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.
PCOS and Diet
Polycystic ovary syndrome (PCOS) is the most common hormonal disturbance in women. It causes irregular periods and the majority of cases of infertility caused by a lack of ovulation. There is hot debate surrounding what is best to eat if you suffer from this condition and there is a great deal of misinformation circulating on social media. In this section we look at:
Dietary and lifestyle guidelines for PCOS
The latest global guidelines for PCOS (which our very own Professor Adam Balen helped develop) recommend lifestyle as the first-line intervention for the treatment of women with PCOS before any medical treatment is attempted. It says:
- Healthy lifestyle behaviours encompassing healthy eating and regular physical activity should be recommended in all those with PCOS to achieve and/or maintain a healthy weight & to optimise hormonal outcomes, general health, and quality of life across the life course
- Lifestyle intervention (preferably multicomponent including diet, exercise and behavioural strategies) should be recommended in all those with PCOS and excess weight, for reductions in weight, central obesity and insulin resistance
- Psychological factors such as anxiety and depressive symptoms, body image concerns and disordered eating, need consideration and management
The PCOS diet
So the recommended first-line treatment for women with PCOS is a dietary and lifestyle approach and this should always be included as part of your medical treatment. In practice this usually means your doctor will encourage you to lose weight and there isn’t a medically validated diet for the treatment of PCOS. However, there is a lot you can do in order to optimise the different parameters associated with PCOS, including menstrual cycle irregularity, insulin resistance and hormonal disturbances. A good diet is the foundation for adequate levels of key nutrients that are important for reproductive health, management of symptoms PCOS and fertility. The principles that we cover in our Fertility and Preconception Care course are especially important for women with PCOS in terms of following a healthy, balanced Mediterranean-style diet and optimising nutrient levels and the gut microbiota (the “good” bacteria in your gut). Eating enough fibre, plenty of vegetables and dietary diversity all help support the health of the gut. There is growing evidence to suggest a link between certain profiles of bacteria in the gut and PCOS. It has also been suggested that the changes in the gut microbiota following bariatric surgery may be the underlying factor that improves fertility and PCOS parameters in the women treated, so always pay attention to any digestive symptoms you may experience.
In terms of gluten, there is no evidence that women with PCOS need to avoid gluten though some find symptoms improve when they do. Also be aware that Coeliac Disease is commonly misdiagnosed and many do not suffer classic digestive symptoms or noticeable reaction to wheat. In general, there is individual variation in intolerances to different foods. Balance is key plus paying attention to how you feel after eating certain foods to identify any specific intolerances. There is a specific process to undertake to do this that we cover in our Fertility and Preconception Care course.
In terms of hormones and fertility treatment, women with PCOS may be disproportionately affected by low vitamin D when it comes to IVF outcomes, so your nutrient status takes on an added significance if you suffer from this condition. One study showed that vitamin D and calcium supplementation together may improve menstrual regularity, hyperandrogenism, weight loss and fertility in women with PCOS. Other studies have found that micronutrient supplementation for a period of three months improves PCOS parameters including the ratio of LH to FSH and serum testosterone levels. This particular supplementation protocol included folic acid, vitamin E, omega-3, co-enzyme Q10, catechin (a flavonoid) and glycyrrhizin (liquorice extract). These tend to be small studies and there isn’t good consensus on the best approach but in our patients, we find that additional zinc, magnesium and vitamin B6 are usually helpful. Interestingly, various animal and laboratory studies show that zinc inhibits the enzyme (5-α reductase) that converts testosterone into dihydrotestosterone and that vitamin B6 increases this effect. Dihydrotestosterone is the more potent androgen that leads to typical symptoms in PCOS of acne, alopecia and hirsutism. However, the effects of zinc in terms of 5-α reductase and related symptoms in women with PCOS have not been well studied in humans and the underlying processes are complex. Likewise, data is mixed in terms of the effects of fatty acids on 5-α reductase and vitamin D was found not to have an effect in one study, contrary to what you may read online. We urge caution in terms of sourcing information online that often presents early or suggestive evidence from animal and laboratory studies as established scientific fact for humans.
Other significant factors include exercise and food choices, with exercise improving menstrual cycle regularity in women with PCOS. Soy is likely to be beneficial for women with PCOS, as is reduced carbohydrate and slightly higher levels of protein. Including some protein with each meal is therefore particularly important, but ensure you eat a balanced diet. A very high-protein or ketogenic diet is not recommended and ensuring sufficient intake of wholegrains and dietary fibre will feed the bacteria in your gut and fuel exercise adequately. Avoiding refined carbohydrate is especially important for women with PCOS. Having only one meal that is ‘carb-heavy’ (for example, one that includes a small or medium-sized jacket potato or a portion of brown rice) is a good rule of thumb. This may look like poached eggs, grilled tomatoes and spinach or scrambled eggs and home-made guacamole for breakfast, a chicken salad for lunch and a fish or tofu Thai curry with vegetables and a medium portion of brown rice for your evening meal. Including five portions of beans and legumes per week will help to ensure good intake of fibre. Don’t forget to include two or three portions of fruit daily and a snack of nuts and seeds to ensure a good spread of nutrients. As always, adjust portion size so that you feel satisfied after each meal and properly hungry by the next. The proportion of macronutrients that is optimal for each of us varies, and some people find they need more carbohydrate than this. We recommend monitoring your response carefully when changing your diet and seeking professional advice where needed.
