Seed cycling for fertility: what's the evidence

What is seed cycling?

Seed cycling is the proposed practice of eating certain seeds during each phase of the menstrual cycle in order to support healthy levels of the key reproductive hormones. During the follicular phase, from the first day of your period until approximately day 15 (or when you ovulate), consuming 1 tablespoon of pumpkin seeds and 1 tablespoon of freshly ground flaxseed is advocated to promote healthy oestrogen levels for egg maturation and ovulation. During the luteal phase (days 15-28) post-ovulation, 1 tablespoon of sunflower seeds and 1 tablespoon of freshly ground sesame seeds daily is encouraged to promote the levels of progesterone required for fertilisation and implantation.

Hormone imbalances can lead to conditions such as severe premenstrual symptoms, polycystic ovary syndrome (PCOS), and irregular menstrual cycles and can affect fertility. Advocates of seed cycling suggest its hormone-balancing effects can overcome many of these problems and promote fertility.

The evidence for seeds and fertility

Seeds are a rich source of nutrients, they contain protein, healthy omega-3 fatty acids, fibre, vitamins and minerals as well as polyphenols and other bioactive phytochemicals. They are a great addition to any diet as regular consumption is associated with better overall health, lower risk of cardiovascular disease and type 2 diabetes and may reduce the risk of breast cancer risk. Some of the health-promoting components of seeds may also be beneficial for fertility and reproductive health.

Phytoestrogens are a type of polyphenol found in seeds such as flax, of which there are 2 classes isoflavones and lignans. These are structurally and functionally similar to oestrogen and bind to the oestrogen receptor in our bodies suggesting they may have the potential to induce hormonal changes. There is conflicting evidence however as to whether lignans can actually alter human levels of sex hormones with some studies showing they can while others do not.

Consumption of lignans has been linked with a shorter time to conception. To try to understand the mechanism behind this a study looked at their effects on the menstrual cycle, they found that phytoestrogens were not associated with menstrual cycle length, but were associated with menstrual cycle regulatory which could possibly explain the reduced time to conception. A 1993 study found that while a lignin supplement had no effect on overall cycle length it did increase the luteal phase. Together this suggests that their consumption could have beneficial overall effects on the menstrual cycle but there isn’t enough evidence to say that seed cycling could positively affect fertility.

One tablespoon of ground flaxseed contains approximately 1.8 grams of omega-3 fatty acids, linked to improved egg quality and delayed ovarian ageing, incorporating it into the diet has been shown to improve oocyte quality in older females, prolonging the female reproductive lifespan. Flaxseed is a good plant source of omega-3 fatty acids to include in the preconception diet.

The gut microbiome plays a role in regulating circulating oestrogen. Gut microbiome disruption, through dietary changes or antibiotics, could impair oestrogen metabolism contributing to diseases such as endometriosis, PCOS and metabolic syndrome which could all ultimately affect fertility. Consuming enough fibre (30g per day is recommended) can promote gut diversity, seeds such as flax are high in fibre and therefore have the potential to positively affect fertility through the gut.

PCOS is characterised by hormonal imbalance, in a rat model of the disease flaxseed has been shown to fix the hormonal disturbances by increasing progesterone and decreasing testosterone levels. A case study of one female with PCOS suggests that supplementation with 30g per day of flaxseed is beneficial for balancing hormone and androgen levels.

While the above-discussed evidence suggests that seeds have the potential to contribute to our overall hormonal health there is no direct evidence to show which seeds could have benefits over others or if it makes a difference to our fertility when we consume them. Currently, no research has assessed the cycling aspect of this practice. However, incorporating seeds regularly into the diet is recommended due to their rich nutrient load and their potential to promote reproductive health at all stages of the menstrual cycle.