Everywhere you look, there are fitness enthusiasts gulping down protein shakes and eating protein bars. But can protein shakes affect your liver enzymes? As long as they are not consumed in excess and you don't have a liver condition, they shouldn't.
Standard Protein Requirements
Protein is a macronutrient, which means that unlike vitamins and minerals, which your body only requires in small quantities, you need larger quantities of protein. The human body stores carbs and fats, but it cannot store protein, so it's important that you get enough from your daily diet.
The recommended dietary allowance (RDA) is 56 grams per day for most adult men and 46 grams per day for most women, according to the National Academy of Medicine. This is the minimum amount of protein that you require. The USDA notes that the average intake in the U.S. is close to the recommended amounts. In fact, the USDA finds that males who eat a lot of meat, poultry and eggs often surpass the RDA by a considerable amount.
Elevated Protein Requirements
Your body requires more protein if you're pregnant, lactating, recovering from an injury or working out and trying to build muscle.
While average adults need 0.8 grams of protein per kilogram of body weight, athletes need anywhere between 1.2 to 2.0 grams of protein per kilogram of body weight, depending on the intensity and duration of training, according to the Academy of Nutrition and Dietetics.
Read more: Do Protein Shakes Really Help You Get Big?
Natural Protein Versus Supplements
A May 2018 study published in the Journal of Dietary Supplements recommends that you try to fulfill your protein requirements from natural food sources and resort to protein supplements only if you are not getting enough protein from your normal diet.
Meat, fish, eggs, dairy products, nuts, seeds, soy products, beans and lentils are some of the natural sources of protein.
Protein supplements come in the form of protein bars, pills and powders, the latter of which can be added to shakes and smoothies. The most common types of protein supplements are derived from whey, casein, soy, egg and peas.
All of these proteins are complete proteins, which means they contain all nine of the essential amino acids. Whey and casein are derived from milk, so whey, casein and egg proteins are animal proteins whereas soy and pea proteins are plant-based proteins.
Protein supplements can be a good option if you're vegan, since most plant proteins are considered incomplete proteins, although quinoa, soybeans and hemp are a few of the exceptions to this.
How the Liver Processes Protein
Your liver plays an important part in digesting the amino acids that are the building blocks of proteins. The process of breaking down amino acids begins in the stomach and is completed in the liver.
The liver is the checkpoint for the distribution of all macronutrients, including proteins. It synthesizes some of them into the other types of protein that you need, converts some of them into energy and releases some into your bloodstream.
The amino acids in protein contain nitrogen, so breaking them down releases ammonia, which is a toxic compound made up of nitrogen and hydrogen. The liver converts the ammonia into urea, which is then excreted by the kidneys. If you have smelly flatulence, it could be a sign that you're eating too much protein.
Understanding Liver Blood Tests
Your liver is the largest organ in your body and a crucial one. Apart from helping to digest food and making proteins, it also stores nutrients like sugar, vitamins and minerals, produces bile to help digest fat and absorb the fat-soluble vitamins A, D, E and K, produces blood clotting substances, filters your blood and gets rid of harmful bacteria and toxins to prevent infections.
Your liver carries out all these functions with the help of enzymes, which are compounds that speed up the chemical reactions in your body. There are several different types of enzymes, but the most common ones are aspartate transaminase (AST), alanine transaminase (ALT), alkaline phosphatase (ALP), and gamma-glutamyl transpeptidase (GGT).
When the liver is damaged or unable to function properly, these enzymes leak into the bloodstream. They can be detected by blood tests, which show elevated levels of liver enzymes.
Acute liver damage, for example, is marked by greatly increased levels of AST and ALT, with ALT levels generally higher than AST levels and normal or moderately increased ALT and GGT levels.
Factors That Affect Liver Tests
Many factors and health conditions can affect your liver blood tests. For example, AST is also found in your heart and skeletal muscles, so people with heart problems have high levels of AST in the blood.
Over-the-counter pain medications like acetaminophen (found in Tylenol and other painkillers), certain prescription medications like statin drugs used to manage cholesterol, alcohol consumption, heart failure, hepatitis and obesity are some of the other factors and health conditions that can cause abnormal enzyme levels in your liver blood tests.
Protein Shakes and Liver Damage
Protein is vital to liver health; it prevents fat build-up in the liver and helps the liver repair itself. While achieving your protein quota through food is ideal, it is not always realistic. Protein supplements can be a more convenient option; for example, if athletes need protein right after a workout and don't have time for a meal they can drink a protein shake. Protein powder can also make it easier for people who need an extra boost.
As long as you consume a healthy amount of protein, whether through food or supplements, it should not damage your liver. Harvard Health recommends limiting your intake to a maximum of 2 grams per day per kilogram of body weight.
Read more: How Much Protein Powder Should I Drink?
In case you have a pre-existing liver condition, you may be advised to consume less protein. That's because if your liver is badly damaged, it may not be able to process protein, causing a build-up of toxins in your system that can affect your brain.
Is This an Emergency?
- National Academy of Medicine: “Dietary Reference Intakes: Macronutrients”
- USDA: “2015-2020 Dietary Guidelines for Americans”
- U.S. Library of Medicine: “Protein Supplements: Pros and Cons”
- Victoria State Government: “Protein”
- Piedmont Healthcare: “What Is a Complete Protein?”
- Open Educational Resources: “An Introduction to Nutrition”
- Cleveland Clinic: “Elevated Liver Enzymes”
- Lab Tests Online: “Liver Function Tests”
- American College of Cardiology: “Aspartate Aminotransferase (AST)”
- Harvard Health Publishing: “When It Comes to Protein, How Much Is Too Much?”
- National Institutes of Health: “Diet — Liver Disease”
- Ohio State University Wexner Medical Center: “Is Protein Powder Good for You?”
- Academy of Nutrition and Dietetics: “Protein and the Athlete — How Much Do You Need?”
- Mayo Clinic: “Abnormal Liver Enzymes”