Study under review: Protein Intake Greater Than the RDA Differentially Influences Whole-Body Lean Mass Responses to Purposeful Catabolic and Anabolic Stressors: A Systematic Review and Meta-analysis.
The current recommended dietary allowance (RDA) for protein was established in the early 2000s. It’s the relative (grams per kilogram of bodyweight per day) amount necessary for the maintenance of good health in otherwise healthy people. The RDA was created to guide people on how to avoid a progressive loss of lean body mass from inadequate protein intake.
In the time since the recommendations were published, a lot of research has been done on protein intake, leading to debate about whether the current RDA of 0.8 grams per kilogram of bodyweight per day is too low. Questions have also been raised concerning whether the RDA is appropriate for people who are dieting or resistance training. Adequate protein intake is important during energy restriction because losses in lean mass account for 20-30% of total weight loss in the absence of exercise. Higher protein intake also tends to improve lean mass and strength gains with resistance training. Other arguments for a higher protein intake include its promotion of muscle protein anabolism, its thermic effect, and its satiation effect compared to other macronutrients.
The RDA is supported by a meta-analysis of studies with nitrogen balance measurements. However, there are some issues with the use of nitrogen balance to determine protein intake, including loss of food while eating, loss of nitrogen in feces or urine, and potential losses through the skin. These errors tend to overestimate intake and underestimate output, which could lead to incorrect positive balances that translate to a lower estimated protein requirement. Furthermore, nitrogen balance studies are generally less than 30 days in duration, and don’t directly measure what most people actually care about: lean mass.
Other Articles in Issue #64 (February 2020)
A higher protein diet for 48 hours can create a negative energy balance
Swapping carbs for protein may help people with obesity and prediabetes keep the weight off.
Deep Dive: Does early exposure reduce food allergies in infants?
Most early exposure studies to date looked at the effects of early exposure to a single potential allergen. Here, we cover a secondary analysis of a study that used six potentially allergenic foods.
Pomegranate’s possible UV-B(enefits)
Pomegranate contains compounds that could help skin become more resistant to UV-B radiation. How well does it actually work, though?
Interview: Matt Stranberg, MS, RDN, LDN, CSSD, CSCS
Dietitian and exercise scientist Matt Stranberg covers the ins and outs of disordered eating and problematic physical activity in this detailed interview.
Omega-3s may make mild cognitive impairment a little bit milder
This meta-analysis found a small impact of omega-3 supplementation on a measure of cognition in people with mild cognitive impairment.
Deep Dive: Investigating the effects of folate and zinc on male fertility
While folate and zinc are essential for processes necessary for male fertility, it may be possible to have too much of a good thing.
Nulls: November–December 2019
Welcome to the first installment of NERD Nulls — a rapid-fire roundup of some nutritional studies that didn’t find a clear effect!