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 cancers^9-11
•    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

Want more support? Join Dr. Fuhrman’s Nutritarian Membership and gain access to:
🌱 Over 2,000+ recipes using plant-based, cancer-fighting ingredients
📅 Step-by-step meal plans that simplify your health journey
📚 Science-backed guidance from Dr. Fuhrman and his team
👩‍🍳 Tools to help you ditch animal products and transform your plate—without sacrificing flavor
👉 Join the membership today and start optimizing your IGF-1 the delicious way.