Under normal circumstances, about 90 percent of the dietary protein you consume is digested, reports the Institute of Medicine. But protein digestion is influenced by more variables than you may realize. Your overall health, whether you produce enough stomach acid and digestive enzymes, and even your eating habits all play roles in protein digestion.
Protein Digestion and Absorption
Proteins are made from long chains of amino acids, which fold and twist to form complex shapes. Digestion of these large molecules begins in your stomach. Stomach acids denature proteins, causing them to lose their shape while leaving the chain of amino acids intact. An enzyme in the stomach, pepsin, then begins breaking the chain.
The next step occurs in the small intestine, where enzymes from the pancreas break apart the bonds between individual amino acids. Once the amino acids are cleaved into single units, or small chains with only a few amino acids, they’re absorbed through the intestine wall and enter the bloodstream.
Protease Enzyme Supplements
You can improve protein digestion by taking supplemental protease enzymes, which break down protein. When healthy men took a supplemental blend of protease enzymes, they absorbed more whey protein concentrate, according to the Journal of the International Society of Sports Nutrition in July 2008.
Bromelain is a natural protease enzyme extracted from pineapples and used to make supplements that are available in most pharmacies. If you buy bromelain, choose enteric-coated supplements so that they survive stomach acid and releases enzymes in the small intestine.
Be aware that bromelain can cause allergic reactions and interact with some medications. Pregnant women and people with liver disease, high blood pressure, bleeding disorders or kidney disease shouldn’t take bromelain, advises the University of Maryland Medical Center.
Boost Stomach Acid
If you take antacids for occasional heartburn, don't use them when you eat proteins. Because they work by neutralizing stomach acid, antacids will interfere with protein digestion. MedlinePlus recommends taking them one hour before eating.
The inside of the stomach is protected from hydrochloric acid by a mucus-covered lining. When the lining becomes inflamed, less acid is produced and you can’t properly digest protein. Untreated gastritis can cause serious problems, so see a health care professional for appropriate treatment.
As long as gastritis is not the cause of low stomach acid, you may consider taking supplemental betaine hydrochloride, which boosts stomach acid. Talk to your doctor before using betaine hydrochloride if you take medication to treat a peptic ulcer.
Adjust Mealtime Habits
Don’t drink more than a cup of fluids with your proteins, recommends the Baseline of Health Foundation. A larger amount will dilute stomach acid and interfere with protein digestion.
You’ll improve overall digestion and absorption if you spread protein out over several meals rather than eating a large amount at one time. When you cook a protein-rich food with moist heat, it’s easier to digest than foods prepared using dry heat, notes Bellevue College in Washington state.
Don’t underestimate the importance of taking the time to chew your food. Smaller pieces of food improve digestion. Older men who ate minced beef digested and absorbed the protein more quickly than those eating beef steak, reports a 2013 study in the American Journal of Nutrition.
- Bellevue College: Protein
- Institute of Medicine: Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (Macronutrients)
- MedlinePlus: Taking Antacids
- National Institute of Diabetes and Digestive and Kidney Diseases: Gastritis
- University of Michigan Health System: Betaine Hydrochloride
- Journal of the International Society of Sports Nutrition: An Open Label Study to Determine the Effects of an Oral Proteolytic Enzyme System on Whey Protein Concentrate Metabolism in Healthy Males
- University of Maryland Medical Center: Bromelain
- Baseline of Health Foundation: Your Stomach, Part 3
- American Journal of Clinical Nutrition: Minced Beef Is More Rapidly Digested and Absorbed Than Beef Steak, Resulting in Greater Postprandial Protein Retention in Older Men