Changes in small-intestine permeability with aging.
OBJECTIVE
To evaluate small-intestine mucosal integrity and permeability with advancing age as measured by the lactulose/mannitol absorption test in healthy subjects.


METHODS
Prospective cohort study.


METHODS
Clinical research unit of the USDA Human Nutrition Research Center on Aging.


METHODS
Fifty-six subjects were recruited in three age groups: 20 to 39 years (n = 20), 40 to 59 years (n = 19), and > or = 60 years (n = 17). Subjects were healthy, community-dwelling volunteers.


METHODS
After an 8-hour fast, all subjects ingested 10 g of lactulose and 5 g of mannitol. Urine was collected for 6 hours and analyzed for lactulose and mannitol by high performance liquid chromatography. Twenty-four-hour urinary creatinine clearances were determined.


METHODS
Percentages of lactulose and mannitol excreted, the lactulose/mannitol ratio (x100), and the 24-hour creatinine clearance.


RESULTS
With increasing age, both the percentage of lactulose excreted (P = 0.09) and the percentage of mannitol excreted (P = 0.05) tended to decrease progressively. The lactulose/mannitol ratio (x100) did not change with increasing age (P = 0.65) because both the percentages of lactulose and mannitol excreted declined. The creatinine clearance decreased markedly with advancing age (P < .001) and accounted for the decline in percentages of lactulose and mannitol excreted (P < .02).


CONCLUSIONS
There is a progressive decline in the ability to excrete lactulose and mannitol with increasing age. This is probably attributable to a decline in renal function with advancing age. However, because of parallel decreases in lactulose and mannitol excretion, the lactulose/mannitol ratio does not change. Thus small-intestine "leakiness" does not increase with aging as measured by the lactulose/mannitol absorption test.
Saltzman
J R
JR
USDA Human Nutrition Research Center on Aging, Tufts University, Boston, Massachusetts.
Kowdley
K V
KV
Perrone
G
G
Russell
R M
RM
D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D015331:Cohort Studies; D003404:Creatinine / Q000097:blood; D005260:Female; D006801:Humans; D007408:Intestinal Absorption; D007413:Intestinal Mucosa / Q000502:physiology; D007421:Intestine, Small / Q000502:physiology*; D007792:Lactulose / Q000652:urine; D008297:Male; D008353:Mannitol / Q000652:urine; D008875:Middle Aged; D010539:Permeability; D011446:Prospective Studies
D008353:Mannitol; D007792:Lactulose; D003404:Creatinine