Weindruch and Walford ask whether the rejuvenating effect seen after hypophysectomy is not actually the result of voluntary dietary restriction which follows it. They then pose the same question, but extend it somewhat, asking that if the rejuvenating effect of hypophysectomy is the result of voluntary dietary restriction, why do the animals not enjoy an extension of their lives? Answers to such questions are not always available, but it seems unlikely that the pituitary gland controls ageing, although it is certainly involved in it.

The complex interactions of hormones and ageing can also be simplified at this point to suggest that dietary restriction, amongst its other benefits, improves hormonal balance, and that at least some of its benefits relate to the influence it has on growth hormone. So should we supplement with ornithine or arginine? For the increase in youthfulness, possibly, if that end is desired, and if the cautions listed in this chapter are followed (remembering that dietary restriction will achieve this as well, and that growth hormone will be stimulated by periodic short fasting ). But, as far as is now known, amino acids used to stimulate growth hormone will have little if any effect on life extension.

Whether antioxidant nutrition affects life extension is our next target for investigation.