To eat protein or not to eat protien that's my question

Based on the study below, one should avoid high GI foods. We all know this.

RESULTS: Serum IGFBP-1 declined markedly after both meals, but the mean (+/-SEM) change at 4 h was significantly (P < 0.01) more prolonged after the low-GI meal (-55 +/- 20 ng/mL) than after the high-GI meal (-13 +/- 15 ng/mL). Conversely, the change in serum IGFBP-3 concentration at 4 h was significantly (P < 0.05) higher after the low-GI meal (251 +/- 102 ng/mL) than after the high-GI meal (-110 +/- 96 ng/mL); the same pattern was observed at 2 h. Changes in IGFBP-2, free IGF-1, and total IGF-1 responses were minimal and did not differ significantly from those during the 4-h fast.

CONCLUSION: Acute changes in IGFBP-3 after low-GI and high-GI foods may provide a biologic mechanism linking cell multiplication with greater consumption of high-GI carbohydrates.

Source: The glycemic index of foods influences postprandial insulin-like growth factor-binding protein responses in lean young subjects. http://www.ncbi.nlm.nih.gov/pubmed/16087978

According to this study one also must restrict protein,

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: Long-term effects of calorie or protein restriction on serum IGF-1 and IGFBP-3 concentration in humans.
http://www.ncbi.nlm.nih.gov/pubmed/18843793
full: http://onlinelibrary.wiley.com/doi/10.1111/j.1474-9726.2008.00417.x/full

I thought protein was essential for healthy hair, vegans that don't eat enough have hair loss.

But, I also heard that too much protein shortens the life span, increases bad POPs in the body. It is also connected to IGF-1.

How much (organic-grass fed animal, and/or plant-based) protein should I eat??????