Microbial slime and a side helping of sand doesn\u2019t sound like much of a meal, but a startling amount of the food we eat today contains ingredients that are, at the very least, unexpected \u2013 and, at worst, dangerous, such as heavy metals from polluted soils.<\/p>\n
The Guardian\u2019s journalism is independent. We will earn a commission if you buy something through an affiliate link.\u00a0Learn more<\/a>.<\/p>\n Then there is the thorny question of what ultra\u2011processed foods in our diets might be doing to us. \u201cWhile each food additive, so\u2011called processing aid, fortificant and unrecognisably modified ingredient has been tested individually and declared safe, are they really?\u201d asks Chris Young, who runs the Real Bread Campaign for Sustain<\/a>, the alliance for better food and farming, and was named joint winner of Slow Food In The UK\u2019s 2025 person of the year award. \u201cThe studies are relatively small and short, leaving history littered with additives that we were once promised would not harm us but were later withdrawn or banned on health grounds. What might the long-term effect be of eating such substances, individually or in the cocktails created for each product and across our shopping baskets?\u201d<\/p>\n Processing isn\u2019t necessarily always bad \u2013 newly invented fermented fats and proteins could change how we feed the world. But processing and labelling can obscure exactly what it is we\u2019re eating. Here are 16 surprising ingredients that almost all of us consume without realising.<\/p>\n Maggots in your tomato puree Photograph: Dan Matthews\/The Guardian<\/p>\n A small amount of insect contamination is practically unavoidable in the fruit and veg chain. In the US, there is precise guidance<\/a> on how many \u201cfragments\u201d, and of what, are allowed in food, which makes for stomach-churning reading. US consumers may have to put up with 30 insect fragments per 100g of peanut butter, 60 fragments per 100g of chocolate, 225 per 225g of pasta, two maggots per 100g of tomato paste, one maggot per 250ml of citrus juice and up to 35\u00a0fruit fly eggs in one cup of raisins. Fortunately, the rules are tighter here. \u201cFood placed on the market must be free from visible insect contamination \u2026 there are no permitted tolerance levels for insect fragments,\u201d says a spokesperson for the Food Standards Agency (FSA). \u201cWhile minor, unavoidable contamination can occur in natural products, visible contamination, or anything that could compromise safety or quality, will generally trigger enforcement action.\u201d<\/p>\n Estimates suggest people in the US unintentionally eat around 450g\u00a0<\/a>of insects every year, but in many countries insects are a normal ingredient and a staple source of protein. The UK\u2019s edible insect trend of the mid-2000s has abated somewhat (yellow mealworms, house crickets, banded crickets and black soldier flies can be legally sold as food under UK law<\/a>), but if you eat icing, ice-cream, drinks, cake or sweets dyed red or pink with carmine (E120), you\u2019re eating food colouring made from dried and powdered cochineal bugs, also widely used in lipstick.<\/p>\n Cockroaches in your coffee<\/p>\n It has long been claimed that up to 10% of US coffee can be cockroach, but this is putting it a bit strongly: in the US, up to 10%<\/a> of green coffee beans can be infested with bugs before the whole lot has to be thrown away, and it\u2019s fairly easy to tell cockroaches and unroasted coffee beans apart and pick out any \u201cbeans\u201d that are moving, have been nibbled, or are full of eggs (ugh). Fragments of cockroach and other bugs can still make it as far as the packet \u2013 to a lesser extent in the UK and EU than in the US \u2013 but coffee growers tend to worry more about coffee berry borer: a\u00a0beetle that lays eggs inside the berries, before hatching and eating them from the inside out.<\/p>\n Worms in your fish<\/p>\n Eating fish containing dead parasitic worms sounds disgusting, but is \u2013 unfortunately \u2013 quite normal. According to the FSA, fish sold in the UK has to be inspected for visible evidence of parasites<\/a>, and most fish or seafood that is going to be eaten raw or lightly cooked \u2013 such as cold smoked fish, pickled fish and any molluscs destined to become sashimi \u2013 has to be frozen at -20C (-4F) for at least 24 hours to kill any parasites or larvae that remain after gutting and washing. Some worms and larvae are immune to being salted<\/a> or marinated, but all die after one minute\u2019s cooking at 60C. Eating live parasites or larvae can cause serious illness and even allergic reactions, which is why you should never make sushi or ceviche with fish that is not explicitly labelled \u201csushi grade\u201d. There are some exceptions: certain kinds of farmed fish are certified parasite free, as are a few types of freshwater fish.