I used to dabble with protein shakes, but honestly, they often make my stomach hurt, give me gas, and give me burning liquid shits. 

To make such, milk or soy undergoes processing to isolate the protein: heat, acid treatments, or enzymes. This “stripping” process removes the natural enzymes or co-factors, such as fat, that helps the body process the food more gradually and comfortably. To give shakes a “creamy” mouthfeel without the fat, manufacturers add xanthan gum, guar gum, or carrageenan, which can be highly irritating to the intestinal lining for sensitive individuals. To keep calories low while providing sweetness, many brands use erythritol, xylitol, or sucralose. Such are notorious for drawing water into the colon via an osmotic effect, or fermenting in the gut, leading to the aforementioned digestion issues. In addition, consuming 30g of isolated whey in a watery liquid is a heavy “hit” for the small intestine to process all at once, which can cause issues.

Protein shakes can lead to faster digestion with no fat to slow them down, looser stools, and more bile and digestive enzymes reaching the end. Because liquid protein empties from the stomach rapidly, it can bypass the typical absorption window in the small intestine, forcing the colon to deal with an influx of unabsorbed water and active digestive secretions that would normally be neutralized or reclaimed earlier in the tract. These factors can irritate the skin around the anus, creating a burning sensation (liquid fire). Thus it’s not that the stool is highly acidic; it’s more about irritation from rapid transit (diarrhea-like), undigested components (such as lactose or sugar alcohols), and additives (artificial sweeteners, gums, etc.).

Nature designed whole milk as a complete system, balancing whey and casein proteins, carbohydrates (lactose), and bioavailable fats. This natural fat content acts as a buffer, slowing digestion to ensure a gradual absorption of nutrients rather than the metabolic “spike” common with isolated powders. Further, choosing whole milk allows one to obtain naturally occurring sugars while avoiding the sugar alcohols, artificial sweeteners, and thickeners like gums. Humans attempted to artificially recreate something “better,” but I don’t think it is.

For the many people with lactose intolerance, lactose-free milk is an effective and safe solution. “Lactose-free” doesn’t mean the lactose has been removed; it means the milk has been chemically pre-digested for you. 

Manufacturers add the enzyme lactase to regular milk. This breaks the complex milk sugar (lactose) down into two simple sugars: glucose and galactose. Because the sugar is already broken down, your body doesn’t need to produce its own enzymes to digest it. Since the sugars are absorbed in the small intestine, they never reach the colon where they would otherwise ferment and cause gas, bloating, or diarrhea.

You still get the same calcium, protein, and vitamins found in regular whole milk, but it can still cause issues for certain people. Many people are sensitive to milk proteins like casein or whey, and lactose-free milk still contains such. If the issue is an A1 casein sensitivity, even lactose-free milk will cause gut inflammation. If lactose-free milk fails, the issue is likely a sensitivity to the inflammatory A1 beta-casein protein or cow-specific fat structures rather than the milk sugar itself. You may find relief by switching to A2 cow milk, which removes A1 casein.

Further, because the lactose is already broken down into glucose and galactose, lactose-free milk actually has a higher glycemic index than regular milk. It may cause a faster blood sugar spike, which can affect those with high insulin sensitivity. You may notice it tastes sweeter. This is because glucose and galactose hit the tongue’s sweetness receptors more effectively than the complex lactose molecule.

It is crucial to distinguish between a dairy sensitivity (like lactose intolerance) and a dairy allergy, as the two involve very different biological processes.

For those with dairy sensitivity, if you cannot consume lactose-free or A2 milk, you might find relief in goat or sheep milk, which feature smaller, more digestible fat globules and a protein structure that is generally easier on the gut. Another option is fermented dairy such as yogurt, kefir, and aged cheeses; their live cultures and the aging process effectively “pre-digest” much of the lactose for you.

For those who are allergic to milk proteins themselves (casein allergy), it is vital to avoid fermented or aged dairy. While the bacteria in fermented products break down some proteins (proteolysis) into smaller peptides and amino acids—potentially making them less irritating for those with a sensitivity—this process is insufficient for those with a true allergy. The immune system can still identify and react to these protein fragments, meaning even “pre-digested” dairy remains a significant trigger.

This piece is an excerpt from my book Miscellaneous Advice, a collection of research and observations on navigating the complexities of modern living.