Energy intake interpretation

For the interpretation of results, the inverse relation of vitamin C intake with diets rich in fat should also be considered. Diets rich in fat and energy may increase the risk for chronic diseases (La Vecchia, 1992). As a consequence, risk associations with vitamin C should be controlled for fat and/or energy intake in epidemiological studies. This control for confounding in the case of vitamin C is not widespread. 

The most accurate assessments of internal dose can be made when the distribution and total body content of an incorporated radionuclide can be determined reliably by direct in vivo counting of emissions from the body. Nevertheless, biokinetic modelling of retention and biophysical modelling of energy deposition may still be needed to calculate the intake and the committed effective dose, so direct methods can also depend on the interpretation of rates of excretion, which often vary markedly over time and between individuals. 

From experiments mainly with laboratory animals, it has been demonstrated that relatively high intakes of trans fatty acids in the diet in conjunction with marginal intakes of essential fatty acids (less than 2% dietary energy from linoleic acid) can lead to the presence of Mead acid (cis-5,8,11-20 3) in tissue lipids and an increase in the ratio of 20 3 n-9 to 20 4 n-6. This has been interpreted to suggest early signs of essential fatty acid deficiency, with potentially increased requirements for essential fatty acids. Mead acid can accumulate in the presence of linoleic acid, if large amounts of nonessential fatty acids are also present. Two mechanisms have been suggested to explain these observations in relation to intake of trans fatty acids ... 

Both RBP and TTR have a relatively short half-life ( 0.5 and 2-3 days, respectively) and, therefore, they must be synthesized continuously to maintain normal plasma levels. Plasma retinol, RBP, and TTR are reduced in states of impaired protein synthesis, which may be due to an inadequate intake of protein or energy or to impairments in metabolism. Plasma RBP and TTR are sometimes used as clinical indicators of visceral protein synthesis. During infection and/or inflammation, plasma retinol, RBP, and TTR fall transiently, even though liver vitamin A reserves are adequate, due to altered protein synthesis during the acute-phase response. Because multiple nutritional and metabolic disturbances can lead to a similar decrease in plasma retinol, RBP, and TTR, laboratory values must be interpreted with caution. 

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