If you engage in regular, intense exercise, a blood test will show that at least two enzymes, SGOT and SGPT, are elevated. In many instances only one or the other is elevated. Physicians often interpret that as evidence of impending liver problems, since damaged liver cells are known to release those enzymes into the blood. On the other hand, if other liver enzymes are normal, it’s likely that the elevated levels came not from the liver but from other tissues that also release the enzymes, including skeletal muscle, the heart and the brain.
A recent study highlighted liver-enzyme release.1 Rats ran on a treadmill at either moderate (60 percent of maximum oxygen intake) or high (80 percent of maximum oxygen intake) intensity levels for two hours. No increase in liver enzyme release or any damage to liver cells appeared immediately, but six hours later the animals that ran at higher intensity showed cell damage in a particular portion of the liver.
Exercise diverts blood from organs to working muscles. When you eat something right before a workout, that meal just sits in your stomach; the blood needed for digestion is shunted to working muscles. The body goes by a hierarchy of needs and doesn’t know you need your muscles for exercise and not to save your life. So the muscles get priority.
When organs are deprived of regular circulation of blood and oxygen, some cells die. That’s what happens in the liver when you exercise. The reduced blood flow leads to lack of oxygen in some cells. The higher the exercise intensity, the less blood flows to working organs and the greater the subsequent damage.
Another thing that damages cells is known as the ischemia-reperfusion reaction. What happens here is that cells are initially deprived of blood and oxygen. Later the blood, with its payload of oxygen, comes rushing into the deprived organ. The sudden oxygenation leads to a rapid increase in free radicals, which are destructive by-products of oxygen metabolism. The free radicals attack fats in cell membranes, leading to cellular destruction. That commonly occurs in the heart after heart attacks and results in cardiac damage. It also happens in other organs, including the liver, following high-intensity exercise.
The question is whether you can work around that problem. Well, the liver is a highly regenerative organ. You can remove three-fourths of it, and the cells will eventually grow back. The same can’t be said for other organs, such as the brain and heart. That helps explain why regular high-intensity exercise doesn’t lead to liver failure. It does, however, make you wonder what happens to those who combine such exercise with substances that are toxic to liver cells, such as excessive alcohol or oral 17-ankylated anabolic steroids, particularly Anadrol-50 and Halotestin. Perhaps the best way to protect your liver would be to take in nutrients known to increase its antioxidative abilities. Increasing levels of glutathione, a primary intrinsic antioxidant in the liver, would blunt the free-radical processes. Nutrients that generate liver glutathione include whey protein, NAC, alpha-lipoic acid and silmaryin, or milk thistle. Gama-linoleic acid, derived from borage or evening primrose oil, also helps by modifying prostaglandins related to inflammation.
1 Kinoshita, S., et al. (2003). An increase in damaged hepatocytes in rats after high-intensity exercise. Acta Physiol Scand. 178:225-230.