Life Extension Update
Choline “adequate intake” level could be inadequate for some
Research conducted by scientists at the University of North Carolina at Chapel Hill suggests that the current recommended adequate intake (AI) for choline, a member of the B complex, may be insufficient to prevent organ dysfunction that can be caused by inadequate levels of the vitamin. The study is the most complete investigation of choline requirements to date and the first to include women. The research was reported in the May issue of the American Journal of Clinical Nutrition.
Steven H. Zeisel, of UNC Chapel Hill's School of Public Health and School of Medicine and his colleagues gave 26 men, 16 premenopausal women and 15 postmenopausal women a diet providing the adequate intake of choline of 550 milligrams for ten days, followed by a period of up to 42 days when the participants received less than 50 milligrams of the vitamin per day. Blood markers of organ dysfunction (CPK, AST, ALT, GGT, and LD), homocysteine, and other factors were measured at the beginning of the study and at the end of each dietary phase. Magnetic resonance imaging was used to assess liver fat content at the beginning and end of the choline-replete diet, and after day 21 and 42 of the choline deficient diet.
While 77 percent of the men, 80 percent of the postmenopausal women, and 44 percent of the premenopausal women developed fatty liver or muscle damage during the choline deficient phase, 23 percent of the men had these signs while consuming adequate intake levels of the vitamin. As much as 825 milligrams choline per day was required to reverse organ dysfunction resulting from the choline deficient diet. In all participants, choline deficiency was associated with elevated blood homocysteine levels, which may increase the risk of heart disease.
“Subject characteristics (eg menopausal status) modulated the dietary requirement for choline, and a daily intake at the current AI was not sufficient to prevent organ dysfunction in 19 of the subjects,” the authors conclude. Coauthor and UNC Chapel Hill assistant professor Kerry-Ann da Costa, PhD commented, "These study results clearly indicate that some adults, notably men and post-menopausal women, need more choline than is recommended by the current AI. We hope these findings will aid the Institute of Medicine in refining the Dietary Reference Intake (DRI) of this nutrient."
Steatosis (or fatty liver) is a common finding in biopsy of the human liver. Fatty liver is a condition in which fat accumulates within the liver cells (hepatocytes) without causing any specific symptoms. (Fatty liver is defined as either more than 5% of cells containing fat droplets or total lipid exceeding 5% of liver weight.)
The vitamin B complex is a group of vitamins (B1, thiamine; B2, riboflavin; B3, niacin; B5, pantothenic acid; B6, pyridoxine; and B12, cyanocobalamin) that differ from each other in structure and the effect they have on the human body. The B vitamins play a vital role in numerous essential activities including enzyme activities (thiamine, riboflavin, niacin, pantothenic acid, pyridoxine). These enzyme activities also have many roles and are involved in the metabolism of carbohydrates and fats; functioning of the nervous and digestive systems; and production of red blood cells. The B vitamins have a synergistic effect with each other (AMA 1989). They are found in large quantities in the human liver as well as in many foods and yeast.
Another of the B complex vitamins is choline, essential for the use of fats in the body. It comprises a large part of acetylcholine (a nerve signal carrier). Choline also stops fats from being deposited in the liver and helps move fats into the cells. Deficiency of choline can lead to degenerative diseases such as cirrhosis with associated conditions such as bleeding, kidney damage, hypertension (high blood pressure), cholesterolemia (high blood levels of cholesterol), atherosclerosis (cholesterol deposits in blood vessels), and arteriosclerosis (hardening of the arteries) (Glanze 1996).
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