Some elderly people lose the ability to taste umami – the savoury taste that defies the other flavour categories of sweet, sour, salty and bitter – as Takashi Sasano and his colleagues at Tohoku University in Sendai, Japan, discovered several years ago. Now, the team has found that they can boost these people’s umami tastebuds – along with their overall appetite – by feeding them MSG-rich kelp tea, which delivers a huge umami kick. But given all the scare stories about MSG, should we really be recommending it? We look at the evidence.
What is MSG?
Monosodium glutamate is a salt that contains glutamate – an amino acid present in our bodies, and one that plays a role in metabolism and communication between neurons. MSG was first produced by the Japanese chemist Kikunae Ikeda, who was also the first to describe the umami taste, in 1908. Ikeda identified glutamate as the key compound that gives dried seaweed its umami flavour, and went on to develop it in the form of MSG, which could easily be put in food.
Glutamate, and salts of it containing either sodium, potassium, magnesium, ammonium or calcium, are now routinely added to foods as flavour enhancers – and not just Chinese food. In Europe, these salts are listed as E-numbers (E620 to E625) in food labelling. But foods with high levels of glutamate, such as mushrooms, cheeses and fruit juice, won’t be labelled.
"A small fraction of people who eat MSG-rich foods report symptoms including nausea, headache and tingling sensations, collectively lumped under the banner of 'Chinese restaurant syndrome'."
How much MSG are we eating?
Research carried out in the 1990s found that people in the UK consume around 0.5 grams of MSG added to food every day. The figure is higher in Asian countries such as Japan and Korea, where people consume between 1.2 and 1.5 grams of added MSG every day.
Why does MSG have such a bad rep?
MSG has been called the silent killer lurking in your kitchen cabinets. A small fraction of people who eat MSG-rich foods report symptoms including nausea, headache and tingling sensations, collectively lumped under the banner of “Chinese restaurant syndrome”. MSG has also been blamed for obesity, high blood pressure and even snoring.
It sounds as if we should avoid foods containing MSG?
No: none of the above claims stands up to scientific scrutiny. The evidence that MSG is harmful tends to be based on poorly conducted studies with lots of confounding factors.
Some studies have found that large amounts of glutamate in the brain can cause damage – it is thought to be responsible for some of the tissue damage caused by stroke, for example. But this doesn’t translate to dietary MSG. Almost all of the glutamate that we eat, including that from MSG, is used up as an energy source by cells in the gut before it has a chance to get to any other parts of the body.
"The evidence that MSG is harmful tends to be based on poorly conducted studies with lots of confounding factors."
So there’s little point in buying foods advertised as free from MSG?
“MSG-free” foods are widely marketed, but claims made for them are misleading, says the Canadian government health department, Health Canada, because up to a quarter of food proteins contain glutamate naturally. And the amount of MSG added to convenience foods – typically between 0.1 and 0.8 per cent by weight – is in line with the proportion of glutamate found in foods such as tomatoes and parmesan cheese.
And why does kelp tea seem to boost elderly people’s appetite?
Sasano’s team thinks that the umami flavour of the tea stimulates the production of saliva. The researchers found that their volunteers produced more saliva in response to umami than to sour, salty, sweet and bitter flavours.
Saliva plays an important role in our ability to taste – it is thought to break down food into chemicals that our taste buds pick up, as well as protect taste receptors from damage. Sasano and his colleagues think that, by boosting the production of saliva, MSG can enhance the taste of food, stimulating a healthy appetite, something that tends to decline with age.
Journal reference: Flavour, DOI: 10.1186/2044-7248-4-10