Lactose-free, A2, yogurt or plant milk: how the options compare

The dairy case has gotten crowded. Regular milk now sits next to lactose-free milk, A2 milk, a wall of yogurts and half a dozen plant milks, each promising to be easier on your stomach.

If dairy leaves you bloated, which one should you choose? Here's how the main options compare, based on what has actually been studied.

Regular milk

Best for: people who tolerate modest amounts.

Many people with lactose intolerance can handle more than they expect. In a double-blind trial, 30 people who described themselves as severely lactose intolerant drank a cup (240 ml) of regular milk or lactose-free milk with breakfast for a week each. Symptoms were minimal either way, with no significant difference in severity. And 9 of the 30 turned out to absorb lactose normally (Suarez et al., 1995).

Keep in mind: the trial tested one cup a day. Several large servings on the same day are a different situation.

Lactose-free milk

Best for: people whose symptoms clearly track with lactose, or who want larger servings.

Lactose-free milk is cow's milk with the enzyme lactase added, so the lactose is already broken down into simpler sugars. It keeps the protein and calcium of regular milk. It tastes slightly sweeter, which is why the researchers in the trial above sweetened the comparison milk to match (Suarez et al., 1995).

Keep in mind: at one cup a day, lactose-free milk didn't outperform regular milk in that trial. If you're choosing it, it's most useful when your usual amounts are larger than that.

A2 milk

Best for: people who want to test whether it feels different, with realistic expectations.

Regular milk contains two forms of a protein called beta-casein, A1 and A2. A2 milk comes from cows that produce only the A2 form. It still contains lactose.

Some small trials suggest it may be easier on certain people. In one, 40 young women with varying dairy tolerance drank regular milk, A2 milk and lactose-free regular milk on separate days. Among the 10 women with confirmed lactose intolerance, A2 milk reduced some symptoms, such as nausea and urgency, compared with regular milk. But 20 women who reported dairy intolerance without actually malabsorbing lactose had quick, short-lived bloating and gas no matter which milk they drank (Milan et al., 2020).

Keep in mind: the studies are small and short, and for some women, symptoms don't depend on lactose or casein type at all.

Yogurt

Best for: people with lactose malabsorption who want to keep dairy in their diet.

Yogurt contains lactose, but its bacteria help digest it. In a classic study, people with lactase deficiency had 18 grams of lactose in yogurt, or the same amount in milk or water. With yogurt, breath hydrogen was only about a third as high, and fewer people reported diarrhea or gas. The researchers traced this to lactase released by the yogurt bacteria inside the gut (Kolars et al., 1984).

Keep in mind: the effect comes from the bacteria, so look for "live and active cultures" on the label, and check for added sugar.

Plant milks

Best for: people avoiding dairy entirely, for any reason.

Plant milks contain no lactose, but their nutrition varies widely. An analysis of 1,042 plant-based milk alternatives in a US Department of Agriculture database found they were generally low in protein, about 1.1 grams per 100 grams, and often contained added sugar and salt. Only about 11% met proposed nutrient standards, and the best performers were mostly soy milks (Drewnowski, 2022).

Keep in mind: choose unsweetened versions with added calcium and vitamin D, and check the ingredient list for added fibers such as inulin or chicory root. Here's why inulin can backfire if you bloat easily.

Why not just skip dairy?

You can, but do it thoughtfully. A review focused on older adults points out that milk and dairy supply a wide range of nutrients, that diet affects age-related loss of bone and muscle, and that cutting dairy out by default can have real nutritional downsides (Gallo et al., 2023). If you drop dairy, plan for calcium, vitamin D and protein from other sources.

At a glance

• Mild symptoms only with big servings: regular milk in smaller amounts, or yogurt
• Clear lactose symptoms: lactose-free milk or yogurt with live cultures
• Curious about casein: A2 milk, as a short personal trial
• No dairy at all: an unsweetened, fortified soy milk comes closest on protein

If every option leaves you bloated, dairy may not be the main problem. Persistent bloating, especially if it's new, or bloating with weight loss or blood in the stool deserves a conversation with your doctor.

Sources

1. Suarez FL, Savaiano DA, Levitt MD. A comparison of symptoms after the consumption of milk or lactose-hydrolyzed milk by people with self-reported severe lactose intolerance. N Engl J Med. 1995;333(1):1-4. PMID 7776987
2. Milan AM, Shrestha A, Karlström HJ, et al. Comparison of the impact of bovine milk β-casein variants on digestive comfort in females self-reporting dairy intolerance: a randomized controlled trial. Am J Clin Nutr. 2020;111(1):149-160. PMID 31773165
3. Kolars JC, Levitt MD, Aouji M, Savaiano DA. Yogurt--an autodigesting source of lactose. N Engl J Med. 1984;310(1):1-3. PMID 6417539
4. Drewnowski A. Most plant-based milk alternatives in the USDA Branded Food Products Database do not meet proposed nutrient standards or score well on nutrient density metrics. Nutrients. 2022;14(22):4767. PMID 36432454
5. Gallo A, Pellegrino S, Lipari A, et al. Lactose malabsorption and intolerance: what is the correct management in older adults? Clin Nutr. 2023;42(12):2540-2545. PMID 37931373

This article is for general information and isn't medical advice. Talk to your healthcare provider or a dietitian before removing dairy from your diet, especially if you have concerns about bone health.