Protein

Protein requirements for runners are somewhat controversial. I'd recommend starting with these two articles that give good, research-based advice.

• International society of sports nutrition position stand: nutrient timing
• Examine.com How much protein do you need per day?

My personal observation as a relatively lean runner doing relatively high mileage, it seems that higher protein intakes have been beneficial to recovery and body composition. It also seems that timing my protein and carb intake so that my body doesn't break down muscle to replenish Glycogen stores after High Intensity Interval Training is also important.

1 Protein Absorption Rates

This table of absorption rates is useful in determining how quickly protein can be absorbed and how long digestion takes. Some of these numbers seem strange, as a raw egg contains 6g of protein, taking 4.6 hours to digest, and four eggs would take over 18 hours to digest.

Type	Absorption rate (g/h)
Egg protein raw	1.3
Pea flour	2.4
Egg protein cooked	2.8
Milk protein	3.5
Soy protein isolate	3.9
Free AA	4.3
Casein isolate	6.1
Free AA (profile as casein)	7-7.5
Whey isolate	8-10

2 How much protein in a meal?

There's quite a bit of research into how much protein can be consumed in a single meal for optimum muscle growth. Some of this research can be misleading as the protein is often given in a fasted state with no other nutrients, which makes it more likely that some of the protein will be burned for energy rather than going to muscle growth. A review of the available research concluded that >20g of protein in a meal may produced additional muscle growth, and suggests that 0.4 g/Kg/meal for a minimum of four meals/day is optimal. Slower digesting proteins may result in a higher level of protein intake being effective.