A brown cow is a simple two-ingredient drink made from milk of magnesia and prune juice, used for decades in hospitals and nursing homes to relieve constipation. The standard recipe calls for 1 to 2 ounces of milk of magnesia mixed into 6 ounces of warm prune juice. Most people can expect a bowel movement within 6 to 8 hours.
The Recipe
Pour 6 ounces of prune juice into a mug and warm it gently, either on the stove or in the microwave for about 30 seconds. You want it warm, not hot. Then stir in 1 to 2 ounces of plain, unflavored milk of magnesia (the liquid suspension you’ll find at any pharmacy). Mix well and drink the entire glass.
Start with 1 ounce of milk of magnesia if you’ve never tried this before. You can increase to 2 ounces next time if needed. Drink it in the morning rather than before bed, since the onset is typically 6 to 8 hours and you don’t want to be woken up in the middle of the night. If you haven’t had a bowel movement by noon, some clinical protocols suggest repeating the full dose: 2 ounces of milk of magnesia in another 6 ounces of prune juice.
Why It Works
The brown cow is effective because its two ingredients attack constipation from different angles. Prune juice contains a natural sugar alcohol called sorbitol at about 6 grams per 100 grams of juice. Sorbitol is poorly absorbed by the gut, so it pulls water into the intestines through osmosis, softening stool and adding bulk. Prune juice also contains phenolic compounds that may further stimulate the bowel.
Milk of magnesia works through a similar but more powerful osmotic mechanism. The magnesium draws large amounts of water into the intestinal tract, which stretches the bowel wall and triggers the wave-like muscle contractions that push stool through. Combining the two creates a stronger effect than either one alone.
Warming the prune juice isn’t strictly necessary, but warm liquids are generally easier on the stomach and may help stimulate gut motility on their own. There’s no rigorous research proving warmth makes a difference, but it’s a common recommendation and makes the drink more palatable.
Who Uses This Remedy
The brown cow has long been a staple in post-surgical recovery units, oncology wards, and long-term care facilities. Constipation is extremely common in older adults: about 26% of women and 16% of men over 65 experience it regularly, and those numbers climb to 34% and 26% respectively after age 84. In nursing homes, the prevalence reaches as high as 80%. Pain medications, reduced mobility, and lower fluid intake all contribute.
It’s also widely used by people recovering from surgery, anyone taking opioid pain medications, and people dealing with occasional constipation at home who want something stronger than fiber supplements but don’t want to reach for a stimulant laxative.
Side Effects to Watch For
The most common side effects are bloating, gas, and cramping. Sorbitol in particular can cause gassiness, and the magnesium can produce loose, watery stools if you use too much. This is a feature as much as a side effect, but it can tip into uncomfortable diarrhea if you overdo it.
The bigger concern is electrolyte balance. Magnesium-based laxatives pull water into the bowel, which means they can also shift your body’s mineral levels. For most healthy adults using the brown cow occasionally, this isn’t a problem. But people with kidney disease should avoid it entirely, because the kidneys are responsible for clearing excess magnesium from the blood. When they can’t do that job properly, magnesium can build to dangerous levels.
You should also skip this remedy if you have stomach pain, nausea, vomiting, or any kind of bowel obstruction. And if your bowel habits have changed for more than two weeks without an obvious explanation, that’s worth investigating before treating at home with any laxative.
Tips for Better Results
Drink a full glass of water after finishing the brown cow. Osmotic laxatives work by drawing water into the intestines, so you need to give your body enough fluid to work with. Being dehydrated will blunt the effect and can worsen cramping.
Timing matters. Take it first thing in the morning on a day when you’ll be near a bathroom for several hours. The 6-to-8-hour window is an average, not a guarantee. Some people respond faster, especially with the higher 2-ounce dose of milk of magnesia.
If you find yourself needing the brown cow more than occasionally, that’s a signal to look at the underlying cause. Increasing daily fiber intake, drinking more water, and staying physically active resolve most chronic constipation without laxatives. Stool softeners, which work by drawing water directly into the stool to reduce straining, are another gentle option for ongoing use. The brown cow is best kept as a reliable tool for those stubborn days when nothing else has worked.