Here's what Dr. Jonny has to say about the IGF-1 and cancer questions:
We understand that there have been people who are concerned about the supposed connection between very high levels of IGF-1 and some cancers. But it’s very important to understand three things:
These studies do not, in any way, show that IGF-1 cause cancer. They show, at worst, an association with very high levels and some (not all) cancers, a relationship that is not completely understood, but is almost definitely not causal. (There’s a consistent association with the number of television sets in use and the incidence of diabetes, but no one thinks buying a Sony flatscreen is going to give you diabetes!)
And let’s remember that in no way is the Metabolic Factor program going to bring IGF-1 levels up to anything that could remotely be called problematic. Metabolic Factor encourages your body to produce normal, healthy IGF-1 levels: NOT excessively high levels.
Remember, hormones have optimal ranges—take insulin, for example. If you have no insulin production you have type 1 diabetes. If you have tons of insulin you likely have insulin resistance, which sets you up for obesity, diabetes and heart disease. Similar with cortisol, the main stress hormone. Too little cortisol and you’re looking at Addison’s Disease— too much, and you’re looking at Cushing’s Disease. Remember that the goal of the program is to bring your hormones into optional ranges. IGF-1 levels naturally decline as we age, dropping by 14% when you hit your 30’s, 25% in your 40’s, and a whopping 56% by the time you’re in your 60’s (like me!)(1)
With hormones like insulin and IGF-1, you’re looking for the Goldilocks effect: Not too hot, not too cold, just right. That’s what we’re after here and that’s what Metabolic Factor accomplishes.
The second thing to remember— and it’s important— is that there’s a ton of research that links LOW levels of IGF-1 to all kinds of bad things, including a substantially high risk of death by any cause.(2) Low levels of IGF-1 have been shown to be linked to metabolic syndrome and type 2 diabetes(3), obesity, cardiovascular disease(4), Alzheimer’s and dementia (5), as well as substantially increased risk for heart failure (6) and stroke(7). It’s well known that most overweight people tend to have lower levels of the hormone than lean people. And let’s remember that IGF-1 is banned in athletics as a performance enhancer, and for good reason. According to an article in the New York Times it is believed to make athletes bigger, faster and stronger, boosting muscle, reducing fat and improving endurance. And in animals, it heals tendon injuries as well.(8)
The most important thing to remember is that Metabolic Factor is a program designed to encourage healthier eating, regular exercise, improved sleep, stress reduction and optimal IGF-1 and insulin levels, with the key word being optimal. The Metabolic Factor Program is designed to help the body return to normal, healthy IGF-1 levels, as well as healthy levels of other important metabolic hormones such as hGH, T, DHEA and others.
1) Rosario, Pedro Weslley. "Normal values of serum IGF-1 in adults: results from a Brazilian population." Arquivos Brasileiros de Endocrinologia & Metabologia 54.5 (2010): 477-481.
2) Andreassen, Mikkel, et al. "IGF1 as predictor of all cause mortality and cardiovascular disease in an elderly population." European Journal of Endocrinology 160.1 (2009): 25-31.
3) Teppala, Srinivas, and Anoop Shankar. "Association between serum IGF-1 and diabetes among US adults." Diabetes Care 33.10 (2010): 2257-2259.
4) Van Bunderen, Christa C., et al. "The association of serum insulin-like growth factor-I with mortality, cardiovascular disease, and cancer in the elderly: a population-based study." The Journal of Clinical Endocrinology & Metabolism 95.10 (2010): 4616-4624.
5) Westwood, Andrew J., et al. "Insulin-like growth factor-1 and risk of Alzheimer dementia and brain atrophy." Neurology 82.18 (2014): 1613-1619.
6) Andreassen, Mikkel, et al. "IGF1 as predictor of all cause mortality and cardiovascular disease in an elderly population." European Journal of Endocrinology 160.1 (2009): 25-31.
7) Chan, June M., et al. "Insulin-like growth factor-I (IGF-I) and IGF binding protein-3 as predictors of advanced-stage prostate cancer." Journal of the National Cancer Institute 94.14 (2002): 1099-1106.
8) “New To Most Fans, IGF-1 Has Long Been Banned as a Performance Enhancer” Pilon and Kolata, NY Times, Jan 29, 2013 http://www.nytimes.com/2013/01/30/sports/igf-1-has-long-been-banned-as-performance-enhancer.html