You may not have heard of insulin-like growth factor 1 (IGF-1)—but this powerful hormone could be quietly influencing your risk of cancer, aging, and chronic disease. IGF-1 plays a role in healthy childhood development as well as healthy aging, but too much of it may do more harm than good.
Here’s what the science shows—and how a Nutritarian diet may be your most powerful defense.
The Problem: When Growth Turns Dangerous
IGF-1 helps your cells grow and divide. That’s great when you’re a child—but in adults, it’s more complicated. Lower (but not excessively low) IGF-1 activity is linked to longevity, but excessively high IGF-1 can fuel abnormal cell growth, suppress apoptosis (the natural death of damaged cells), and drive the development of cancer. Also, at older ages (over 65 or 70), IGF-1 production slows and levels that are too low become a bigger concern, since IGF-1 is necessary to maintain bone and muscle mass as well as cognitive function.1-8
Higher IGF-1 levels have been linked to: • Increased risk of breast, prostate, and colorectal cancers9-11 • Accelerated aging and premature death12 • Greater resistance to cancer therapies13 • A higher likelihood of developing a second cancer in cancer survivors14
IGF-1 isn’t inherently bad—but it must be balanced. Unfortunately, the standard American diet drives IGF-1 levels dangerously high, especially due to excess animal protein and refined carbohydrates.
Sources: Protein Requirements and Optimal Intakes in Aging: Are We Ready to Recommend More Than the Recommended Daily Allowance? Low protein intake is associated with a major reduction in IGF-1, cancer, and overall mortality in the 65 and younger but not older population Nutrition, GH/IGF-1 signaling, and cancer GH and IGF1 in cancer therapy resistance Is there a role for IGF-1 in the development of second primary cancers?
The Evidence: What the Research Says is the Optimal IGF-1 Level
A meta-analysis of 19 studies including over 30,000 participants found that IGF-1 levels that are too high or too low are associated with a greater risk of early death. The sweet spot? Between 120 and 160 ng/ml.12
Source: Association between IGF-1 levels ranges and all-cause mortality: A meta-analysis
The Solution: Eat for a healthy IGF-1 Level
IGF-1 levels peak in our teens and twenties and decline with age. Apart from age, dietary protein intake is the major regulator of IGF-1 levels, especially animal protein. Since essential amino acids in particular trigger the production of IGF-1, animal protein, which is higher in essential amino acids than plant protein, increases IGF-1 more than plant protein.15-17 High-glycemic, refined carbohydrates also raise IGF-1 somewhat.18-20 Western diets rich in meat, dairy, and refined carbohydrate commonly push IGF-1 levels over 200 ng/ml (in young and middle-aged adults), raising the risk for cancers.4
To extend your lifespan and reduce cancer risk, aim for an IGF-1 level that's low, but not too low—especially after age 75, when IGF-1 is essential for maintaining bone, brain, and muscle health.
Here’s how to do it:
Ditch animal protein for plant protein. Replace meat, eggs, and dairy with beans, lentils, tofu, nuts, and seeds. The amino acid profile of animal protein triggers excessive IGF-1 production. Adopt a Nutritarian diet. This eating style emphasizes plant food diversity and ensures you get adequate protein from greens, seeds, and legumes—without over-activating IGF-1.
Related: How Plant Protein Wins Over Animal Protein
Sources: Nutritional regulation of the insulin-like growth factors Association of animal and plant protein intakes with biomarkers of insulin and insulin-like growth factor axis The insulin-like growth factor axis: a potential link between glycemic index and cancer
Why a Nutritarian Diet Keeps IGF-1 Levels Favorable
Restricting animal protein during most of adult life to maintain a relatively low, but not excessively low IGF-1 is an important objective for those desirous of superior health and life extension. Unlike other plant-based diets that may fall short on protein in later life, the Nutritarian approach is designed to sustain optimal IGF-1 levels throughout life with plant protein-rich foods such as greens, beans (including soybeans), and seeds. By emphasizing phytochemical-rich foods and plant protein, it helps:
Prevent cancer by keeping IGF-1 in the safe range Support longevity by protecting against frailty in older adults Ensure micronutrient completeness and phytochemical variety to reduce inflammation, improve immunity, and reverse disease
Dr. Fuhrman’s medical practice and decades of research show that this is not just a theory—it’s a proven path to a longer, healthier life.
Take Action
Here’s your IGF-1 challenge: This week, swap out meat or dairy in at least 3 meals. Use beans instead of beef. Blend your smoothie with flax seeds, hemp seeds, and kale instead of whey protein. Try a cashew cheese recipe in place of cheddar. If you’ve never had your IGF-1 levels tested, ask your doctor to include it in your next routine blood panel or use an at-home test, especially if you're over age 70. And if you’re working on cancer prevention or recovery, keeping IGF-1 in check is one of the smartest moves you can make.
Related: What blood tests do I need?
Follow Dr. Fuhrman’s Proven Plan
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