Many of you may have heard Dr. T talk about protein and how too much protein can be compromising your health. He uses the analogy that protein is dirty fuel and it is like running it through your engine without a catalytic converter. There are many reasons to not over consume on protein and I would like to comment and share additional reason to the rhyme.
One thing most people know is that protein is for growth. Recently there was a study done by people who study longevity and the research showed some interesting things. They wanted to see how total protein intake fared on some important bio-markers or lab tests for longevity. The results were frightening; too much protein sent a specific growth hormone called Insulin Like Growth Factor 1 (IGF-1) significantly higher. Even excess calorie intake did not affect this as much as protein intake did. Why? Because protein and these hormones promote growth, which is not a good thing for those of us trying to live long. We want to slow down growth not speed it up! We want to decrease the stimulation of growth as much as possible and preserve our cells from turning over rapidly.
Elevated IGF-1 levels in adults can increase the growth rate of all cells, like normal tissue and bones, but it can increase the growth rate of abnormal tissues like cancer as well. High levels significantly increase the risks of colorectal, breast, and prostate cancer.
The researchers have found, that protein absorbability makes a greater difference in IGF-I (and the binding proteins) than total protein. Animal proteins are well known for their increased bioavailability which refers to the proteins ability to be used by the body. Milk is well known for its ability to protect against strong bones. True or not, one thing milk will do is raise IFG-1 more than any other proteins do. This may be good for bones but dying early from cancer with good bones has never been a goal of mine.
Proteins from vegetables, grains, beans, and fruits are LESS BIOAVAILABLE and that may be a really good thing. We should be getting our proteins from plant sources like whole grains, beans, vegetables, nuts and fruits. That way protein intake is kept below 10% intake because too much of a good thing (protein) is still too much. There are a couple caveats with plant proteins too though. Even isolated plant proteins (like soy) can raise IGF-1 levels, so while they may be good for an athlete trying to bulk up and increase muscle, supplementing with plant protein powders and raw protein powders is not the way to go for health maintenance.
So, the take home message from this is keep your total protein low (but adequate at .8g/kg body weight) and choose proteins which are less bio-available, which are plant proteins. The current research is showing that the most available proteins are also the ones that rise IGF-1 the most, which in turn may increase the growth rates of cancer, so avoid animal proteins. Animal proteins ARE more bio-available. But would you want something to be the most "bio-available" when more of it is not good? As Doctor Seuss so eloquently put it “You have brains in your head. You have feet in your shoes. You can steer yourself any direction you choose. You're on your own. And you know what you know. And YOU are the one who'll decide where to go...” Remember, you are the conductor of your health journey.