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Hormones in Meat and Dairy--Should You Be Worried?

Updated: May 18, 2022


According to a Pew Research poll, many Americans are concerned about risks associated with eating food from livestock that have been given antibiotics or hormones during growth and production. At least 32% consider meat consumption from these animals a significant health risk to healthy individuals. As both accurate and fear-based information regarding agriculture, farming, processing, and producing food becomes available via the internet; consumers continue to question the content of the foods they eat. Sustainability, animal and environmental welfare, and the impact on health are all factors that influence buying decisions.

In the 2019, Food and Health Survey from IFIC (The International Food Information Council), between 30% and 50% of consumers are more likely to buy a product because the label states it contains no added hormones or steroids, it's "natural," and that no antibiotics were used during the animal's growing process. The same survey indicated that the participants gained knowledge about food from friends and family. Inaccurate information may lead to unfounded fear and finding appropriate guidance on these matters can be challenging.

Hormones in Agriculture

Hormones are given to livestock to make production more efficient. The hormones used in beef production are estrogen, testosterone, and progesterone or their synthetic versions. Specific hormones can increase milk production and growth of the animals and usually result in more food products using fewer animals. This increase in efficiency translates into using less land, water, and animal feed. By using fewer resources and producing more with less livestock, there is a positive impact on the environment that would not be available without hormones.

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Hormones given to food animals are metabolized by their bodies quickly, and each hormone performs a specific function and communicates with a receptor individually matched to its chemical structure.

For comparison, adult men and women generally consume ten mcg progesterone per day, .1 mcg estrogen per day, and .05 mcg testosterone per day from food sources. These amounts are significantly less than human endogenous production.

A 4-ounce cut of beef from a treated animal contains about 1.6 nanograms of estrogen, while the same amount of meat from an untreated animal contains 1.2 nanograms of estrogen. These amounts are appreciably less than what is synthesized naturally in the human body.

The FDA has stated that the meat from animals treated with hormones is safe for consumption at any time. There isn't a waiting period between when the hormones are administered, the meat is sold and then consumed.

Reasons for Hormone Administration

According to the Food and Drug Administration (FDA), growth-promoting hormones have been used for more than 60 years in beef cattle and sheep. Growth hormone implants are pellets that are typically inserted into the ear of a steer (a young male cow) or heifer (a young female cow that has not given birth). They're designed to slowly release the hormone over time to ensure that the dosage remains low. The implants are not allowed by law to be used to produce pigs, dairy cows, veal calves, and poultry. These animals have other methods of improved growth and production, such as enhanced genetics and feed additives. The naturally occurring hormones are extracted from other animals. If the synthetic version is used, they are created in a lab and mimic the natural versions.

Some estimates suggest that growth promotants may increase beef production by 700 million pounds while increasing lean tissue anywhere from 8-20% within the United States beef industry. Feed efficiency is also improved while utilizing land more effectively, which may be beneficial for the environment. Feed efficiency measures animals' ability to turn the nutrients into products (milk or beef). Animal feed is formulated by a licensed veterinarian and monitored regularly.

Most male bulls are neutered when they are young and then become steers to reduce aggression, prevent aggressive animals from hurting themselves or other bulls, and make them calmer and more compliant when employees work with them. The implants cattle receive are male hormones produced by their bodies, estrogen, progesterone, and testosterone. These same hormones also cause bulls to grow faster with more substantial muscle tissue and less fat distribution. Heifers (female cattle that have never given birth to a calf) produce much less of these hormones than older or pregnant cows. Administering these hormones to younger female cattle allows them to grow more quickly.

The Food and Drug Administration is responsible for the approval or disapproval of hormone drugs given to livestock. Growth hormones are only approved for use after studies have proven their safety to the animals treated, those who consume animals treated, and the environment via feces. The information obtained through these studies and their findings are available to the public via a "Freedom of Information Summary."

There is what is referred to as a "zero-day withdrawal period" for an animal that has had hormone implants. This refers to the fact that the meat from treated animals is safe for human consumption immediately following slaughter. Unlike antibiotic treatment, there isn't a specified number of days between injection and when an animal can be sold for food. Because hormones are administered at very low doses from implants, they have been metabolized and excreted via bodily processes and are not present in tissue in amounts over the FDA-designated safe levels.

