Archive for the ‘Protein’ Category

Calorie-restriction, Protein-restriction and free-IGF-1 / SHBG

Monday, November 22nd, 2010

Studies pertaining to Calorie-restriction (CR), Protein-restriction (PR) and free-IGF-1 and SHBG.

1)

Br J Cancer. 2000 Jul;83(1):95-7.
Hormones and diet: low insulin-like growth factor-I but normal bioavailable androgens in vegan men.

Allen NE, Appleby PN, Davey GK, Key TJ.
Cancer Epidemiology Unit, Imperial Cancer Research Fund, Radcliffe Infirmary, Oxford, UK.

Abstract

Mean serum insulin-like growth factor-I was 9% lower in 233 vegan men than in 226 meat-eaters and 237 vegetarians (P = 0.002).

Vegans had higher testosterone levels than vegetarians and meat-eaters, but this was offset by higher sex hormone binding globulin, and there were no differences between diet groups in free testosterone, androstanediol glucuronide or luteinizing hormone.

PMID: 10883675 [PubMed - indexed for MEDLINE]PMCID: PMC2374537

http://www.ncbi.nlm.nih.gov/pubmed/10883675

Full text PDF: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2374537/pdf/83-6691152a.pdf
PDF file: Hormones and diet-83-6691152a.pdf

2)

Aging Cell. 2008 Oct;7(5):681-7.
Long-term effects of calorie or protein restriction on serum IGF-1 and IGFBP-3 concentration in humans.

Fontana L, Weiss EP, Villareal DT, Klein S, Holloszy JO.

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Protein is a Stimulator of Free IGF-1

Friday, November 19th, 2010

It seems that protein (in meat or dairy) is a stimulator of free-IGF-1

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Aging Cell. 2008 Oct;7(5):681-7.
Long-term effects of calorie or protein restriction on serum IGF-1 and IGFBP-3 concentration in humans.

Fontana L, Weiss EP, Villareal DT, Klein S, Holloszy JO.

Division of Geriatrics & Nutritional Sciences, Washington University School of Medicine, St Louis, MO 63110, USA. lfontana@dom.wustl.edu

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.

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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.

Source: http://www.ncbi.nlm.nih.gov/pubmed/18843793
Full: http://onlinelibrary.wiley.com/doi/10.1111/j.1474-9726.2008.00417.x/full

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