Living Healthy: plant

Friday, October 12, 2012

How Much Soy Is Too Much?

If animal proteins promote cancer because they boost our blood levels of the growth hormone IGF-1, what about the few plant proteins that have amino acid ratios similar to animal proteins such soy foods? One of soy’s selling points is that it has “high quality” protein, but as we saw in my Care2 article on Wednesday, Animal Protein and IGF-1, higher quality may mean a higher risk of cancer.

In my 2-min. video, Animalistic Plant Proteins, I show that animal protein consumption is associated with significantly higher levels of the cancer promoter IGF-1 and non-soy plant protein is associated with significantly lower levels. There was no significant association with soy protein, though. This suggests that if all we do is replace animal protein with soy protein, we may not see as dramatic a drop in IGF-1 as that enjoyed by those replacing meat, eggs, and dairy with a variety of plant proteins. You can see what lower IGF-1 levels can mean for prostate and breast cancer growth in my videos Ex Vivo Cancer Proliferation Bioassay and The Answer to the Pritikin Puzzle.

In my NutritionFacts.org video pick above I show that vegans consuming the equivalent of 7-18 servings of soy foods per day may end up with circulating IGF-1 levels comparable to those who eat meat. For more on the cancer reversal study mentioned in the video, see Cancer Reversal Through Diet. It’s important to remember in this discussion that soy food consumption is associated with an array of health benefits. See, for example, Breast Cancer Survival and Soy, The Effect of Soy On Precocious Puberty, and Soy Foods & Menopause. But how much may be too much?

From the above video it seems that 7 to 18 servings of soy a day may neutralize some of the beneficial effects of avoiding animal protein. At the same time, studies have repeatedly found that women who eat a lot of soy appear to have a lower risk of getting breast cancer and a better chance of surviving breast cancer than those who don’t. So is there some magic number of soyfood servings we should shoot for?

In my 2-min. video, How Much Soy Is Too Much, I run through all the studies to date that have measured the effects of varying levels of soy consumption on IGF-1 levels. Five to ten servings per day increased IGF-1 levels, but two to three servings did not. The bottom-line is that legumes are one of the healthiest things we can eat and should be a part of everyone’s daily diet. This means lentils, peas, and/or beans every day—in fact, ideally every meal! Soy is an excellent choice, but we should probably stick to no more than 3-5 servings a day.

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my videos for free by clicking here and watch my full 2012 presentation Uprooting the Leading Causes of Death.

Image credit: Andrea_Nguyen / Flickr

Source : care2[dot]com

Wednesday, October 10, 2012

Animal Protein and IGF-1

At first we didn’t know why eating a plant-based diet for just a couple weeks appeared to so dramatically improve cancer defenses. Then, last year, researchers figured it out: eating healthy lowers the level of the cancer promoting growth hormone IGF-1. This saga was detailed in my last four Care2 articles:

What is the mechanism by which a simple dietary change can alter the levels of this cancer promoter? Imagine you’re a kid with some tinker toys. Then for your next birthday you get one of those huge tinker toy sets dumped down in front of you. All excited with this new load of raw building materials, you may really start scaling up. Basically it’s the same with your liver and insulin-like growth factor 1.

When you dump a load of protein in your body, your liver’s like, “Whoa, look at all this! What are we going to do with it all? We can’t just waste it, we’ve got to do something with it.” Thus, your liver starts pumping out IGF-1 to tell all the cells in the body, “it’s growin’ time! Be fruitful and multiply. Spare no expense, go crazy—look how much excess protein we got to work with!”

The problem is that some of the new additions spurred by this growth hormone may be tumors. When you’re a fully-grown adult, cell growth is something we want to slow down—not accelerate. The goal, therefore, would be to maintain adequate, but not excessive, overall protein intake.

Wait a second, though. As I show in my 3-min. video Protein Intake and IGF-1 Production, studies have found no association between total protein intake and IGF-1 levels, but that’s because they didn’t take into account animal versus plant protein. It took a study comparing meat-eaters to vegans to show that higher IGF-1 levels were only associated with animal protein intake. In fact, plant protein seemed to decrease IGF-1 levels. Animal protein appears to send a much different signal to our livers than most plant proteins. Even vegans eating the same amount of protein as meateaters still had lower levels of the IGF-1, so it’s apparently not about excessive protein in general, but about animal protein in particular. To understand why, see the above NutritionFacts.org video pick.

For those who haven’t been following along, see IGF-1 as One-Stop Cancer Shop for the reason we’re so concerned about IGF-1 levels and my videos The Answer to the Pritikin Puzzle and How Plant-Based to Lower IGF-1? to learn about the role diet plays in cancer development. If the reason animal proteins raise IGF-1 levels is because they resemble our own proteins, what about the few plant proteins that just coincidently happen to have amino acid ratios similar to proteins such as soy? Great question! That will be the subject of my Care2 article on Friday.

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my videos for free by clicking here and watch my full 2012 presentation Uprooting the Leading Causes of Death.

Image credit: StuartWebster / Flickr

Source : care2[dot]com