Do some foods actually make you more fertile?

There’s a lot of questionable information about how your diet interacts with your fertility goals. Your reproductive hormones fluctuate throughout the menstrual cycle and have been linked to changes in food intake, energy levels, and metabolism (1, 2, 3). Also there’s a lot of information centered on the ideal menstrual cycle and hormone fluctuations, with little note to those who don’t fit into that ideal. Honestly, it’s difficult to sift through all the so-called “fertility foods” to tell truth from fiction, especially when you consider all the conflicting information out there with some sites saying, “stay away from dairy” and others saying, “eat dairy, it supplies vitamin D!” It could be that the conflicting information was from smaller studies that came to different conclusions. It’s tempting to say that it’s too complicated to sort out. In reality, there haven’t been many large-scale studies with long-term follow-up on the subject of diet and fertility until fairly recently. Now we have access to information from the National Institutes of Health’s BioCycle Study (4) with 259 participants and the Nurses’ Health Studies (5) on cohorts of women as large as 116,430.

We investigated what the current scientific consensus is regarding the possibility to enhance your fertility through diet and found that there are some foods and nutrients with consistent evidence and others with mixed or insufficient evidence to really draw conclusions.

Spoiler alert: the consensus is that yes, you can enhance your fertility by eating a generally healthy diet, taking a multivitamin, exercising, and avoiding junk food.

While you may get pregnant regardless of what you eat, recently, large studies have suggested that yes, some foods can improve fertility. Aside from other potential causes of infertility such as stress levels (6), environment, and genetic predispositions (7), following a fertility diet may help ward off infertility. A study of 17,544 women found that a lifestyle which included diet, weight control, and physical activity was associated with a 69% lower risk of infertility caused by ovulation disorders (8). A study of 259 women in the US found a link between diet and luteal phase deficiency (9), where your uterine lining doesn’t grow properly (10) causing infertility.  It seems that these larger studies confirm what smaller studies hint at: there is, indeed, a link between diet and hormone balances which may lead to enhanced fertility. Whether there’s a need to eat and exercise differently depending on which menstrual phase you’re in is still up in the air… there’s a need for more attention to the fertility aspect of menstrual phase-determined diets, or Menstralean diets, as only the weight loss aspect has been studied so far (11).

Over the past decade or so, there has been enough evidence in the body of research to recommend food sources for the key nutrients they provide.

Vitamin B9

Photos by  Gaelle Marcel ,  Pille-Riin Priske ,  Reinaldo Kevin , and  rawpixel   Vitamin B9 foods: Lentils, spinach, black beans, sunflower seeds, turnip greens, broccoli, orange juice, peanuts, fortified foods

Photos by Gaelle Marcel, Pille-Riin Priske, Reinaldo Kevin, and rawpixel

Vitamin B9 foods: Lentils, spinach, black beans, sunflower seeds, turnip greens, broccoli, orange juice, peanuts, fortified foods

Several large studies have shown that incorporating foods that supply vitamin B9 at above the level recommended for neural tube defect prevention (400 micrograms/day of synthetic folic acid) may enhance fertility (12). In its natural form found in foods like the ones above, it’s called “folate.” Other foods, like fortified nutritional yeast and cereals, have it added and may call it “folic acid.” Folic acid is not naturally found in food but is often added to those labelled “fortified” in amounts detailed on the package. Both folate from food and supplemental folic acid need to be activated by the body to be turned into vitamin B9. Since they both wind up as vitamin B9, they can be thought of as essentially the same.

                 

A Nurses' Health Study found that supplemental folic acid seemed to explain why women who consumed six or more multivitamins each week had a 41% lower risk of ovulatory infertility than women who didn't take the multivitamin (12)

Folate intake has also been found to reduce the number of cycles where the ovary fails to produce, mature, or release an egg (13).

In the past, however, there’s been mixed conclusions caused by methodological errors which appeared to show increased risk of fetal death from pre-conception folic acid use (12). Now, the CDC and the scientific literature on fertility outcomes suggest that yes, a higher intake of preconception folate (or folic acid) can increase fertility and the likelihood of carrying a pregnancy to term. So eating all of those leafy greens, orange juice, and beans may help you in your fertility journey!

