1. How does low IGF-I bioactivity decrease cancer risk?

    . IGF-I (insulin-like growth factor-I) is often referred to as “the universal cancer promoter”.  This reflects the fact that a high proportion of the tissues most likely to give rise to cancer are sensitive to its growth factor activity.   In the many body tissues that are responsive to it, high IGF-I activity can accelerate the onset of cancer by increasing the rate at which mutations occur in DNA, and also by blocking a protective process whereby pre-cancerous cells commit suicide to protect the body from cancer.  Conversely, relatively low IGF-I bioactivity is protective in these respects.  More scientific detail →

  2. I’ve read that reduced IGF-I activity is the real reason why calorie-restricted diets increase longevity and prevent or postpone cancer. Yet you say little about IGF-I. Will a CC diet reduce IGF-I levels?

    Not necessarily. But what is important is IGF-I bioactivity. Because CC diets keep insulin low most of the day, the liver makes more of a protein called IGFBP-1 that binds to the IGF-I in the blood and prevents it from interacting with its receptor. So IGF-I activity should go down even if the IGF-I level doesn’t . And it seems likely that even the level of IGF-I will go down on a CC diet if it is vegan (plant-based and moderate in protein content).

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