.

Oxidative Stress Biomarkers, Nut-Related Antioxidants, and Cardiovascular Disease. (2020)
Lorenzon Dos Santos J. et al
This article briefly highlights the interaction between oxidative stress, atherosclerosis, and cardiovascular disease, in addition to the effect of the consumption of different nuts and related dietary antioxidants—like polyphenols and vitamin E—on biomarkers of oxidative stress in primary and secondary cardiovascular prevention.

Changes in Nut Consumption and Subsequent Cardiovascular Disease Risk Among US Men and Women: 3 Large Prospective Cohort Studies. (2020)
Liu X. et al.
This study of 3 large prospective cohorts, evaluated the association of within-individual changes in consumption of total and specific types of nuts and the subsequent risk of incident cardiovascular disease (CVD) in over 34,000 US men from the Health Professionals Follow-Up Study, and over 158,000 women from the Nurses’ Health Study I and II. Compared with participants who made no changes to their nut intake, participants who increased their total nut consumption had a lower risk of CVD, CHD, and stroke. The findings support the recommendation of including a variety of nuts as part of healthy dietary patterns, and provide theoretical evidence that replacing animal‐based protein with plant‐based protein can be helpful in the prevention of CVD.

Replacing Saturated Fats with Unsaturated Fats from Walnuts or Vegetable Oils Lowers Atherogenic Lipoprotein Classes Without Increasing Lipoprotein(a). (2020).
A randomized, crossover, controlled-feeding study was conducted in 34 individuals at risk of cardiovascular disease (CVD). Participants were assigned each of the following diets for six weeks: 1) walnuts diet (57-99g/day); 2) walnut fatty-acid matched diet devoid of walnuts, and; 3) a diet replacing ALA with oleic acid without walnuts. The study concluded that the replacement of saturated fatty acids with unsaturated fats from walnuts improved lipid/lipoprotein classes, including LDL-cholesterol, non-HDL cholesterol, and total cholesterol.

Walnuts and Vegetable Oils Containing Oleic Acid Differentially Affect the Gut Microbiota and Associations with Cardiovascular Risk Factors: Follow-up of a Randomized, Controlled, Feeding Trial in Adults at Risk for Cardiovascular Disease. (2019)
Researchers found that eating walnuts daily as part of a healthy diet was associated with increases in certain bacteria that can help promote health. Additionally, those changes in gut bacteria were associated with improvements in some risk factors for heart disease.

Does Nut Consumption Reduce Mortality and/or Risk of Cardiometabolic Disease? An Updated Review Based on Meta-Analyses. (2019)
This review updates a previous review published in December 2018 by the same authors. The results of this update found that nut consumption has beneficial effects on cardiometabolic disease with reduced CVD mortality, CHD mortality, stroke mortality, CVD incidence, CHD incidence and stroke incidence comparing high with low categories of nut consumption.

Mechanisms underlying the cardiometabolic protective effect of walnut consumption in obese people: A cross-over, randomized, double-blind, controlled inpatient physiology study. (2019)
Results from a small RCT showed walnut consumption improved several cardiometabolic variables in obese adults.

Comparative effect of different types of tree nut consumption on blood lipids: a network meta-analysis of clinical trials. (2020).
Researchers compared the effects of diets enriched with almonds, cashews, hazelnuts, pistachios or walnuts, and ranked the pistachio-enriched diet as the best for lowering total cholesterol, LDL and TGs; walnut-enriched diets were ranked second for reducing total cholesterol and TGs, while almond-enriched diets were second for lowering LDL.

Replacing saturated fat with walnuts or vegetable oils improves central blood pressure and serum lipids in adults at risk for cardiovascular disease: A randomized controlled‐feeding trial. (2019).
Replacing saturated fatty acids with walnuts into a healthy dietary pattern significantly lowered diastolic BP as well as reducing total and LDL cholesterol – which the authors suggest could be due to their unique fatty acid profile and phenolic compounds.

Effects of daily consumption of cashews on oxidative stress and atherogenic indices in patients with type 2 diabetes: A randomized, controlled-feeding trial. (2019).
A recent RCT concluded daily consumption of cashews significantly reduced insulin and LDL: HDL cholesterol ratio in patients with diabetes.

Nut consumption in relation to cardiovascular disease incidence and mortality among patients with diabetes mellitus. (2019).
In men and women with diabetes, higher tree nut consumption, is associated with a lower risk of CVD and CHD incidence by 20% and 23% respectively.

