In recent years, there has been a growing market for people to sell their excess breast milk online. Some nursing mothers overproduce milk for various reasons, and instead of letting it go to waste, they sell it online, typically to other mothers who are unable to breast feed their own children. But a new clientele of breast milk buyers have emerged: weightlifters and bodybuilders.

Rafaela Lamprou, 24, told the New York Post she made $6,000 selling her breast milk. Lamprou, who gave birth in August of 2018, overproduces milk. Leaving an oversupply of breast milk untreated can be very uncomfortable for nursing mothers, resulting in breast engorgement and plugged ducts, according to Health.com. Lamprou initially sold her breast milk to mothers who had trouble nursing, but soon started receiving an influx of orders from men, particularly men pursuing bodybuilding. Her customers claim that breast milk is ideal for building muscle mass. Weird flex, but okay.

But is breast milk really an effective way for bodybuilders to gain muscle? The USDA says that breast milk is typically 87 percent water, seven percent lactose, 3.8 percent fat, and one percent protein. The nutritional value of the milk, however, changes depending on the baby’s age and the mother’s diet. On average, one cup of breast milk has 172 calories, 2.5 grams of protein, 10 grams of fat, and 16 grams of carbs.

This may seem like a good option until you remember that one cup of cow’s milk or soy milk both have around eight grams of protein. Suddenly, someone else’s breast milk you bought over the Internet seems slightly less appealing. “When you actually look at the nutrition facts, that’s not a lot of protein for a grown man,” New York City fitness expert Chris Ryan, CSCS, CPT tells Health.com.

Breast milk is also pretty expensive, typically going for around $1 an ounce online. This isn’t even taking into consideration the health of the stranger and the cleanliness of the breast pump. Supporters of breast milk claim the milk contains certain growth factors that can be beneficial in muscle growth, but Ryan goes on to say that if you’re looking to bulk up, there a lot more effective and affordable options, such as grass-fed whey protein, containing around 20 grams of protein per scoop.

Let this be a lesson to us all to leave breast milk to the babies.