The Significance of Plant-based Eating on Reproductive health in Men (S.P.E.R.M) Study

Project lay summary

Infertility affects around 1 in 6 couples and in almost half of all cases, a sperm issue is identified. Around the world, sperm counts have reduced by over 50% in the past 50 years. Scientists are therefore trying to identify ways that men can improve their reproductive health through changes in lifestyle.

Plant-based eating (defined for the purpose of this study as the exclusion of all meat, fish, eggs and dairy products from the diet) has become increasingly popular due to its low environmental impact and its reported benefits to cardiovascular and gut health. A small number of studies have shown that plant-based diets may also positively affect reproductive health in men, potentially increasing the production and quality of their sperm as well as improving erectile function. Most of these studies however compare plant-based men with those who follow a diet containing animal products (omnivorous dietary pattern). This makes it difficult to be sure that any differences are due to diet alone. More targeted research is therefore required to explore this in more detail and to help determine the mechanisms that may lead to improvements in reproductive health.

This study will look for changes in reproductive health in the same subjects by asking omnivorous men to adopt a plant-based diet for 3 months (enough time for the body to produce a new batch of sperm which would not have been affected by their old diet). Throughout the study period, we will provide support in the form of menu plans, nutritional advice, recipe ideas/eating out guides and support calls.

Before adopting the plant-based diet, we will test the following:

• A semen sample – for sperm number, function and health (advanced semen analysis).
• A blood sample – for cholesterol, inflammation markers and reproductive hormones.
• A stool sample – to analyse the variety and types microbes present in the gut.

A baseline BMI, waist-to-hip ratio measurement and blood pressure will also be taken as markers of general health. In addition, participants will be offered the opportunity to take part in a very novel arm of research by self-testing their erectile function using a ‘Rigiscan’ device. This is a non-invasive test which uses painless penile loops to record the frequency and rigidity of erections while watching stimulatory material in a private room. The information is collected in a small data-logger which is returned to us for analysis.

All tests will be repeated at the end of the study to look for any changes and to determine if plant-based eating can be used to improve male reproductive health.

This research will allow us to look more closely at the effects of this dietary pattern on male reproductive health to identify any benefits or risks. The hope is that men affected by infertility may be able to adopt a plant-based diet to increase their chances of natural conception. Improving semen quality may also facilitate less invasive/costly procedures for those requiring fertility treatment.

Outputs

I have presented the preliminary findings from my primary outcome measure (semen parameters) at the Phytochemicals in Health Symposium (winner of ‘best oral communication’ prize) and the Association of Clinical and Reproductive Scientists (ARCS) Symposium (both September 2025). The same abstract (below) has just been accepted for oral presentation at Fertility 2026 in January (shortlisted for ARCS post-registration prize).

A high phytochemical diet positively impacts markers of fertility in adult males
Joanne Wilson1,3, Luciana Torquati 2, Michael Carroll 3

1 Fertility Exeter, Royal Devon University Healthcare NHS Foundation Trust

2 Public Health and Sport Sciences, Exeter Medical School, University of Exeter

3 Department of Life Sciences, Manchester Metropolitan University Manchester.

Background: Fertility rates are declining in high income countries including the UK, with a current prevalence of 1 in 6 couples requiring fertility treatment. Approximately 30% of cases have a male factor diagnosis which can be genetic, metabolic or idiopathic, but emerging evidence implicates increased oxidative stress as a culprit. Phytochemicals could play an important role in reducing oxidative stress, however there is limited evidence on the effect of high-phytochemical diets on improving fertility outcomes in men.

Methods: Males aged 18 to 50 were recruited for this within-participant, controlled study. Participants were asked to follow a plant-based diet for 12-weeks and received weekly compliance checks. Sperm concentration, motility and morphology were measured in accordance with WHO guidelines. Oxidation reduction potential (ORP) was measured using MiOXSYS analyser and sperm chromatin integrity was assessed using aniline blue staining (WHO protocol) . All tests were conducted at baseline and 12 weeks.

Results: From this ongoing trial, we present pre-post preliminary data from n=13 intervention males aged 27-46 (mean 38.4). A significant improvement (p<0.01) was seen in relative sperm motility for all classes measured; total motility (60.8% vs 57.5%), total progressive motility (60.8% vs 48.4%) and rapid progressive motility (49.4% vs 34.8%). A significant improvement (p=<0.05) was also found in the percentage of sperm with optimal chromatin condensation (93.5% & vs 87.5%). Although not significant, we observed positive trends in sperm concentration, optimal morphology and ORP

Conclusion: We found that following a high-phytochemical diet for 12 weeks resulted in improvements in sperm number and morphology and significantly improved sperm motility. Additional improvements in chromatin integrity and ORP suggest improved DNA packaging and potentially improve fertilisation rates and healthy embryo development. Our findings warrant further investigation and corroboration with changes in the control group to confirm causality and effect sizes in our outcomes.