Dairy for Fertility: Friend or Foe?

Dairy in the Fertility Diet

Many couples facing infertility have turned their attention to the “fertility diet”. The fertility diet originates from the Nurses’ Health II Study, which is the largest ever prospective study on women’s risk factors for major chronic disease. One interesting finding from the study is that whole milk consumption is associated with lower rates of infertility in women1. Many of us are surprised by this finding considering that many tout dairy to be inflammatory and in some cases detrimental to overall health. With many conflicting viewpoints, what are we to believe about dairy for fertility? Is dairy harmful or helpful when trying to conceive?

Dairy for Fertility: A Summary of the Research

We’ll start off with data from the well-known Nurses’ Health Study II. Over an 8-year period, 18,000 women were followed and asked to complete questionnaires. Researchers looked at patterns between diet and fertility in these women. They found that high intake of low fat dairy foods (about 2 servings a day) was associated with an increased the risk of anovulatory infertility, whereas intake of high fat dairy foods (1 or more servings a day) was associated with a decreased risk3. These dietary patterns were also associated with a decreased risk of infertility due to other causes.

In 2015, a small study looking at 24 women with PCOS found that an 8-week low starch/low dairy diet improved insulin sensitivity, reduced testosterone levels, and led to weight loss5, all of which are important in optimizing fertility. However, the diet in this study included 1 ounce of cheese daily, a form of full fat dairy5. Since both a low starch AND low dairy diet were implemented at the same time, it is impossible to say if restricting either one on it’s own would have the same impact. It is completely feasible that a low starch diet on it’s own would have the same impact on these metabolic parameters in this population.

In 2017, two preconception cohort studies  were completed looking at dairy intake and ability to get pregnant in women trying to conceive. For 12 months, 2426 women attempting pregnancy completed a validated food frequency questionnaire assessing intake of dairy foods. Inconsistent with previous findings, no clear association was found between low- or high-fat dairy intake and fecundability in either cohort4.

In 2016, a prospective cohort study was completed looking at full-fat dairy consumption and fertility in men. For 8 years, 142 men in couples undergoing in vitro fertilization (IVF) completed dietary assessments prior to their IVF procedures. Researchers found that intake of both full-fat and low-fat dairy was not associated with fertilization, implantation, clinical pregnancy or live birth rates11. The study concluded that men’s dairy intake was not associated with treatment outcomes in IVF11.

In 2016, another prospective cohort study looked at dairy consumption and live births among women undergoing IVF. Between 2007 and 2013, 232 women about to undergo IVF completed dietary assessments before treatment. Researchers concluded that dairy intake did not appear to harm IVF outcomes, and if anything was associated with higher chances of a live birth12.

Although these studies do illuminate some interesting information regarding dairy for fertility, many limitations do exist. Namely, it is extremely difficult to conduct accurate studies on dietary interventions; it is difficult to collect accurate data, and it is difficult to conduct randomized control trials to determine cause and effect.

Dairy Intolerance

One very important caveat to dairy consumption is dairy intolerance. Approximately 75% of the world’s population loses the ability to digest lactose in adulthood13. In its most obvious form, lactose intolerance is characterized by digestive upset after consuming dairy14. Lesser intolerances to dairy, known as sensitivities, also exist 10. Dairy sensitivity may not cause digestive upset, but may appear in other clinical manifestations. For example, there is a small body of evidence suggesting dairy consumption is linked to acne15. Although there may be an association between dairy and acne, no randomized controlled trials have been completed at this time. If you find that dairy impacts your digestion or skin health, it may be best for you to avoid it.

Bottom Line

So what are we to make of all of this? To date, there is no conclusive evidence showing that dairy is helpful or harmful to fertility. However, based on some studies there seems to be a benefit of consuming full fat dairy over low fat dairy when trying to conceive. If you are able to tolerate dairy, enjoy it in moderation. Since dairy consumption is linked to insulin resistance7, and has been associated with endocrine disrupting chemicals9, it is best to limit intake to 1-2 servings per day.