Naturally Occurring Hormones

Hormones are chemical "messengers" produced by endocrine glands that travel through the blood to various organs and tissues throughout humans and animals' bodies. They perform several functions, including reproduction, appetite regulation, growth, sexual functions, and metabolism.

Estrogen, progesterone, and testosterone are naturally occurring hormones produced in humans and animals throughout the life cycle. For non-pregnant women, the estrogen average is 5 mg/day, and adult men create approximately 10 mg/day of testosterone and androstenedione.

When the amount of hormone produced is insufficient to perform these functions, it can have health implications and cause disease. Several factors contribute to a hormone deficiency, including aging, illness, environmental, genetics, and stress.

Synthetic Hormones

The synthetic compounds used for growth promotion in beef and dairy cows are zeranol, trenbolone acetate, and melengestrol acetate . Each of these is a manufactured version of the naturally occurring hormones and is administered via an implant in an animal, usually behind the ear. The implants release the hormones into the bloodstream over a specified period. Once the animal is harvested, the ear with the implant is discarded, so there is no danger of the implant entering the food chain.

Before using synthetic versions, the hormones must undergo toxicological testing in laboratory animals to establish that they're safe for consumption. They can then be used in agriculture animals. Toxicology testing is used to determine the degree to which a substance can harm a living animal and define levels that do not cause injury or distress. Additionally, livestock producers must demonstrate that hormone levels that remain in the animal tissues are below levels deemed appropriate and safe via testing. A safe level is an amount of hormone that remains in edible tissues that have been proven to have no harmful effects on humans.

In assessing risk for hormonal implantation in a recent meta-analysis including estrogen, progesterone, testosterone, zeranol, trenbolone, and melengestrol acerate, it indicated that steroid hormones have zero impact on human health when they are used according to instructions and under acceptable veterinary practices.

Risk Factors for Using Hormones

When assessing veterinary drugs, the toxicological impact and maximum safe intake for humans are determined. The toxicological implications are defined as biologically adverse effects in humans that directly cause the drugs being administered to the food animal. These effects might include weight changes, immune system abnormalities, or any other disruption of humans' normal biological functions. In addition to physical adversities, whether or not a drug changes, the gut microflora is tested and treated with equal importance during procedural testing. The drugs are approved when proven that they will not affect human health with any of the above health complications.


The public's concern that the hormonal treatment of animals for growth and production will harm human health by increasing tumor growth in people who have cancer or will increase cancer prevalence in healthy individuals. Estrogen given to the animal will mimic estrogen already present in the human body. It's been proposed that consuming meat from animals given estrogen will increase humans' levels and promote cancer cell proliferation. After examining the research, which cites several meta-analyses, there appears to be an unsubstantial connection between consuming livestock products treated with hormones and the cancer increase The amount eaten via treated animals is substantially lower than what's produced naturally in humans. Estradiol ingested from meat would not exert hormonal effects due to its low bioavailability after passing through the gastrointestinal and hepatic systems.

In short, although many industry-funded studies on the impact of administering hormones to animals indicate there is no risk to human health, there are smaller, independent studies that show there may be a potential risk but fail to prove this. More research is needed in this area.


One area of concern is the exogenous hormones, estrogen, testosterone, progesterone, and their synthetic counterparts, ingested from an outside source and may have a disruptive endocrine effect on prepubertal adolescents. These effects include altered growth and development and sexual reproduction abnormalities. In both boys and girls, the age of puberty onset has decreased for the last 150 years.

Researchers have explored the possibility that hormone administration to food animals may be partially responsible for reducing puberty in adolescents.

Although it's been suggested that there's a correlation between consumption of hormones and early puberty, the research does not support it . In a meta-analysis of studies about this issue, the conclusion was that there was no clear indication that hormone administration to food animals leads to early puberty onslaught in adolescents.

The residual amount of hormones allowed in livestock before it is sold gets processed via human digestion when the food animal has been eaten and is not biologically active. However, some consumers and researchers would like to see more studies in this area before concluding that livestock hormones are not related to early-onset puberty. In short, more research is a need because, to date, results have been inconclusive and unable to pinpoint livestock hormones as being the cause of adverse health effects.

Several factors can influence puberty onset, including stress, high-quality nutrition in the early years, and obesity. Both obesity rates and increased availability of nutrient-dense foods have grown alongside the early beginning of puberty rates. Moreover, some studies point to a correlation between the increase in rates of obesity and growth in early puberty. However, more research is needed to be able to state this definitively.