Foods to fight infertility

Packing your diet with plant foods may help you beat endometriosis and infertility, says dietitian Lisa Simon.

Just before my 30th birthday, when I was studying to become a dietitian, I suddenly experienced excruciating pain low down in my abdomen. I struggled to even stand up straight, let alone walk. It lasted for a few days, and then I was able to resume some sort of normal activity.

My doctor put it down to IBS, but when it happened again a few weeks later, I sought private help, and I was told it was likely endometriosis. I ended up having a laparoscopy, during which endometrial tissue was removed. But it grew back a few years later and I had a repeat procedure.

My husband and I had no problems conceiving our first child when I was 27. But after two years of trying for another baby several years later, we were diagnosed with unexplained infertility, although endometriosis may have played a part.

We decided to go the IVF route, mainly due to our ages, and I searched for any information that would help to optimize our chances of a successful outcome. One line kept jumping out at me: a plant-based diet can help to optimize fertility.

Although I was skeptical at first, after reading through many studies showing the likely negative effects of animal products on fertility, and the fertility-optimizing effects of plant foods, I chose to eliminate meat, fish and eggs from my diet. Dairy remained as our first round of IVF was successful, but when my breastfed baby was diagnosed with cow’s milk protein allergy (CMPA) at 6 weeks, I made the final leap and eliminated dairy completely.

Within three months of going fully plant-based, I saw my menstrual cycle return after being absent for years and my cystic acne disappear. In addition, I have rarely experienced any endometriosis pain over the past four years.

My experience, along with the ever-mounting evidence base, made me feel strongly about helping others optimize their chances of conceiving with a plant-based diet. If you, like many of my clients, are struggling with endometriosis or infertility in general, here’s a guide to plant foods that may help.

Animal foods and endometriosis

Endometriosis is when cells similar to those that line a woman’s uterus, which grow and bleed with each menstrual cycle, are found elsewhere in the body, most commonly the pelvic cavity. Unlike those in the womb, which are shed as a woman’s monthly period, these cells have nowhere to go and so become inflamed, leading to pelvic pain, bowel and bladder symptoms, painful and/or heavy periods, painful sex and infertility.

Oxidative stress seems to be one factor in the development of endometriosis as it may cause an inflammatory response in the peritoneal fluid.1 This fluid is made in the abdominal cavity to act as a lubricant and covers most of the organs in that space.

We know that heme iron in animal foods acts as a source of oxidative stress, so minimizing or eliminating this from your diet makes sense to reduce the risk of this inflammatory response. 

Standard Western diets high in animal foods and processed meat, in particular ham, beef and other kinds of red meat, are associated with a significantly higher risk of developing endometriosis.2 Poultry has also been shown to increase the risk but not as significantly as red meat.

Dairy has not been consistently shown to increase the risk and has actually been shown in a recent review to reduce the risk of developing endometriosis for women regularly consuming cheese and high-fat dairy. Butter, on the other hand, may increase the risk.3

One explanation may be the vitamin D and calcium content in dairy. Vitamin D has been shown to regulate immune function, and as women with endometriosis display immune changes, it may be beneficial.

Women with higher blood levels of vitamin D have a 24 percent lower risk of endometriosis than those with the lowest, and adequate calcium and vitamin D intakes from dairy are also linked to a lower risk.4 If you want to avoid dairy, you can easily meet your calcium and vitamin D requirements without it. Foods such as leafy green vegetables, nuts and seeds are good alternatives.

The power of plants

Whole plant foods are high in fiber, which plays a key role in optimizing fertility, especially in hormone-driven conditions like endometriosis. Fiber binds with excess hormones, like estrogen, to remove them from your body. The insulin-lowering effects of fiber are also significant because higher levels of insulin increase estrogen and endometrial cell production.

Fertility-friendly sources of fiber include fruit, vegetables, beans, nuts, seeds, whole grains such as brown rice, barley and wholemeal couscous, and pseudo grains such as quinoa and buckwheat.

Fruit is associated with a reduced risk of endometriosis, particularly citrus fruit, and this may be due to its content of beta-cryptoxanthin and vitamin C.5 Both are potent antioxidants that can help to neutralize the damage caused by oxidative stress.

Data from the Nurses Health Study II, which looked at over 18,000 women without a history of infertility as they attempted to become pregnant over an eight-year period, show that vitamin C from food and supplements combined, or from supplements alone, does not have the same association, so there may be a threshold to the beneficial effects of vitamin C. 

