Fertility Nutrition explains the dietary principles that are important for good fertility and when planning a pregnancy to give you the best chance of conceiving and having a healthy pregnancy and a healthy baby. It provides evidence-based information on what to eat and why good diet before pregnancy is so important for the future health of your child. Reliable scientific information underpins everything we do and helps you to get ready for pregnancy.
Nutrients and Supplements for Fertility
Alongside a good diet, it’s important to ensure you have sufficient levels of vitamins and minerals, firstly for your own health in preparation for conception and pregnancy, but also for the health of the baby as part of a preconception care programme. We cover this in more detail in our Fertility and Preconception Care course and in The Fertility Book: Your Definitive Guide to Achieving a Healthy Pregnancy. In this section, we give an overview of:
- The importance of having sufficient nutrient levels
- Do you need supplements?
- Key vitamins for fertility and pregnancy
- Folic acid
- Vitamins D and K
- Vitamin A
- Can you take too many supplements?
- Minerals for fertility and pregnancy
- Zinc and copper
- The impact of previous oral contraceptive use
- The importance of getting tested
- Testing nutrients
- Antioxidant Supplements
- Co-enzyme Q10
- Omega-3 and omega-6
- Nutrients and supplements for male fertility
- Take-home message
The importance of having sufficient nutrient levels
Good nutrition is essential for reproductive pathways to work well for both men and women and is especially important when trying to conceive. Overall, the science clearly shows an association between nutrition and reproductive health, as well as the interdependent relationship between vitamins and minerals. We cover this in detail in our Fertility and Preconception Care course and in The Fertility Book: Your Definitive Guide to Achieving a Healthy Pregnancy.
Because western diets often have low dietary intake of numerous vitamins and minerals, many women enter pregnancy with low levels of key nutrients including iron, zinc, iodine, vitamin D and magnesium. A cumulative effect of poor diet from teenage years into adulthood can build up over time meaning the body stores of these nutrients that are crucial in pregnancy are running low. This means that a tipping point of different deficiencies can come together to impact the ability to conceive, as well as embryonic development.
The annual National Diet and Nutrition Surveys (NDNS) in the UK repeatedly highlight this poor dietary intake, including the latest study published in 2020 with a significant percentage of the population consuming below the Lower Reference Nutrient Intake (LRNI – the minimum intake we should be aiming for) value for the 11 nutrients surveyed and a decrease compared with previous surveys including lower folate and vitamin A levels and much lower blood folate. Findings from the NDNS are also reinforced by conclusions of preconception care papers by The Lancet, which highlight that young women are particularly at risk of mineral deficiency and most women of reproductive age are not nutritionally prepared for pregnancy. Poor dietary intake of nutrients is equally reported in men.
Given pregnancy can also be very depleting on the body, with nutrients diverted to the fetus before a woman’s own body’s needs are met (in biological terms, the embryo can be termed a parasite!), starting with good nutrient levels before you conceive, is crucial for your own health and well-being, especially in preparation for the early stages of motherhood when you are likely to be sleep-deprived and tired. Good preconception health also sets you up well for breastfeeding, which confers significant health benefits on mother and baby. Low nutrient levels after having a baby may also be a factor in problems conceiving a second or subsequent child.
For women, ensuring good body stores of vitamins and minerals is crucial in order to meet the demands of pregnancy. It’s much better to work on this before you conceive rather than trying to ‘catch up’ by topping up low levels of specific nutrients after conception as research suggests this is not effective in correcting the negative effects of a preconception deficiency.
Do you need supplements?
For all of us, the aim is for the main sources of nutrients to be from food and we cover important dietary principles in our Fertility and Preconception Care course and in The Fertility Book: Your Definitive Guide to Achieving a Healthy Pregnancy. This doesn’t always happen, however, and if you have had low nutrient intake for many years, especially where there is a history of digestive issues or restrictive diets, you will usually need to take supplements, at least in the short-term.
We routinely see outright deficiencies in our patients on testing as well as suboptimal levels of certain nutrients, despite most taking a preconception multivitamin and mineral and often eating relatively healthy diets. Supplements tend to contain the recommended daily allowance (RDA) for a particular nutrient, but this may not be enough to bring levels back up to normal from a place of deficiency.
Getting all our nutrients from food means they are in a natural, bioavailable form with the cofactors needed for their absorption and functioning in the body. When this doesn’t happen, deficiencies may develop and so testing also gives us information about how best to change our diets to meet the needs of the body. We should never address gaps and deficiencies through supplementation alone – we should always aim to improve and modify diet where needed to correct the underlying causes of the deficiency, alongside any supplementation required to correct the deficiency.
