Research into a hormone called insulin-like growth factor 1 may be the key to understanding cancer growth — and how to stop it. Studies indicate that higher levels of the hormone promote tumor development, and lowering IGF-1 levels can help the body increase its natural cancer defenses.

A hormone similar to insulin, IGF-1 is produced throughout life, primarily by the liver. IGF-1 has growth-promoting effects on almost every cell in the body, especially in cartilage, bone, skin, the liver, and the kidneys. It plays an important role in childhood growth and development, and the highest rates of IGF-1 occur during puberty, when it’s needed to help cells multiply. In adulthood, however, IGF-1 has been linked to the growth and spread of cancer cells.

Eating a high-protein diet increases IGF-1 levels, regardless of how many total calories you consume. Other factors that influence levels of IGF-1 include your individual genetic makeup, insulin levels, age, gender, fitness level, stress level, BMI, and race.

IGF-1 and tumor growth

Every day, 50 billion of our cells die, and are replaced by new ones. At certain points in life, we need to replace cells at a faster rate than they die — this is what allows us to grow. But once we reach adulthood and stop growing, we want the rate of cell death and cell development to be roughly the same. We still need cells to grow and divide, but only to replace the cells that die. We no longer need extra cells for growth.

But if IGF-1 levels are too high, they send a constant message to our cells to divide and multiply. This can promote abnormal cell growth, which leads to cancer. The more IGF-1 in your bloodstream, the higher your risk for cancer.

Not only does IGF-1 promote abnormal cell growth, but it also helps abnormal cells break away from the original tumor, grow, invade the bloodstream, migrate into surrounding tissue, and stabilize into new tumors. IGF-1 is what allows breast cancer to migrate to the bone, or the liver, or the lungs. It’s these metastases — secondary malignant growths — that are most often the cause of death from cancer, not the original tumor.

Rare genetic defect protects against cancer

Some people have a rare genetic mutation that causes them to produce very little IGF-1, which seems to make them immune to cancer. In people with the condition, known as Laron syndrome or Laron-type dwarfism, the body is unable to use growth hormone. Affected people may be normal size at birth, but have a slow growth rate that results in a short stature. People with Laron syndrome may not grow more than 4.5 feet tall, but they never get cancer. They are also almost completely free of diabetes, even though they may become obese, which often triggers type 2 diabetes.

Inspired by low cancer rates among people with Laron syndrome, scientists began to look at ways to keep IGF-1 levels low in adulthood, and discovered that it may be possible through diet.

The effect of plant-based diets on IGF-1

Even people eating a standard American diet have some ability to fight cancer cells. But in a study known as the Pritikin experiment, after 12 days on a plant-based diet, participants had significantly increased their cancer defenses. After eating a healthy diet, their bodies were able to reprogram the cancer cells, forcing them into apoptosis, or cell death.

A separate study confirmed that 11 days on a plant-based diet, combined with exercise, results in significantly lower levels of IGF-1. In addition, IGF-1 binding protein levels significantly rise. These binding proteins are produced by the liver to protect the body from cancer — the proteins bind to IGF-1 so that action of the molecules is inhibited. Exercise alone can decrease IGF-1 levels, but only a plant-based diet triggers the increase in IGF-1 binding proteins. Participants in the study experienced a 20 percent decrease in IGF-1 levels and a 50 percent increase in IGF-1 binding protein. When a blood sample from these individuals was introduced to cancer cells, there was dramatic cell die-off among the abnormal cells.

Researchers state that low-level, regular exercise — such as daily walking — combined with a plant-based diet can lower IGF-1 levels and reverse cancer growth.

Cycles of prolonged fasting and protein restriction can have the same effect. A certain type of low-protein diet that mimics the effects of fasting has also been shown to reduce IGF-1 levels. The ProLon fasting mimicking diet was developed by Dr. Valter Longo, a researcher on aging at the University of Southern California, one of the scientists who studied IGF-1 levels in Laron patients. The five-day diet can be purchased for at-home use provided individuals are in good health, not taking any glucose-lowering drugs, and free of any liver of kidney deficiency. Learn more about ProLon and find out if it’s right for you.