Inadequate dietary intake of methyl groups leads to hypomethylation in many important pathways, including 1) disturbed hepatic protein (methionine) metabolism as determined by elevated
plasma homocysteine concentrations and decreased S - adenosylmethionine concentrations, and 2) inadequate hepatic fat metabolism, which leads to steatosis (fatty accumulation) and subsequent plasma dyslipidemia.
Betaine supplementation decreases
plasma homocysteine concentrations but does not affect body weight, body composition, or resting energy expenditure in human subjects
Among the 50 trials, 30 were primary prevention trials (general populations, smokers and workers exposed to asbestos, patients with oesophageal dysplasia, male physicians, patients with non-melanoma skin cancer, postmenopausal women, patients undergoing chronic haemodialysis, patients with end stage renal disease, ambulatory elderly women with vitamin D insufficiency, patients with chronic renal failure, older people with femoral neck fractures, patients with diabetes mellitus, elderly women with a low serum 25 - hydroxyvitamin D
concentration, health professionals, people with a high fasting
plasma total
homocysteine concentration, or kidney transplant recipients), and 20 were secondary prevention trials (patients with cardiovascular disease, coronary heart disease, acute myocardial infarction, unstable angina, transient ischaemic attack, stroke, angiographically proved coronary atherosclerosis, vascular disease, or aortic valve stenosis).