How much protein is enough?

The recommended dietary allowance (RDA) is an estimate of the minimum average dietary intake level that meets the nutrient requirements of nearly all (~97%) healthy individuals.

According to this recommendation, the RDA for protein is 0.8 g/kg/d

Interestingly, as pointed out in a recent commentary by Robert Wolfe and Sharon Miller from the University of Arkansas published in the June 25 issue off JAMA, the term “recommended dietary allowance” is misleading as it is often misinterpreted as being the “optimal” rather than the “minimal” dietary requirement.

In fact, as illustrated in the commentary, if protein requirements are calculated based on a recommended proportion of energy intake [i.e. 10 to 35%], for a 70 Kg man requiring 3067 kg calories per day, 10% of energy as protein would translate into a protein intake of 0.95 g/kg/d whereas 35% of energy intake would translate to 3.3 g/kg per day. These values are obviously substantially higher than the RDA.

As blogged before, given the importance of maintaining appropriate protein intake to maintain muscle mass, strength and function, the issue of ensuring adequate protein intake during a caloric restricted diet becomes even more challenging. This means that caloric restricted diets need to at least provide a protein intake at the higher end of the Dietary Reference Intakes [DRI] or around 35% of total caloric intake and should perhaps err on the side of too high rather than too low.

The issue of maintaining appropriate protein intake is particularly important as close monitoring of body composition to detect disproportionate loss of lean body mass during weight loss is not routine part of patient monitoring during obesity treatment.

Perhaps, as recommended by Wolfe and Miller, the term “recommended dietary allowance” should be replaced by the term “minimal dietary requirement” to more accurately reflect the functional definition of RDA and avoid confusion regarding what is considered adequate protein intake.

AMS
Edmonton, Alberta