Saturday, June 09, 2012

Low-Protein, Low-Calorie Intake May Lower Cancer Risk

This study:
Long-Term Low-Protein, Low-Calorie Diet And Endurance Exercise Modulate Metabolic Factors Associated With Cancer Risk, American Journal of Clinical Nutrition, 2006

Looked at 3 groups of middle-aged (53 +/- 11 years old), nonsmoking, healthy men and women:
  • 21 sedentary subjects, low-protein (about 9% of calories), low-calorie (about 2000) diet*
  • 21 endurance runners
  • 21 sedentary subjects (non-obese), Western diet
And found:
  • Levels of insulin, free sex hormones, leptin (released from body fat), and C-reactive protein (marker for inflammation) were lower and sex hormone–binding globulin (protective against cancer) was higher in the low-protein, low-calorie diet and runner groups than in the sedentary Western diet group.
  • Levels of insulin-like growth factor I (IGF-I) was lower in the low-protein, low-calorie diet group.
So, even though the low-protein group was sedentary, they had lower levels of growth factors and anabolic hormones that are linked to an increased risk of cancer, plus they had the lowest levels of of IGF-I, also linked to cancer. (IGF-I "promotes tumor development by stimulating cell proliferation and inhibiting cell death." IGF-I is linked, in humans, to a greater risk of breast, prostate, and colon cancers.):
"Subjects eating a low-protein, low-calorie diet had much lower plasma IGF-I concentrations and IGF-I:IGFBP-3 than did BMI-matched endurance runners, which suggests that dietary factors may provide additional protective effects, independent of body fat mass."
Perhaps this is why Campbell could turn cancer on and off in rats by changing the amount of protein they ate (Liver Cancer: Now You See It, Now You Don't).
* They ate uncooked, unprocessed, plant-based foods, "vegetables, fruit, nuts, seeds, sprouted grains and cereals, and olive oil and strictly avoided processed and refined foods (eg, partially hydrogenated oils, refined flours, sweets, free sugars, and soft-drinks) and foods of animal origin." Lots of fat, about 42% of calories, although most of it was unsaturated. They ate the least saturated fat. They ate an ungodly amount of fiber, the women about 40 grams, men about 60 grams a day.


Alessandro Adami, MD said...

to your opinion/knowledge is it reasoneable ramified amino acids supplementation while on a vegan diet? I had a definite muscles lowering and this might have contributed to a recent sport injury with bone fracture. Thanks. Alessandro

Bix said...

Hi Alessandro,

I don't know about the supplements, but I can speak to the food part of your question.

A good rule of thumb for protein intake is the Institute of Medicine's 0.8g protein/kg body weight. It varies of course depending on age, gender, disease state, activity (e.g. bodybuilders may need more). But if you go with 0.8, and you weigh say 130 pounds (59 kg), that's about 47 grams of protein a day, from food.

If you were eating about 2000 calories a day, 9% of that, which this study considered "low," is 45 grams.

I'm just passing on the RDAs (Recommended Dietary Allowances) here. It's always good to meet with a professional who can ascertain your specific needs.

Bix said...

If you want to convert your weight in pounds to your weight in kilograms (or vice versa), go to Google and type in:

118 pounds in kg


218 lbs in kg


54 kg in pounds

Google is a great conversion tool!

Alessandro Adami, MD said...

Thanks Bix.
In my intention the RAA supplementation might make the diet easier as you have not to excessively worry about the quality and variety of the vegetal protein intake. another option is to reintroduce a modest amount of meat.

Thanks again!


preserve said...

I wonder if all three groups maintained the same muscle mass levels.

A few years ago I read that that elevated muscle mass weakens the immune system by taking up the white blood cells.

Ie. The runners eating protein, are probably taking a greater toll on their immune system through muscle development then their sedentary vegetarian counter parts.