Hormones Used in Dairy Products and Their Impact on Public Health

Providing consumer information about the relationship between diet and health over the last decade has raised and consequently elevated the awareness and demand for functional food ingredients. Milk or dairy products such as cheese, butter, and yoghurt are the most important components of the human diet, especially in the Western culture and recently in Asia.

Cow’s milk is frequently consumed, although there is some other geographical variation in consumption of goat, sheep and camel milk. It is well known apart from dairy foods' basic nutritional role many of them contain a number of hormones, which they have capability to mediate specific physiological and pathological functions.

       
           
       
Moreover, the presence of hormones in dairy products that have the potential to disrupt the physiological function of endocrine systems has raised great concern worldwide. Any subtle changes in endocrine function may alter the growth, development, and reproduction in exposed animals and humans.

Below is the quantity of all hormones present in cow’s milk:

       
           
       
 Oestrogen:

Estrogens are sex steroid hormones, and as such display a broad spectrum of physiological functions. These include regulation of the menstrual cycle and reproduction, bone density, brain function, cholesterol mobilisation, development of breast tissue and sexual organs, and control of inflammation.

While estrogens play diverse roles in normal male and female physiology, in certain physiological situations they can play similar roles in both sexes (Rotstein). In females, estrogens are responsible for primary and secondary sexual characteristics. Estradiol promotes epithelial cell proliferation in the uterine endometrium and mammary glands starting in puberty. During pregnancy, estrogens produced by the placenta help prepare the mammary gland for milk production.

 On the other hand, lower levels of estrogens produced in men are essential for functions including sperm maturation, erectile function and maintenance of a healthy libido. It is important to mention here that all the estrogenic physiological functions previously described are mediated by oestrogen receptors, which we describe in the next sections.

• Progesterone:

 Progesterone plays a vital role in the maintenance of the uterus during pregnancy. As such, an important issue of concern regarding the loss of this steroid hormone correlates with miscarriage and preterm labour. One of the primary responsibilities of progesterone throughout pregnancy is to maintain a decreased level of vascular tone in the myometrium. Progesterone also influences the production of inflammatory mediators, such as human T-cells within the uterine cavity. Thus, a loss of progesterone leads to an increase in myometrial contractility coupled with a decrease in fighting off immunologic threats, ultimately leading to a higher risk of miscarriage and early delivery of the foetus. Loss of progesterone is also associated with decreased fertility, increased endometrial hyperplasia, and subsequent risk of endometrial neoplasia. During the second phase of the menstrual cycle, the effects of progesterone result in the proliferation of the endothelial lining in the endometrium, resulting in a thickened endometrial wall. The result is an increased thickness and surface area of the endometrium in which implantation can occur.

The pathogenesis behind infertility in the setting of low levels of progesterone is due to the loss of these necessary endometrial changes, resulting in an impaired ability of the endometrium to allow for proper implantation of a fertilised egg.The loss of progesterone during the menstrual cycle also gives rise to the setting of unopposed oestrogen on the uterus, which is a common risk factor for endometrial hyperplasia, potentially resulting in endometrial cancer.

• Testosterone:

Testosterone is the primary male hormone regulating sex differentiation, producing male sex characteristics, spermatogenesis, and fertility. Testosterone’s effects are first seen in the foetus. During the first 6 weeks of development, the reproductive tissues of males and females are identical. Around week 7 in utero, the SRY (sex-related gene on the Y chromosome) initiates the development of the testicles. Sertoli cells from the testis cords (foetal testicles) eventually develop into seminiferous tubules. Sertoli cells produce a Mullerian-inhibiting substance (MIS), which leads to the regression of the Fallopian tubes, uterus, and upper segment of the vagina (Mullerian structures normally present in females). Foetal Leydig and endothelial cells migrate into the gonad and produce testosterone, which supports the differentiation of the Wolffian duct (mesonephric duct) structures that become the male urogenital tract. Testosterone also gets converted to dihydrotestosterone (DHT) in the periphery (discussed below) and induces the formation of the prostate and male external genitalia. Testosterone is also responsible for testicular descent through the inguinal canal, which occurs in the last 2 months of foetal development. When an embryo lacks a Y chromosome and thus the SRY gene, ovaries develop. Foetal ovaries do not produce adequate amounts of testosterone; thus, the Wolffian ducts do not develop. There is also an absence of MIS in these individuals, leading to the development of the Mullerian ducts and female reproductive structures.

Recombinant bovine growth hormone (rBGH):

Recombinant Bovine Growth Hormone (rBGH), also known as recombinant bovine somatotropin (rBST), is a synthetic hormone used to increase milk production in dairy cows. Developed by Monsanto in the 1980s, rBGH is a genetically engineered version of a naturally occurring bovine growth hormone. Despite its effectiveness in boosting milk yield, its use has raised health and ethical concerns regarding both animal welfare and potential effects on human health.

