What should we advise heavily exercising patients about extra protein intake?


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26 Apr 2018

A growing trend for exercise has led to a surge in products designed to up pr protein intake. Rod Tucker looks into the research behind the craze

Our supermarket shelves carry a wide range of high protein products such as shakes or snack bars and there are even high protein versions of cereals (e.g. Weetabix, Shreddies) and chocolate bars (Mars, Snickers).

According to a report by Mintel, the most common reason for taking high protein products among non-athletes was a belief that they did not obtain enough through their diet. Current Government recommendations are that men and women aged 19 to 64 require 55.5g and 45g/protein per day respectively and the reference nutrient intake (RNI) for protein is 0.75g/kg

Data on our actual intake suggests that men and women on average consume 65g and 54g per day. However, a recent review suggests that an intake of protein higher than the RNI leads to an increase in lean body mass and health benefits particularly in older adults. One concern with higher protein intake is the effect on the kidneys. Though glomerular filtration rates increase in response to a greater protein load, this only becomes a problem for those with existing kidney disease. In fact, there is little evidence that a high protein diet (1.5g/kg/day) is dangerous for healthy adults and may, in fact, be associated with some health benefits.

Many people who engage in resistance training (ie weight lifting) take extra protein in the belief that it will help build stronger muscles. So does adding extra protein to our diet really help us mere mortals if we pump iron a few times a week? A recent study has attempted to answer this question.

The study was a systematic review of the effect of protein supplementation on resistance training induced gains in muscle mass and strength. The authors included 49 studies with 1863 patients that were longer than 6 weeks in duration. The review found, unsurprisingly, that resistance training lead to increases in the one rep maximum (ie the maximum amount someone can lift once) and muscle mass.

The addition of protein supplements increased the one rep max and muscle mass significantly, though the increases were small – 2.49kg and 0.3kg respectively. Changes in muscle mass and strength occurred to a greater extent in younger people and those who were already training compared with older adults who seemed more resistant to increases in muscle mass. The review also noted that consuming more than 1.62g/kg/day provided no additional benefit.

What this review demonstrated is that the practice of lifting weights is by far the greatest stimulus to improved strength and muscle size, though consuming more protein does offer a small, additional benefit.

So, next time someone asks about buying one of those ‘high protein’ products, provided they are healthy, it is unlikely to be harmful and may even offer some benefits. For those desperate to have huge muscles, extra protein might help, but nowhere near as much as the workout itself. Just tell them the old maxim: no pain, no gain.

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