Once all the different dietary and lifestyle factors have been optimised, we routinely see improvements in symptoms including regularisation of the menstrual cycle, weight loss and return of ovulation. Some patients who have struggled with symptoms and subfertility for years are able to conceive naturally purely through these interventions. At the very least, taking these steps will help put you in the best possible place prior to any medical treatment that may be needed.
Is dairy bad for PCOS?
The popular narrative, especially on social media, is that dairy is bad for hormones and PCOS. This isn’t backed up by consistent evidence, however, and the data is still mixed in terms of the effects of dairy on PCOS, though it is possible that cow’s milk may worsen symptoms. A recent meta-analysis found an association between dairy and increased likelihood of acne but the authors concluded these results should be interpreted with caution as the studies used different methodologies and evaluated different outcomes. Many health and alternative practitioners still also claim dairy produce is inherently inflammatory, but a 2017 systematic review of 52 clinical trials found a strong anti-inflammatory effect in those with metabolic disorders and, unsurprisingly, a strong pro-inflammatory response in those with an allergy to cow’s milk. Further, recent research has shown that dairy lipids (fats) specifically act against chronic inflammation in the body.
However, you must always take into account your body’s individual response to foods and, while some women with PCOS may be absolutely fine with moderate consumption, you may do better by cutting out dairy. Some people may also be lactose intolerant where they don’t produce lactase, the enzyme that digests lactose, the main sugar in dairy produce. This can be tested by your doctor. There is also some evidence that A2 dairy products are less likely to have a negative effect. The major protein in milk is casein and it has two major sub-types: A1 and A2. A2 dairy contains the latter and some studies suggest this is less likely to cause an inflammatory response, digestive discomfort and loose stools. It is possible to buy both A2 cow’s milk and also sheep and goat milk products, which both contain predominantly A2 casein.
On balance, if you have PCOS, you may benefit from cutting out dairy products, however, particularly cow’s milk, though we still don’t have sufficient evidence on this topic. Indeed, eating moderate amounts of full-fat dairy is associated with better fertility. Pay attention to how you feel after specific foods and, in the absence of testing, this will be your best clue as to how well you tolerate different aspects of your diet. Plant-based milks including soy, almond, coconut and oak milk can all be used as substitutes if you want to try eliminating dairy. Choose fortified varieties to replace the nutrients found in dairy like calcium and iodine. The message with all of these things is to achieve a healthy balance and avoid over-consumption of any one type of food, and with this advice you will avoid most significant pitfalls.
Supplements for PCOS
If you are already following a healthy diet and lifestyle, there are various supplements that have been tested in women with PCOS. One that has seen a growing evidence base to demonstrate benefit, especially when it comes to fertility, is myo-inositol. Inositol is a naturally occurring substance in the B vitamin family found in foods including nuts, seeds, oranges, grapefruit and melon, to name a few. Numerous studies have shown improvements to hormonal parameters of PCOS, including significantly decreased levels of testosterone and dehydroepiandrosterone sulfate (DHEA-S) and increased levels of SHBG following inositol supplementation. Research has also shown improvements in metabolic factors in terms of fasting insulin and fasting glucose. When it comes to fertility, studies have demonstrated that frequency of the menstrual cycle and ovulation rates both increased following supplementation with inositol and no serious adverse events. In other words, inositol seems to be very safe to take.
Evidence to suggest the number of women having a healthy baby increases following inositol supplementation is also starting to emerge. A recent small study concluded that the combination of two different forms of inositol (myo-inositol and D-chiro-inositol) at high doses of D-chiro-inositol improved the pregnancy rates and live birth rates and also reduced the risk of ovarian hyperstimulation syndrome (OHSS) in women with PCOS undergoing IVF treatment with intracytoplasmic sperm injection (ICSI). Over half – 55.2 per cent – of women in the group treated with the combined inositol supplement went on to have a baby compared with 14.8 per cent in the control group, so this is significant indeed (perhaps implausibly so and may be due to the small number of patients), and the effects need to be demonstrated in larger trials. Overall, however, evidence supports a ratio of 40:1 ratio between myo-inositol and D-chiro-inositol for the treatment of PCOS. Myo-inositol has also shown to be beneficial in preventing gestational diabetes and early studies indicate it is safe to supplement during pregnancy, though it is especially important to seek the advice of your treating doctor before taking any supplements while pregnant.
Finally, supplementation with the protein alpha-lactalbumin may improve absorption of myo-inositol, which is impaired in some patients. Taken together, alpha-lactalbumin and inositol may increase the chance of experiencing benefit but, importantly, alpha-lactalbumin is a protein derived from milk and should not be taken by those with milk allergies or intolerances.
Other supplements that have shown benefit in women with PCOS include cinnamon (improved antioxidant status, insulin resistance and serum lipid profile) and evening primrose oil together with vitamin D (significantly improved various parameters including triglycerides and cholesterol). These supplements have not been suitably tested in terms of fertility, and care should always be taken in the weeks leading up to fertility treatment and in the second half of your cycle when you may become pregnant.
- Adam Balen and Grace Dugdale. The Fertility Book: Your Definitive Guide to Achieving a Healthy Pregnancy. Penguin Random House (Vermilion) 2021
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