Overview of rBGH

• Purpose: rBGH is injected into dairy cows to stimulate milk production by increasing levels of another hormone called Insulin-like Growth Factor 1 (IGF-1), which regulates growth and milk production in cows.
• Regulatory Status: rBGH has been approved for use in the U.S. since 1993 by the Food and Drug Administration (FDA). However, it is banned in the European Union, Canada, Japan, and other countries due to animal welfare concerns and unresolved human health risks.

Mechanism of Action

• In Cows: rBGH acts on the cow’s pituitary gland, increasing the production of IGF-1. This hormone stimulates milk-secreting cells, thus increasing milk yield.
• In Milk: Milk from rBGH-treated cows generally has higher levels of IGF-1 compared to untreated milk.

Potential Health Risks and Side Effects for Humans

1. Increased IGF-1 Levels in Milk
   • Human Implications: rBGH-treated milk has elevated IGF-1 levels. Although IGF-1 is naturally present in humans, excess levels have been linked to various health issues.
   • Cancer Risk: Some studies have suggested a correlation between high IGF-1 levels and increased risks of breast, prostate, and colorectal cancers. The hormone IGF-1 can promote cell growth, potentially contributing to tumor formation and growth in tissues.
   • Hormonal Imbalance: Excessive IGF-1 intake may disrupt the body’s natural hormonal balance, leading to health effects on growth and metabolism. However, the exact amount of IGF-1 that transfers from milk into the human bloodstream is still under debate.
2. Potential for Antibiotic Resistance
   • Indirect Health Impact: rBGH use is associated with an increase in health problems in cows, such as mastitis (udder infections). To treat these infections, farmers often administer antibiotics, which can lead to antibiotic residues in milk and contribute to antibiotic resistance in humans.
   • Public Health Concern: Increased antibiotic resistance makes bacterial infections harder to treat and poses a significant public health risk.
3. Early Puberty and Endocrine Disruption
   • Potential Link to Early Puberty: Some researchers have hypothesized that exposure to hormones like IGF-1 through dairy products may be associated with earlier onset puberty in children. While conclusive evidence is limited, endocrine disruptors in milk are suspected to contribute to shifts in developmental timelines.
4. Possible Allergic Reactions and Digestive Issues
   • Digestive Discomfort: Some individuals report digestive issues when consuming milk from rBGH-treated cows, although research on this is limited. It is unclear if these reactions are due to rBGH itself or other milk components.
   • Allergic Reactions: Elevated hormone levels may increase sensitivity or allergic responses in some people, although evidence here is also not fully established.

Animal Welfare Concerns

Use of rBGH has significant impacts on dairy cows:

• Increased Mastitis: rBGH-treated cows have higher rates of udder infections, leading to pain and discomfort. Mastitis is one of the primary concerns associated with rBGH, as it requires antibiotic treatment and can contribute to antimicrobial resistance.
• Shortened Lifespan: Cows treated with rBGH often experience a shorter lifespan due to the strain of increased milk production, along with greater susceptibility to lameness, metabolic disorders, and other health issues.

The presence of hormones in dairy products has been a topic of significant scientific inquiry and public discourse due to their potential implications for human health. This complex issue encompasses various aspects, including the types of hormones present, their potential effects on human physiology, public health considerations, regulatory frameworks, and potential mitigation strategies.

The primary hormones under scrutiny in dairy products can be categorized into two main groups:

1. Recombinant bovine growth hormone (rBGH):

   - Utilized to enhance milk production in bovine populations

   - Also known as recombinant bovine somatotropin (rBST)

   - Synthetic version of the naturally occurring bovine growth hormone

   - Potential health implications:

     - Elevated levels of insulin-like growth factor 1 (IGF-1) in milk

     - Hypothesized associations with oncogenesis, particularly in breast and prostate tissues

     - Possible contribution to precocious puberty in paediatric populations

     - Concerns about increased antibiotic use in treated cows due to higher incidence of mastitis

2. Endogenous hormones:

   - Naturally occurring estrogen, progesterone, and testosterone in milk

   - Present in all milk, including organic and hormone-free labeled products

   - Potential effects:

     - Endocrine system disruption

     - Possible influence on hormone-dependent neoplasms

     - Concerns about cumulative effects of hormone exposure through regular dairy consumption

Public health considerations surrounding hormone presence in dairy products are multifaceted and include:

1. Carcinogenesis risk:

   - Inconclusive evidence regarding the correlation between consumption of hormone-treated dairy and cancer incidence

   - Some studies suggest a potential increased risk, particularly for hormone-sensitive cancers such as breast, prostate, and ovarian cancers

   - Other research reports no significant association between hormone-treated dairy consumption and cancer risk

   - Ongoing debate within the scientific community regarding the long-term effects of chronic exposure to exogenous hormones through dairy consumption.

2. Precocious puberty:

   - Concerns regarding the potential role of dairy hormones in accelerating pubertal onset in children

   - Conflicting research outcomes, with some studies indicating a correlation and others finding no definitive link

   - Possible confounding factors, such as overall diet, obesity rates, and environmental exposures

   - Need for longitudinal studies to better understand the potential relationship between dairy hormone exposure and pubertal timing.

