April 15, 2016

What is IGF-1?

IGF-1 (Insulin-Like Growth Factor) is a small polypeptide that’s produced primarily in the liver in response to signals originating from the pituitary gland. IGF-1 synthesis can also be induced in other tissues in response to signals produced by nearby cells. IGF-1 plays a critical role in normal overall childhood growth, as well as in the proper regulation of adult cellular growth in almost all tissue types.* In addition, IGF-1 production can indicate nutritional status by signaling the availability of nutrients.*

Is IGF-1 absorbed in the gastrointestinal (GI) tract?

Studies suggest that IGF-1 is stable and can be absorbed in the GI tract by newborn infants, but clinical studies on adults are inconclusive. Two clinical studies reported that supplementation increased serum IGF-1 in healthy adults, but other studies were inconclusive. One reason could be that there are no standard pharmacokinetic studies evaluating the absorption of external supplementation with IGF-1 versus the IGF-1 synthesized in the body. These studies would need to be performed to confirm absorption.

What foods naturally contain IGF-1?

IGF-1 is typically found in dairy products, as well as in other foods of animal origin, such as meat and liver.

What is the source of NOW Foods IGF-1 available in spray and lozenge forms?

NOW® IGF-1 is extracted from New Zealand deer antler velvet.

Are there any specific precautions or contraindications associated with supplementary IGF-1?

NOW® IGF-1 products are intended for use by adults only and should be kept out of reach of children. IGF-1 supplements are not meant for administration to pets. Do not use if you are pregnant or nursing; if you are taking medication or have a medical condition, consult your physician before using any of these products. If you are a competitive athlete who is regularly tested, please check with your sanctioning body for their regulatory status regarding IGF-1.


Nussey SS, Whitehead SA. Endocrinology: an integrated approach. Chapter 7: The Pituitary Gland. Taylor & Francis; 2001. 
Livingstone C. Clinical Science. 2013;125(6):265-280. 
Bartke A, Dominici F, Turyn D, Kinney B, Steger R, Kopchick J. Biogerontology. 2003;4(1):1-8. 
Mero, A, Kähkönen, J, et al. Journal of Applied Physiology. 2002;93(2):732-739.
Mero, A, Miikkulainen, H, et al. Journal of Applied Physiology.1997;83(4):1144-1151.
Ma J, Giovannucci E, Pollak M, et al. Journal of the National Cancer Institute. September 5, 2001 2001;93(17):1330-1336. 
Kang S, Kim J, Kim Y, et al. Asian Ausatralisian Journal of Animal Sciences. 2007;20(1):119.

*These statements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure or prevent any disease.