Studies examine optimal protein amount
Two new studies, one from the University of Stirling and another published in the Journal of Clinical Investigation (JCI) have both added to the mounting body of research into the benefits of dietary protein from both a health and athletic fitness standpoint, with both outcomes challenging preconceived notions that consuming more protein automatically equals more health benefits.
More muscles might not need more protein
Sports nutrition recommendations may undergo a significant shift after research from the University of Stirling has found individuals with more muscle mass do not need more protein after resistance exercise. Health and exercise scientists from Scotland’s University for Sporting Excellence found no difference in the muscle growth response to protein after a full body workout between larger and smaller participants.
Kevin Tipton, Professor of Sport, Health and Exercise Science in the Faculty of Health Sciences and Sport, said:
“There is a widely-held assumption that larger athletes need more protein, with nutrition recommendations often given in direct relation to body mass.
In our study, participants completed a bout of whole-body resistance exercise, where earlier studies - on which protein recommendations are based - examined the response to leg-only exercise. This difference suggests the amount of muscle worked in a single session has a bigger impact on the amount of protein needed afterwards, than the amount of muscle in the body.”
Experts also found participants’ muscles were able to grow and recover from exercise better after a higher dose of protein. Consuming 40 grams of protein after exercise was more effective at stimulating muscle growth than 20 grams. This increase occurred irrespective of the size of the participants.
Until now the consensus among leading sports nutritionists, including the American College of Sports Medicine and the British Nutrition Foundation, is that weightlifters do not need more than around 25 grams of protein after exercise to maximally stimulate the muscle’s ability to grow.
Low protein diets could support glucose metabolism but
The research published in the JCI has concluded that very low protein diets (referred to as ‘dietary protein dilution’ in this study) could improve glucose metabolism in mice and humans- only five humans were researched. This review looked at stress response pathways in the liver and a link to obesity.
Commenting on the study, Dr Emma Derbyshire, public health nutritionist and a member of the Meat Advisory Panel, notes:
“The research was carried out in several phases, on both laboratory mice and humans. At this stage, however, it should be considered that the ‘human study’ was only comprised of five lean males with a mean body weight of 75.9kg. They were asked to consume a diet very low in protein – the equivalent to around 9% of calories from protein, or 12.8MJ/day for 7 days. This is ‘very’ low considering that mean protein intakes in the UK National Diet and Nutrition Survey are around 17-18% for adults. So, whilst changes in glucose metabolism were seen in the ‘short-term’, the longer-terms effects of sustaining such low levels of intake requires further research."
It should be considered that protein from sources such as lean, red meat is an important source of essential micronutrients including B vitamins and readily absorbed haem iron. For example, beef, lamb and pork are rich in niacin, vitamin B6 and vitamin B12 and zinc. Pork is a rich source of thiamin and beef a source of iron. The application of low protein/’protein dilution’ diets to the wrong population groups, such as young women, could exacerbate their risk of medical conditions such as iron deficiency anaemia.