We all know that our overall health and wellbeing can be influenced by our diet. There are currently no formal guidelines for nutrition and fertility, however it makes logical sense that diet could also play a role in our reproductive health. In this article we look at the available evidence considering both male and female nutrition, to see if making dietary changes can really help you to conceive.
Infertility is on the rise in the developed world and estimated to be experience by around 15% of couples of child bearing age (1). The definition of infertility is an inability to conceive after 12 months of regular unprotected sex. There are several important factors influencing a successful pregnancy including the health of our reproductive organs, the quality of the egg and sperm, the quantity of sperm produced and the quality of the lining of the womb enabling implantation. The burden of fertility issues lies equally between men and women, with each sex contributing to around 30% of infertility cases, with the remaining 40% due to unknown causes (2).
Risk Factors for Infertility
It may be difficult to control or avoid some risk factors for infertility such as age (over 35), environmental pollutants and metabolic diseases such as diabetes and obesity. However, there are a number of modifiable lifestyle factors that we can avoid, such as unhealthy diet, smoking, drinking high levels of caffeine and alcohol and taking part in intense exercise regimes. Optimising our diets to give ourselves the best chance of a healthy conception is something that is within our control, but it can be difficult to know where to start.
Diets which are high in saturated fat and sugar have been linked to reduced fertility in both men and women. In contrast diets such as the ‘Mediterranean Diet‘, high in olive oil, nuts and seeds, oily fish, fruit and vegetables has been shown to improve IVF outcomes (3). The majority of carbohydrates consumed as part of the Mediterranean diet are wholegrains such as rolled oats, brown bread and rice. These are recommended over simple carbohydrates such as sugar, white bread, white rice and pasta due to the influence of these types of carbohydrate on blood glucose levels. There are a number of sources of fat which have been shown to be beneficial; supplementation with both DHA and EPA omega-3 fatty acids has been found to increase sperm motility and concentration in men (4), whilst swapping low fat dairy options for full fat dairy, has been shown to improve fertility in women (5).
Oxidative stress has been associated with a decrease in fertility of both men and women. Occurring when our bodies natural defence system is overburdened by toxins. Micronutrients such as vitamin C and E are strong antioxidants, which may support our bodies with the removal of toxins. The process of growing a healthy embryo requires successful DNA replication and toxins in the body are thought to damage DNA, creating errors which makes the cell less likely to survive. One study found women who experienced miscarriage had lower levels of vitamin C and E in their blood than women who achieved a successful pregnancy (6). Good sources of vitamin C are fruits, berries and Vitamin E is found in avocado, nuts and seeds.
Folic acid supplementation of 400ug a day is recommended when planning for a healthy pregnancy to prevent neural tube defects of the brain and spinal cord (7), however folic acid (or folate as it occurs naturally) has also been associated with improved egg quality and increased fertility in women (8). As well as supplementation, a diet high in folate would include peas, spinach, rice and oranges.
Iron and Vitamin B12
Iron is thought to support ovulation and help to optimise the womb lining ready for egg implantation, however evidence on a link with fertility is conflicting (9). Some good food sources of iron are green leafy vegetables, nut seeds and wholegrains. Likewise, vitamin B12 is critical for many biological processes in the body including DNA replication, repair and cell division. Good sources of B12 include, fish, meat and animal products such as eggs and dairy. A good vegetarian source of B12 is nutritional yeast.
Being both under and over-weight has been linked to lower levels of fertility and higher miscarriage rates, due to the impact of inadequate and excess calories on ovulation. If you experience irregular periods it may be more difficult to conceive. If your BMI (body mass index) is less than 19 or greater than 30, then loosing or gaining weight to bring your BMI inside of this range may help to regulate periods and improve the chance of conception (7). In fact, one study found that pregnancy and live birth rates were so closely correlated to BMI that altering BMI by one unit toward ideal had a significant impact on fertility levels (10).
The gut : hormone connection
Oestrogen is a critical hormone that drives ovulation and build-up of the womb lining. One of the main regulators of oestrogen levels in the body has been found to be the community of microbes that colonise our guts, also known as the microbiome. Some species of bacteria produce an enzyme that alters oestrogen into its active form. Studies have linked dysbiosis (a lack of diversity) of the microbes to a reduction in circulating blood oestrogen levels (12). Eating a wide variety of different fruits and vegetables, a diet high in fibre and fermented foods has been show to improve gut diversity (13).
Whatever changes you decide to make to your diet, it is helpful to start implementing them at least 90 days pre-conception for women and 3 months pre-conception for men, due to the time frame involved in egg and sperm maturation.
Silvestris, E (2019). Nutrition and Female Fertility: An Interdependent Correlation. Frontiers in endocrinology, 10, 346. https://doi.org/10.3389/fendo.2019.00346
Dimitrios, K (2018) Adherence to the Mediterranean diet and IVF success rate among non-obese women attempting fertility, Human Reproduction, 33(3), 494–502, https://doi.org/10.1093/humrep/dey003
Hosseini, B. (2019) The Effect of Omega-3 Fatty Acids, EPA, and/or DHA on Male Infertility: A Systematic Review and Meta-analysis. J Diet Suppl. 2019;16(2):245-256. doi: 10.1080/19390211.2018.1431753.
Chavarro, J.E. (2007) A prospective study of dairy foods intake and anovulatory infertility. Hum Reprod. 2007 May;22(5):1340-7. doi: 10.1093/humrep/dem019. Epub 2007 Feb 28. PMID: 17329264.
Chavarro, J.E. (2008) Use of multivitamins, intake of B vitamins, and risk of ovulatory infertility. Fertility Steril. (2008) [89:66]8–76. 10.1016/j.fertnstert.2007.03.089
Chavarro, J.E. (2006) Iron intake and risk of ovulatory infertility. Obstet Gynecol. doi: 10.1097/01.AOG.0000238333.37423.ab. PMID: 17077236.
Silvestris, E (2018). Obesity as disruptor of the female fertility. Reproductive biology and endocrinology : RB&E, 16(1), 22. https://doi.org/10.1186/s12958-018-0336-z
Baker, J.M. (2017) Estrogen-gut microbiome axis: Physiological and clinical implications. doi: 10.1016/j.maturitas.2017.06.025..
Heiman, M.L.(2016). A healthy gastrointestinal microbiome is dependent on dietary diversity. Molecular metabolism, 5(5), 317–320. https://doi.org/10.1016/j.molmet.2016.02.005
Helen has an MSc in Human Nutrition from the University of Chester and a BSc in Food Science and Technology. and is also a registered Associate Nutritionist (ANutr) with the Association for Nutrition. https://www.rndnutrition.co.uk/