For decades, the food additive monosodium glutamate (better known as MSG) was demonized in the West. More recently it has been discovered to be harmless, or at least the sodium component is no worse than salt. Now, however, we're seeing evidence the once-derided molecule could be the gateway to sticking to an intended diet.

Despite anecdotal accounts of people experiencing reactions after eating MSG-heavy meals, there is no strong evidence the flavor-enhancing amino acid is unsafe. Indeed historians have traced the widespread belief of its harms to racism, a consequence of MSG synthesis being discovered in Japan, and Americans and Europeans mostly encountering the molecule in Asian restaurants.

A new paper in Nature Neuropsychopharmacology concludes people who allowed the xenophobic scare campaigns about racing hearts and headaches after MSG-rich meals to affect their diet weren’t just missing out on sensational tastes. They were also making it harder to keep their other choices healthy.

Studies of people who are struggling to lose weight have usually, but not always, found eating broth with MSG before meals reduces their overall calorie consumption, compared to consuming an otherwise identical soup without MSG. However, the mechanism was unexplained. Consequently, Dr Miguel Alonso-Alonso of Harvard Medical Center ran a similar test, but tracked the participants' behavior when presented with a buffet meal, including using computerized eye-tracking and neuroimaging of brain responses.

Such detailed observations are only practical with small sample sizes, in this case, 30 women aged 18-30. Consequently, the findings need to be treated with care.

Nevertheless, Alonso-Alonso reports the MSG did not significantly reduce calorie consumption in his subjects, but led to healthier choices, particularly eating less saturated fats. Moreover, the greatest effects were seen among the women who described themselves as lacking self-control and being prone to binge eating.

The eye-tracking showed that after eating MSG, participants were more focused on the meals they had chosen, rather than being distracted by other options in the buffet, or even switching between portions.

After MSG consumption there was more activity in the left prefrontal cortex, the part of the brain that has previously been linked to self-control when it comes to food choices.

Although understanding of the mechanism remains incomplete, Alonso-Alonso and co-authors think it may have been a result of glutamate sensing in the stomach, rather than its umami taste, since the participants were usually unable to tell which broth they had been given.

The study only looked at one meal, so the question of whether the effects of glutamate delivered would wear off if taken too often remains unanswered. Moreover, the old cliché runs that an hour after eating Chinese-American meals people feel hungry again – the truth of which Alonso-Alonso didn’t investigate.

[H/T: Haaretz]