What should women eat for fertility?

UPDATED SEPTEMBER 2020

Many people in the health arena talk about a "fertility diet," like the top 10 things you should eat to get pregnant. And the truth is, there really isn't a true fertility diet. In fact, many people get pregnant by eating whatever they want - which is great, but can be incredibly frustrating for those people who've been trying a long time to become pregnant and are tracking everything - including the food they eat.

However, diet does play a huge role in how we feel and function, and provides the necessary building blocks to support conception.

Carbohydrates and Fertility

Carbohydrates typically make up a significant part of a persons diet. It's made up of many components like monosaccharides (single sugars: glucose, fructose, galactose), disaccharides (two sugars combined: sucrose and lactose), and polysaccharides (complex sugars: starch and dietary fibre).

Most of our processed food these days often contain a significant quantity of artificial sugars which can lead to negative outcomes.

Studies have shown that eating whole grains have been correlated to increased implantation and live birth rates, possibly because they help to thicken the endometrial lining.

In women undergoing IVF and who regularly consumed artificial sugars experienced lower success rates. In those using ICSI, drinking beverages higher in artificial sweeteners also had a negative impact.

Additionally, the glycemic index and load have been associated with fertility outcomes.

The glycemic index is a value assigned to a particular food on how fast or slow it causes an increase in your blood glucose level.

The glycemic load combined quality and quantity of carbohydrates. It’s calculated by the amount of food you eat and the glycemic index of the particular food.The glycemic load is also associated with higher risks of ovulatory infertility.

In PCOS, it’s been found that women will often consume foods with a higher glycemic index. When women reduce their carb intake (or perhaps choose carbs with a lower index and load), their insulin sensitivity will improve, testosterone will decrease, and ovulation will occur (this is important, because anovulation is a key symptom in PCOS).

Fats, Fatty Acids and Fertility

Let’s clear something up. Fat isn’t bad. Yes, some are better than others and there are some you should avoid completely. But you need fat to make hormones, help your eggs mature and to get that tiny blastocyst to implant! Fats provide energy for all your daily activities, and they help to make up your cell membranes.

Fats can be divided into two types based on their structure - saturated and unsaturated. Animal foods are largely made up of saturated fats, while plants are largely made up of unsaturated fats.

Unsaturated fats can be broken up into omega 3 fatty acids - EPA and DHA, omega-6 and omega-9 fatty acids. Omega 3 fatty acids are associated with progesterone production in the luteal phase and a reduced risk of anovulation. In women undergoing IVF, omega 3 fatty acid intake was associated with better embryo quality and implantation, and linked to high live birth rates.

Unsurprisingly, there is a particular fat you should be avoiding - trans fat. This is a type of unsaturated dat that can increase insulin resistance, may prevent ovulation from happening, and decrease your chance of getting pregnant.

Dairy and Fertility

It's been thought that dairy can negatively impact fertility, however no relationship between full-fat dairy foods and anovulation has been found.

Protein and Fertility

Protein intake is not just important for fertility, but it's important for your overall health. Ideally you should be eating at least 1g of protein per kg of body weight (more if you're active).

Protein comes in different forms: animal and vegetable. Animal proteins can be further divided into red and white meat. Red meat often gets a bad rap because it contains saturated fatty acids and can also contain hormones, antibiotics and toxins.

Seafood is thought to be a better protein source because it also contains omega-3 fatty acids. If you're going to start incorporating more fish in your diet, be mindful that eating fish that's exposed to more toxins (like mercury - which can interfere with hormones), might offset its actual benefits.

Studies show that women who eat a large amount of vegetables and fish had higher rates of blastocyst formation; whereas women who ate more red meat, drank alcohol and smoked had lower rates of blastocyst formation. Obviously it would have been interesting to see a direct comparison between fish and red meat without including alcohol and smoking to the mix.

I often get asked if soy is a suitable protein for fertility, because its affect as a phytoestrogen. Studies have shown that soy causes little harm in women, and in fact might be beneficial. Soy isoflavone supplements were associated with improvement in reproductive outcomes, increased live birth after clomiphene administration, and higher endometrial thickness and ongoing pregnancy rates after IVF and ICSI. 

Before ordering your soy latte – choose organic, non-GMO soy. And if you have a thyroid condition, it may be best to avoid dietary soy altogether.

Antioxidants and Fertility

Many people believe that antioxidants can be helpful for fertility, the reasons why they're often used is because oxidation regularly occurs in the body. When nutrients are used in the body, the mitochondria use them for energy, which also produces oxidation and an abundance of reactive oxidative species can cause damaging effects in the body if there aren't enough antioxidants to "quench" them and repair the damage the cause.

When produced in high amounts, reactive oxidative species can lead to DNA damage and cell death. In cells associated with fertility, the most common cause of oxidative stress are environmental pollution, smoking, alcohol, poor nutrition, and obesity.

