A food source with a high concentration of onion protein may not be a bad choice for vegetarians and vegans.
In a recent study published in the British Medical Journal, researchers at Imperial College London looked at the nutritional content of foods purchased from supermarkets across the UK and found that an onion’s nutritional value was higher in supermarkets with a higher percentage of vegetable protein.
They found that, while vegetable protein content was the highest in supermarkets, the highest percentage of protein in an onion was in the proportion of protein from plant-based sources.
In this way, their research found, it was the more plant-derived ingredients in a vegetable such as onions that could boost the nutritional value of a food.
The study was carried out by researchers from Imperial College’s Department of Nutrition and Dietetics, and the University of Birmingham.
The researchers compared the nutritional profiles of foods that were labelled as containing vegetable protein and those labelled as not containing it with those of foods containing either animal or plant protein.
The scientists found that the higher the percentage of plant- derived protein in a food, the greater the nutritional benefit.
The nutritional value can be influenced by factors such as its processing, preparation and cooking methods, the researchers found.
However, for the research to be credible, the study had to be carried out with a larger sample size than the other studies the researchers had studied before.
However the researchers also found that there was a clear difference between vegetable and animal protein in terms of nutritional value.
For example, while the average protein content in a cooked vegetable such a carrot or eggplant was about 0.8%, in a meat-based chicken or beef steak the average was about 4%.
The researchers also looked at food types in which the average vegetable protein was higher than that of the average meat- or poultry-based protein.
For instance, an eggplant cooked with meat would have a protein content that was 2% higher than an egg or steak cooked with a chicken or turkey.
Similarly, an onion cooked with beef would have an average protein level of 6% higher, compared with a vegetable or a non-vegetable vegetable.
However these differences were not as great as they could be when the researchers took into account other nutritional factors such the processing and preparation of the food.
For the study, the team included about 1,000 people aged 18 and over and had access to a range of foods.
Foods were identified from food packaging, food-related labels, food safety and nutrition advice.
The food was then analysed using a statistical method that takes into account the characteristics of the foods and the proportions of plant and animal proteins in them.
For this analysis, the group of people who ate a diet of meat, eggs, poultry and eggs or fish were excluded.
This meant that, of the 1,019 people, 2,904 people ate no meat or eggs, 1,099 people ate eggs and 1,095 people ate fish.
The research team found that people who consumed a vegetarian diet had significantly lower intakes of protein and vegetables, but significantly higher intakes of animal protein.
Onions were the highest on the list, with an average of about 2.7%.
In contrast, the average plant protein intake was 4.1% of the people’s total protein intake.
This is consistent with previous research, in which plant- and animal-based proteins are also found in different foods, such as tomatoes, cauliflower and potatoes.
The authors conclude that a vegetarian or vegan diet is likely to be more likely to provide higher levels of dietary protein than a meat or poultry based diet.
However this may be down to the different plant-protein requirements in different countries.
The nutrition findings in this study may help inform future dietary guidelines and food labels for vegetans and vegan, and vegan-only diets.
For more information on nutrition and health, please visit the British Dietetic Association.
The ABC’s The Feed has been running a series of posts exploring nutrition and the environment for many years.