The study, which was partially funded by monosodium glutamate (MSG) supplier Ajinomoto and published in Neuropsychopharmacology, assessed the changes in the brains of healthy young women after they ate chicken broth with added MSG or plain chicken broth as a control.
The researchers used three ways to detect changes in the subjects, 41 healthy, non-obese women aged between 18 and 30.
Firstly, a computer test measured inhibitory control, a mental process that plays a role in self-regulated eating. Secondly, participants wore special glasses that tracked eye movements as they freely selected food during a buffet meal, and thirdly, functional neuroimaging scanned the brain while they chose food.
They found that those in the MSG group performed better in the inhibitory control test and had a more focused gaze during the buffet. The brain scanning also showed a heightened activation of a left prefrontal cortex region related to successful self-control.
The MSG soup group also ate less saturated fat than the control.
According to the researchers, the findings represent the first evidence to date regarding a potential effect of MSG on neurocognitive processes that are relevant in supporting healthy eating behaviours and food choice.
“They also extend our understanding of how this umami substance may influence energy balance,” they add.
However, the authors note that the findings should be considered preliminary due to the limited sample size and "marginal" levels of significance.
Senior author Miguel Alonso-Alonso, assistant professor at the Center for the Study of Nutrition Medicine at the Beth Israel Deaconess Medical Center (BIDMC), noted that while much research has focused on the effects of sugar and sweetness on the brain, the study of savoury taste has been limited.
"The health impact of savoury foods is still a very understudied territory. As an observation if you go to parts of the world with exceptional health and longevity such as Asian countries like Japan or South Korea, there is a strong preference for foods in the savoury range, also the amount of daily intake of free glutamate is very high in those regions, and products are generally less sweet than in the US," he told FoodNavigator, adding that while these were observations only, they might point to something.
"I hope we can inspire more people to conduct research in this field and learn more about the connection between taste, eating behavior and health."
Too much of a good thing?
Glutamic acid is an amino acid that occurs naturally in tomatoes, soy sauce and certain cheeses, such as Parmesan, responsible for the umami flavour.
Glutamic acid and its salts (E 620-625), commonly referred to as glutamates, are authorised food additives in the EU and are added to a wide range of foods to enhance their flavour by giving them a ‘savoury’ or ‘meaty’ taste.
Last year, the European Food Safety Authority (EFSA) set a safe level for glutamate food additives but, since many Europeans are over this level, it asked the Commission to revise the current maximum levels permitted in food.
EFSA set an acceptable daily intake (ADI) level of 30 mg per kilo body weight (bw) per day for six food additives - glutamic acid (E 620), sodium glutamate (E 621), potassium glutamate (E 622), calcium glutamate (E 623), ammonium glutamate (E 624) and magnesium glutamate (E 625).
According to Alonso-Alonso, there are "lots of opportunities" for manufacturers to get involved in making food healthier.
"I think food manufacturers should invest more in R&D and understand more extensively the effects of the foods they produce, especially health and long-term implications. These days, with so much awareness and information available, consumers have high expectations on food.
"There is actually a lot that can be done from the industry perspective by reformulating food composition and guiding decisions on new products based on knowledge and research."
Source: Neuropsychopharmacology Journal
"Neurocognitive effects of umami: association with eating behavior and food choice"
Available online ahead of print, https://doi.org/10.1038/s41386-018-0044-6
Authors: Greta Magerowski, Paola Garza-Naveda, Joanna Radziejowska, Miguel Alonso-Alonso et al.