High intakes of cruciferous vegetables are associated with an increased risk of endometriosis,5 but this could be because many of them are high in certain carbohydrates, known as FODMAPs, that can exacerbate symptoms of IBS. These symptoms can be difficult to differentiate from chronic abdominal pain caused by endometriosis.

Cruciferous vegetables include cauliflower, broccoli, cabbage and brussels sprouts. They are packed with fiber, phytonutrients, vitamins and minerals that are known to reduce the risk of many chronic conditions as well as helping to optimize fertility. So rather than avoiding them, if you notice eating them makes you feel bloated, causes wind or means you are urgently dashing to the loo, try including them initially in small quantities, then increase your portion sizes until you find a level you can tolerate.

What does plant-based  really mean?

The phrase plant-based diet can have several meanings. It can imply that you still include animal products but in lower quantities so that your diet is based on plant foods. It can also mean you have eliminated all animal products and consume a diet based purely on plants.

Most studies examining plant-based diets have looked at plant-predominant diets, meaning small amounts of animal products are still consumed. The most studied diet in these terms is the Mediterranean diet, which emphasizes a variety of fruit and vegetables, beans, whole grains, nuts, seeds, olive oil and fish, with lower amounts of meat and dairy.

It would be wrong to say the evidence is clear that following a whole-food, plant-based diet will give greater benefits in terms of fertility compared to following a plant-predominant diet. This is important for those trying to conceive who want to make big improvements to their diet but do not necessarily want to remove every animal product.

Any positive change will give some degree of benefit, and if that means still including some non-processed meat, fish, eggs or dairy but building the majority of meals around plants, that is okay.

Phytonutrients for fertility

Phytonutrients, health-giving compounds in plants, are particularly beneficial for fertility. Their antioxidant, anti-inflammatory actions make them essential to protect sperm and egg quality, and they promote an optimal internal environment for conception.

The basic rule is to “eat the rainbow,” which means include as many different colored fruits and vegetables in your diet as you can. This way you will be consuming a wide range of phytonutrients, all of which have slightly different or mutual benefits to the body. By eating in-season varieties, you will be eating even more concentrated quantities of these compounds because they are much fresher and have higher nutritional value. 

The most common types of phytonutrients are polyphenols. Aim for a minimum of 30 different plant foods a week, and you’ll get all you need.

Polyphenols and where to find them

The best fats for fertility

There are two types of unsaturated fat: monounsaturated fatty acids (MUFAs) and polyunsaturated fatty acids (PUFAs). Individually or together, they have been shown to have positive effects on fertility.

For women, MUFAs seem to be more important than PUFAs. Diets higher in MUFAs have been associated with higher fertility rates, and consuming foods rich in this type of fat in place of saturated and trans fats may help to improve fertility.

In fact, it has been shown that a Mediterranean diet rich in MUFAs is associated with almost a 70 percent lower risk of ovulatory infertility, or inability to regularly release a properly developed egg, when compared with diets high in trans fats.6 Such a diet is also associated with up to a 90 percent lower risk of preterm delivery.7

The richest sources of MUFAs are olives, olive oil, avocados and most nuts (walnuts and pine nuts are the exception).

What about protein?

Data from the Nurses Health Study II shows that higher intakes of animal protein are associated with higher rates of ovulatory infertility.6 Having just one extra daily portion of animal protein, in particular poultry and red meat, significantly increased the risk, but replacing this with plant protein significantly reduced it.

One reason might be the beneficial effects of plant protein in lowering insulin resistance, the authors explained, but the presence of the amino acid arginine may also have something to do with it. Arginine is involved in the production of nitric oxide in the body, which is vital for good blood flow to the male and female reproductive organs.

Meat is also a vector for exposure to hormones and antibiotics, with the exception of organic versions, and a major source of advanced glycation end products, or AGEs, which are linked to fertility problems in men.8

As I recommend eliminating or at least reducing meat to the couples I work with, the most common question I am asked is, “But where will I get enough protein?”

As long as you are eating a varied diet containing whole grains, legumes, lentils, chickpeas, vegetables, fruit, nuts and seeds, and importantly, meeting your energy needs, you will also be meeting your protein needs.

Fit for the future

Nutrition is, of course, only one piece of the puzzle, and many lifestyle factors can affect fertility. But I believe that by laying these foundations, you can help to improve not only your own health but that of your unborn child.

Adapted from The Plant-Based Dietitian’s Guide to Fertility by Lisa Simon, RD (Hammersmith Health Books, 2023)