Whey Protein and Lactose Intolerance: Why Isolate Works

Plenty of people give up on protein shakes because of how they feel afterward: bloated, gassy, rumbling for an hour. Many of them assume they cannot handle whey. Usually the problem is not the whey protein at all. It is the lactose that comes along with the cheaper forms of it.

Here is how lactose ends up in protein powder, how much is really there, and how to choose a whey you can drink comfortably.

Lactose intolerance is common, and it comes in degrees

Lactose is the natural sugar in milk. To digest it, your small intestine makes an enzyme called lactase. Most people make plenty of it as children and less as adults. A large review in The Lancet Gastroenterology & Hepatology estimated that about two in three adults worldwide have some degree of lactose malabsorption, with rates far higher in East Asian, West African and Native American ancestry than in Northern European.

It is not all or nothing. The National Institutes of Health consensus panel on lactose intolerance found that most people who malabsorb lactose can take in about 12 grams of it at a time, roughly the amount in a cup of milk, with little or no discomfort. Symptoms tend to show up when the dose climbs past that, or when lactose arrives on an empty stomach in a drink that moves through quickly. A protein shake can be exactly that.

Where the lactose in protein powder comes from

All whey starts as the liquid left over from cheesemaking. That liquid is mostly water, with some protein and a good deal more lactose. Turning it into powder is a filtering job, and how far the filtering goes decides how much lactose is left in the tub.

Whey concentrate is filtered lightly. The common grade is about 80 per cent protein, with the rest largely lactose, fat and minerals. Depending on the product, a scoop can carry anywhere from about 1 to 3 grams of lactose, and cheaper concentrates with lower protein content carry more.
Whey isolate goes through further filtration that pushes the protein above 90 per cent and strips out almost all of the lactose and fat along with everything else. A scoop typically carries well under half a gram.

We cover the full difference between the two in whey isolate vs concentrate. For a sensitive stomach, lactose is the part that matters most.

Why a scoop of concentrate can still cause trouble

A few grams of lactose sounds like nothing next to a cup of milk. In practice it adds up quickly:

Two scoops. Most people use more than one scoop, and many labels recommend two or more.
Mixed with milk. A shake made with a cup of milk adds about 12 grams on top of whatever is in the powder.
More than once a day. A morning shake and a post-workout shake double the load again.
On an empty stomach. A liquid shake with no food alongside it reaches the gut fast, which is when lactose is most likely to cause symptoms.

So someone who is fine with milk in their coffee can still feel a two-scoop concentrate shake made with milk. With isolate, the lactose from the powder is close to zero, and the only lactose left in that glass is whatever you choose to mix it with.

How to tell what is in your tub

Marketing words are not much help here. “Isolate” appears on the front of plenty of blends that are mostly concentrate. Check these three things instead.

1. Read the ingredient list

Ingredients are listed by weight, largest first. If the first protein listed is “whey protein concentrate,” or the product lists a “protein blend” that starts with concentrate, most of the protein in the tub is concentrate, whatever the front says. You are looking for “whey protein isolate” as the first, and ideally only, protein.

2. Check the sugars line

Lactose is a sugar, so it counts toward Total Sugars on the label. In an unflavored or stevia-sweetened powder with no added sugar, the sugar grams are mostly lactose. A few grams per scoop points to concentrate. Zero or close to it points to isolate.

3. Use protein per scoop carefully

Dividing the grams of protein by the weight of the scoop gives a rough protein percentage. For an unflavored product, anything above about 85 to 90 per cent is almost certainly isolate. Be careful with flavored powders, though. Cocoa, natural flavors and thickeners all add weight, so a flavored pure isolate can land around 80 per cent and look, on this test alone, like a concentrate. The ingredient list settles it.

If isolate still does not agree with you

Most people who react to concentrate do fine on a good isolate. If you still have symptoms, lactose may not be the cause. Look at the rest of the label:

Sugar alcohols such as sorbitol, maltitol and xylitol cause gas and loose stools in many people at modest doses.
Added fibers such as inulin and chicory root ferment in the gut and are a common source of bloating.
Large volumes, drunk fast. Try one scoop in water, sipped over ten or fifteen minutes, and see whether that changes things.

A lactase supplement taken with the shake is another option for people who want to keep using milk as the base. We cover how enzyme supplements work in digestive enzymes.

Lactose intolerance is not a milk allergy

This matters. Lactose intolerance is a problem digesting milk sugar. A milk allergy is an immune reaction to milk proteins, and whey is one of those proteins. Isolate removes the lactose, not the protein, so no whey product, isolate included, is safe for someone with a milk allergy. If you have been diagnosed with a milk allergy, or you get hives, swelling or breathing trouble after dairy, choose a non-dairy protein and talk to your doctor. Our guide to whey vs casein, soy, pea and egg covers the alternatives.

And if digestive symptoms are persistent or severe with or without dairy, it is worth seeing a doctor rather than guessing. Lactose intolerance is common, but it is not the only thing that causes those symptoms.

What we make, and why

This is the reason we make ProEnergy as an isolate and not a concentrate. It is a cross-flow microfiltered whey protein isolate from grass-fed, rBGH-free cows, with 20 grams of protein per scoop and zero sugars. The label states it is safe for the lactose intolerant. There are no sugar alcohols or added fibers in it: the Natural Unflavored is one ingredient, whey protein isolate, and the flavored versions add natural flavors, a little xanthan gum and sunflower lecithin, stevia leaf, and cocoa in the chocolate.

Isolate costs more to make than concentrate. For anyone whose stomach has put them off protein shakes, it is the difference between a shake you tolerate and one you do not notice.

The bottom line

If whey has given you trouble, do not write off whey. Switch from concentrate to a true isolate, check the ingredient list and the sugars line to make sure that is what you are buying, mix it with water or a low-lactose milk at first, and see how you feel. For most lactose-intolerant people, that solves it.