Hormones in milk are inevitable. Cows are mammals, which means they naturally produce hormones of their own — just like humans. Many people, especially men, specifically worry about the estrogen in milk since estrogen is associated with being a predominantly female hormone.
Cow's milk is a popular source of many nutrients, including calcium, protein and vitamin B12. There are pros and cons of dairy, and the hormones in dairy products is one of the cons.
Since the alternative to cow's milk is often soy milk, men may wonder if the phytoestrogens in soy milk will affect their estrogen levels. Fortunately, research has shown that the phytoestrogens in soy milk do not add to estrogen levels in the blood. Soy milk even has several health benefits.
The estrogen in milk from cows can affect the blood estrogen levels in men and cause them to increase. The growth hormones in cow’s milk may also be of concern since research confirms they increase risk of prostate cancer in men.
Function of Estrogen
Many people associate estrogen with females, but males have estrogen levels, too. In general, estrogen is considered the female hormone while testosterone is considered the male hormone. However, both sexes have both estrogen and testosterone levels.
Estrogen is not just one hormone. Rather, it is a class of related hormones. According to an April 2014 study published in The Journal of Clinical Endocrinology and Metabolism, the three main types of estrogen include estriol, estradiol and estrone.
Researchers found that men have smaller amounts of estrogen than women. In women, the role of estrogen is to assist with female puberty, menstruation and pregnancy. In men, estrogen supports bone health and may regulate cholesterol.
Estrogen levels can rise and fall in both men and women. Both sexes should have their estrogen levels checked regularly, as too much or too little estrogen can have negative consequences on bodily functions that depend on this hormone.
Read more: Can Vitamins Increase Estrogen?
Estrogen in Milk
There is a myth that cows naturally produce milk on their own. Like humans, female cows produce milk as a result of becoming pregnant with a baby cow. Also like humans, pregnant cows have higher levels of estrogen than non-pregnant cows. Some researchers are concerned with the consumption of milk, especially in men and children, from pregnant cows that have been genetically improved to lactate more.
A February 2010 study published in Pediatrics International found that commercial cow's milk contains large amounts of estrogen and progesterone, which are two sex hormones.
The small study of just 18 participants found that the female sex hormones significantly increased while the male sex hormones decreased in men following the consumption of cow's milk. Estrogen levels increased significantly in all participants — men, women and children.
The study also suggested that the sexual maturation of prepubertal children could be affected by the regular intake of cow's milk. This is due to the suppressing effect of estrogen in milk on gonadotropin, which are hormones that increase the production of sex hormones needed for puberty.
Read more: How to Detox From Dairy
Hormones in Dairy Products
There are naturally occurring hormones in milk, as well as synthetic hormones. According to the U.S. Food and Drug Administration, a number of steroid hormone drugs have been approved for use in raising cows. While these drugs are mainly used in cows raised for beef, there are naturally occurring hormones in dairy cows.
Per the FDA, naturally occurring hormones found in cows include estrogen, progesterone and testosterone. The FDA states that consuming animal products that contain these hormones is safe because the levels are small compared to what is naturally produced by the human body.
Aside from sex hormones, other hormones found in dairy products include growth hormones. There has been controversy and concern surrounding the presence of recombinant bovine growth hormone (rBGH), which is man-made and designed to increase milk supply in cows, and whether this hormone increases insulin-like growth factor (IGF-1) in people who drink cow's milk.
Read more: The Effects of Growth Hormones in Food
Effects of Hormones in Milk
According to the American Cancer Society, cows treated with rBGH have higher levels of IGF-1, which means cow's milk may have higher levels of IGF-1. Adults who drink cow's milk have approximately 10 percent higher IGF-1 blood levels, which may contribute to an increased risk of some cancers. More research is needed to determine the link between IGF-1 from cow's milk and cancer risk.
Men who are concerned about the estrogen in milk may want to turn their attention to the IGF-1, as it may increase the risk of prostate cancer. According to a June 2017 study published in Cancer Causes & Control, there is a positive association between cow's milk intake and the risk of prostate cancer. Researchers attribute the risk partially due to the IGF-1 content in cow's milk.
An earlier 2004 study published in Medical Hypotheses attributed the connection between dairy products and increased prostate cancer risk to the estrogen in milk. Researchers found that estrogen levels are increasing in men following a Western diet, which is high in dairy and meat. Compared to Asian men, Western men have higher estrogen levels and consume more cow's milk.
Cow's milk may also increase the risk of other cancers. A January 2015 study published in the British Journal of Cancer studied the correlation between people with lactose intolerance and cancer risk. Researchers found that people who avoid dairy products due to food intolerances have lower risk of lung, breast and ovarian cancers. Their non-intolerant family members had higher risks of these cancers, which may be due to their consumption of dairy products.
Read more: Is Soy Milk Bad for Men?
Should Men Drink Cow’s Milk?
According to the U.S. Dietary Guidelines, consuming dairy products is part of a balanced diet. Americans are recommended to consume between 2 and 3 cups of dairy products per day. However, this requirement can be satisfied by consuming fortified soy milk in place of cow's milk.
Men can consume cow's milk for the nutrient content, but they should be aware of the hormones in milk. There is estrogen in milk as well as other sex hormones like progesterone and testosterone. Other hormones in milk include growth hormones, which can affect IGF-1 blood levels in humans, which is known to increase the risk of certain cancers.
If possible, avoid milk from cows treated with hormones. Both naturally occurring and man-made hormones are given to cows raised for beef and dairy products in order to increase production. While these hormones are good for production purposes, they may have negative health consequences on the men, women and children who consume them. Fortified soy milk is a naturally hormone-free and non-dairy alternative to cow's milk.
- The Journal of Clinical Endocrinology and Metabolism: “What Does Estrogen Do?”
- U.S. Food and Drug Administration: “Steroid Hormone Implants Used for Growth in Food-Producing Animals”
- American Cancer Society: “Recombinant Bovine Growth Hormone”
- Cancer Causes & Control: “Does Milk Intake Promote Prostate Cancer Initiation or Progression Via Effects on Insulin-like Growth Factors (Igfs)? A Systematic Review And Meta-analysis”
- British Journal of Cancer: “Lactose Intolerance and Risk of Lung, Breast and Ovarian Cancers: Aetiological Clues From a Population-based Study in Sweden.”
- Medical Hypotheses: “Estrogen: One of the Risk Factors in Milk for Prostate Cancer.”
- U.S. Dietary Guidelines: “Appendix 3. USDA Food Patterns: Healthy U.S.-Style Eating Pattern”
- Pediatrics International: “Exposure to Exogenous Estrogen Through Intake of Commercial Milk Produced From Pregnant Cows.”
- Human Reproduction Update: "Effects of Soy Protein and Isoflavones on Circulating Hormone Concentrations in Pre- and Post-Menopausal Women: A Systematic Review and Meta-Analysis"