The German popular science publication understands what the "fifth taste" is, where glutamates come from in food and how they affect the human body. Do taste enhancers actually cause obesity, cancer, and even Alzheimer's? Maybe they are even good for health - or is it the machinations of fast food manufacturers?
Chefs and foodies alike nod when they hear that glutamate is not good for food. It is probably even unhealthy. A certain amount of skepticism is indeed justified.
Anyone who makes a soup from a bag, a ravioli from a tin, or a handful of cereals, in most cases consumes monosodium glutamate with these products. Glutamate is used as an additive in various foods to make them taste better. But this substance has been controversial for decades. Obesity, Alzheimer's, Parkinson's and diabetes are just some of the diseases that are discussed in the context of glutamate. Is it right? Or is it over-worrying? And why are foods with added glutamate so much tastier? Here are the answers to basic questions.
What is Glutamate?
Glutamate is an additive used in food products as a flavor enhancer. Moreover, glutamate is not an artificial product invented by man. Glutamates occur naturally and are a salt of glutamic acid, one of the amino acids. Vegetable protein contains up to 20% glutamic acid, animal protein - eggs, milk or meat - up to 40%. That is, every product containing protein also contains glutamic acid.
It is especially abundant in eggs, fish, soybeans, yeast, tomatoes and cheese. For example, Roquefort cheese contains 1,280 mg, Parmesan cheese 1,200 mg, and soy sauce 1,090 mg per 100 grams. It is during the fermentation of food that, among many other substances, glutamate is also released. Salt occurs even when cooking sauerkraut or beer, albeit in small quantities.
Paul Breeslin, a taste researcher at Rutgers University in New Jersey, suggests that people began to prefer foods containing glutamate when foods that used fermented foods with a long shelf life were introduced.
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Glutamic acid acts on the taste buds on the human tongue and produces what is called the umami sensation - a taste that is perceived as spicy or meaty and described as strong, earthy, or gourmet. In 1908, Japanese chemist Kikunae Ikeda came up with the idea of a fifth taste, "umami," in an attempt to figure out the source of the spicy aroma of kombu dashi broth. He discovered that glutamate was found not only in Justus Liebig's then successful meat extract, but also in this traditional Japanese seaweed soup. Both were "umami", which means "good taste" in Japanese. It was only with the discovery of umami receptors in the tongue about 20 years ago that Ikeda's theory that umami is a separate taste was finally proven.
What foods contain glutamate?
Instant food manufacturers have used glutamate as a flavor enhancer for over 100 years. Salt is produced mainly from molasses by genetically modified bacteria. Consumers recognize these substances by the “E” designations from E620 to E625. As a flavor enhancer, glutamates are used in instant products, soups, sauces, canned meat, fish and vegetable preserves, as well as chips, seasonings and a substitute for table salt.
Glutamic acid and its salts are permitted in almost all food categories with a maximum of 10 g of supplement per kg. The most famous glutamate is the sodium salt of glutamic acid, that is, monosodium glutamate (E621).
What does it work for?
The body itself produces glutamate - about 50 g per day. It is found in muscles, brain, kidneys and liver. This glutamate is endogenous - in contrast to exogenous glutamate, which enters the human body with food. They are identical in chemical composition.
Central Europeans get an average of 0.3 to 0.5 g of glutamate per day from instant foods, while Asians get as much as 1.5 g. From natural foods, Europeans get 1 g of free and 20 g of protein-bound glutamate. Only free glutamate has an aromatic taste.
In the body, glutamate is decomposed only in the small intestine and helps to deliver energy to its cells or participates in the construction of important molecules in the intestine. Only a small part of it ends up in the blood. Glutamate affects more than just the taste cells on the tongue. Umami receptors are also found in the intestines and sperm.
Endogenous glutamate also has many functions. For example, it is the most abundant neurotransmitter in the central nervous system. It allows the transmission of signals between cells and also contributes to memory. Too much glutamate in the brain, however, can cause brain cells to die. Diseases such as Alzheimer's, Huntington's, Parkinson's, or multiple sclerosis are associated with an increased concentration of glutamate in the brain.
Harmful to health, especially for children?
Back in 1968, skepticism arose about the supplement after American physician Robert Ho Man Kwok published an article entitled "Chinese Restaurant Syndrome" in the New England Journal of Medicine. He wrote about himself: after visiting a Chinese restaurant, he was bothered by numbness, weakness and palpitations. His fellow doctors diagnosed him as allergic to soy sauce. He objected that at home he also uses soy sauce for cooking and tolerates it perfectly.
