Protein is an essential nutrient needed to build muscle, repair and maintain connective tissue, and synthesize enzymes. Most Americans are not protein deficient, although extreme poverty, old age and vegetarianism are significant risk factors. In contrast, many bodybuilders and serious athletes not only eat protein-rich foods, but they also supplement with protein bars and powders to maximize the “building blocks” or amino acids available to their bodies for muscle building. However, consuming too much protein on a daily basis for many weeks or months is damaging to the body, especially the kidneys and possibly the liver. Blood liver tests are an accurate way of measuring liver function.
Liver Blood Tests
Your liver is primarily a filtering and detoxification organ, although it’s also important for storing glycogen and producing cholesterol and protein-based compounds such as albumin and a variety of enzymes. A series of blood tests are used to assess liver function. Some compounds, such as albumin, are decreased with liver damage, whereas bilirubin levels and many enzymes become elevated within the blood. High levels of bilirubin, commonly known as jaundice, lead to yellowing of the eyes and skin, which is a classic indication of liver damage and dysfunction. Enzymes that are most commonly measured in liver function assessments are best known by their abbreviations and include ALT, AST, ALP, GGT and LDH. These enzymes are present in liver cells and leak into the blood with liver damage.
Factors That Affect Liver Tests
Many factors, diseases and conditions can increase liver enzymes and affect liver blood tests. For example, AST is also found in heart and skeletal muscle, so raised blood levels are also seen with heart attacks and skeletal muscle damage from strenuous exercise. As such, elevated liver enzymes don't always indicate serious liver damage. ALT enzyme is more liver specific because it’s only found in liver cells, so its elevated value is more indicative of liver damage. However, other factors are more damaging to the liver than high protein consumption, including alcoholism, pharmaceutical use and liver infection or hepatitis, according to “Harrison's Principles of Internal Medicine.” High protein consumption is much more likely to cause kidney damage and dysfunction long before any serious liver issues.
The recommended amount of daily protein needed to maintain normal bodily functions ranges from about 40 to 70 grams, depending on your gender, age and body composition and weight. However, if you exercise and lift weights to build muscle, your requirements are higher. Modern research indicates that athletes should consume between 0.5 and 0.8 grams of protein per pound of body weight on days they workout, which equates to between 90 and 160 grams for most male bodybuilders. Amino acids must be processed by your liver, which can be taxing in large amounts, but your kidneys take more of a beating by having to filter out the byproducts and excesses.
Common protein supplements include whey, casein, egg albumin, soybeans and wheat proteins. They are sold as powders or mixed into a variety of protein and energy bars. Whey and casein are both found in milk and are complete proteins, as are supplements derived from egg and soybeans. Wheat-based protein supplements are incomplete, which means they are missing at least one essential amino acid. Overall, protein supplementation in moderation does not damage the liver, although the act of lifting heavy weights can raise certain liver enzymes in your blood. In high doses over many weeks or months, protein is damaging to your kidneys and acidic for your blood, which would likely lead to noticeable symptoms before any liver damage occurs. Consult your doctor about the symptoms of liver dysfunction and the most common causes.
- Textbook of Functional Medicine; David S. Jones
- Harrison's Principles of Internal Medicine; A. Fauci et al.
- Exercise Physiology: Energy, Nutrition, and Human Performance; William D. McArdle et al.