Can diet affect fertility? 

Infertility is defined by the World Health Organisation (WHO) as “a disease of the male or female reproductive system defined by the failure to achieve a pregnancy after 12 months or more of regular unprotected sexual intercourse” ¹. The latest figures from the National Health Service (NHS) suggest that infertility sadly affects 1 in 7 couples ².  

As the child bearers, emphasis may be put on the female’s role in pregnancy and consequently, infertility. However, whilst approximately 30% of infertility cases are related to women, 30% are also related to men, 30% to both men and women, and the remaining 10% is unexplained ³. 

It is well-evidenced that diet has an impact on fertility. Therefore, it is important that both men and women maintain a healthy, balanced diet and may potentially need to make some diet and lifestyle changes to help them conceive. Let’s dive deeper into the science behind this. 

What are the latest dietary recommendations to optimise fertility? 

Here are some top line recommendations: 

Eat a Mediterranean style diet 

A healthy balanced diet aligned to the Mediterranean diet, is recommended by dietitians to protect fertility for both men and women^3,4. The Mediterranean diet is high in fruit, vegetables, wholegrains, nuts, legumes, fish and olive oil, with lower quantities of meat and meat products such as dairy and eggs. On the other hand, a diet high in saturated fat, salt and sugar should be avoided, especially for men, as it has a negative impact on sperm quality⁵. 

Take vitamin and mineral supplements such as folic acid 

The NHS recommends that women take a daily folic acid supplement of 400µg for three months before trying to conceive and during the first twelve weeks of pregnancy. This is because folic acid supports the normal development of a baby’s brain and spine.⁶ It is also recommended for men to consume adequate amounts of folic acid up to three months before conception. However, the recommendation for men is half the recommendation for women at 200µg/day. In addition to folic acid, women could consider taking a combined prenatal multivitamin and mineral supplement containing folic acid as well as iodine and vitamin D. 

Maintain a healthy weight 

Men and women with a BMI of ≥30 kg/m² have an increased risk of infertility. It is recommended that they be informed of this by their healthcare professional and make diet and lifestyle changes for weight loss⁷. 

Limit caffeine intake 

The British Dietetic Association (BDA) recommends that women trying to conceive should aim for less than 200mg of caffeine.³ This is less than two cups of coffee and three cups of tea per day. High energy and sugary fizzy drinks should also be limited due to their caffeine content. 

Avoid alcohol 

Guidelines advise against drinking alcohol when planning pregnancy as it could increase the time it takes to conceive.³ Drinking alcohol also increases the risk of miscarriage and birth defects.³ 

Are there emerging areas of research in fertility nutrition? 

Antioxidants are currently being studied as to their effect on fertility. Oxidative stress reduces the synthesis of the male reproductive hormone testosterone in males. Surprisingly, significant levels of free radicals that cause oxidative stress have been found in the semen of up to 25% of infertile men ⁸. Antioxidants offer a potential solution as they can neutralise free radicals and therefore potentially improve male fertility. However, more research needs to be undertaken before recommendations relating to antioxidants are provided. 

The gut microbiota is also an exciting new area for research. The relationship between gut microbiota and testis, the gut-testis axis, is currently being researched in the context of fertility. A study in 2022 found that factors which damage gut microbiota negatively impact male reproductive function, although the correlation remains to be investigated⁹. Another study found that a faecal microbiota transplantation in mice improved the quality of semen that had been diminished due to a high-fat diet¹⁰. Watch this space for more research in this area. 

Lastly, new guidelines from the National Institute for Health and Care Excellence (NICE) on fertility problems are currently being developed and are expected to be published in November of next year. 

What are common myths and misconceptions about nutrition and infertility? 

Gluten must be avoided when trying to conceive 

Unless you have coeliac disease, you do not need to exclude gluten from your diet. However, a high carbohydrate diet is associated with greater infertility risks and so a moderate carbohydrate intake is recommended by dietitians³. The BDA suggests choosing wholegrain varieties of carbohydrates such as oats, rice, barley, millet, quinoa, wholewheat pasta and wholegrain bread, instead of refined carbohydrates such as white bread and pasta. 

You cannot drink any tea or coffee when trying to conceive 

As above, it is recommended that women trying to conceive should limit their caffeine intake to less than 200mg per day³. This is the equivalent of two cups of coffee or three cups of tea. 

Women only need to take a folic acid supplement when trying to conceive 

It is recommended that women take a combined prenatal supplement which, as well as folic acid, includes iodine and vitamin D. On the contrary, vitamin A supplements should not be taken, as there is a risk of consuming an excess amount, which can lead to birth defects and miscarriage³. The BDA also state that enough vitamin A can be obtained from diet alone. 

In addition, for those following a vegan diet, supplements may need to be taken for iodine, vitamin B12, zinc and selenium before trying for a baby to avoid nutritional deficiencies. 

