Plant-based diets, quality of life and outcomes with prostate cancer

Aim

The authors of this study previously established that following a more plant-based diet eating pattern is associated with a lower risk of advanced or fatal prostate cancer.

In this follow-up study, researchers examined patients with prostate cancer after diagnosis to see if a more plant-based eating pattern improved their quality of life (QoL), which included hormonal, sexual, urinary, and bowel health.

Method

Data analysed was from the Health Professionals Follow-Up Study, which is an ongoing prospective cohort study which began in 1989.

Dietary data is collected at baseline and every four years, using validated food frequency questionnaires, to generate an overall plant-based diet index (PDI) score and a healthy PDI (hPDI).

The hPDI gives positive weight to food items such as fruits, vegetables, wholegrains, tea, and coffee.

The PDI assigns positive weights to "other" plant foods like refined grains, potatoes, fruit juice, and sugar-sweetened beverages. Animal-derived foods are given negative weights on both ratings.

Key findings

Participant characteristics

3,505 participants who completed both a food frequency and QoL questionnaires post-prostate cancer diagnoses were included in this analysis.

92% of the participants were white health professionals, with a mean age of 75.

The average time from diagnosis to taking the first QoL questionnaire was 7 years (although ranged from 1-25 years).

Most common prostate cancer treatments for the cohort included radical prostatectomy and radiation therapy (48%, 35% respectively).

Results

Sexual function: Both PDI and hPDI scores were associated with better sexual function.

This included both the patients who received radiation therapy and who underwent radical prostatectomy.

This finding is consistent with those from the Health Professionals Follow-Up Study who did not have prostate cancer – greater consumption of plant-based foods was associated with lower risk of erectile dysfunction.

The authors quote one study that reported a 2% reduction in erectile dysfunction risk for each one-unit increase in the hDPI.

Urinary health: A higher PDI was associated with significantly less urinary irritation, obstruction, and incontinence (no significant associations found for hPDI).

Predominantly plant-based diets are associated with lower risk of illnesses such as obesity, diabetes, and constipation, which are frequently related with urinary issues and may account for the better results.

Bowel function: a greater hPDI was associated with significantly less bowel dysfunction (no significant associations found for overall PDI).

Plant-based foods are rich in fibre. The author’s research suggests that greater consumption of dietary fibre can improve stool frequency and reduce constipation.

It should be noted that none of the participants in this study followed a strictly vegan diet. All were consuming some animal proteins.

The authors suggest the possibility of greater outcomes with more substantial dietary modification; however, results using a flexitarian approach are still meaningful.

Conclusion

In this large cohort of prostate cancer patients, a greater consumption of overall and healthful plant-based foods was associated with better QoL scores.

Individuals with prostate cancer should be advised that including more plant-based foods into their diet could improve their QoL and functional outcomes.

Additional studies including more diverse populations are needed. The author intends to contribute to existing literature by focusing on dietary modifications from pre- to post-diagnosis.

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