Takeaway Tips

  • Harvard Health University, a contributor to the Nurse’s Health Study II and supporter of the Fertility Diet states “If you drink milk, choose whole milk while trying to get pregnant, or have a small dish of ice cream or full-fat yogurt every day8”. We do agree that if you’re going to have dairy, make sure it is full fat, but please pass on the ice cream. One of the reasons full fat dairy may be better is that it doesn’t cause as large of an insulin spike. This no longer applies if you’re eating full fat dairy that is loaded with sugar.
  • To that end, yogurts are a great source of full-fat dairy. Although there are no studies, people seem to better tolerate yogurt as opposed to other forms of dairy. Unfortunately they are often high in sugar as well. It is best to consume unsweetened yogurt and sweeten it naturally with low glycemic fruits (https://www.healthline.com/health/diabetes/low-glycemic-fruits-for-diabetes#grapefruit).
  • Whole milk is full-fat, skim milk is no-fat. Always opt for whole milk if you choose to drink milk.
  • Cheese is the least insulinemic of any dairy products7. Enjoy in moderation. Stick to one serving a day (https://www.canada.ca/en/health-canada/services/food-nutrition/canada-food-guide/choosing-foods/milk-alternatives/what-food-guide-serving-milk-alternatives.html).
  • Healthy fats found in foods other than dairy have similar health benefits on blood sugar. When trying to conceive, ensure you are eating plenty of healthy fats including fatty fish, nuts, avocados, and olive oil.
  • Dairy sensitivity is common10. If you notice dairy consumption upsets your digestion, or causes acne, dairy may not be right for you.

Most importantly, always remember that diet should be individualized. None of us have identical nutritional requirements and intolerances. Speak to a health care provider to find out if dairy for fertility is right for you.

References

  1. Chavarro J, Willett W, Skerrett P. The fertility diet. New York: McGraw-Hill; 2008.
  2. Are you TTC? A look at the ‘fertility diet’ [Internet]. USA TODAY. 2018 [cited 25 January 2018]. Available from: https://www.usatoday.com/story/news/2018/01/04/you-ttc-look-fertility-diet/1003885001/
  3. Chavarro J, Rich-Edwards J, Rosner B, Willett W. A prospective study of dairy foods intake and anovulatory infertility. Human Reproduction. 2007;22(5):1340-1347.
  4. Wise L, Wesselink A, Mikkelsen E, Cueto H, Hahn K, Rothman K et al. Dairy intake and fecundability in 2 preconception cohort studies. The American Journal of Clinical Nutrition. 2016;105(1):100-110.
  5. Phy Ali M J. Low Starch/Low Dairy Diet Results in Successful Treatment of Obesity and Co- Morbidities Linked to Polycystic Ovary Syndrome (PCOS). Journal of Obesity & Weight Loss Therapy. 2015;05(02).
  6. Hoyt G, Hickey M, Cordain L. Dissociation of the glycaemic and insulinaemic responses to whole and skimmed milk. British Journal of Nutrition. 2005;93(02):175.
  7. Publishing H. Follow The Fertility Diet? – Harvard Health [Internet]. Harvard Health. 2018 [cited 25 January 2018]. Available from: https://www.health.harvard.edu/diseases-and-conditions/follow-fertility-diet
  8. Endocrine Disrupting Chemicals [Internet]. The Learning and Developmental Disabilities Initiative; 2009 [cited 20 March 2018]. Available from: https://www.healthandenvironment.org/uploads-old/EDCs.pdf
  9. Jackson, J., Neathery, S. and Kirby, R. (2007). Hidden Food Sensitivities: A Common Cause of Many Illnesses. Journal of Orthomolecular Medicine, 22(1), pp.27-30.
  10. Xia W, Chiu Y, Afeiche M, Williams P, Ford J, Tanrikut C et al. Impact of men’s dairy intake on assisted reproductive technology outcomes among couples attending a fertility clinic. Andrology. 2016;4(2):277-283.
  11. Afeiche M, Chiu Y, Gaskins A, Williams P, Souter I, Wright D et al. Dairy intake in relation to in vitro fertilization outcomes among women from a fertility clinic. Human Reproduction. 2016;31(3):563-571.
  12. Mattar R, Mazo, Carrilho. Lactose intolerance: diagnosis, genetic, and clinical factors. Clinical and Experimental Gastroenterology. 2012;:113.
  13. Misselwitz B, Pohl D, Frühauf H, Fried M, Vavricka S, Fox M. Lactose malabsorption and intolerance: pathogenesis, diagnosis and treatment. United European Gastroenterology Journal. 2013;1(3):151-159.
  14. Kucharska A, Szmurło A, Sińska B. Significance of diet in treated and untreated acne vulgaris. Advances in Dermatology and Allergology. 2016;2:81-86.

 

 

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