3. Antimicrobial resistance:

   - Increased antibiotic usage in hormone-treated bovine populations, particularly due to higher incidence of mastitis

   - Potential contribution to the emergence of antibiotic-resistant microorganisms

   - Public health concerns regarding the transfer of antibiotic-resistant bacteria through the food chain

   - Need for responsible antibiotic use in animal husbandry to mitigate this risk.

4. Nutritional implications:

   - Potential alterations in milk composition due to hormone administration

   - Ongoing debates regarding the impact on overall nutritional value of milk from hormone-treated cows

   - Possible changes in protein content, fat composition, and micronutrient levels

   - Need for comprehensive studies comparing the nutritional profiles of milk from treated and untreated cows.

Regulatory frameworks governing the use of hormones in dairy production vary significantly across different regions:

1. United States:

   - Food and Drug Administration (FDA) approval of rBGH use in dairy cattle

   - Absence of mandatory labeling requirements for hormone-treated milk

   - Voluntary labeling allowed for products from cows not treated with rBGH, with specific FDA guidelines

   - Ongoing debate regarding the adequacy of current regulations and the need for more stringent oversight.

2. European Union:

   - Prohibition of rBGH use in dairy production since 2000

   - More stringent regulations on hormone use in animal husbandry

   - Precautionary principle applied to potential health risks associated with hormone use

   - Import restrictions on dairy products from countries where rBGH use is permitted

3. Canada:

   - Prohibition of rBGH use in dairy cattle since 1999

   - Decision based on animal welfare concerns rather than human health risks

   - Ongoing monitoring of scientific evidence regarding potential health implications

4. Other countries:

   - Varying approaches to hormone use in dairy production

   - Some nations following the EU model of prohibition, while others align with the US approach

   - Increasing global trend towards more restrictive policies on hormone use in food production.

Mitigation strategies to address concerns about hormones in dairy products include:

1. Organic dairy products:

   - Produced without the use of synthetic hormones

   - Increasing consumer preference for organic alternatives

   - Strict certification processes to ensure compliance with organic standards

   - Potential limitations in terms of production scale and affordability.

2. Enhanced agricultural practices:

   - Emphasis on animal welfare and natural production methodologies

   - Reduced dependence on hormone treatments

   - Implementation of sustainable farming practices to optimize milk production without synthetic hormones

   - Focus on breeding programs to naturally enhance milk production efficiency.

3. Consumer education:

   - Enhanced awareness regarding hormone use in dairy production

   - Empowering consumers to make informed decisions about their dairy consumption

   - Clear and transparent labeling of dairy products to indicate hormone treatment status

   - Public health campaigns to disseminate accurate information about the potential risks and benefits of hormone-treated dairy

4. Ongoing research:

   - Further investigations into the long-term effects of hormone exposure through dairy consumption

   - Development of alternative methods to enhance milk production without the use of synthetic hormones

   - Studies on the environmental impact of hormone use in dairy farming

   - Exploration of potential biomarkers for monitoring hormone levels in dairy products.

5. Policy development:

   - Continuous review and updating of regulations based on emerging scientific evidence

   - International collaboration to harmonize standards and ensure food safety across global markets

   - Development of comprehensive risk assessment protocols for evaluating the safety of hormone use in food production

6. Alternative dairy sources:

   - Promotion of plant-based milk alternatives for consumers concerned about hormone exposure\

- Research into the nutritional equivalence of plant-based alternatives to dairy products

   - Development of novel food technologies to produce hormone-free dairy-like products

LIST OF STUDIES AND REPORTS DONE BY VARIOUS COUNTRIES WITH DIFFERENT HORMONES PRESENT IN DAIRY PRODUCTS

THE PRESENCE OF ANTIBIOTICS AND OTHER     SUBSTANCES IN THE DAIRY PRODUCTS

The milk contaminated with drug and chemical residues particularly in a concentration higher than the MRL (Maximal Residual Level) is harmful to health and should not be used for consumption. The infants and growing children are at high risk because they consume large quantities of milk and milk products on a body-weight basis.

 The contamination of milk by antibiotics is usually not expressed by milk producer nor by consumer but dairy processors may express it because of the inhibition of starter culture and altered dye reduction tests due to the contamination. Some contaminants like penicillins, tetracycline, chloramphenicol, streptomycin and oxytetracycline are not inactivated by the process of pasteurization and even drying cannot detoxify the penicillin residues in milk. The drug residue hazards are classified as a direct-short term and indirect-long term hazards based on the duration of exposure to residues and the time of onset of adverse effects.

The direct-short term hazards usually appear immediately following the drug exposure, for example, the occurrence of allergic and hypersensitivity reactions in sensitized individuals immediately after consumption of penicillin contaminated milk. On the contrary, long term exposure to the residues provokes indirect and long-term hazards such as Antibiotic Resistance, carcinogenicity, teratogenicity and reproductive effects.

Further, the presence of drug residues in milk and milk products itself is an aesthetic issue because these are not appealing for the consumers.