Dr Ray O’Connor continues his look at the latest clinical articles on disease prevention, with a particular emphasis on diet and health
Diet and Health
The recommendation to limit dietary saturated fat intake is primarily drawn from observational studies rather than randomized controlled trials of cardiovascular disease (CVD) prevention. The authors of this systematic review and meta-analysis1 aimed to investigate the efficacy of saturated fat reduction in preventing mortality and CVD. Randomized controlled trials were selected.
Cardiovascular and all-cause mortality and cardiovascular outcomes were evaluated. Nine eligible trials with 13,532 participants were identified (2 were primary and 7 were secondary prevention studies).
Dr Ray O’Connor
The findings were dramatic! No significant differences in cardiovascular mortality (relative risk [RR] = 0.94, 95% confidence interval [CI]: 0.75-1.19), all-cause mortality (RR = 1.01, 95% CI: 0.89-1.14), myocardial infarction (RR = 0.85, 95% CI: 0.71-1.02), and coronary artery events (RR = 0.85, 95% CI: 0.65-1.11) were observed between the intervention and control groups. However, owing to limited reported cases, the impact of stroke could not be evaluated. The authors concluded that a reduction in saturated fats cannot be recommended at present to prevent CVD and mortality. Clinical trials are needed to evaluate the effects of saturated fat reduction under the best possible medical care, including statin administration.
Age-related cognitive impairment and dementia pose a significant global health, social, and economic challenge. While Alzheimer’s disease (AD) has historically been viewed as the leading cause of dementia, recent evidence reveals the considerable impact of vascular cognitive impairment and dementia (VCID), which now accounts for nearly half of all dementia cases.
The Mediterranean diet—characterized by high consumption of fruits, vegetables, whole grains, fish, and olive oil—has been widely recognized for its cardiovascular benefits and may also reduce the risk of cognitive decline and dementia. To investigate the protective effects of the Mediterranean diet on cognitive health, the authors conducted a systematic literature review.2 23 studies met the inclusion criteria. The authors found that the combined overall hazard ratio (HR) for cognitive impairment among those adhering to the Mediterranean diet was 0.82 (95% CI 0.75–0.89).
For dementia HR was 0.89 (95% CI 0.83–0.95); and for AD, the HR was 0.70 (95% CI 0.60–0.82), indicating substantial protective effects. The authors’ conclusion was that adherence to the Mediterranean diet is associated with an 11–30 per cent reduction in the risk of age-related cognitive disorders, including cognitive impairment, dementia, and AD. These findings underscore the Mediterranean diet’s potential as a central element in neuroprotective public health strategies to mitigate the global impact of cognitive decline and dementia and to promote healthier cognitive aging.
While several studies have assessed the potential effect of intermittent fasting on reducing cardiovascular risks, the findings are inconclusive. The aim of this meta-analysis3 was to compare the relative effectiveness of intermittent fasting methods in reducing key cardiovascular risks.
Outcomes were reported as mean differences (MD) with their corresponding 95% confidence intervals (CI). Fifty-six studies were included in the analysis. With high certainty of evidence, modified alternate-day fasting was found to be the most effective intervention compared to a usual diet in reducing body weight (MD= -5.18 kg), waist circumference (-3.55 cm), systolic blood pressure (-7.24 mmHg), diastolic blood pressure (-4.70 mmHg).
With high certainty, time-restricted eating was the most effective intervention compared to usual diet in reducing fat-free mass (-0.82 kg), waist circumference (-3.00 cm), diastolic blood pressure (-3.24 mmHg) and fasting plasma glucose (-3.74 mg/dL). The authors’ conclusion was that modified alternate-day fasting, and time-restricted eating appear to be promising approaches for reducing most cardiovascular risk factors. The authors recommend that intermittent fasting methods may be considered as potential components of lifestyle interventions aimed at managing cardiovascular disease risk factors. However, they also caution that further long-term randomised controlled trials comparing intermittent fasting methods are needed to confirm their efficacy and assess their safety over time.
To achieve mutually beneficial outcomes for both human health and the environment, the EAT-Lancet Commission proposed the Planetary Health Diet (PHD) as a reference diet.4 The PHD aims to mitigate diet-related Greenhouse Gas emissions (GHGe) and other environmental impacts while promoting human health.
The health benefits of the Planetary Health Diet (PHD) require further validation. The authors of this study5 examined associations between PHD adherence and risks of mortality and chronic diseases using data from two prospective cohorts—the US National Health and Nutrition Study (NHANES) (1999–2018, 42,947 participants) and the UK Biobank (UKB) (125,372 participants)—and a meta-analysis of 37 published cohort studies (3,244,263 participants).
The findings were that higher adherence to PHD was associated with lower all-cause mortality in both cohorts. In the UKB, it was also associated with reduced the risk of cancer and respiratory disease mortality. In the meta-analysis, higher adherence to the PHD was associated with lower risks of all-cause, cancer, and CVD mortality and reduced risks of colorectal cancer, lung cancer, CVDs, coronary heart disease, stroke, and diabetes. The authors conclude that higher adherence to the PHD may offer substantial health benefits.
Probiotics are live bacteria that colonise the gastrointestinal tract and have been studied in many clinical trials for preventing allergic conditions.
The objective of this systematic review and meta analysis6 was to evaluate the benefits and harms of a probiotic, or a probiotic with added prebiotic (‘synbiotic’), compared with control (placebo or no treatment) for preventing allergic diseases (asthma, eczema, allergic rhinitis) and dietary allergies in infants by two years of age. The authors’ conclusion was that there is insufficient evidence to make conclusions about the effect of probiotics and synbiotics on preventing the development of allergic diseases by two years of age and during childhood up to 10 years of age. Although there were no serious adverse events reported for the use of probiotics in infants, incorporating probiotics and synbiotics into routine practice requires further information to support their use.
References:
Yamada S et al. Saturated Fat Restriction for Cardiovascular Disease Prevention: A Systematic Review and Meta-analysis of Randomized Controlled Trials. JMA Journal 2025 8(2):395-407. DOI: 10.31662/jmaj.2024-0324 https://www.jmaj.jp/
Fekete M et al. The role of the Mediterranean diet in reducing the risk of cognitive impairement, dementia, and Alzheimer’s disease: a meta‑GeroScience (2025) 47:3111–3130 https://doi.org/10.1007/s11357-024-01488-3
Tilahun Kibret K et al. Intermittent Fasting for the Prevention of Cardiovascular Disease Risks: Systematic Review and Network Meta-Analysis. Current Nutrition Reports (2025) 14:93 https://doi.org/10.1007/s13668-025-00684-7
Willett W et al. Food in the Anthropocene: The EAT-Lancet Commission on healthy diets from sustainable food systems. Lancet 393, 447–492 (2019). DOI: 10.1016/S0140-6736(18)31788-4.
Wang Y et al. Planetary Health Diet and risk of mortality and chronic diseases: Results from US NHANES, UK Biobank, and a meta-analysis. Sci. Adv. 11, eadq5147 (2025) 5 September 2025. DOI: 10.1126/sciadv.adq5147.
Wang HZ et al. Probiotics in infants for prevention of allergic disease. Cochrane Database Syst Rev 2025 Jun 13;6(6):CD006475. DOI: 10.1002/14651858.CD006475.pub3.
Dining and Cooking