moxsom said:
Speaking of good diets in general has anybody much knowledge on Calorie Restriction (CR) increasing life spans in most all taxa by a significant amount? I think this new(ish) research program is very interesting.
Yes. The whole concept of calorie restriction is to lower IGF-1 levels, which is shown to extend the lifespan and slow the aging process in many types of animals.
But. There was a study that got groups of humans together. One group of humans got a standard American diet, another group got the same food type just a much much smaller portion...then they looked at their IGF-1 levels...and guess what? They were the same!
Then the looked at a group of vegans; their IGF-1 levels were much much lower than the people eating the calorie-restricted-standard-American-diet. The scientist came to the conclusion that calorie restriction is not a factor in IGF-1 levels. They found out that it was the overall protein restriction that really makes a difference to IGF-1 levels.
Long-term effects of calorie or protein restriction on serum IGF-1 and IGFBP-3 concentration in humans.
Luigi Fontana 1,2,3 , Edward P. Weiss 1,2,4 , Dennis T. Villareal 1,2 , Samuel Klein 1,2 and John O. Holloszy 1,2
1 Division of Geriatrics & Nutritional Sciences and 2 Center for Human Nutrition, Washington University School of Medicine, St. Louis, MO 63110, USA
3 Division of Food Science, Human Nutrition and Health, Istituto Superiore di Sanitá, via Regina Elena 299, 00161, Rome, Italy
4 Department of Nutrition and Dietetics, Saint Louis University, St. Louis, MO 63104, USA
Correspondence
Luigi Fontana, Washington University School of Medicine, Campus Box 8113, 4566 Scott Avenue, St. Louis, MO 63110, USA. Tel.: +314 747 1485; fax: +314 362 7657; e-mail:
lfontana@dom.wustl.edu
Copyright Journal compilation © 2008 Blackwell Publishing Ltd/The Anatomical Society of Great Britain and Ireland
KEYWORDS
aging • calorie restriction • IGF-1 • metabolism • protein restriction
ABSTRACT
Reduced function mutations in the insulin/IGF-I signaling pathway increase maximal lifespan and health span in many species. Calorie restriction (CR) decreases serum IGF-1 concentration by ~40%, protects against cancer and slows aging in rodents. However, the long-term effects of CR with adequate nutrition on circulating IGF-1 levels in humans are unknown.
Here we report data from two long-term CR studies (1 and 6 years) showing that severe CR without malnutrition did not change IGF-1 and IGF-1 : IGFBP-3 ratio levels in humans. In contrast, total and free IGF-1 concentrations were significantly lower in moderately protein-restricted individuals. Reducing protein intake from an average of 1.67 g kg?1 of body weight per day to 0.95 g kg?1 of body weight per day for 3 weeks in six volunteers practicing CR resulted in a reduction in serum IGF-1 from 194 ng mL?1 to 152 ng mL?1. These findings demonstrate that, unlike in rodents, long-term severe CR does not reduce serum IGF-1 concentration and IGF-1 : IGFBP-3 ratio in humans.
In addition, our data provide evidence that protein intake is a key determinant of circulating IGF-1 levels in humans, and suggest that reduced protein intake may become an important component of anticancer and anti-aging dietary interventions.
