I am concerned to see stories that some fertility clinics have started to advise their patients to follow a low carbohydrate diet in order to improve their chances of conception. The advice includes limiting carbohydrate intake to one portion a day and to ensure that carbohydrates do not exceed 40% of total daily energy intakes.
The advice states that there is strong evidence that high carbohydrate intakes affect the body’s metabolic functions and can fuel obesity which in itself can negatively impact fertility and patients are therefore advised to reduce their carbohydrate intakes and to increase their protein intakes (lean animal sources) by up to 35% of their total energy intake.
This advice concerns me because not all carbohydrates have the same effect on the body and, like sugar, carbohydrates should not all be classed in one group. I have written a previous blog which explains in detail their role, why they are so important and the differences between refined carbohydrates and wholegrains, but I would like to highlight the role of wholegrain carbohydrates in optimising fertility and explain why they are such an important component of a plant based diet.
Below I have set out the World Health Organization’s (WHO) recommendations for macronutrients and you can see that carbohydrates, in the form of wholegrains, fruit and vegetables, should make up the majority of our diets:
• Protein should make up 10-15% of our total daily energy intakes
• Carbohydrates should make up 55-75% of our total energy intakes
• We should be consuming less than 10% free sugars and ideally 5%
• Fat should make up 15-30% of our diets, with saturated fat making up less than 10%
• We should aim for less than 5g of salt daily Ideally we should be aiming for 30g fibre daily and at least 5 portions of fruit and vegetables
Eating adequate fibre is essential for our gut health and also for our fertility. You cannot get fibre from animal protein; only from plants. The best sources of fibre in a plant based diet are wholegrains, fruit, vegetables, nuts and seeds. If you reduce your carbohydrate intake and replace it with animal protein, you will not be getting enough fibre and this can adversely affect your fertility via a number of mechanisms. There are also a number of studies which have shown the negative effects of animal protein on fertility.
A large study of over 18,000 women revealed that 1 in 6 experienced difficulty conceiving, with hundreds experiencing ovulatory infertility. When these women’s diets were compared to those who fell pregnant easily, several key differences emerged and this led the authors to translate their findings into a possible “fertility diet”. The recommendations included eating plenty of slow release carbohydrates, such as wholegrains, beans, vegetables and fruit and avoiding refined carbohydrates and added sugars in foods and drinks. The authors stated that it is not the amount of carbohydrates eaten that is important in terms of fertility; it is the quality . Research has also shown that a diet rich in slow release carbohydrates can reduce the risk of gestational diabetes.
Adopting a healthy diet should begin pre-pregnancy and continue long term to help prevent chronic disease later in life and to create a healthier food environment in the family home. In terms of carbohydrates, my advice for optimising fertility remains ensuring that each ¼ of your plate contains a source of wholegrains (eg oats, brown rice, whole wheat pasta, buckwheat), as not only are they rich in fibre, they also contain a wide variety of beneficial nutrients vital to reproductive health, such as folate and other vitamins, antioxidants, zinc and iron. While it is true that we should be reducing our intakes of refined carbohydrates and certainly added sugars, advising that all carbohydrates should be severely restricted is likely to result in nutritional deficiencies and impaired fertility rather than optimised fertility.