PHYSIOLOGY OF AGING

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Studies of age changes in physiologic systems have included renal, cardiovascular, and metabolic areas. Of particular interest, has ben the relationship of dietary intake of nutrients to physiology. These have included the effects of protein intake on renal function (creatinine clearance), the effect of calcium and protein intake on bone loss, and the effect of dietary fiber intake on cardiovascular risk factors. The effects of both protein intake and calcium intake differed form those theorized. Thus, higher protein intake had no effect on simultaneous renal function nor did it have any effect on kidney function measured at lease 10 years after diet estimates) had no relationship to bone mineral (estimated on X-ray by the thickness of cortical bone) either at the same time as the dietary measurements or at least 10 years later. Fiber estimates were related to certain risk factors for cardiac disease (blood pressure, triglyceride and fasting pasma glucose) (see Metabolism Section). The two hour glucose levels of females undergoing glucose tolerance test was not related to psychological test of memory, vocabulary, or reaction time but were significantly related to performance on a test of cognitive ability (conceptual problem solving.) Mean blood pressure values were not related to the rate to fall in renal function in 254 normal men with blood pressures in the normal range. When higher levels of blood pressure were included in the analysis there was a relationship with higher pressures being associated with more rapid loss of renal function.