Although many studies don't agree on the 'best' antioxidant outcomes leading to live births, or the dosage - there are many antioxidants to choose from. We'll focus on this in a future blog post.

Vitamins and Fertility

B Vitamins

The family of B vitamins are needed for energy production. Studies have specifically looked at folate. We know that this important B vitamin is needed for neural tube defects - which is why many people will start to take folate when planning a pregnancy.

Studies have shown that using folate in the preconception period may increase chances of becoming pregnant and hopefully result in a live birth. In a Danish study, folic acid was associated with a shorter time to pregnancy. In addition, a Polish IVF study demonstrated that supplementation led to better quality and more mature eggs - compared to women who did not have folic acid supplementation.

Oftentimes, folic acid and folate are used interchangeably. Methylfolate is the active form of folic acid, and while it does the same thing as folic acid, the active form may be better absorbed and used.

Vitamin D

Vitamin D is an important vitamin, with receptors on the ovary, endometrium, and placenta. Studies have shown that a vitamin D deficiency in women undergoing IVF, can negatively impact egg and embryo quality and reproductive function. A vitamin D deficiency was also higher in women with recurrent miscarriages - although recurrent miscarriages can happen for a variety of reasons (ex. hypothyroidism).

Vitamin D is also thought to support endometrial receptivity and implantation of the embryo. In women older than 40, there was a relationship between decreased AMH and a vitamin D deficiency.

Mediterranean Diet and Fertility

I mentioned in the intro that there's no true fertility diet. That said, a lot of people turn to the Mediterranean diet as a standard because it has been shown to be beneficial in those using IVF. The Mediterranean diet consists of fish, monounsaturated fats from olive oil, fruits, vegetables, whole grains, legumes/nuts, and moderate alcohol consumption (read: red wine). Unlike other diets, it does not limit foods or calories.

In non-obese women under 35, the live birth rate was 20% higher in those following a Mediterranean diet, compared to other diets. There wasn't any difference in women older than 35; as well as no difference in egg collection or embryo grades.

So while the Mediterranean diet has been shown to be helpful for fertility, it's often studied in people who go on to use IVF. Again, that doesn't mean this will be the right diet for you, but if you are looking to improve outcomes - particularly if you feel it's taking you a 'long' time to get pregnant, it may be worth exploring this diet further.

Final Thoughts

It might be obvious that a diet that leans towards fast food/processed foods and few fruits and vegetables is probably not ideal. Reviewing the Mediterranean diet may be a good idea if you're hoping to improve outcomes.

That said, no matter what you may be eating, be mindful of pesticides and other chemicals in your foods as they also affect reproductive success. Therefore, if possible, choose organic when you can. Basically, if any of the fruits and vegetables that you eat appear on the Dirty Dozen, eat the organic version instead. For the foods that appear on the Clean Fifteen, you don't need to choose organic versions of these products.

Keep in mind that when choosing organic version of products, you want to look for a specific seal - otherwise you can't be certain that the product you're buying is indeed organic. The picture below demonstrates a Canada Organic seal, as well as a USDA organic seal. The Non GMO project seal may be good to remember when choosing products containing soy.

When choosing meats, aim to get your meats from local farms if possible. Choosing grass-fed and antibiotic-free are great options too. I haven't been able to find a seal for this (I'm not sure one exists), but in my experience the packaging will usually state if a product is grass-fed or antibiotic free.

Lastly, you may also be considering taking some supplements during the preconception period. This may include a prenatal that includes methylfolate, a fish oil supplement that contains EPA and DHA, and vitamin D - although you may want to get your level assessed by a Naturopathic Doctor to see if you're experiencing any deficiencies.

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References

Chiu, Y., Chavarro, J. and Souter, I. (2018). Diet and female fertility: doctor, what should I eat?. Fertility and Sterility, 110(4), pp.560-569.

Gaskins, A., & Chavarro, J. (2018). Diet and fertility: a review. American Journal Of Obstetrics And Gynecology, 218(4), 379-389. https://doi.org/10.1016/j.ajog.2017.08.010

Koga, F., Kitagami, S., Izumi, A., Uemura, T., Takayama, O., Koga, T., & Mizoguchi, T. (2020). Relationship between nutrition and reproduction. Reproductive Medicine And Biology, 19(3), 254-264. https://doi.org/10.1002/rmb2.12332

Lu, J., Wang, Z., Cao, J., Chen, Y., & Dong, Y. (2018). A novel and compact review on the role of oxidative stress in female reproduction. Reproductive Biology And Endocrinology, 16(1). https://doi.org/10.1186/s12958-018-0391-5

Smits, R., Mackenzie-Proctor, R., Fleischer, K., & Showell, M. (2018). Antioxidants in fertility: impact on male and female reproductive outcomes. Fertility And Sterility, 110(4), 578-580. https://doi.org/10.1016/j.fertnstert.2018.05.028