Dried fruit, benefits for the heart and metabolism

Why dried fruit protects the heart: meta-analysis data

Reduction of cardiovascular risk

The  meta-analyses most recent document unequivocally demonstrate the protective effects of dried fruit on the cardiovascular system. The study by Aune et al. (2016), which analyzed 20 prospective studies with over 819,000 participants, highlighted that consumption of 28 grams per day of dried fruit is associated with:

• 21% reduction of coronary heart disease risk

• 21% reduction of cardiovascular disease risk

• 22% reduction of all-cause mortality

These results were confirmed by the umbrella review of Balakrishna et al. (2022), which synthesized evidence from several systematic reviews finding a  19% reduction in the incidence of cardiovascular diseases and of  25% cardiovascular mortality when comparing high with low consumption of nuts.

Reduction of risk of heart attack, stroke and atrial fibrillation

A comprehensive review of prospective cohort studies (Glenn et al., 2023) documented that higher nut consumption is associated with:

• 24% reduction in the incidence of coronary heart disease;

• 27% reduction in mortality from coronary heart disease;

• 18% reduction in stroke mortality;

• 15% reduction in the risk of atrial fibrillation;

• 19% reduction in total mortality.

The Swedish study by Larsson et al. (2018) on over 61,000 adults confirmed aninverse dose-response association between nut consumption and incidence of atrial fibrillation, with an 18% risk reduction, demonstrating that benefits increase proportionally with consumption.

The role of nuts in cholesterol and blood pressure control

Blood lipids: action on LDL and triglycerides

The mechanisms by which nuts exert their cardioprotective effects are multiple and synergistic. An updated meta-analysis (Nishi et al., 2024) on  randomized clinical trials demonstrated that nut consumption significantly reduces:

• total cholesterol;

• LDL cholesterol (i.e. ‘bad’ cholesterol);

• triglycerides.

Without negatively affecting HDL cholesterol (i.e. ‘good’ cholesterol). The reduction of LDL cholesterol is a key mechanism but does not fully explain the cardiovascular risk reduction, suggesting the involvement of other beneficial factors (Rajaram et al., 2023).

Endothelial function and anti-inflammatory molecules

Studies have shown improvements in  blood pressure and of the  endothelial function, crucial parameters for vascular health. The presence of  L-arginina, precursor ofnitric oxide, contributes to the maintenance of vascular tone and vasodilation (Khalili et al., 2022).

Inflammation and oxidative stress

Nuts are rich in compounds with properties  antioxidant e antimicrobial, including:

• monounsaturated and polyunsaturated fatty acids;

• dietary fiber;

• B vitamins and vitamin E;

• minerals (magnesium, potassium, zinc, selenium);

• polyphenols highly bioactive.

A narrative review by Rajaram et al. (2023) examined the effects of nuts on  biomarkers of inflammation and oxidative stress, highlighting an overall protective effect. A systematic review of clinical trials has in turn documented that regular consumption of dried fruit can improve oxidative stress parameters, contributing to the prevention of oxidation-related pathologies (Silveira et al., 2022).

These effects are mediated by the activation of cellular antioxidant pathways and by the reduction of inflammatory markers such as interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α) (Khalili et al., 2022).

Metabolism and type 2 diabetes: prevention and management

Evidence in diabetic patients

As for  type 2 diabetes, the evidence is complex. The study by Liu et al. (2019) on diabetic patients demonstrated that the consumption of dried fruit is associated with a reduction in risk of cardiovascular disease and total mortality even in this vulnerable population, suggesting an important protective role for those already living with the condition.

Primary prevention

The most recent meta-analyses have not found a statistically significant association between total nut consumption and reduced risk of developing type 2 diabetes, although some specific species (such as walnuts) can have favorable effects (Becerra-Tomás et al., 2021).

Nuts can nevertheless contribute to  glycemic control in subjects with diabetes or at metabolic risk, thanks to the content of fibre, proteins and healthy fats which modulate the post-prandial glycemic response and improve insulin sensitivity (Khalili et al., 2022).

Not only heart: impact on longevity and cognitive functions

Mortality from specific causes

The protective effect of nuts extends to  Mortality from specific causes. The meta-analysis by Aune et al. (2016) documented significant reductions in mortality from:

• respiratory diseases: -52%;

• diabetes: -39%;

• infectious diseases: -75%;

• neurodegenerative diseases: -35% (not statistically significant).

Impact on longevity

The review by Fadnes & Balakrishna (2024) estimated that the consumption of  one serving of nuts per day (28-30 g) is associated with a 20% reduction approximately in the risk of cardiovascular diseases and premature deaths.