Vitamin B12

Photo by  Caroline Attwood ,  Danielle MacInnes ,  Kim Gorga  and  Nyana Stoica   Vitamin B12 foods: Fish, meat, poultry, eggs, milk, milk products, fortified nutritional yeast, fortified breakfast cereals

Photo by Caroline Attwood, Danielle MacInnes, Kim Gorga and Nyana Stoica

Vitamin B12 foods: Fish, meat, poultry, eggs, milk, milk products, fortified nutritional yeast, fortified breakfast cereals

These foods supply vitamin b12, which is generally absent in plant-based foods (13).  Smaller studies have provided evidence suggesting that when a vitamin B12 deficiency first develops, it may lead to pregnancy loss. A continued deficiency may result in infertility by changing ovulation, ovum development, or ovum implantation (14, 15). If you’re vegetarian or vegan, consider going out of your way to find fortified foods that supply vitamin B12.

Fats

Photos by  Gregor Moser ,  Tom Hermans ,  Kelly Sikkema , and  Roberta Sorge   Monounsaturated and polyunsaturated fats: Fish, walnuts, avocado, flaxseeds, vegetable oils (corn, safflower, soybean, sunflower, olive)

Photos by Gregor Moser, Tom Hermans, Kelly Sikkema, and Roberta Sorge

Monounsaturated and polyunsaturated fats: Fish, walnuts, avocado, flaxseeds, vegetable oils (corn, safflower, soybean, sunflower, olive)

These foods contain monounsaturated and polyunsaturated fats (16). Take caution when selecting fish; eating fish that have high concentrations of pollutants or mercury may dampen the overall fertility benefit to an unknown extent (12). There has been a lot of attention given to consumption of fatty acids in studies of different populations but they have often  lumped polyunsaturated fatty acids (PUFAs) with monounsaturated fatty acids, transfats, and saturated fatty acids. Overall though, the body of research seems to agree that higher intake of PUFAs, especially long-chain omega-3 fatty acids, rather than transfats, may enhance female fertility (17). These PUFAs play crucial roles in ensuring high quality oocyte maturation and embryo implantation (18). Saturated fatty acids, monounsaturated fatty acids, and polyunsaturated acids were not correlated with infertility in a Nurses’ Health Study, so consider choosing these over transfats in your fertility diet.


Low-glycemic carbohydrates and high iron foods

Photos by  Monika Grabkowska  and  rawpixel   Low-glycemic carbohydrates and high iron foods: Whole-grain bread, steel-cut oats, brown rice, pasta

Photos by Monika Grabkowska and rawpixel

Low-glycemic carbohydrates and high iron foods: Whole-grain bread, steel-cut oats, brown rice, pasta

Low-glycemic carbohydrates cause less of a spike in blood sugar, which helps avoid insulin resistance (19). Insulin resistance has been linked to infertility (8). A large study found that a diet high in low-glycemic carbs like those listed above instead of high-glycemic carbs like white rice, instant oatmeal, and white bread may lead to a decreased chance of infertility (8). Foods with a glycemic index of 0-55 are considered “low” (20), so stick with those and you may ward off infertility. Grains are also good for fertility from an iron-supplying standpoint. Total iron from plants and supplements has been found to have a beneficial effect on fertility in a Nurses’ Health Study (21). Iron can take the form of heme and non-heme iron, but the type associated with increased fertility was the plant-based non-heme form. Plant proteins contain non-heme iron while animal-based proteins contain both types of iron. So plant proteins may be twice as helpful on your journey towards conception because of the additional nutrients they provide.


Summary

After all of our research into fertility foods, we’ve found agreement that a diet high in protein from vegetable sources, full-fat dairy foods, iron, monounsaturated and polyunsaturated fatty acids (as opposed to transfatty acids), and that includes multivitamins may actually impact your hormones and help you on your fertility journey. We found only slight evidence supporting the idea that you should eat certain foods during certain phases of your menstrual cycle, probably due to the lack of attention to the topic. We’re quite interested in this topic though, so we’ll let you know if we come across any additional research supporting this idea.




