A regular exercise program helps to lower high blood levels of homocysteine, according to a study from multiple medical centers (European Journal of Applied Physiology, November 2006). High blood levels of homocysteine increase your risk for heart attacks, but at this time, nobody knows why. More than 200 papers show high blood levels of homocysteine are associated with increased risk for heart attacks, strokes and dementia. However, three studies showed that lowering blood levels of homocysteine does not prevent these conditions. This has disturbed many researchers because they cannot explain how lowering a risk factor for a disease does not help to prevent that disease.
It may be that homocysteine does not cause heart attacks, strokes or dementia, but is just a marker associated with them. For example, homocysteine comes from methionine, an essential amino acid found primarily in meat. Meat is also a source of saturated fats which may increase risk for heart attacks and strokes in people who ingest too many calories. So, lowering homocysteine does not prevent heart attacks, strokes and dementia because homocysteine does not cause these conditions. However, lowering saturated fats may help prevent heart attacks and strokes.
Saturated fats are only a problem if a person gets too many calories. Dietary saturated fats go to the liver where they are broken down to 2-carbon units. If the body has enough calories, the liver uses these 2-carbon units to make cholesterol. On the other hand, if the liver does not get enough calories, the 2-carbon units are burned for energy to carbon dioxide and water and never form cholesterol. Exercise helps to burn calories. So exercise uses up calories that would other wise have been used to manufacture cholesterol.
Meat is also a source of carnatine which is converted by intestinal bacteria to TMAO, which is a risk factor for coronary artery disease. So high homocysteine may only be a marker for high levels of TMAO. Stay tuned; the issue is not settled.