Dr. Gregor says not to consume over 25 grams of soy protein per day. What are your thoughts?

I

ichthymom

New member
*Greger

This caught my attention not only because I was surprised there was a limit (according to him) but also because that's pretty low. I go way over that between tofu, tempeh, and soy milk.

He mentioned this in an interview with Simnett Nutrition. Timestamped link below.


Edit: Here's more information from Dr. Greger https://nutritionfacts.org/blog/how-much-soy-is-too-much/ His main argument is regarding IGF-1 levels.
 
@ichthymom He says this because he believes that you should be consuming whole foods as a protein source, and accumulating the micro and macronutrients that your body needs along the way. He also says the same thing about seitan, and explains that is basically a wheat plant with lots of the nutrients removed. But most people view tofu and seitan as pure protein and then get their micronutrients elsewhere, so it really isn’t anything to worry about if the rest of your diet is balanced.
 
@terryc This is entirely not the point.

The idea of an upper limit for soy protein isolate is due to our liver response and has nothing to do with impacting micronutrient variety.

In short:

Plant protein contains every essential amino acid, most animal proteins do as well. Animal proteins, especially mammalian, are composted of amino acids more similarly structured to human flesh. The liver goes into overdrive to process this protein fast, and prompts the body by releasing hormones to prepare for the new protein. These hormones are responsible for cellular growth. As an adult, this growth hormone (IGF-1) is detrimental to our health, directly linked to most cancer development. Increasing levels of IGF-1 in our bloodstream for hours after consuming animal protein, proportion to the amount we consumed.

Plant protein, while containing all the amino acids, is structured differently so it’s theorized that when our liver get it, the rapid response doesn’t trigger because the protein will take a bit more time to prepare and so there’s no hormone response, and blood levels will continue to decrease with more plant protein meals.

Soy and pea protein isolates are different than other plant protein, being more similar structure to human flesh. While they don’t trigger the igf-1 at the same rate as animal protein, they do increase IGF-1 to undesirable levels after a certain point (approx 25g of protein itself, not soy).

Eating whole food soy and pea does not appear to be an issue, though I’d have to read his linked studies to understand why that was concluded.

Consuming 40g of soy protein supplements does increase IGF-1 levels. Eating two servings of soy foods does not.
 
@ctender01 But we don't have evidence linking high supplemental soy consumption with higher rates of cancer, right? That's the main concern with increased IGF-1 yeah? If anything evidence shows a decreased incidence of cancer with increased soy consumption.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8931954/

Higher intake of soy and soy isoflavones were inversely associated with risk of cancer incidence, which suggested that the beneficial role of soy against cancer might be primarily attributed to soy isoflavones. These findings support recommendations to include soy as part of a healthy dietary pattern for the prevention of cancer.
Click to expand...

My question would be: is the link between IGF-1 and cancer causally related to the IGF-1 itself, or rather another factor like red meat consumption?
 
@terryc This is why I avoid soy protein powder - if I'm already eating tofu, tempeh, tvp, and soy curls I think that's enough soy.

Not saying those are my only proteins - I alternate those with seitan, beans, lentils -
 
I didn’t answered you, the other guy is also you? Even your comback (that shows in my notifications) is no where to be found in the comments.

What I wrote was not answering this comment about whole foods.
 
@gianghomobile Exactly - his books are called "How Not to Die" for a reason. I really appreciate his research and dedication to facts, but just like everything else in life, context matters as does personal preference.
 
@historia That's actually somewhat debatable; there's some fairly interesting evidence of the possible benefit to longevity of extreme caloric restriction.
 
@ichthymom Nothing to worry about really. IIRC he's saying more than 5 servings of soy per day increases inflammation, but if you're lifting you want the inflamation for optimal muscle growth, so who cares? Dr. Greger is a cool guy but following his word to the letter isn't necessary. He's just one of many, many different perspectives on what an "optimal" plant based diet looks like.
 
@timmdogg I agree with the overall takeaway, but just for clarity, isn't it more that you don't want to interfere with the natural inflammatory response of your muscles...more so than you want to increase overall inflammation?
 
@2911music You're correct but also iirc igf-1 also promotes muscle synthesis, which is a big reason things like whey are so popular in the mainstream. So soy mimics that. Of course, inflammation in general is considered bad, but intense athletic activities are also associated with inflammation, but also associated with improved health. So I think the thing to consider is, where is the inflammation and why is it occurring? Soy is also associated with numerous health benefits, so I think we can say it's a perfectly safe source of protein.
 
@ichthymom Older Japanese people eat 3 servings of tofu (35-40g soy protein) every day and are among the oldest living people.

There is, as far as I know, no solid evidence indicating a dangerous level of soy protein in any realistically meaningful way.
 
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