Online exclusive
As well as Jennifer Bowden’s columns in the NZ Listener and here at listener.co.nz, subscribers can access her “Myth busters” column, in which she explores myths around food and nutrition. This week, she explores the truth about protein.
In the world of nutrition, protein often takes the spotlight as the hero of the diet. It’s praised for everything from building muscle to boosting energy. But is more protein always better, or are we overestimating its benefits? Research suggests there is more to the topic than the marketing slogans promise.
Protein, fat, and carbohydrates are vital dietary macronutrients that our body requires. Protein is used for energy and as a building block in numerous complex molecules that perform different roles.
These include functional roles, such as digestive enzymes, oxygen transport in the blood, immune system antibodies, and structural roles in our muscles. The body of an average 70kg adult contains about 11kg of protein, of which around half is skeletal muscle.
In New Zealand, the recommended dietary intake (RDI) of protein for adults is 52g daily for men and 37g for women. That increases for ages 70 and over to 65g for men and 46g for women daily, due to their higher protein maintenance requirements.
The average Western diet provides enough protein for most adults, with just 2% of New Zealand adults eating inadequate protein levels, according to the 2008/09 NZ Adult Nutrition Survey. However, the over-70s didn’t fare so well, with 13%-16% not meeting their higher protein needs.
Athletes, too, often have elevated requirements because their protein needs for fuel and muscle maintenance increase with training intensity and duration. Some athletes do take protein supplements for specific reasons, noted a 2019 review in Nutrients. For example, branched-chain amino acid supplements, which studies suggest may improve training performance and reduce muscle soreness post-training.
However, according to the Australian Institute of Sport, even athletes with tough training regimes can typically meet all their protein needs without supplementation.
Interestingly, gym goers and non-professional sportspeople often consume protein and amino acid-based supplements in addition to a protein-rich diet, even though their workload typically does not meet the levels of athletes. Their physical activity levels generally fall within the boundaries of the protein RDI advice for the general population. Yet they still choose to unnecessarily supplement with more protein.
High protein diets result in more undigested protein transiting through the stomach into the large intestine, where it is fermented and alters the gut microbiota. One clinical trial found a high-protein diet increased the production of hazardous metabolites and reduced the production of cancer-protective metabolites in the colon, increasing the long-term risk of colon disease. Concerns have also been raised about high-protein diets negatively affecting bone health and kidney function. They are certainly harmful for those with existing kidney dysfunction.
Moreover, nutritional supplements, including protein-based ones, are often contaminated with banned substances such as anabolic steroid-like compounds and hormones, noted a 2023 article in Frontiers in Sports and Active Living. A 2008 review found some 15% of supplements were contaminated with anabolic steroids or other banned substances, and a 2017 review found between 12% and 58% were contaminated.
Indeed, a 2022 Consumer New Zealand investigation found six sports supplements sold in New Zealand contained illegal drugs – including amphetamine-like stimulants and medications used to treat ADHD and Parkinson’s disease.
Most athletes rely on expert guidance to manage their protein intake, avoiding the risks associated with accidental doping or unnecessarily overdoing their protein intake. Many consumers would benefit from a similar approach, as a well-balanced diet typically provides enough protein. Both animal and plant foods contain protein, so a varied diet ensures you get enough.
For the general population, including gym goers and weekend athletes, incorporating a small serving of protein-rich foods such as meat, poultry, fish, legumes, eggs, nuts, and seeds into 3-5 meals or snacks daily will meet your protein needs. Other foods such as milk, cheese, yoghurt, whole grains, vegetables, and fruit contain protein, too, which contributes to overall intake.
Focusing on a diverse and balanced diet allows you to easily maintain optimal protein levels for a healthy lifestyle, rather than singularly focusing on protein and following the misguided belief that “more is always better”.