<\/p>\n Rocks in your tofu<\/p>\n Although lots of minerals occur naturally in food, many are added during processing, to fortify or as additives to give structure or colour, and that means digging them out of the ground. Calcium carbonate<\/a>, a\u00a0dough conditioner, is basically chalk, mined from pure chalk, limestone or dolomite, and both food-grade phosphoric acid<\/a>, a\u00a0preservative, flavour enhancer and acidity regulator, and monocalcium phosphate<\/a>, which is used in baking powder, are made from phosphate, which also has to be mined, mainly in Morocco and China.<\/p>\n Titanium dioxide, a bright white food colouring, is extracted from ilmenite, rutile or anatase ores. Small\u00a0amounts of silicon dioxide occur\u00a0naturally in our bodies, but when it is used to keep powdery foods, such as drinking chocolate, powdery, it is made from silica-rich sand and rocks. Both titanium dioxide and silicon dioxide are also used in toothpaste. There are concerns about whether nanoparticles of both might build up in the body and pose health risks. Titanium dioxide has been banned in the EU since 2022, and in 2024 the FSA and the Committee on Toxicity investigated claims that titanium dioxide might be able to cause DNA damage<\/a> or affect the immune system; they concluded that\u00a0more research is\u00a0needed.<\/p>\n Gypsum is used to make plaster for walls, but it is also added to packaged breads and baked goods as calcium sulphate to stop dough becoming sticky, and is used to firm up tofu. It\u2019s\u00a0generally considered safe, but eating a\u00a0lot of it can cause bloating and gas.<\/p>\n More obviously, rock salt comes from salty deposits laid down by receding oceans millions of years ago, which is why it\u2019s amusing to see it with\u00a0a use-by date.<\/p>\n Wood in your ice-cream Photograph: Dan Matthews\/The Guardian<\/p>\n Carboxymethyl cellulose and methyl cellulose, or cellulose gum, are used as thickeners, stabilisers and emulsifiers in everything from ice-cream and gluten-free pastries to low-fat desserts and chewing gum (they are also used in medicines, detergents and to make paper). Often described rather obliquely as coming from the cell walls of plants, they are usually made as a\u00a0byproduct of the wood pulp industry. (Carboxymethyl cellulose is odourless and tasteless, and fish processors and traders are occasionally caught surreptitiously injecting it<\/a> into prawns and other seafood<\/a> to make them heavier and therefore more valuable. This is harmless to human health but counts as food fraud.)<\/p>\n Things such as egg and mustard have been safely used for centuries to blend fats into liquids and to moisten food, but whether it is safe to eat the amount of modern emulsifiers that most of us currently consume is up for debate. A small study<\/a> published in 2022 suggested that carboxymethyl cellulose can cause stomach pain after eating and, in the longer term, may destabilise the balance of useful microbes in the gut.<\/p>\n Laxatives in your veggie sausage<\/p>\n Methyl cellulose is thermoreversible, meaning it forms a gel when heated but can melt when cold. It can help burgers and sausages made with pea or soy hold together when cooked, and it makes foods juicy, like meat. \u201cWhen you eat these things, they\u2019re pretty convincing,\u201d says Prof Barry Smith, co-director of the Centre for the Study of the Senses at University College London and a researcher into the interactions between flavour, taste and smell. \u201cThey have the texture of meat and some contain a\u00a0plant-based heme [iron-containing molecule] that smells of blood. But the fibre that makes them like meat is\u00a0so tough, our gut can\u2019t deal with it, so they put methyl cellulose in, which is a laxative.\u201d Some contain psyllium husk, too, also a\u00a0bulk-forming laxative.<\/p>\n Wax on your bananas Photograph: Dan Matthews\/The Guardian<\/p>\n Recipes often call for unwaxed lemons if the zest is going to be used, but it\u2019s not just citrus fruit that is given a\u00a0coating to prevent moisture loss \u2013 in\u00a0some countries, bananas are sprayed with chitosan, a preservative made from shellfish shells, and melons, avocados and grapes<\/a> are often coated, too. Some coatings are synthetic, while others are made from fruit peel; Tesco made headlines in 2022<\/a> when it flagged that some of its fruit was coated in shellac, a wax secreted by the lac beetle, making it unsuitable for vegans, while other brands use equally non\u2011vegan beeswax to keep their apples gleaming. Carnauba wax, which comes from the Brazilian palm\u2019s leaves, is a\u00a0less buggy alternative. (It\u2019s legal to wax organic fruit, but the wax cannot be synthetic.) Fruit waxes are considered food safe, but the wax sometimes contains fungicides and can also trap dirt, fungi and traces of pesticides, so it\u2019s worth scrubbing fruit well in hot water if you\u2019re going to eat the peel.