Ld. Youngman, PROTEIN RESTRICTION (PR) AND CALORIC RESTRICTION (CR) COMPARED - EFFECTS ON DNA-DAMAGE, CARCINOGENESIS, AND OXIDATIVE DAMAGE, MUTATION RESEARCH, 295(4-6), 1993, pp. 165-179
Protein restriction (PR) and caloric restriction (CR) similarly imping
e upon various physiological factors that can significantly inhibit th
e growth of DNA-damaged tissue and, therefore, carcinogenesis. Whether
this effect is largely, or only in part, due to simple inhibition of
body weight gain is examined. Among their many other health-improving
effects, PR and CR delay the onset of puberty. It has been suggested t
hat animals have developed mechanisms to cope with lean periods and th
at, when food is limited, resources are diverted from those physiologi
cal functions that offer no benefit for immediate survival (e.g., repr
oductive capacity) to thereby support an increase in the maintenance f
unctions that prolong life. PR has also been shown to affect numerous
other varied mechanisms that can affect carcinogenesis, including gene
expression and metabolism of xenobiotics. The effects of PR on initia
tional and promotional growth of DNA-damaged tissue is also discussed.
PR also seems to boost antioxidant defenses and inhibit the accumulat
ion of oxidative damage (as does CR). Protein restricted animals have
been shown to accumulate more calories, but develop fewer preneoplasti
c lesions and tumors than their high-protein counterparts. This observ
ation seems quite counter to most ideas about dietary restrictions and
CR. Despite the fact that both PR and CR induce many beneficial physi
ological effects in common, it is possible that PR is the more feasibl
e option for human consideration. The levels of PR likely to improve h
ealth without negative side effects are discussed.