Why men should eat more plants: the effect of mediterranean plant-forward diets on health

In a recent study published in the Urology journal, researchers in the United States (US) performed a systematic review of existing data to investigate whether plant-forward (PF) diets could improve male health to prevent and manage benign prostatic hyperplasia (BPH), erectile dysfunction (ED), and prostate cancer (PCa).

Study: Should Men Eat More Plants? A Systematic Review of the Literature on the Effect of Plant-Forward Diets on Men's Health. Image Credit: Stock-Asso/Shutterstock.com

Background​​​​​​​

Plant-based or vegan diets predominantly comprise plant-sourced foods, whereas PF or Mediterranean diets incorporate animal-sourced foods, such as dairy products and meat, in lesser proportions than foods sourced from plants.

Factors driving the switch from plant-based to PF diets include improved health, animal well-being, and environmental concerns. Plant-based diets have been thought to protect against BPH, ED, and PCa by regulating sex hormone levels, nitric oxide level augmentation, and improvements in comorbid conditions related to the diseases. However, the benefits of PF diets in preventing and managing BPH, ED, and PCa are unclear.

About the study

In the present systematic review, researchers evaluated the relationship between consuming PF diets and commonly observed male health conditions such as BPH, ED, and PCa.

Databases such as Medline and PubMed were searched for English articles on studies comprising human participants consuming plant-based or PF diets published between 1989 and 2022, excluding reviews, editorials, commentaries, and abstracts.

Two researchers independently screened the titles and abstracts, and a third researcher settled disagreements. PCa outcomes included alterations in the levels of prostate-specific antigen (PSA) with time and PCa development risk based on the hazard ratio (HR), odds ratio (OR), and relative risk (RR) values.

ED-associated outcomes included the ED development risk, endothelial function marker levels, and the international index of erectile function (IIEF-5) score. BPH-associated outcomes included symptomatic BPH risk, prostatic volume, and international prostate symptom scores (IPSS).

Bias risks were assessed in randomized controlled trials (RCTs) and non-RCTs using the risk of bias (RoB) assessment tool and the Newcastle Ottawa scale (NOS), respectively.

Results

In total, 346 records were identified initially, of which 121 with unmet eligibility criteria were excluded, and the remaining 225 records were screened. One hundred seventy-two records were excluded since the title and/or abstract did not include PF diets as an intervention or variable.

After the full-text review of 53 records, only 24 eligible records were considered for the final analysis. Bias risks were low in 19 non-RCTs, and one RCT, moderate in one RCT, could not be assessed for four RCTs in which the participants were not randomized or compared to comparator groups.

Significant heterogeneity was found in the data search concerning study designs, including evaluation of diets, exposure duration, sample population, and utilization of other modalities (such as mindfulness). The findings indicated a benefit of consuming PF diets, especially against PCa.

A study comprising 1,399 national health and nutrition examination survey (NHANES) participants reported that higher healthful plant-based diet index (hPDI) scores were associated with lower PSA levels (OR 0.5).  

In the case-control-type ProtecT study, comprising 13,811 individuals, an inverse association was observed between the risk of PCa development and PCa dietary index scores (assessing tomato product, selenium, and calcium intake).

Likewise, PF diets lowered the probability of PCa development (odds ratio (OR) 0.9). In a prospective cohort-type study comprising 14,000 individuals aged >25 years, diet assessments using lifestyle questionnaires indicated that PCa risk was inversely associated with the intake of legumes (RR 0.5) and tomatoes (RR 0.6).

The findings of other prospective cohort studies indicated that consuming plant-sourced foods conferred protection against PCa (HR 0.7) and PCa-associated deaths (HR 0.8). PCa development risks were especially lower for individuals aged ≤65, having body mass index (BMI) values ≤25.

In a cross-sectional-type study comprising 440 individuals, the odds of ED development were significantly lower among males consuming more vegetables and nuts, with OR values of 0.5 and 0.4, respectively. Mediterranean diet consumption for two years was significantly associated with IIEF-5 scores above 21, indicative of ED symptom resolution, compared to controls (37.0% versus 6.7%, respectively).

Among 21,469 Health Professionals' follow-up study participants, males aged <60 with higher Mediterranean diet scores and alternative healthy eating index 2,010 scores had lower risks of new-onset ED.

Among men aged 60 to 69 years, higher PDI scores and healthful PDI scores were associated with a lowering of ED development risks by 9.0% and 18%, respectively. Among 2,549 NHANES participants aged 20 to 70, hPDI scores were inversely associated with ED risk (OR 1.0).

After 2.0 years of Mediterranean dietary intake, significant endothelial functional improvements in ED patients, assessed using L-arginine tests, were reported, with a mean change of 1.6, compared to controls.

Among 2,820 males residing in Italy aged <75, BPH risks were inversely associated with consuming legumes/pulses, citrus fruits and cooked vegetables, with OR values of 0.7, 0.8, and 0.7, respectively. Likewise, the risk of BPH was inversely associated with polyunsaturated fatty acid intake (OR 0.7), abundantly present in nuts and seeds.

Among 868 male Australians, BPH risks were lower among those with increased vegetable intake (OR 0.8). Similar results were reported for 1,564 men above 65 years of age residing in China.

Among PCa prevention trial participants, men consuming vegetables ≥4.0 times daily had a 32% lower risk of BPH than those consuming vegetables once daily (OR 0.7). Greater vegetable and fruit intake was associated with lower IPSS scores; dark leafy vegetables particularly lowered urinary tract symptom progression over 4.0 years by 37%.

Conclusion

Overall, the study finding showed that consuming plant-forward diets could aid in preventing and managing male urologic conditions such as BPH, PCa, and ED.

Journal reference:
Pooja Toshniwal Paharia

Written by

Pooja Toshniwal Paharia

Dr. based clinical-radiological diagnosis and management of oral lesions and conditions and associated maxillofacial disorders.

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