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IGF-1: The Growth Hormone That Can Fuel Cancer

9 min read

IGF-1 is a hormone our bodies make naturally. But when we consume meat and dairy products, our levels tend to become elevated to an extent that could be dangerous. In this article, we’ll explore what you need to know about IGF-1, including why and how to keep your IGF-1 at a healthy level.

Short for insulin-like growth factor 1, IGF-1 is a hormone that helps control the growth and development of organs, muscles, and tissues in the body. IGF-1 also has a hand in controlling glucose metabolism and brain function. Originally called somatomedin C, IGF-1 is synthesized mainly by the liver but is also produced locally in other types of tissue.

As a hormone, IGF-1 assists with normal development in babies and children, and its natural presence in the body gradually decreases with age. But levels of circulating IGF-1 can vary greatly depending on a number of factors, including age, gender, genetics, nutrition, physical activity, and stress.

Having the right amount of IGF-1 is important to your natural bodily development, but having too much of it can negatively affect your health.

Protein Triggers IGF-1 Production

Problems arise when IGF-1 continues to increase, rather than decrease as biologically programmed, throughout adulthood. Of all the factors that can raise IGF-1 levels, the most powerful seems to be dietary — particularly the consumption of foods that are high in protein.

Industrialized countries eat a lot of protein already, arguably much more than is necessary. Thanks to marketing by the meat and dairy industries, the scientific research they fund, and the legislation they lobby for, many people think that the more protein, the better. While fats and carbs take turns being dietary villains, so far, protein is usually portrayed as wholly positive — with no potential downsides to overconsumption.

But the truth is that protein promotes growth, and excess protein promotes excess growth. Part of the reason for this is that large quantities of protein trigger the liver to release IGF-1, which tells cells to grow. While cell growth is part of our development early in life, it’s not something we want going full throttle during adulthood. In fact, overgrowth of cells can lead to health complications.

The Type of Protein Matters

early morning portrait of a dairy farmer walking away from camera

While excess protein of all kinds can contribute to health problems such as osteoporosis and kidney stones, when it comes to IGF-1 production, the type of protein matters.

Studies have found that higher IGF-1 levels are not associated with overall protein, but animal protein intake, specifically. That means all types of meat, dairy products, and eggs, which constitute about 30% of the standard American diet, are implicated. The reason animal protein triggers the release of IGF-1 may be because the relative ratios of amino acids in animal proteins closely resemble our own — so they send signals to our liver where IGF-1 is released. In a sense, upon eating animal products, the proteins in them deceive the human body into thinking it’s responding to its own amino acids. Like many-a-horror movie, the call is coming from inside the house.


But amino acids alone may not account for the full effect. There may also be a relationship between consumption of the growth hormones given to cows in modern dairy farms and IGF-1 levels in humans. Evidence shows the synthetic hormone ​​rBGH (recombinant bovine growth hormone) — also known as rbST (recombinant bovine somatotropin) — in dairy products may increase levels of IGF-1.

Farmers use rBGH to increase milk production in dairy cows, a practice the industry has embraced since the early 1990s. However, most people don’t know it ends up in their food because there’s no labeling requirement. And the dairy industry is savvy enough not to advertise that the milk we buy comes from chemically turbocharged animals. The good news is that many companies have stopped using it due to consumer demand for its removal (a good reminder to vote with your dollar!).

Sadly, whatever the dietary factors that ultimately increase circulating IGF-1 in the body, the result is clear: higher levels pose a greater risk for the development of serious chronic diseases.

Cancer & IGF-1

pink ribbon concept

It seems the more IGF-1 you produce in response to animal protein in your diet, the higher your risk of contracting cancer. And for people who have previously had a cancer diagnosis, it could be even more of a concern because high IGF-1 levels may also increase the risk for secondary cancers.

Why is there a correlation between IGF-1 and cancer? It turns out that IGF-1 can inhibit cell death, or apoptosis — a natural and healthy process by which old and damaged cells self-destruct for the good of the entire organism. Activation of IGF-signaling pathways promotes growth, metastasis, and even drug resistance in many types of human tumors. Too much IGF-1 appears to tell these cells not only to keep living, but to grow and replicate, which may lead to malignant tumors.

Here again, animal protein may be critical. One study found that people ages 50 to 65 who ate a diet high in animal protein were four times more likely to die from cancer or diabetes — about the same relative risk as smoking cigarettes. Upon the replacement of animal protein with plant protein, the adverse health effects were, in the stark words of the researchers, “either abolished or attenuated.”

Several types of cancer, in particular, have been associated with IGF‐1, including lung, breast, colorectal, and prostate cancer.

Lung Cancer

In a 2016 literature review, researchers noted that individuals with lung cancer often have high circulating levels of IGF-1. Research showed that targeted therapy to bring down IGF-1 levels in these patients may offer some benefit for prognoses and aid in cancer therapy resistance.

Breast Cancer

A 2020 press release from the Annals of Oncology shared findings from two large studies conducted on the role of IGF-1 in breast cancer development. In the first study, researchers examined blood levels of IGF-1 among 206,263 women and their chances of developing the disease. They found that the women with the highest concentrations of circulating IGF-1 were 25% more likely to develop breast cancer than those with the least amount of IGF-1.

That study showed correlation, but not causation. In other words, it was possible that some other factor, as yet undetermined, was the cause of both high IGF-1 levels and breast cancer. And that’s where the second study came in. In order to figure out if high levels of IGF-1 actually increase the risk of breast cancer, researchers used a method called Mendelian randomization to look at data from 265 variants of genes associated with IGF-1 concentrations. They analyzed data involving over 200,000 women, about half of whom had breast cancer, and found a “probable causal role of the IGF pathway in breast cancer development.” The researchers suggested that using diet and lifestyle to alter IGF-1 levels may be an effective strategy for primary prevention — that is, decreasing the odds of developing breast cancer in the first place.

