ALT

Your liver is a factory of a kilo or so that processes everything that comes out of your gut: sugars, fats, proteins, alcohol, medicines. ALT, alanine aminotransferase, is one of the enzymes the liver cells use to do that, and it sits almost exclusively in those cells. As long as they are intact, it stays inside. If they become damaged, inflamed or overfull with fat, ALT leaks into the bloodstream and the value rises. So ALT is not a measure of how well your liver works, but of whether cells are under strain. It is the most sensitive of the ordinary liver values, and at the same time the least specific about the cause. Fatty liver, alcohol, a virus, a medicine and a hard training session all give the same thing: a higher number. The pattern with the other liver values points the way. If AST rises more than ALT, the muscles or alcohol are more likely; if gamma-GT rises with it, it is the liver; if ALP and bilirubin rise with it, it sits in the bile drainage. Your report shows ALT in U/L. Normal is up to about 45 U/L for a man from age 19 and up to 34 U/L for a woman. A healthy liver sits well below that, and the value moves within weeks with what you eat, drink and do.

ALT is the value by which you see fatty liver before you notice anything of it, and fatty liver is by now the most common liver condition in the Netherlands: in roughly one in four adults there is fat in the liver that does not belong there. It gives no symptoms, not for years. It goes together with belly fat, insulin resistance, a high triglyceride level and a low HDL, and it is a forerunner of diabetes and cardiovascular disease. A slightly raised ALT in someone otherwise healthy is nine times out of ten this, and it is fully reversible. That reversing is exactly where ALT has its value. Fat leaves the liver with weight loss, less sugar and refined carbohydrates, less alcohol and more exercise, and ALT falls with it within weeks. A liver that is clean again recovers completely. Anyone who sees a raised ALT and three months later a normal one has achieved something you do not see from the outside but that makes a difference of years. Coffee helps too: two to three cups a day go together with less fatty liver and less scarring. The other reasons are worth ruling out. Alcohol lifts ALT, usually together with a higher gamma-GT and an AST that rises more than ALT. Medicines and supplements do it too: paracetamol in high doses, some antibiotics, statins at the start, and herbal preparations such as green tea extract and kava. A viral hepatitis usually gives a sharp rise. And rarer are iron overload, coeliac disease and an autoimmune inflammation of the liver, which can be recognised with a few extra values.

A high ALT means liver cells under strain. From common to rare: fatty liver, alcohol, medicines or supplements, hard training in the days before, and rarely a viral hepatitis, iron overload, coeliac disease or an autoimmune inflammation. A slightly raised value, up to one and a half times the upper limit, is in someone without symptoms usually lifestyle and falls with it; a value of a few times the upper limit should be repeated; a value of ten times the upper limit or more is an acute picture, usually a virus or a medicine, and then the day counts. A low ALT means nothing. In older people with little muscle mass or with a vitamin B6 deficiency the value sits somewhat lower, and that is not a finding. Set ALT beside AST, gamma-GT, ALP and bilirubin, and with a rise beside your triglycerides, HDL and fasting glucose, because those tell whether it is the fat metabolism. Do not have blood drawn in the days after hard training, and compare over time at the same lab.