It soon became clear that the glutamate added to the dishes was the cause of the malaise. Scientific articles have appeared on the dangers of glutamates. Public pressure became so great that these substances were banned from adding to infant formula.
The so-called "glutamate intolerance" became an explanation for all possible nonspecific symptoms such as headache, itching, nausea, feeling of heaviness in the abdomen, joint pain or colic in infants. From a medical point of view, all this is inexplicable. Ian Mosby, a historian at New York University in Toronto, believes that racism also played a role in discussions about Chinese restaurant syndrome in the 1960s and 1970s. The food of Chinese migrants was considered "exotic, rare and extremely unusual."
The skeptical attitude towards glutamate persists today. In addition to intolerances, it is believed that the supplement can cause inflammation, pain syndromes, heart problems, as well as diseases of the brain and liver. Although the suspicions that have arisen have been refuted, the European Food Safety Authority is now re-checking the research data for preventive purposes. Recently, it has become clear that many people are consuming more than the safe 30 g per kg of body weight per day, primarily due to the large amount of instant foods in the diet.
Additionally, some new research questions the safety of glutamate. However, in a recent review - independent, that is, not commissioned by a company interested in promoting glutamate - scientists concluded that these controversial studies are often of poor quality. They are based on a very small number of volunteers, often without control groups, and in some animal experiments, the dose was extremely high and was injected into the blood.
The role of glutamate in its intolerance, cancer and obesity, as well as its effects on the brain, on the contrary, have been studied in detail and professionally. In highly sensitive people, after consuming products containing glutamate, hypersensitivity may indeed develop. But this requires really large doses of the supplement, that is, more than 3 g of free glutamate on an empty stomach. Doctors advise asthmatics to avoid excessive consumption of instant foods, including due to the fact that the body may react to the additive.
However, the 2012 survey was unable to confirm the relationship. Two studies with just 24 participants found no evidence that reducing glutamate intake reduced asthmatic symptoms. On the other hand, there is more data about healthy people who use glutamate in small doses. And no research proves that Chinese restaurant syndrome actually exists.
Glutamate in instant soups and similar foods has been consistently accused of developing brain diseases such as Alzheimer's, Parkinson's, or multiple sclerosis. After all, there is research supporting that excessive amounts of glutamate in the brain may contribute to these diseases. But here we are talking about endogenous, that is, glutamate formed in the brain. Glutamate, which enters the body from the outside, according to the unanimous opinion of scientists, in healthy adults cannot overcome the blood-brain barrier and, therefore, cause these diseases. However, it is not known whether the blood-brain barrier is not more patent in infants with meningitis or, for example, internal bleeding.
There is little evidence that glutamate contributes to cancer. Although it is known about the increased content of glutamate in the blood and tumor tissues in prostate cancer, which is why it was suggested that this substance may play a role in the onset of cancer. But this issue has not been fully investigated.
Most often, researchers are studying the appetite-enhancing effects of a flavor enhancer, which is also added to animal feed. Critics conclude that glutamate can be addictive and lead to obesity. But this fear has not yet been confirmed. Only in very high doses does glutamate increase appetite. And some works even talk about the opposite effect: the feeling of fullness occurs earlier, which may be associated with the pleasant taste of products with glutamate.
Maybe glutamate is even useful?
According to a 2009 study, seniors have better appetite when they eat especially flavorful soups. So glutamate may even be beneficial - especially for the elderly. Umami taste can counteract age-related loss of appetite and related problems, when weight loss increases the risk of various diseases.
However, it is suspected that these and other studies on the beneficial effects of the flavor enhancer were funded by interested companies. A truly neutral picture emerges only as a result of a series of completely independent studies.
What are the alternatives?
Glutamate is not allowed in organic foods and baby food. As the industry has noticed that consumers are looking to buy products without a lot of additives, they are looking for an appropriate alternative. For example, in instant products, including their ecovariants, yeast extract is used as a seasoning, which naturally contains a large amount of glutamate. It does not require an “E” or lettering, but its availability must be indicated on the packaging.
Thanks to the efforts of consumer advocates, the word “seasoning” can be seen in the description of such products: behind it are decomposed proteins, for example, from meat, yeast or soy, which affect the “taste and / or smell of soups, broths and other products”. And here most often glutamate is contained, which does not have to be indicated. So, soy sauce is a seasoning, and glutamates give it a rich taste.
In general, instant products with a lot of spices are not recommended to be consumed in large quantities, since they do not give the subtleties of taste and often mask poor quality ingredients. The German Nutrition Society has long been recommending the abandonment of flavor enhancers, especially in children's diets, since they lose understanding of the variety of natural foods.
Kathrin Burger