Monday, April 29, 2013

How Much Protein Should You Be Eating?

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The answer – wait for it – depends on who (and what) you are. Your goals, your age, your activity levels, your size, and your health status all impact how much protein you need. And although individual protein requirements ultimately depend on dozens of variables that we can’t really know, there are some baseline intakes that can serve as a foundation for different groups. Let’s take a look.

The Sedentary

The RDA of 0.8 g protein/kg bodyweight or 0.36 g protein/lb bodyweight assumes you are sedentary, uninterested in gaining muscle, and free of health issues that might compromise your lean mass. If that describes you, the RDA is a good baseline from which to experiment. Just don’t go below that.

The Active

Athletes need more protein than the average person, but perhaps not as much as most fitness enthusiasts think (or consume). A 2011 paper on optimal protein intakes for athletes concluded that 1.8 g protein/kg bodyweight (or 0.8 g protein/lb bodyweight) maximizes muscle protein synthesis (while higher amounts are good for dieting athletes interested in preserving lean mass), whereas another settled on “a diet with 12-15% of its energy as protein,” assuming “total energy intake is sufficient to cover the high expenditures caused by daily training” (which could be quite high). One study even found benefit in 2-3 g protein/kg bodyweight (0.9-1.4 g protein/lb bodyweight) for athletes, a significant increase over standard recommendations. That said, I wouldn’t be too quick to discount anecdotal evidence or “iron lore.” A significant-enough portion of the strength training community swears by 1-2 g protein/lb bodyweight that it couldn’t hurt to try if lower amounts aren’t working for you.

The Dieters

Weight loss involves a caloric deficit (whether arrived at spontaneously or consciously). Unfortunately, caloric deficits rarely discriminate between lean mass and body fat, while most people are interested in losing fat, not muscle/bone/tendon/sinew/organ. Numerous studies show that increasing your protein intake during weight loss will partially offset the lean mass loss that tends to occur. In obese and pre-obese women, a 750 calorie diet with 30% of calories from protein (about 56 grams) preserved more lean mass during weight loss than an 18% protein diet. Another study in women showed that a 1.6 g protein/kg bodyweight (or 0.7 g protein/lb bodyweight) diet led to more weight loss, more fat loss, and less lean mass loss than a 0.8 g protein/kg bodyweight diet. Among dieting athletes, 2.3 g protein/kg bodyweight (or a little over 1 g protein/lb bodyweight) was far superior to 1.0 g protein/kg bodyweight in preserving lean mass. And, although specific protein intake recommendations were not stated, a recent meta-analysis concluded that high-protein weight loss diets help preserve lean mass.

The Injured

Healing wounds increases protein requirements. After all, you’re literally rebuilding lost or damaged tissue, the very definition of an anabolic state. One review recommends around 1.5 g protein/kg bodyweight or close to 0.7 g protein/lb bodyweight for injured patients.

The Elderly

The protein RDA may not suffice for older people, who lose thigh muscle mass and exhibit lower urinary nitrogen excretion when given the standard 0.8 g protein/kg bodyweight. What’s good for the goose may not be good for the elderly, frail gander. More recent studies indicate that a baseline intake of 1.0-1.3 g protein/kg bodyweight or 0.5-0.6 g protein/lb bodyweight is more suitable for the healthy and frail elderly to ensure nitrogen balance. As always, active seniors will probably do better with slightly more, and evidence suggests that increasing protein can both improve physical performance without necessarily increasing muscle mass and increase muscle mass when paired with extended resistance training in the elderly.

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