This may be due to the fact that serum magnesium levels may not reflect total body or tissue magnesium levels [ 22, 23].
This is because components of fitness are likely to trade-off against each other, such that any particular component may poorly reflect total fitness.
Similarly, drinking water arsenic measurements represent a single point source of arsenic use but may not reflect total arsenic dose in the body from all routes of exposure.
It follows, that the ex-vivo cell-based efflux system may highly reflect total in vivo macrophage cholesterol efflux, and is quite useful for examining the first step in the RCT pathway [79], [135], [136] (Fig. 3).
The effect of measuring fat at individual or a limited number of sites was discussed by Thompson [ 57], who proposed that individual depots may not reflect total body fat in the animal.
For instance, self-reported physical activity is a subjective method of assessment; it may yield higher estimates of activity than the objective measurements obtain with an accelerometer and may not accurately reflect total energy expenditure of participants [ 48, 49].
Furthermore, because hypoalbuminemia may influence the relationship between serum selenium and total body selenium status, the measured serum selenium may not accurately reflect total body selenium in advanced HIV-1 infection.
Circulating sKlotho concentration may not necessarily reflect total renal Klotho production, and despite similar sKlotho levels in diabetic and non-diabetic individuals, membrane-bound renal Klotho expression might be affected as a consequence of diabetes.
However, tissue production in vitro may not necessarily reflect total secretion of these hormones in vivo, especially because the ovaries of exposed mice were smaller than those of unexposed mice.
In contrast, other approaches such as duplicate diet sampling may not sufficiently reflect total lead exposure/intake because duplicate diets do not reflect potentially important environmental sources of lead to children living in older housing or in the proximity of soils with high lead content.
