April 12, 2024 — Creamy, thick, and velvety: Without emulsifiers, your favorite ice cream or muffin might not taste the same. Yet research warns that there is a darker side to these substances, from polysorbate-80 to carrageenan. Evidence links emulsifiers with upset gut microbiome, inflammation, and several conditions, from heart attacks to breast cancer.
What’s more, emulsifiersdon’t necessarily equal junk food. Such substances can be found in many foods that are often considered healthy, such as some low-fat Greek yogurts, trail mix bars, or oat milk.
There are over 100 different emulsifiers that can be added to foods. They prevent separation of oil and water, improving texture. A 2023 study found emulsifiers in as many as 95% of British supermarket pastries and cakes, 55% of breads, and 36% of meat products.
Certain goods that contain emulsifiers may not fit neatly into traditional dietary categories. Reduced-fat dairy products are a good example, said Benoit Chassaing, PhD, a microbiologist at the French National Institute of Health and Medical Research (INSERM). “If [producers] remove fat, they need to replace it with something else. So very often, if you buy fat-free or low-fat cream or cream cheese, it will be loaded with dietary emulsifiers,” he said.
From a health perspective, that’s bad news. In 2024, Chassaing and his colleagues published a study based on 92,000 French adults who provided detailed records of foods they ate, brand names included. The results revealed that people who ate the highest levels of emulsifiers had a significantly elevated risk of cancer. For carrageenans, which are emulsifiers derived from seaweed, the risk of breast cancer went up by 32%. Another type of emulsifier, mono- and diglycerides of fatty acids, upped the risk of prostate cancer by 46%. A related 2023 study linked the dietary intake of emulsifiers with an increased risk of cardiovascular disease. Among the worst offenders were microcrystalline cellulose and carboxymethylcellulose (CMC), which may be found in ice cream or processed cheese.
While population studies suggest a link between food emulsifiers and poor health, they do not prove that the additives directly cause the negative health outcomes. What can help are lab studies. For such experiments, researchers often use a human gut simulator, a machine that may resemble a row of old-school milk bottles connected via tubes to a telephone switchboard. The bottles contain gut microbiota taken from human stool, to which scientists add various emulsifiers (admittedly, the lab may smell pretty bad). In one such study published in 2024, researchers from Belgium showed that polysorbate 80, a synthetic emulsifier often used in dairy products and salad dressings, decreases the numbers of friendly gut bacteria, such as Faecalibacterium prausnitzii, while increasing the numbers of those associated with inflammation.
Andrew Gewirtz, PhD, a microbiologist at Georgia State University, said emulsifiers have long been considered safe for consumption because many of them pass through the body unabsorbed. It was “presumed that therefore they can’t possibly do anything negative,” he said. This view began to shift as we recognized the importance of gut microbiota for health. Now the fact that emulsifiers could reach the gut almost unchanged made them “prime suspects involved in perturbing the microbiota,” Gewirtz said.
When you eat something that contains emulsifiers, the nutrients and water in the food will be absorbed along your digestive tract. Various additives, however, will stay relatively intact. “We think that they can reach higher concentration in the gut,” Chassaing said. Once there, some emulsifiers can change microbiota composition and function, prompting gut bacteria to give off pro-inflammatory molecules. This, in turn, could lead to a variety of chronic inflammatory diseases, from diabetes to cardiovascular disease.
One of the strongest arguments for the negative effects of food emulsifiers came from a 2022 trial conducted by Gewirtz, Chassaing, and their colleagues. For that experiment, 16 volunteers were randomized to either eat an emulsifier-free diet or one containing high doses of CMC. For 11 days the participants were housed at a local hospital and fed an identical diet, with one exception: some of them received desserts made with CMC. The results showed that eating the emulsifier was linked with more complaints of abdominal discomfort, as well as the loss of health-promoting metabolites released by gut microbes such as the short-chain fatty acids.
“It did confirm the notion that emulsifiers are impacting gut microbiota, changing the species composition,” Gewirtz said.
