Optimal IGF-1 Levels for Longevity

July 19, 2016 by Joel Fuhrman, MD

The relationship between IGF-1 levels and health is somewhat complicated. Excessively low or high IGF-1 levels could lead to health problems. In adults, a high IGF-1 level is linked to accelerated aging and an increased risk of cancer and premature death.1-5 Maintaining a relatively low IGF-1 level throughout most of one’s adult life is thought to be an important factor by which centenarians are able to live that long without developing cancer.

However, low IGF-1 in the elderly is linked to frailty and disease risk as well. Adequate IGF-1 levels are required for maintenance of bone mass, muscle mass and brain function at later ages. 6-8

So to prolong our lifespan, the goal is to maintain a relatively low IGF-1 throughout most of our adult life, and then as we get into our eighties and beyond, to consume enough protein so that our IGF-1 level does not get excessively low.

It is important to pay attention to our diet, to ensure our IGF-1 levels are favorable throughout life.

How IGF-1 works in our body

IGF-1 stands for insulin-like growth factor 1. It is a hormone with a similar structure to insulin. IGF-1 is a cell growth-promoter, important during childhood, contributing to brain development and muscle and bone growth. Growth hormone (GH) from the pituitary gland stimulates IGF-1 production in the liver; IGF-1 levels peak during our teen years and twenties, and then levels decline with age.

Circulating IGF-1 is also regulated by dietary protein intake, especially animal protein. Animal protein is more biologically complete, meaning it has high levels of all essential amino acids, so it can trigger excessive body production of IGF-1, whereas plant protein does not.9-10 High-glycemic, refined carbohydrates can also raise IGF-1.11-13

Optimal IGF-1 levels

A meta-analysis analyzed ten studies on IGF-1 levels and all-cause mortality. The authors found a “U-shaped” association, meaning that IGF-1 levels on the low end and the high end of the spectrum were associated with increased risk of premature death.14

The lowest risk was at the 55th percentile of serum IGF-1, and increased in both directions for all-cause, cancer, and cardiovascular mortality.14 This data suggests that we should aim for an IGF-1 level near the lower to middle for healthy people in our age range. A few studies, primarily in European populations, have attempted to define average IGF-1 levels for healthy people in different age ranges:15-17


Average Serum IGF-1 (ng/ml)















These numbers are somewhat lower than the average IGF-1 levels reported in several other studies in U.S. and European populations.

The European Prospective Investigation into Cancer and Nutrition (EPIC) study reported an average serum IGF-1 level of 200-210 ng/ml, suggesting that this is a typical level for adults on a Western diet.18 The amount of animal products consumed by most Americans drives their IGF-1 into this danger zone (above 200), increasing their risk of cancer.

Two studies comparing adults on a vegan (or raw vegan) diet (9-10 percent of calories from protein, no animal protein) to those on a Western diet (16-17 percent of calories from protein) found the Western diet average IGF-1 level of 200 ng/ml and vegan average lower than 150 ng/ml. One of these studies also evaluated IGF-1 in non-vegan endurance runners, and their average was about 175.19-20 The average age of subjects in these studies was in the mid-50s.

Low IGF-1 levels associated with an increased risk of disease or mortality are generally about 70-80 ng/ml or lower.15,21-26 Studies in elderly men (average age 75) have found increased risk of cardiovascular events and deaths from cancer in high IGF-1 groups, approximately 190 ng/ml.22-23

In the Nurses’ Health Study, premenopausal women with IGF-1 levels higher than 207 had a substantially higher risk of breast cancer.2,7 In the Physicians’ Health Study, there was an increase in prostate cancer risk once IGF-1 increased above 185 ng/ml.28

Taking all of this information into account, for most adults, keeping IGF-1 below 175 ng/ml is likely important, and below 150 ng/ml should be even more protective. Serum IGF-1 levels below 80 ng/ml may be detrimental, especially after the age of 75.

Restricting animal protein during most of one’s adult life to maintain a relatively low, but not excessively low IGF-1, is an important objective for those desiring superior health and life extension.  Protein assimilation can decline in the elderly. The use of greens, seeds and beans in the Nutritarian diet, to assure protein adequacy with aging, prevents the excessive lowering of IGF-1 in the elderly, often seen with other plant-based diets. The attention to micronutrient completeness and plant protein adequacy on a Nutritarian diet makes it the most scientifically supported diet-style to push the envelope of human longevity.

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Joel Fuhrman, M.D. is a board-certified family physician, seven-time New York Times bestselling author and internationally recognized expert on nutrition and natural healing, who specializes in preventing and reversing disease through nutritional methods. Dr. Fuhrman coined the term “Nutritarian” to describe his longevity-promoting, nutrient dense, plant-rich eating style.
For over 30 years, Dr. Fuhrman has shown that it is possible to achieve sustainable weight loss and reverse heart disease, diabetes and many other illnesses using smart nutrition. In his medical practice, and through his books and PBS television specials, he continues to bring this life-saving message to hundreds of thousands of people around the world.