Did you know insufficient protein can cause serious health problems? Kwashiorkor is a condition, children with a protein deficiency could develop. The symptoms include a protruding belly, thin hair, overall weight loss, and discolored skin and hair. Left untreated, it can lead to stunted growth, mental impairments, and death.

Insulin-like Growth Factor and Protein

Insulin-like growth factor (IGF) (also known as somatomedin), is any of several peptide hormones whose primary function is to stimulate growth, and also possess some level of ability to decrease blood glucose levels. The name insulin-like growth factor reflects the insulin-like actions these substances have in some tissues, although far less potent than insulin in decreasing blood glucose concentrations. Even though IGFs share this ability with other growth factors—IGFs are the only ones with well-documented hormonal, chemical messenger actions in humans.

There are two IGFs: IGF-1 and IGF-2. These two growth factors, despite the similarity of their names, are very different in terms of specific actions on tissues because they bind to and activate different receptors: IGF-1 binds to IGF-1 receptor (IGF1R) and IGF-2 binds to IGF-2 receptor (IGF2R). Most of the actions of pituitary growth hormones are induced by IGFs, primarily IGF-1. 

Growth hormone stimulates many tissues, particularly the liver, to synthesize and secrete IGF-1, which in turn stimulates both hypertrophy (increase in cell size) and hyperplasia (increase in cell number) of most tissues, including bone. Serum IGF-1 concentrations and growth hormone secretion progressively increase during childhood, peak at the time of puberty, and progressively decrease as we age.

Under normal healthy circumstances the IGF-1 hormone efficiently manages the rates at which cells grow, reproduce new cells and discard old dying cells. When conditions are not normal and healthy, the IGF-1 becomes more active, increasing the rate of creating and growing new cells, while at the same time inhibiting the removal of old cells. Both of these conditions, by the way, favor the development of cancer. 

So, how does this relate to food? Eating animal based sources of protein, increases the level of IGF-1 growth hormone, circulating in the blood stream. 

And what does that do? It has been shown, in regards to prostate cancer, people who have higher than normal levels of IGF-1, have 5.1 times greater risk of advanced stage prostate cancer. Science has shown, we make more IGF-1 when we consume animal based foods like meat and dairy, than when we eat plant-based sources of protein.

The prostate is not the only body part negatively impacted by increased IGF-1 levels. The cancer risk affecting the breast, colorectal and lung is also greatly increased by animal foods. 

Animal Protein And Osteoporosis

In 1992, a summary report authored by researchers at Yale University School of Medicine, found 70% of the hip fracture rate for women aged 50 years and older, was attributable to the consumption of animal protein. The researchers provided this explanation: Animal protein increases the acid load in the body. An increased acid load means our blood and tissues become more acidic. Since the body does not like this acidic environment, it begins to fight it. In an attempt to neutralize the acid, the body uses calcium. The calcium must come from somewhere, so it begins being pulled from the bones, leaving the bones weak and at greater risk for fracture. 

Plant based sources of protein do not increase the acid environment in the body. We’ve known this since 1920. Additional studies done in 1974, 1981, and 1990 continue to clearly show, the amount of animal protein typically consumed by most non-vegans, can cause substantial calcium loss in the bones.

When the ratio of plant based sources of protein increase and animal protein consumption greatly decreases, bone fractures from calcium loss virtually disappear.  In studies conducted in China, where the animal-to-plant ratio is about 10%, the fracture rate is only one-fifth of what we experience here in the US. Nigeria experiences an animal-to-plant protein ratio only about 10% to that of Germany, and the hip fracture rate is lower by over 99%. 

Even today we are still influenced by advertising telling us we need protein rich dairy products to provide calcium and protect our bones. The research does not support this claim. In fact, in one study of ten different countries, a higher consumption of calcium from dairy foods, was associated with a higher (not lower) risk of bone fracture. 

Animal Protein and Kidney Stones

W. G Robertson from the Medical Research council in Leeds, England has been studying kidney stone formation since the mid 1960’s. He has authored or co-authored at least 100 papers on the topic since that time.  His research displays the relationship between animal protein consumption and formation of kidney stones. The study shows consuming animal protein at the amount of about one ounce per day is closely correlated with a high number of kidney stones. 

Animal protein consumption is not the only factor responsible for the formation of kidney stones of course, yet Robertson and his team identified animal protein as the major culprit. 

Animal protein affects recurring stones as well. With his patients who suffered from recurring stones, he was able to resolve the problem simply by changing their diet away from animal protein foods. 

Robertson explains it this way – When animal protein-containing foods are consumed, the concentrations of calcium and oxalate in the urine rise sharply. When the kidney is under persistent, long term attack from increased calcium and oxalate, kidney stones may form.

In regards to kidney stone formation, he states “Evidence points, in particular, to high-meat protein intake as being the dominant factor.”

Animal Products and the Eyes

Cataracts and macular degeneration affect millions of people. Macular degeneration is the leading cause of irreversible blindness among people over the age of sixty-five. This condition destroys the macula, which is the bio-chemical intersection in the eye, where the energy of light coming in through the eye, is transformed into a nerve signal. The macula must function in order for sight to occur. 

Around the macula are fatty acids which can react with the incoming light to produce highly reactive free-radicals. These free-radicals can destroy nearby tissue, including the macula. Antioxidants found in vegetables and fruits can stop this damage. 

Studies suggest that as much as 70-88% of blindness caused by macular degeneration could be prevented if the proper high antioxidant foods are eaten. A higher intake of carotenoids is associated with a lower frequency of macular degeneration. Carotenoids are a class of phytonutrients found in the cells of a wide variety of plants, algae and bacteria. They help plants absorb light energy for use in photosynthesis.

Carotenoids are found in the colored parts of fruits and vegetables.  Fruits and vegetables are the most abundant sources of carotenoids. Animals cannot manufacture carotenoids themselves; they have to get it in from their plant-based food. Any carotenoids found in animal products, would have come in from the plants previously eaten by an animal.

You might be wondering if supplement forms of carotenoid are as effective as plant-based food sources. Vitamin A (retinol), vitamin C, and E in pill or capsule form, showed little or no benefits when compared to the carotenoids found in dark leafy green vegetables. 

Animal protein provides no protection against blindness caused by macular degeneration, while plant-based sources of antioxidant-rich foods do. 

How do we start eating more plant based protein?

Start by adding one plant based meal to your daily nutrition plan.





Chan JM, Stampher MJ, Ma J, et al. “Insulin-like growth factor-1 (IGF-1) and IGF binding protein-3 as predictors of advanced prostate cancer.” J Natl Cancer Inst 94 (2002): 1099-1109.

Itay Bentov, Haim Werner, in Handbook of Biologically Active Peptides (Second Edition), 2013

Ivanoff, George. Protein (What’s in My Food?). Mankato, MN: Smart Apple Media, 2001.

JNCI: Journal of the National Cancer Institute, Volume 92, Issue 18, 20 September 2000, Pages 1472–1489

Linus Pauling Institute: Carotenoids


Role of the Insulin-Like Growth Factor Family in Cancer Development and Progression, Herbert Yu, Thomas Rohan