For two of the participants, things got particularly bad — their gut bacteria invaded the normally sterile inner mucus layer of the gut, a condition which may lead to Crohn’s disease or ulcerative colitis. A 2024 follow up study revealed that this was likely due to the composition of the two participants’ gut microbiome.
They had “microbiota that were highly sensitive to the perturbation,” Chassaing said. If you transfer gut bacteria from such patients to mice, “you can drive very strong colitis,” he said. However, the trial was small, and, as Aaron Bancil, MD, a gastroenterologist at King’s College London, said, the participants were fed quite high doses of CMC: 15 grams per day. While some people may indeed ingest these kinds of doses with their regular diet, “it’s not going to be something that’s consumed often,” he said.
Other research suggests, meanwhile, that emulsifiers may impact human gut directly. When researchers from Italy applied dietary emulsifiers to human cells derived from colon cancer, they found that it made such cells proliferate faster. This could point to a role of emulsifiers in cancers of the gastrointestinal tract, confirming the results of the French population studies. Emulsifiers could also act as a gateway for other potentially harmful chemicals. In experiments conducted on both human cell lines and on rats, polysorbate 80 damaged the mucus barrier in the intestine, leading to its increased permeability — the infamous “leaky gut.” This helped phthalates, chemical compounds that are commonly added to plastics and which, once ingested, can be transformed into endocrine disruptors, to be easier absorbed by the body.
Animal research shows that consuming emulsifiers could also lead to anxiety. Mice fed CMC and polysorbate 80 showed changes in the brain areas responsible for the stress response, such as the amygdala. And if emulsifiers are fed to mice during pregnancy, such effects may be transferred to their offspring, too. However, according to Bancil, while animal models are informative, “we can’t fully translate those things over to humans.”
What’s more, not all emulsifiers appear equally harmful. When Chassaing, Gewirtz, and their colleagues tested 20 common dietary emulsifiers, they found that some, such as carrageenans, guar gum, and xanthan gum, had striking detrimental effects, while others, such as lecithin, were less damaging. Lecithin is a natural emulsifier, commonly derived from eggs and soy. As such, Gewirtz said, it doesn’t reach the gut unabsorbed the way synthetic emulsifiers do. On the other hand, “polysorbate 80, carrageenans, and also a lot of the gums, xanthan gum, guar gum — those ones are really, really aggressive for the microbiota,” Chassaing said.
There may be ways to protect the gut microbiome from harmful effects of dietary emulsifiers. When researchers fed mice mucus-fortifying bacteria, Akkermansia muciniphila, it prevented the damage caused by eating CMC and polysorbate 80. Yet Gewirtz warned that this doesn’t mean we should all rush to stock on akkermansia pills, since such supplements are “just not really well tested.”
The safest bet to keep your gut healthy would be to eat homemade foods and shy away from emulsifiers altogether. However, Bancil said, for some people, especially those with a busy lifestyle, this may be tricky to do. As such, checking out labels might be a better approach. “Very often there is an alternative,” Chassaing said. “You have a lot of dietary emulsifiers in ice cream, but you can find some brands that will be doing emulsifier-free ice cream,” he said.
Counterintuitively, cheaper foods are sometimes less loaded with emulsifiers than are pricier options. “There might be a branded ketchup, and there might be a supermarket’s own brand. The branded one, which might be more expensive, might have emulsifiers in it, but the own brand might not have emulsifiers,” Bancil said.
Same goes for foods marketed as healthy, said Megan Rossi, PhD, a nutritionist at King’s College London. “Let’s just be cautious and not automatically assume that they’re better for you,” she said.
Yet studying labels is not without its challenges. That’s because “emulsifiers might be labelled as different things,” Bancil said. So carboxymethylcellulose could appear on a label as CMC, cellulose gum, modified cellulose or, in Europe, as E466. Carrageenan could be called Irish moss, Eucheuma extract, or E407.
According to Gewirtz, considering the results of animal research and in vitro studies, as well as of the preliminary human trials, the food industry should be encouraged to look for safer alternatives, particularly to synthetic emulsifiers. Chassaing hopes that “in the future we’ll be able to select and to favor the use of additives that are much more well tolerated by the microbiota.” However, he said, “this is not yet the case.”
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