Consumption of soy reduces male fertility  

Isoflavones found in soybeans have oestrogen-like effects and therefore have caused concern as to their effects on fertility in males. There is limited evidence on this. However, a meta-analysis of human studies, individual trials and evidence-based reviews found no statistically significant effects of soy consumption on levels of reproductive hormones¹¹. 

In summary

To summarise,  it is evident that nutrition plays a crucial role in the area of fertility and conception. The evidence suggests that the foods we consume and our lifestyle behaviours impact our reproductive health and chances of conception. Both partners should adopt a healthy, balanced diet, with additional supplements pre and post conception such as folic acid, iodine and vitamin D. Those following a vegan diet may require additional supplementation. Additionally, maintaining a healthy weight, avoiding alcohol and reducing consumption of caffeine are essential for optimising nutritional status for improved fertility.  

If you’re a healthcare professional or are working in the fertility space, please see below for key resources to help provide evidence based information and guidance. 

Plus, if you’d like to hear more, listen to the latest episode on The Dietitian Café with Ro Huntriss, Specialist Fertility Dietitian. 

Key resources:

• British Dietetic Association (2021) Female Fertility Factsheet. [online] Available at: https://www.bda.uk.com/uploads/assets/dbe84def-09ff-4dbe-b3d703551dc75674/Female-Fertility.pdf [Accessed 10/07/2023] 

• British Dietetic Association (2021) Male Fertility Factsheet. [online] Available at: https://www.bda.uk.com/uploads/assets/4d16eadb-85fd-4c07-8a0d0f83879623a9/Male-Fertility.pdf [Accessed 10/07/2023] 
• National Institute for Health and Care Excellence (2017) Fertility Problems: Assessment and Treatment [online] Available at: https://www.nice.org.uk/guidance/CG156 [Accessed 10/07/2023] 
• BDA Maternal and Fertility Specialist Group: https://www.bda.uk.com/specialist-groups-and-branches/maternal-and-fertility-specialist-group.html  

This article has been written in collaboration with one of the HRS Communications Interns, Olivia Broadbent.

References 

1. World Health Organisation (WHO) Infertility. [online] Available at: https://www.who.int/news-room/fact-sheets/detail/infertility [Accessed 12/07/2023] 

2. National Health Service (2020) Infertility. [online] Available at: https://www.nhs.uk/conditions/infertility/ [Accessed 10/07/2023] 

3. British Dietetic Association (2021) Female Fertility Factsheet. [online] Available at: https://www.bda.uk.com/uploads/assets/dbe84def-09ff-4dbe-b3d703551dc75674/Female-Fertility.pdf [Accessed 10/07/2023] 

4. British Dietetic Association (2021) Male Fertility Factsheet. [online] Available at: https://www.bda.uk.com/uploads/assets/4d16eadb-85fd-4c07-8a0d0f83879623a9/Male-Fertility.pdf [Accessed 10/07/2023] 

5. Tomada, I., and Tomada, N. (2023) Mediterranean Diet and Male Fertility, Endocrines, 4(2):394-406. Available at: https://www.mdpi.com/2673-396X/4/2/30 

6. National Health Service (2022) Pregnancy, breastfeeding and fertility while taking folic acid. [online] Available at: https://www.nhs.uk/medicines/folic-acid/pregnancy-breastfeeding-and-fertility-while-taking-folic-acid/ [Accessed 10/07/2023] 

7. Chavarro JE, Rich-Edwards JW, Rosner BA, Willett WC. Diet and lifestyle in the prevention of ovulatory disorder infertility. Obstet Gynecol. 2007 Nov;110(5):1050-8. doi: 10.1097/01.AOG.0000287293.25465.e1. PMID: 17978119. Available at: https://pubmed.ncbi.nlm.nih.gov/17978119/ [Accessed 12/07/2023]  

8. Majzoub A., Agarwal A., (2018) Systematic review of antioxidant types and doses in male infertility: Benefits on semen parameters, advanced sperm function, assisted reproduction and live-birth rate. Arab J Urol. 16(1):113-124. 

9. Cai H., Cao X., Qin D., Liu Y., Liu Y., Hua J., Peng S. (2022) Gut microbiota supports male reproduction via nutrition, immunity, and signaling. Front Microbiol. 13. 

10. Hao, Y., et al. (2022) Gut Microbiota-Testis Axis: FMT Mitigates High-Fat Diet-Diminished Male Fertility via Improving Systemic and Testicular Metabolome, ASM Journals, 10(3). 

11. PEN Nutrition (2023) Nutrition and Fertility Summary of Recommendations and Evidence. [online] Available at: https://www.pennutrition.com/KnowledgePathway.aspx?kpid=27449&trid=29410&trcatid=42 [Accessed 10/07/2023]