What Is IGF-1?

IGF-1 stands for “insulin-like growth factor”. This is a key growth hormone that powers our development as children and regulates cell growth throughout our life.

As children, we want higher levels of IGF-1 so that we grow into healthy-sized adults. As we get older, the IGF-1 levels down regulate, or we hope they do. If that down-regulation doesn’t happen, IGF-1 becomes a major risk factor for cancer. This is because it tells the cells to grow, divide, multiply, hold onto old cells and keep going and growing.

Our body makes IGF-1 but we can control our levels largely by what we eat. There are three mechanisms that occur:

  1. The release of IGF-1 is triggered by the consumption of animal protein.
  2. There’s a binding protein that resides in the liver. This protein ties up IGF-1, making it ineffective.
  3. When Vitamin D levels are suppressed, this causes IGF-1 to become more active. It’s been shown that animal protein and too much calcium suppress Vitamin D.

What we’re seeing here is a coordinated effort by Vitamin D, IGF-1 and the binding hormone to keep our cells healthy; whether it’s helping muscle grow and repair after a workout or regulating the 50 billion cells that are dying and being replaced every day. This coordination depends on us to keep the IGF-1 levels low by limiting or better yet, eliminating animal products.


  • Men who have a higher than normal IGF-1 levels have been shown to have 5.1 times the risk of advanced-stage prostate cancer. When men have low blood levels of the binding protein, their risk of advanced-stage prostate cancer increases 9.5 times.

  • The binding protein was shown to increase by 50% after cutting back on animal consumption after only 11 days. In this same time frame, IGF-1 levels dropped 20%. This is after only 11 days. Imagine what would happen if this was for a year or more.

  • 6,381 adults aged 50+ years were followed for 18 years. It showed that those between 50 to 65 years, who ate the most protein, had a 430% higher chance of dying from cancer and a 7,300% increase in diabetes compared to the low protein group. About this study, Dr. Kristi Funk says in her book, “Breasts: The Owners Manual”: “IGF-1 emerged as an important moderator of the association between protein consumption and mortality, since wherever protein went, IGF-1 levels were sure to follow”.

  • It’s also been shown that women who have high circulating levels of IGF-1 have 38% more estrogen-driven cancers than those with low IGF-1.

If one doesn’t respond to IGF-1, they have Laron Syndrome. This rare genetic mutation causes these people to have stunted growth. Interestingly, they don’t develop diabetes and only one person with this condition has ever had cancer. This goes to show how substantial a role IGF-1 plays for the development of both diabetes and cancer.

These studies have consistently shown that a plant-based diet lowers IGF-1 and has twice the effect that exercise alone does in doing so. Not only do you lower
IGF-1 within days on a plant-based diet but you also substantially increase the production of the IGF-1 binding protein as well as make your body a cancer fighting machine because of the phytonutrients, fiber, vitamins and minerals you’re now consuming.



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