The study by Malmir and colleagues (2023) on long-term cardiovascular mortality confirmed that a high intake of  whole grains, fruits, vegetables, and nuts significantly reduces cardiovascular mortality, with a  27% reduction for every 10 grams more of nuts consumed daily as part of a balanced diet.

Cognitive function and brain health

Although nuts contain numerous compounds  neuroprotective - including omega-3 fatty acids, polyphenols, B vitamins and vitamin E, minerals – the evidence on the effects on  cognitive function still requires further investigation.

A recent narrative review (Nishi et al., 2023) examined the epidemiological, clinical, and mechanistic evidence on the effect of nut exposure on cognitive performance, highlighting the potential benefits of these foods for  brain health throughout the entire life span.

PREDIMED-Plus Study

The 2023 PREDIMED-Plus cohort study, conducted on 6,630 older adults (55-75 years) at risk of cognitive decline, observed  positive associations between high nut consumption and favorable changes in  cognitive performance over two years (Ni et al., 2023).

Proposed mechanisms include:

• reduction of  oxidative stress in the brain;

• attenuation ofinflammation systemic and neuroinflammation;

• beneficial effects on  intestinal microbiota (gut-brain axis);

• improvement of  cerebral flow through endothelial function.

Longer randomized controlled trials will be useful to confirm these promising results.

Nutritional identikit: what makes dried fruit a ‘nutrient-dense food’

Dried fruit represents a food ‘nutrient-dense’ with a particularly favorable nutritional profile (Fadnes & Balakrishna, 2024):

a) macronutrients:

• unsaturated fats (55-75%): monounsaturated fatty acids (oleic) and polyunsaturated (linoleic, alpha-linolenic);

• plant proteins (15-25%): rich in L-arginine;

• fiber dietary (5-10%);

• complex carbohydrates with low glycemic index;

b) micronutrients:

• vitaminsVitamin E (tocopherols), group B (folates, thiamine, niacin);

• mineralsmagnesium, potassium, zinc, selenium, calcium, phosphorus;

• bioactive compoundspolyphenols, phytosterols, sphingolipids.

Integrated mechanisms

The mechanisms of action include synergistic effects on:

1. Improvement of lipid profile (reduction of LDL-C, triglycerides);

2. Reduction of blood pressure (NO-mediated vasodilation);

3. Enhancement of endothelial function (nitric oxide bioavailability);

4. Attenuation of inflammation systemic (reduction of pro-inflammatory cytokines);

5. Modulation of oxidative stress (antioxidant activity);

6. Prebiotic effects on the composition of the gut microbiota (Rajaram et al., 2023).

Practical consumption guide: recommended doses and methods

Recommended daily portion

Accumulated scientific evidence supports the inclusion of nuts in  dietary guidelines for the prevention of cardiovascular diseases. A standard portion of 28-30 grams per day (about a handful), equivalent depending on the species to:

• 7-8 walnuts;

• 15-20 almonds;

• 15-20 hazelnuts;

• 2 tablespoons of peanuts;

• 45-50 pistachios.

This amount is associated with benefits documented by research,  without negative effects on body weight when consumed within the context of a balanced diet also in terms of overall energy intake.

International guidelines

The  Nordic Nutrition Recommendations 2023 have classified the protective effect of nuts on cardiovascular diseases as ‘probable’, recommending an increase in their consumption up to one portion per day (Fadnes & Balakrishna, 2024).

TheAmerican Heart Association has included nuts among cardioprotective foods in its recent guidelines, emphasizing the importance of regular consumption within a healthy dietary pattern (Lichtenstein et al., 2021).

Ways of consumption

To maximize benefits:

• prefer unsalted nuts  unsalted

• avoid roasting at high temperatures (>150°C) to prevent acrylamide formation and oxidation of polyunsaturated fats which can negate some of the described benefits;

• therefore consume dried fruit natural or gently roasted;

• integrate consumption at different times of the day (breakfast, snacks, main meals);

• vary the species to integrate nutritional benefits.

Conclusions

The body of available scientific evidence shows that the  daily consumption of a modest portion (28-30 g) of natural dried fruit in the daily diet represents a long-term investment in health. The synergy between good fats, fiber, and bioactive compounds offers a protective shield against the most common chronic diseases, improving life expectancy and its quality at every stage of life. A simple, sustainable, and science-validated gesture to strengthen the benefits of the Mediterranean diet.

Dario Dongo

Bibliography

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