Key vitamins for fertility and pregnancy
Of course, all nutrients are important for fertility and pregnancy, but we highlight some of the important ones here. You can find out more detail in our Fertility and Preconception Care course and in The Fertility Book: Your Definitive Guide to Achieving a Healthy Pregnancy.
The current advice for pregnant women and those trying to conceive is to take 400μg (4mg) folic acid and 10μg (400iu – international units) of vitamin D, and nothing more, with recommendations to take higher doses of folic acid (500μg or 5mg) for some, including those with high body mass index (BMI – >30), diabetes, coeliac disease, taking medication including metformin, anti-epilepsy drugs and anti-retroviral drugs, or if either parent has a neural tube defect or family history of neural tube defects. Men may also benefit from supplementation.
Although the standard NHS advice is to supplement with folic acid in the preconception stage and through the first trimester in pregnancy to avoid neural tube defects in the baby such as spina bifida, what is actually protective is adequate maternal levels of folate (vitamin B9), which is the natural form of folic acid used by the body. Sufficient levels of blood folate are important for egg quality and maturation, as well as fertilisation and implantation. Supplementing with folic acid is also associated with improved outcomes including reduced levels of infertility and miscarriage, and improved chance of conceiving via IVF. There are certain gene variants, however, that reduce the body’s ability to convert folic acid into its bioavailable form. If you have been supplementing with folic acid for some time and your blood folate levels are low on testing, it may be that you have such a gene. Methylenetetrahydrofolate reductase (MTHFR) mutations are variants of a particular gene responsible for metabolising folate. It may therefore be beneficial for most people trying to conceive to supplement with folate rather than folic acid, either as part of a preconception multivitamin supplement. We cover this in more detail in our Fertility and Preconception Care course and in The Fertility Book: Your Definitive Guide to Achieving a Healthy Pregnancy.
Vitamins D and K
Adequate levels of vitamin D are important for both men and women. Deficiency of maternal vitamin D has been associated with reduced chance of in vitro fertilisation (IVF) success in some studies. A recent study also showed reduced chance of having a baby naturally in women with low vitamin D, but when researchers looked at overall diet quality and other nutrients such as iron and folate, vitamin D on its own wasn’t found to reduce the chance of pregnancy, reinforcing the need for a healthy diet generally and good levels of all nutrients. Once your levels get into the normal reference range much higher amounts have not been shown to offer further benefit and may even impact your egg quality (possibly by lowering vitamin A).
Magnesium is needed to produce vitamin D from sunlight or to process vitamin D taken in supplements and most people don’t get enough magnesium. Vitamin K is also needed for vitamin D to work well, and growing evidence suggests you should supplement vitamin D with vitamin K2. Vitamin K2 is a fat-soluble vitamin and dietary sources include butter, cheese, egg and yolks, so vegetarians and those who have been following low-fat diets or restricted diets may be at risk of deficiency.
Vitamin K2 supplements are contraindicated for those on blood thinners that work through their action on vitamin K. We recommend discussing this with your doctor or nutritionist.
Vitamin A works alongside vitamin D, with the body not able to properly utilise vitamin D without sufficient levels of vitamin A. Vitamin A is also important for egg quality and the formation of the blastocyst (day 5 embryo). Both deficiency and excess vitamin A can cause problems for fertility and embryonic development, with extremely high levels of preformed retinol (the animal-sourced form of vitamin A) having the potential to cause birth defects. Standard advice in the UK is therefore to avoid supplements containing retinol and not to eat organ meats such as liver and kidneys (which contain high levels of preformed vitamin A). However, vitamin A is important for fertility. Low dietary intake is relatively common and pregnancy supplements in the UK only contain plant-based sources which are the precursor of vitamin A, which needs to be taken in much higher quantities to convert to adequate quantities of vitamin A.
Gene variants that limit conversion of beta-carotene to retinol are also common so vegans and anyone avoiding eggs and dairy may be at risk. In the UK, it is likely to be safe to take 750µg of preformed vitamin A daily for a short period before conception, with outright deficiency less likely to be an issue, though always seek professional advice to avoid the risk of birth defects. Synthetic versions of vitamin A (etretinate and isotretinoin) can cause birth defects and should be avoided altogether.
