IGF-1 and Cancer Risk

articles Feb 21, 2023

While there are many reasons why the consumption of animal-based foods promotes cancer growth, one of the strongest links has to do with a hormone called insulin-like growth factor 1 (IGF-1).  

IGF-1 is a growth hormone that is responsible for regulating cell growth. During periods of growth, such as when we are babies or during puberty, levels of IGF-1 in the body increase to promote the growth of new cells and power our development. After we’ve gone through puberty, we no longer need to produce as many new cells, and IGF-1 levels diminish. If your levels of IGF-1 remain too high once you’ve reached adulthood, your cells will constantly receive a signal to keep on growing and dividing. Obviously, this is not a good thing when it comes to cancer.

Therefore, the more IGF-1 you have in your blood, the higher your risk for developing certain cancers, such as prostate cancer.

You may have heard of a rare form of dwarfism called Laron’s syndrome that is caused by the body’s inability to produce IGF-1. People with Laron’s syndrome grow to be only a few feet tall. Additionally, they almost NEVER get cancer! This discovery led scientists to ask the question: What if we could downregulate IGF-1 as adults, thereby turning off excess growth signals and reducing our cancer risk?

It turns out, we can… through simple dietary choices!

IGF-1 production is triggered by the consumption of animal protein, including muscle proteins in meat, egg-white protein in eggs, and milk protein in dairy products. When it comes to dairy, the levels of IGF-1 in the bloodstream increase after the consumption of both low-fat and full-fat dairy. Animal studies show that IGF-1 promotes prostate cancer cell proliferation and prevents their breakdown and elimination.  

But how do we know that cutting back on animal protein can decrease the production of IGF-1?

One study, the OXFORD-Epic study, done in 2000, compared the hormone levels of 750 males, including some vegetarians, non-vegetarians, and vegans. Researchers found that the vegans had the lowest IGF-1 levels- 9% lower than the meat-eaters and 8% lower than the vegetarians.

Another one of my favourite studies showing the powerful effects of dietary habits on IGF-1 levels examined breast cancer risk factors among 50 postmenopausal women who were either overweight or obese and did not have active cancer. Researchers wanted to see what a plant-based diet, combined with daily walking for 30-60 minutes, could do in just 11 DAYS against three different types of human breast cancer. The women’s blood was analyzed to determine levels of several breast cancer risk factors, including insulin levels, IGF-1, IGF-1 binding protein, and estradiol levels, both before and after undergoing dietary and exercise changes. Next, their blood was also dripped on three different breast cancer cell lines, before and after these changes. Even when eating a Standard American diet, their blood had some ability to kill cancer cells. However, after just 11 days on eliminating animal protein and eating a low-fat, high-fibre, plant-based diet, the women's blood became MUCH more hostile to cancer:

- Insulin levels plummeted
- IGF-1 levels plummeted by 20%
- IGF-1 binding protein levels skyrocketed by 50% (this protein binds up excess IGF-1- it is one of the body’s way of protecting itself from cancer!)
- Estradiol levels dropped

But that’s not all! After 11 days of eating a plant-based diet and walking, the women’s blood was able to slow down cancer cell growth AND reprogram cancer cells to commit suicide (in vitro), eliminating almost ALL the cancer cells.

A more recent study was done on 400,000 participants and published in the journal Cancer Research. It was a collaboration between the Cancer Epidemiology Unit (CEU) in NDPH, and the International Agency for Research on Cancer (IARC) in Lyon. It is the largest and most comprehensive investigation on IGF-1 and cancer risk to date. For the first time, the link between elevated IGF-1 levels and a wide range of cancers, including less common cancer types, was analyzed. The results confirmed a link that has been demonstrated in pervious studies between raised IGF-1 levels and colorectal, breast, and prostate cancer. Yet, some cancers did not show a link between raised IGF-1 levels, including lung, bladder, pancreatic, endometrial and kidney cancer.

But just how plant-based does your diet have to be to lower IGF-1 levels? Interestingly, lacto-ovo-vegetarians (i.e. vegetarians who consume eggs and dairy products) do not seem to achieve a reduction in IGF-1 levels. Only those who avoid all forms of animal protein are able to significantly drop their levels of this cancer-promoting hormone while raising their levels of cancer-protective IGF-1 binding protein!

If you're facing a cancer diagnosis and don't know what to eat to support your healing, schedule a free 15-minute phone consultation with me here: https://calendly.com/backtobalancenutrition/15min 

I would love to chat and give you as much information about navigating and supporting your cancer treatment by using nutrition and other natural healing modalities.


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Study of almost 400,000 confirms that higher blood levels of IGF-1 are a risk factor for several types of cancer — Cancer Epidemiology Unit (CEU) (ox.ac.uk)

Hormones and diet: low insulin-like growth factor-I but normal bioavailable androgens in vegan men | British Journal of Cancer (nature.com)

A meta-analysis of individual participant data reveals an association between circulating levels of IGF-I and prostate cancer risk - PMC (nih.gov)


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