Nutrition and Dietary Factors

Deficiency of essential nutrients or vitamins can directly cause toxic effects. For example, lack of enough Vitamin A reduces the ability of the MFO enzyme system to metabolize chemicals, which has the effect of making most chemicals more toxic. Lack of available cofactors that are necessary in order for some metabolic reactions to occur could also limit the amount of metabolic detoxification. This could also result from a low protein diet. Also, poor nutrition (for example, starvation) might lead to mobilization of fat, which could release stored amounts of chemicals and lead to toxic effects. 

Some essential elements, like zinc, can protect against the absorption of toxic metals like lead when they are present in the GIT. This is because the two elements compete for absorption, and zinc is favored over lead by the active processes that occur in our intestine. 

There is a large increase in enzyme production and activity at birth, especially in the liver. However, even after birth small children are more sensitive than adults to many chemicals because the defense mechanisms do not mature quickly. This is why some drugs taken by adults should be given to a smcdl child only in smaller doses (e.g., ibuprofen). Ibuprofen is stored in the body almost exclusively in plasma proteins. These proteins are not fully developed in infcmts. Because less ibuprofen is stored in the proteins, more is available to act in the body. This increases the effective dose a small child receives as compared with cm adult. It is not until children are several years old that all of their chemical defenses are fully developed. 

In chapter 7 we will discuss more fully how all of these variables are handled in developing safe concentrations for humans. 

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