What is IGF-1?
IGF-1 and Human Growth Hormone work hand in hand to make you grow from child to adult and then later in life, to help you replace the billions of cells your body sheds every day. IGF-1 stands for Insulin Like Growth Factor and it’s structure is similar to insulin, hence the name.
What’s all this talk about IGF-1 and Cancer?
Studies going back to at least the 90s began showing a link between higher IGF-1 levels and cancer. A six-year study of over 30,000 nurses and over 14,000 physicians found higher rates of rectal cancer in women with high IGF-1 levels. The study concluded that men ran the same risk.
https://news.harvard.edu/gazette/story/1999/04/growth-factor-raises-cancer-risk/
The strongest link exists mainly between IGF-1 and either breast cancer or prostate cancer.
Breast cancer – https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4335664/
Prostate cancer – https://www.ncbi.nlm.nih.gov/pubmed/25348852
IGF-1 itself isn’t a mutagen that causes (i.e. creates) cancer, its a growth factor that stimulates cancer cells into growing faster and spreading into new tissues (like from your prostate to your bones or from your breast to your brain).
Does body building lead to higher cancer rates?
This is the main question that inspired this article. If people eating western diets high in animal protein and fat have the highest IGF-1 levels and they workout to build muscle, do they have a higher cancer risk because of this?
To answer that we need to break this down into a a few smaller questions.
First, do you even need IGF-1 to build muscle?
That would be most people’s assumption. Growth hormone leads to IGF-1 which in turn leads to muscle growth after corresponding resistance training exercise.
That’s not what the research says.
From the research IGF-1 appears to have less effect than people give it credit for. In one study they had participants do an arm exercise that elicited a small increase in growth hormone/IGF-1. Then they had them perform the same arm workout after doing a heavy leg workout that produced a high increase and blood levels of growth hormone/IGF-1. Neither set was shown to significantly increase muscle growth in the arms. The expectation was that you would get better arm growth due to the higher circulating growth hormone/IGF-1 levels. So it appears that other factors contribute more to muscle growth than just growth hormone or IGF-1.
https://www.physiology.org/doi/abs/10.1152/japplphysiol.01147.2009
In another study on women, they gave one group IGF-1 injections for a year and a second group a placebo. Afterwards they measured bone density, lean mass growth and body fat levels using DXA, blood lipid profiles, and many more. Neither group had any significant change in lean mass levels.
https://academic.oup.com/jcem/article/86/4/1496/2848277
So high IGF-1 levels aren’t really need to build muscles. Sounds good. But what’s high, what’s low, and what’s normal?
Optimal Levels of IGF-1 to build muscle and avoid negative health consquences (i.e. cancer et al.)
In an attempt to figure out what levels are optimal (i.e. least likely to cause early death), researchers discovered that both high levels of IGF-1 as well as low levels of IGF-1 both led to negative health results (i.e. death). One study found that high IGF-1 levels increased cancer risk while low IGF-1 levels increased heart disease risk.
https://academic.oup.com/jcem/article/96/9/2912/2834729
Low levels in the study were less than 70 nanograms per millileter (ng/ml) of IGF-1.
High levels were more than 190 ng/ml of IGF-1.
Taking a moment to return back to the above-mentioned nurses and physician’s studies. Increased breast cancer risk was found when IGF-1 was above 207 ng/ml and increased prostate cancer risk was found when IGF-1 was above 185 ng/ml.
The safe zone then for IGF-1 is between 70 – 190 ng/ml. The closer you are to the middle of that range the better. Further studies and charts of optimal ranges can be found at the link below.
https://www.drfuhrman.com/library/eat-to-live-blog/60/igf-1s-link-to-cancer
So what are some common IGF-1 levels out there and what was the diet behind them?
Typical western diet eaters had IGF-1 levels around 200 ng/ml. In other words this was in the high range with increased cancer risk and increased all-cause mortality.
http://cebp.aacrjournals.org/content/18/5/1333.short
Vegan eaters had IGF-1 levels around 150 ng/ml falling in that middle safe zone.
Do bodybuilders have more IGF-1?
As stated above, you can get spikes in IGF-1 activity from large muscle group resistance exercises like squats but this doesn’t produce long-lasting changes in IGF-1 and higher IGF-1 isn’t the main cause of muscle growth.
How can you lower cancer risk while still building muscle?
Get your protein from plants mainly. The more plants you eat the lower your IGF-1 levels will be while still giving you the protein you need to build muscle.