Colorectal Cancer

In a 2020 study based in the UK, researchers analyzed blood samples from almost 400,000 participants and found that a higher level of IGF-1 was associated with a higher risk for colorectal cancer. It turns out that IGF-1 is involved in activating multiple pathways that determine how aggressive a colorectal tumor may be. It also contributes to increased resistance to conventional and targeted anticancer therapies such as chemotherapy, endocrine therapy, and radiation.

Prostate Cancer

In healthy amounts and at the proper stages of development, IGF-1 is necessary for growth and development. Males need IGF-1 to grow healthy prostate glands, for example. But when the production of too much IGF-1 goes on for too long into adulthood, that growth can turn cancerous. We see this in lab studies, where pouring IGF-1 onto human prostate epithelial cells in cultures stimulates their growth and proliferation.

And the effects have real-world consequences, too: High circulating serum IGF-1 levels are associated with a higher risk of developing advanced prostate cancer later in life. In fact, a UK-based study involving over 200,000 men found that for every 5 nmol/L (nanomoles per liter) increase of IGF-1 in blood, men were nine percent more likely to develop prostate cancer.

What You Can Do

happy young black woman preparing vegetable salad

The best strategy for keeping IGF-1 levels in check and preventing the type of cell overgrowth associated with multiple types of cancer is by replacing animal protein with plant protein. For example, substitute ingredients like beans, lentils, tofu, nuts, and seeds in meals where you might normally have meat. Try an unsweetened plant milk in place of dairy milk. And experiment with making your own cashew- or potato-based cheeses and cheese sauces at home.

One study found that people on a vegan diet had significantly lower IGF-1 levels than people on a vegetarian or meat-eating diet. And vegans were better able to bind and remove excess IGF-1 in their bloodstreams. People who ate plant-based diets for 14 years had half the amount of IGF-1 in their bodies and more than twice the amount of IGF-binding protein than those on the standard American diet.

But healthy food choices aren’t the only way to bring down your IGF-1 levels. It turns out that physical inactivity is not only a contributing factor to some of the major chronic diseases, it’s also associated with higher IGF-1 levels.

One study on men found that low-intensity aerobic training decreased the circulating levels of IGF-1 by nine percent (while also improving insulin sensitivity by 20%). But keep in mind that more isn’t always better. Too much exercise can have the opposite effect. “Overtraining” also increases unfavorable IGF-1 levels and contributes to the increased incidence of hormone-dependent cancers and osteoarthritis. In other words, exercising regularly has its benefits, including helping to lower IGF-1 to an extent, but there’s no need to go overboard.

Healthy Recipes Using Plant Rather Than Animal Protein

Below you’ll find three delicious recipes that bring loads of flavor and textures, while leaving meat and dairy behind — thus helping to keep your IGF-1 levels well-managed. Vegan Mince Lettuce Tacos use peas and corn, plus lots of colorful veggies, to create a “mince meat-like” appetizer (but without the meat). Ditch that cheese habit and replace it with a healthier habit by making (and enjoying!) creamy Herbed Cashew Cheese. And try the Champion Tempeh and Bean Chili, and you may find yourself adding it to your “family favorites” list thanks to its “meaty” texture, delicious flavors, and feel-good ingredients.

1.  Vegan Mince Lettuce Tacos

You can easily use minced veggies, legumes, and herbs in place of the conventional ground meat to create the same hearty and flavorful dish but with healing ingredients that won’t spike your IGF-1 levels. Create your own version by mincing or dicing any veggies you have on hand, and then adding them to the lentil, pea, and corn mixture. Make vegan mince for the week and use it as a side dish, on top of rice, in grain bowls, or as tacos in these lettuce wraps.

2. Herbed Cashew Cheese

Now that you’ve learned about IGF-1, you might be wondering what your options are if you like cheese. We get that IGF-1 can be worrisome, and we also get that cheese is pretty darn difficult to ditch. But we do have a solution for you! Herbed Cashew Cheese creates a creamy and delicious-tasting cheese when you have the right ingredients (cashews and your favorite herbs) and the right equipment (a decent blender to get it extra creamy). Use this IGF-1-lowering cheese as a veggie dip, on sandwiches, or in grain bowls.

3. Champion Tempeh and Bean Chili

Protein lovers, this one’s for you. Swap out the red meat with tempeh and add even more plant protein with the beans. The result is a protein-powered, “meaty” textured, and delicious bowl of chili that won’t wreak havoc on your IGF-1 levels. Seems like a reasonable swap — you receive great protein, flavors, and textures but without harmful ingredients. Make this recipe for one and enjoy it throughout the week. Or serve it to your family — it’s perfect for a group!

Another Win for Plant-Based Eating

plant-based proteins like nuts seeds and legumes

Although IGF-1 is a natural hormone produced by the body, dietary intake of animal protein may cause levels to become excessive and cause health issues. Associations exist between IGF-1 and the development of multiple types of cancer. But the good news is that adopting a plant-based diet — emphasizing plant proteins instead of animal proteins — and exercising regularly can decrease your risk of IGF-1-associated cancers and help protect against other health complications.

When you prioritize plants in your diet, you benefit doubly: you get all the health-promoting compounds found in plants, and you avoid elevated IGF-1 and all the other ways animal-based foods can cause harm.

Tell us in the comments:

  • If you eat animal protein, where are some places that you can start substituting plant proteins instead?
  • Have you ever had your IGF-1 levels tested?
  • What other things have you heard about IGF-1 and animal products?

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