Resources

1. Pliner, P. and A.S. Fleming, Food intake, body weight, and sweetness preferences over the menstrual cycle in humans. Physiology & Behavior, 1983. 30(4): p. 663-666.

2. Kammoun, I., et al., Change in women's eating habits during the menstrual cycle. Ann Endocrinol (Paris), 2017. 78(1): p. 33-37.

3. Oosthuyse, T. and A.N. Bosch, The effect of the menstrual cycle on exercise metabolism: implications for exercise performance in eumenorrhoeic women. Sports Med, 2010. 40(3): p. 207-27.

4. Wactawski-Wende, J., et al., BioCycle study: design of the longitudinal study of the oxidative stress and hormone variation during the menstrual cycle. Paediatric and perinatal epidemiology, 2009. 23(2): p. 171-184.

5. Bao, Y., et al., Origin, Methods, and Evolution of the Three Nurses' Health Studies. American journal of public health, 2016. 106(9): p. 1573-1581.

6. NIH. NIH study indicates stress may delay women getting pregnant. 2010  [cited 2019 2/13/19]; Available from: https://www.nih.gov/news-events/news-releases/nih-study-indicates-stress-may-delay-women-getting-pregnant.

7. Burd, I. and D. Freeborn. Infertility risk factors for men and women. Available from: https://www.urmc.rochester.edu/encyclopedia/content.aspx?ContentTypeID=85&ContentID=P01533.

8. Chavarro, J.E., et al., Diet and lifestyle in the prevention of ovulatory disorder infertility. Obstet Gynecol, 2007. 110(5): p. 1050-8.

9. Andrews, M.A., et al., Dietary factors and luteal phase deficiency in healthy eumenorrheic women. Human reproduction (Oxford, England), 2015. 30(8): p. 1942-1951.

10. Schliep, K.C., et al., Luteal phase deficiency in regularly menstruating women: prevalence and overlap in identification based on clinical and biochemical diagnostic criteria. The Journal of clinical endocrinology and metabolism, 2014. 99(6): p. E1007-E1014.

11. Geiker, N.R.W., et al., A weight-loss program adapted to the menstrual cycle increases weight loss in healthy, overweight, premenopausal women: a 6-mo randomized controlled trial. The American Journal of Clinical Nutrition, 2016. 104(1): p. 15-20.

12. Gaskins, A.J. and J.E. Chavarro, Diet and fertility: a review. American Journal of Obstetrics & Gynecology, 2018. 218(4): p. 379-389.

13. NIH. Vitamin B12. 2018; Available from: https://ods.od.nih.gov/factsheets/vitaminb12-healthprofessional/.

14. Bennett, M., Vitamin B12 deficiency, infertility and recurrent fetal loss. J Reprod Med, 2001. 46(3): p. 209-12.

15. Reznikoff-Etievant, M.F., et al., Low Vitamin B(12) level as a risk factor for very early recurrent abortion. Eur J Obstet Gynecol Reprod Biol, 2002. 104(2): p. 156-9.

16. Harvard Health Publishing. The truth about fats: the good, the bad, and the in-between. 2018; Available from: https://www.health.harvard.edu/staying-healthy/the-truth-about-fats-bad-and-good.

17. Chavarro, J., et al., Dietary fatty acid intakes and the risk of ovulatory infertility. Vol. 85. 2007. 231-7.

18. Nehra, D., et al., Prolonging the female reproductive lifespan and improving egg quality with dietary omega-3 fatty acids. Aging Cell, 2012. 11(6): p. 1046-54.

19. Harvard Health Publishing. A good guide to good carbs: the glycemic index. Available from: https://www.health.harvard.edu/healthbeat/a-good-guide-to-good-carbs-the-glycemic-index.

20. Glycemic Index Foundation. About glycemic index. https://www.gisymbol.com/about-glycemic-index/

21. Chavarro, J.E., et al., Iron intake and risk of ovulatory infertility. Obstet Gynecol, 2006. 108(5): p. 1145-52.