potatoprotein.com
potatoprotein.com

An independent research resource on potato protein isolate.

Reference

Lactose Intolerance

**Lactose intolerance** is the inability to fully digest lactose, the principal sugar in milk and dairy, because of insufficient lactase enzyme in the small intestine. It affects approximately 65% of the global population, which makes whey and casein problematic for many people.

Why it causes symptoms

When lactose is not broken down in the small intestine, it passes intact into the colon. There, two mechanisms generate symptoms: an osmotic effect, in which lactose molecules draw fluid into the gut, and bacterial fermentation of the undigested sugar, which produces gas and raises exhaled hydrogen. The result is bloating, diarrhea, gas, nausea, and abdominal pain (Leis et al., Nutrients, 2020, PMID 32443748; NIDDK).

Symptoms typically appear within half an hour of consuming lactose and peak around 1.5 to 2 hours afterward. Severity varies considerably between individuals.

How much lactose is tolerated

Lactose intolerance is rarely all-or-nothing. Most affected people tolerate up to 12 grams of lactose at once — roughly the amount in 250 mL, one glass, of milk — and up to 24 grams spread across a day (IQWiG, 2024). In blinded studies, most patients with self-reported lactose intolerance ingested at least 12 grams without symptoms, and when lactose was taken alongside other foods, up to 18 grams was often tolerated (Misselwitz et al., United European Gastroenterology Journal, 2013, PMID 24917953).

Relevance to protein powder

Dairy-derived protein powders differ in lactose content. Whey protein concentrate is lower in protein and higher in carbohydrate, retaining more lactose, while whey protein isolate undergoes more extensive processing and contains less than 1% lactose, which makes it tolerable for many people with lactose intolerance (Monash University FODMAP). Casein, the other major milk protein, is also a dairy fraction.

Plant isolates avoid lactose entirely, but they are not automatically free of digestive triggers: proteins such as soy and pea can be difficult to purify and sometimes carry FODMAPs like galacto-oligosaccharides and fructan (Monash University FODMAP). For people who react to multiple inputs, a single-ingredient option removes the guesswork — see the allergen-free protein guide for how minimal-input proteins compare. Potato protein isolate contains no lactose and no dairy fractions, so the colonic fermentation pathway behind lactose intolerance does not apply to it.