Deficiency of vitamin A can also lead to fetal growth restriction and developmental problems, with a recent study showing that malformations in the baby were associated with nutrient deficiencies, including vitamin A. Vitamin A deficiency can also impact egg quality and may cause infertility. To ensure sufficient vitamin A intake, it is beneficial to include vitamin A-rich foods such as butter (in moderation) and eggs in your diet, along with plant-based sources such as sweet potato and butternut squash.
Can you take too many supplements?
Although both poor dietary intake of minerals and mineral deficiencies are common, some patients come to see us who are taking a combination of different supplements that takes them well above the RDA for particular nutrients.
Selenium is often included in male fertility supplements, for instance, and if taken either alongside other (say) selenium-containing antioxidant supplements as well as dietary intake of brazil nuts, which are high in selenium, it can be easy to push intake above recommended levels. We see this scenario reflected in test results, sometimes even after patients have followed professional advice from others. Good levels of selenium are important for thyroid function, sperm health in men and for pathways involved in DNA repair generally, but selenium can be toxic if levels rise significantly above the normal reference range. This can be especially important for couples who have been trying to conceive for a long time and may have been supplementing at quite high levels throughout without any assessment.
We explain more about how to work out which supplements are right for you in our Fertility and Preconception Care course and in The Fertility Book: Your Definitive Guide to Achieving a Healthy Pregnancy.
Minerals for fertility and pregnancy
Zinc and copper
For women, numerous studies demonstrate the importance of zinc for oocyte development and ovulation, for instance, as well as for the production of DNA, and synthesis and metabolism (production and processing) of hormones in the body.
For fertility, zinc levels should be higher than copper, but this is usually turned on its head in our patients. Both zinc and copper are needed for good fertility, but when copper is too high and zinc is too low, this can be a cause of inflammation. Inflammation can have a negative effect on your health. Studies have also shown that an imbalance between zinc and copper is associated with poor cognitive development in childhood and later educational attainment in adult life. High-copper diets, including vegetarian and vegan diets, can worsen an impaired balance between zinc and copper. In particular, vegetarians who have been on the pill for a long time without supplementing are at risk of low iodine, low zinc, impaired zinc–copper balance and low iron, nutrients that are important for fertility and pregnancy and also thyroid function.
The impact of previous oral contraceptive use
The majority of women start trying to conceive following a period on oral contraceptives. Anything that contains or raises oestrogen in the body increases the absorption and retention of copper in the body. This includes pregnancy, oral contraceptives and being overweight. High copper levels can inhibit zinc absorption (and vice versa). You may benefit from testing your zinc and copper levels if you have recently stopped taking the pill or a history of prolonged use of the pill.
Iodine is a vital mineral for thyroid function. and also for the baby’s brain development during pregnancy. A significant percentage of women do not have sufficient dietary intake; even minor deficiencies can affect things like IQ in the baby. Excess can also be damaging, especially during pregnancy, so never exceed the recommended allowances. It can be difficult to test for iodine levels, as it is not routinely available on the NHS, so the standard advice is to take 150μg daily for at least three months prior to conception. The link between iodine and thyroid function is complex and getting this right for you if you have thyroid problems is important, especially if you have thyroid autoimmunity. You can find out about iodine and thyroid function in more detail in our Fertility and Preconception Care course and in The Fertility Book: Your Definitive Guide to Achieving a Healthy Pregnancy.
The importance of getting tested
Given we know that many women enter pregnancy with low levels of key nutrients and nutrient deficiencies may contribute to subfertility function, we recommend starting your preconception function programme by having your levels of key nutrients tested. Even for those from strong socio-economic backgrounds, it is estimated that between 30 and 50% of women are deficient in iron, for instance, and low ferritin (a measure of iron store) in the umbilical cords of new-born babies is common. Given iron is crucial for the development of the baby’s brain and iron is needed to build blood volume and develop the placenta during pregnancy, these are easy things we can do to help ensure our babies get the best start in life.
If you think you may have nutrient deficiencies, especially when it comes to minerals, it’s best to seek professional help. You need to get tested, supplement as needed, and then be retested until all your nutrient levels are normal. If you are healthy and symptom-free with a history of eating a healthy diet, you can start with a preconception multivitamin supplement and consider basic tests including vitamin D and ferritin as a minimum.
We explain more about how to work out what tests you may need in our Fertility and Preconception Care course and in The Fertility Book: Your Definitive Guide to Achieving a Healthy Pregnancy.