Mixed nut consumption may improve cardiovascular disease risk factors in overweight and obese adults. (2019).
Supplementation of 42.5g/day of mixed nuts into a usual diet significantly decreased insulin levels, glucose, BMI and body weight, compared to an isocaloric pretzel snack in an 8-week RCT.

Almond oil for patients with hyperlipidaemia: A randomized open-label controlled clinical trial. (2019).
10ml of almond oil twice daily for 30 days significantly reduces total and LDL cholesterol in hyperlipidemic patients.

Cardiovascular mortality attributable to dietary risk factors in 51 countries in the WHO European Region from 1990 to 2016: a systematic analysis of the Global Burden of Disease Study. (2019).
An altered diet is the most effective means of preventing premature deaths, with a diet low in nuts and seeds one of the top three dietary risk factors across the 51 countries analysed.

Patterns of plant and animal protein intake are strongly associated with cardiovascular mortality: the Adventist Health Study-2 cohort. (2018).
Associations between the ‘Meat’ and ‘Nuts & Seeds’ protein factors and cardiovascular outcomes were strong and could not be ascribed to other associated nutrients considered to be important for cardiovascular health. Healthy diets can be advocated based on protein sources, preferring low contributions of protein from meat and higher intakes of plant protein from nuts and seeds.

Effect of hazelnut on serum lipid profile and fatty acid composition of erythrocyte phospholipids in children and adolescents with primary hyperlipidaemia: A randomized controlled trial. (2018).
Hazelnuts, both with and without skins significantly reduced LDL cholesterol and increased HDL: LDL cholesterol ratio.

The effect of almonds on vitamin E status and cardiovascular risk factors in Korean adults: a randomized clinical trial. (2018).
The addition of 56g of almonds/day as snack to the typical Korean diet resulted in increases in healthy fats, vitamin E, fibre and a decrease in the amount of energy from carbohydrates. Almonds also improved lipid status, thereby reducing the risk for CVD.

The impact of nuts consumption on glucose/insulin homeostasis and inflammation markers mediated by adiposity factors among American adults. (2018).
Participants with a higher nut intake had a more cardioprotective profile of glucose/insulin homeostasis and inflammatory markers. The authors suggest the low GI and anti-inflammatory effects of nuts provides reasons for their inclusion in diets aimed at reducing the risk of type 2 diabetes, impaired glucose metabolism and CVD.

Primary prevention of cardiovascular disease with a Mediterranean diet supplemented with extra-virgin olive oil or nuts. (2018).
The new results published in June, (after the mistake was rectified) still concluded that those who ate a Mediterranean diet supplemented with nuts or olive oil resulted in a 30% reduction in cardiovascular events, compared to the low-fat group.

Nuts and cardiovascular disease. (2018).
A review of literature spanning the last 25 years – increasing evidence to suggest mechanisms for this benefit related to lowering of oxidative stress, inflammation; and improvement in endothelial function; in addition to the primary mechanism of improvement of lipid and apolipoprotein profile.

Walnut consumption in a weight reduction intervention: effects on body weight, biological measures, blood pressure and satiety. (2017).
Walnut-enriched reduced energy diet promotes weight loss and improves heart health via reducing cholesterol and blood pressure more-so than reduced energy diet without walnuts.

Consumption of nuts and legumes and risk of incident ischemic heart disease, stroke, and diabetes: a systematic review and meta-analysis. (2014).
This systematic review supports inverse associations between eating nuts and incident IHD and diabetes, and eating legumes and incident IHD.

Nuts, inflammation and insulin resistance. (2010).
As chronic inflammation is a key early stage in the atherosclerotic process that predicts future CVD events and is closely related to the pathogenesis of insulin resistance, many recent studies have focused on the potential effect of nut consumption on inflammation and insulin resistance. Through different mechanisms, some components of nuts such as magnesium, fibre, alpha-linolenic acid, L-arginine, antioxidants and MUFA may protect against inflammation and insulin resistance.

The effect of nuts on inflammation. (2008).
The relationship observed between frequent nut consumption and the reduced risk of cardiovascular mortality and type 2 diabetes in some prospective studies could be explained by the fact that nuts are rich in all of these modulator nutrients. In fact, frequent nut consumption has been associated with lower concentrations of some peripheral inflammation markers in cross-sectional studies. Nut consumption has also been shown to decrease the plasma concentration of CRP, IL-6 and some endothelial markers in recent clinical trials.


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