Unless labeled “A2,” most regular milk contains both types of casein, meaning most milk can be difficult for a lot of people to digest. “Consumption of milk containing A1 beta-casein was associated with increased gastrointestinal inflammation, worsening of post-dairy digestive discomfort symptoms, delayed transit, and decreased cognitive processing speed and accuracy,” one study that looked at the effects of casein on the gut and brain reports.

Lactose intolerance

Lactose is a sugar found in dairy products. To break it down efficiently, our bodies use the enzyme lactase. However, the body’s ability to produce its own lactase often declines with age, making lactose difficult to digest—especially as we get older.

The inability to digest lactose is called lactose intolerance, and according to the National Institutes of Health (NIH), approximately 65% of the world’s population experiences some degree of lactose intolerance. In other words, most people are actually lactose intolerant.

What happens if you can’t digest lactose? Well, it ferments in the intestines and produces gas, causing abdominal pain, bloating, and more. “Lactose intolerance is a clinical syndrome characterized by gastrointestinal symptoms, such as bloating, abdominal pain, flatulence, nausea, borborygmi [intestinal rumbling], and diarrhea following the ingestion of lactose-containing food,” the National Library of Medicine confirms.

Antagonistic minerals

Milk is well-known as a source of calcium, but from a nutritional standpoint, the balance of magnesium shouldn’t be overlooked. Calcium and magnesium are called “antagonistic minerals,” meaning they compete for absorption. The ideal ratio of calcium to magnesium is 2:1, but milk is calcium-dominant at about 10:1 and up to 12:1. As a result, it can contribute to magnesium deficiency.

Incidentally, calcium causes muscle contraction, while magnesium has the opposite effect of relaxing muscles. Excess calcium without a balance of magnesium can cause stiff shoulders, back pain, and muscle cramps.

Antibiotics and hormones

Antibiotics and hormones are administered to cows in order to promote growth and prevent infections—but they can cause a residual problem for some milk consumers. “Significant portions of antibiotics are released through milk of dairy animals unaltered and exert serious harmful effects on human health,” one scientific review that looked at antibiotic residues in milk states.

Residual antibiotics can not only build antibiotic resistance, but they can destroy the balance of intestinal bacteria and worsen an inflammatory condition of the intestines called leaky gut. Additionally, “residues of antibiotics possess potential carcinogenic impacts by interacting with cellular elements, such as DNA and RNA,” the aformentioned review finds.

What happened after I cut back on cow’s milk

Though I still like the taste of milk, I no longer drink it on a daily basis—and as a result, I’ve noticed a dramatic improvement in my physical condition. The biggest impact? Less frequent stomach upset and reduced allergies, including hay fever. My chronic fatigue and brain fog have also improved, and my body no longer feels as generally inflamed.