Oxidative stress occurs in the body when reactive oxygen species (ROS) produced during normal metabolism or external factors cannot be balanced by the body’s supply of antioxidants, a situation that can affect fertility through the impact on sperm, oocytes and/or the mitochondria (the ‘batteries’ of the cell responsible for energy production). Oxidative stress can be caused by things like smoking, excess alcohol, being over- or underweight, exposure to environmental toxins and older age, as well as with conditions such as polycystic ovary syndrome (PCOS) and endometriosis.
The natural conclusion, therefore, is that antioxidant supplements have the potential to improve fertility. However, the exact roles of different antioxidants have not yet been fully worked out and it can be difficult to know from the research what is best for you as it depends on many different individual factors. Also, it is possible to have too high an intake of antioxidants, depending on your starting point. Assessing the level of oxidative stress in your body isn’t easy and it’s important to know that minerals, including zinc and selenium, and vitamins, including vitamins C and E, are also antioxidants. A recent review concluded that only very low-quality evidence suggests that antioxidants generally may improve the chances of a woman conceiving and going on to have a baby.
Antioxidant supplements include carnitines, alpha lipoic acid, resveratrol and co-enzyme Q10, among others, and you should only take these supplements during the preconception phase if indicated for you. We explain how to work out if you may benefit from taking antioxidant supplements in our Fertility and Preconception Care course and in The Fertility Book: Your Definitive Guide to Achieving a Healthy Pregnancy. The costs of supplements can soon add up so it’s helpful to get this right from a financial perspective as well as for your health and fertility.
Co-enzyme Q10 is perhaps one of the most studied antioxidant supplements, but also perhaps the most difficult to get right given the raft of conflicting information you may come across from various different sources. Co-enzyme Q10 is a naturally occurring antioxidant that declines with age and also with certain medications such as statins, something that is more relevant today with many delaying parenthood. Co-enzyme Q10 has an important role to play in fertility and preconception care, with numerous human and animal studies indicating benefit including for egg quality, but you must use it appropriately based on your personal circumstances. You can find out how to tell what dose of co-enzyme Q10 may be right for you in our Fertility and Preconception Care course and in The Fertility Book: Your Definitive Guide to Achieving a Healthy Pregnancy.
Omega-3 and omega-6
Omega-3 fatty acids are polyunsaturated fatty acids (PUFAs). The two main omega-3s needed for fertility and pregnancy are docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) and are mainly found in fish. DHA is needed for the baby’s brain development and EPA is needed for DHA to cross the placenta. Alpha-linolenic acid (ALA) is another type of omega-3 fatty acid found in vegetable oils, nuts and flaxseeds, but is not a form the body can easily use. Algae is a better vegetarian source of omega-3, but shouldn’t be used if you have thyroid problems. Dietary sources of DHA are almost exclusively from fish and, given DHA is needed for the baby’s brain development, supplements are usually needed if you are vegetarian. Healthy sources of omega-6 include walnuts, avocado oil, sunflower seeds, almonds, chicken and eggs, and these are good foods to include in your diet.
Nutrients and supplements for male fertility
For male fertility, it’s likely to be beneficial to ensure sufficiency of all micronutrients to optimise reproductive function as there is growing evidence to suggest paternal diet, can impact pregnancy and child health outcomes. Some of the nutrients that are especially important for men are vitamin D, folate, selenium, manganese, copper and zinc. However, we advise caution so as not to take excessive amounts or supplements that are not needed. It is much better to start with diet, and lifestyle before trying different supplements. This means reducing sources of oxidative stress where possible in terms of things likely ultra-processed foods and being overweight, before you try to use supplements as a sticking plaster.
There is growing evidence to support the potential benefit of certain supplements to improve semen quality, though with mixed results. Some research does suggest that supplements may improve fertilisation and pregnancy rates during IVF treatment, especially where there is a male factor fertility issue, or previous failed IVF, cycles. However, there is considerable variability between studies in terms of supplements used, the outcomes measured and the men included in the trials.
You can find out more about male fertility, how to work out which supplements may be beneficial and optimising the preconception health of the father in our Fertility and Preconception Care course and in The Fertility Book: Your Definitive Guide to Achieving a Healthy Pregnancy.
There are numerous important nutrients for male and female fertility and pregnancy and we’ve just covered some of the important ones here. You can find out much more in our Fertility and Preconception Care course and in The Fertility Book: Your Definitive Guide to Achieving a Healthy Pregnancy. Overall, the evidence supports ensuring adequate levels of all the key nutrients to ensure you are nutritionally prepared for pregnancy. Learning to recognise your individual needs can help you avoid potential negative effects of low levels of particular vitamins and minerals and may help improve your fertility.
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