On the thread about cranberries, Rodney got us talking about prunes, and how they may be good for maintaining bone health via increased IGF-1, which is a double-edged sword. This is pretty well-known among knowledgeable CR practitioners, but I thought it worth highlighting, particularly since I came across this interesting discussion & video on the potential tradeoff between "performance" and longevity with respect to IGF-1.
It discusses (and gives citations) for many of the benefits of IGF-1, including muscle repair/preservation as well as long-term cognitive health. Interestingly, it doesn't mention helping maintain bone health as another benefit of the anabolic effects of IGF-1. But on the downside, it talks about increased cancer risk and the widely-observed reduced longevity (in humans and animals) associated with higher levels of IGF-1.
Here is the summary paragraph:
There you have it. It’s a trade-off when it comes to growth hormone and IGF-1. More of it enhances muscle and neuronal growth while simultaneously preventing atrophy. Less of it will increase the expression of stress resistance genes and extend your lifespan. Which do you prefer, having better muscle and cognitive performance or living longer?
Overall, it seems like a good primer for anyone who wants to learn about the pros and cons of the reduced IGF-1 often associated with practicing CR.
We're famous again!
In his weekly newsletter out today, Dr. Greger did a story on Calorie Restriction vs. Plant-Based Diets which highlighted results from two of Luigi's studies on us (PMIDs 18843793 and 17158430). He discusses the important health and lifespan benefits of keeping IGF-1 low, and uses Luigi's studies to (allegedly) argue that it is a plant-based diet, and not the reduced calories, that results in low IGF-1.
I didn't remember this part of Luigi's study, which Dr. Greger used as evidence that it is the plant-based diet rather than CR that drops IGF-1:
Therefore, we conducted additional studies to evaluate the importance of long-term protein intake in modulating serum IGF-1 concentration in humans. In one study, we evaluated serum IGF-1 and IGFBP-3 concentrations, and IGF-1 : IGFBP-3 ratio in 28 vegans who had been consuming a moderately protein-restricted (PR) diet (0.76 g kg−1 per day; ~10% of intake from protein) for ~5 years age-matched with 28 members of the Calorie Restriction Society who consume a high-protein diet (1.73 g kg−1 per day; ~24% of energy intake from protein) (Table 3). Protein intake was significantly lower in the moderately PR group than in the CR group, while energy intake tended to be higher (Table 3). Both serum IGF-1 concentration and IGF-1 : IGFBP-3 ratio were significantly lower in the moderately PR diet group than in the severe CR diet group, whereas fasting insulin and C-reactive protein were similarly low in the moderately low-protein vegan and CR groups (Fig. 2), as previously reported in a smaller group of raw food vegans (Fontana et al., 2006a, 2007a). This effect of a moderate protein restriction is independent of body weight and body fat content, as serum total and free IGF-1 concentrations were lower in the moderately PR group than in the severe CR high-protein diet group, despite the PR groups’ higher body weight, BMI and body fat content (Table 4).
Dr. Greger's summary of these results is pretty accurate:
Only the vegan group got a significant drop in IGF-1. These findings demonstrate that, unlike in rodents, long-term severe caloric restriction in humans does not reduce the level of this cancer-promoting hormone. It’s not how many calories we eat, but the protein intake that may be the key determinant of circulating IGF-1 levels in humans, and so reduced protein intake may become an important component of anti-cancer and anti-aging dietary interventions.
But once again Dr. Greger's agenda (bless his heart) shines through a bit. Given the title of this article ("Calorie Restriction vs. Plant-Based Diets") he seems to be hoping his readers will equate "plant-based" or "vegan" with "low protein". While generally this is the case, the two don't necessarily go together. It's possible to eat a high protein vegan diet (e.g. with concentrated soy products, vegan protein isolates etc), just as it's possible to keep protein low on a diet that includes animal products (not so easy, but ketogenic diet folks do it w/ lots of butter etc.).
My personal data might seem to support Dr. Greger's conjecture. Since I eat a lot of calories, I also eat a lot of protein (96g/day, or 2x the RDI). But since I'm vegan, all of it plant-based and so my IGF-1 remains low (83, RR 61-200). In fact my IGF-1 now is less than half what it was when Luigi tested me in 11/2002, when (as I recall) I believe I was eating a lacto-ovo-(maybe pesco...)-vegetarian diet, with many fewer calories, more animal products, and about the same total protein. But don't hold me to that - since that was around that time I went vegan IIRC. Unfortunately I don't have records going back that far (except blood tests). Tom, anything in the archives?
Regardless, my example is not very definitive anyways, because despite my high calorie and relatively high (plant-based) protein diet, I'm maintaining a net calorie deficit, which may explain my low IGF-1 level, independent of protein amount or source.
So maybe it is low animal protein and not just low protein that makes the difference. But I don't think Dr. Greger makes a very good case for this hypothesis in his article, to put it mildly.