Older people often have a decreased appetite but an increased protein requirement. Photo Shutterstock A balanced plant-based diet stimulates muscle development in active elderly people just as much as an omnivore diet does. That is the conclusion PhD student Jacintha Domić (Human Nutritional Biology) reached based on new research results.
Some target groups require extra attention for the protein transition to be successful. These are the groups more likely to suffer from nutrition deficiencies, says Jacintha Domić. ‘There are factors leading us to suspect the elderly will face health risks if they opt to switch to a vegetarian diet.’
Plant proteins, for example, contain fewer muscle-stimulating amino acids than animal proteins. Domić: ‘Moreover, plant-based foods contain relatively less protein; the quantity is lower. That means you would have to eat more in absolute volume to ingest all the necessary building blocks through plant-based foods. But older people often have a lower appetite and an increased protein requirement.’
Lunch on the campus
Domić studied the effect of a plant-based diet versus an omnivore diet on the elderly in two consecutive ten-day periods. Half of the participants started off with a vegetarian diet and switched to omnivore after ten days; the other half did the exact opposite. ‘The menus were as similar as possible in terms of proteins and calories, with the only difference being whether the products were plant-based or animal-based in nature. Soy yoghurt instead of dairy yoghurt, and diner with chickpeas or a meat substitute instead of minced meat,’ Domić explains.
Because of the stringent rules for food intake, the test subjects had lunch in Helix every day, and they were given their takeaway dinner, snack, and breakfast the following morning. Domić used so-called heavy water (in which a marker attached to hydrogen atoms latches on to the test subjects’ amino acids, to study how rapidly these building blocks were absorbed into the muscles.
Very active
The muscle protein synthesis, a marker for muscle retention, showed no difference in either of the eating patterns, contrary to Domić’s expectations. She offers an explanation: ‘Our research dieticians meticulously designed the menus, which were highly balanced and included ample proteins and products containing relatively high-quality proteins compared to most plant-based products.’
‘Moreover, the participants in this study were highly active, putting in an average of 12500 steps a day. Even the least active subject still managed to log 9000 steps. The more active a person is, the more protein-sensitive their muscles. We expect that the quality of the protein is less of a factor in such cases, as the muscles are eager to absorb these building blocks. It is possible that the reduced protein sensitivity in older people is not the result of ageing but of reduced activity levels.’
Do-it-yourself
In a follow-up study, which was completed, but the results of which have not yet been published, the doctoral candidate studied the long-term effect a plant-based diet has on muscle volume. She also studied the added effect of weight training in combination with a plant-based diet,
That study allowed subjects to select what they wanted to eat as long as there were no animal products. ‘That also provides us with insight into how people choose their own plant-based diet, which mimics reality closer.’