<\/p>\n Microbial slime in your yoghurt<\/p>\n A lot of food additives are now made via microbial fermentation, and xanthan gum, a widely used thickener and stabiliser, was one of the first to be discovered, back in the 1950s. If you\u2019ve ever left a cabbage in your salad crisper long enough for it go slimy, you\u2019ve made your own xanthan gum, the result of a\u00a0bacteria called Xanthomonas campestris fermenting the plant\u2019s sugars and secreting a polysaccharide ooze (yum). It\u2019s used in everything from gluten-free breads and cakes to dairy-based and dairy-free desserts. Researchers recently found our gut bacteria can break down xanthan gum<\/a> and that eating it encourages particular groups of bacteria to thrive. What isn\u2019t clear yet is whether that is a\u00a0good, bad or neutral thing.<\/p>\n Food waste in your protein\u00a0powder<\/p>\n Understandably, most of the companies using waste to make new foods prefer to say they\u2019re using \u201cfood industry side streams\u201d to repurpose some of the vast quantity of potentially edible food that gets lost in the supply chain. Wellness addicts might be surprised to learn that byproducts from the meat industry are turned into peptides and other so-called functional ingredients to be used in supplements, while fruit and vegetable waste is turned into powdered fibre and added to prebiotics (non-digestible food ingredients), or made into dyes and antioxidants. Crushed grapes left behind after wine making are particularly useful, as is the pomace (pulpy residue) left after making juices. Whey protein powder is a byproduct of dairy processing, bovine collagen is made from cow skin and bones, marine collagen is made from fish skin and bones, and some omega 3 is taken from fish heads and viscera<\/a>.<\/p>\n Petrochemicals in your pudding<\/p>\n If a flavouring is described as \u201cnatural\u201d, it just means it\u2019s not synthetic. (Legally, there are \u201cnatural flavourings\u201d and \u201cflavourings\u201d, which are made using synthetic ingredients and chemical processes.) Natural flavour sources include citrus oil from discarded peel, which can be turned into terpineol or perillyl alcohol, both floral flavourings, and carvone, which can taste of spearmint or caraway. Sugarcane pulp gives us coconutty 6-pentyl-2\u00a0pyrone. Isoamyl alcohol, AKA banana flavour, can be extracted from used coffee husks, and 1-phenylethanol, rose flavour, can be made from grape pomace. Even synthetic flavours are often chemically identical to those found in the original food \u2013 for example, methyl anthranilate, which is grape flavour and now mostly mass\u00a0produced from petrochemicals for sweets and puddings.<\/p>\n None of this is necessarily a bad thing, says Jane Parker, professor of flavour chemistry at the University of Reading. \u201c\u200aWe can\u2019t have it both ways: sustainable and natural. Take vanillin. Growing vanilla is so labour intensive \u2013 the plants take years to come to maturity, have to be hand-pollinated and are susceptible to drought, pestilence and disease. It\u2019s a hugely unsustainable practice.\u201d The quest for a\u00a0cheap way to make vanilla flavour started in the 1870s, when vanillin was first synthesised from pine bark. The food industry\u2019s argument for using petrochemical or industrial byproducts to make things such as vanillin, benzaldehyde (almond essence) or menthol is that they are usually chemically identical and easier to produce at scale than, say, growing acres of real mint to flavour toothpaste.<\/p>\n Microbes in all your meals<\/p>\n Flavours such as ethyl butyrate, which tastes of ripe pineapple, can now be made using microbes rather than from petrochemicals, which means they can be described as \u201cnatural\u201d. \u201cBiotech is making good inroads into making things that are technically natural,\u201d Parker says. \u201c\u200aAnd the food industry is moving from chemical to biochemical synthesis. You end up with the same molecules, and safety\u2011wise, there\u2019s no difference. We can use microorganisms and enzymes to carry out the same reactions as in the chemical industry, and it\u2019s more sustainable than using fossil fuels as long as you give them something sustainable to live on, and you can do it at scale because you only need a tiny quantity of the aroma compounds.\u201d There is no requirement for labels to tell us where a flavour has come from.<\/p>\n Precision fermentation means feeding carefully chosen or genetically modified microbes in bioreactors specific foods so they produce oils or proteins that are chemically identical to an original food or ingredient. \u201cIt has been used for decades to produce ingredients such as rennet for cheesemaking,\u201d says Dr Stella Child, senior research funding adviser at the Good Food<\/a> Institute Europe thinktank, which champions the development of alternative proteins. \u201cBut it\u2019s now being used to develop animal-free fats and proteins that can bring the flavour of meat and dairy to plant-based foods.\u201d<\/p>\n Some campaigners say these processes obfuscate what is really in our food, or how it has been made. \u201cFor example, if certain bacteria are used to generate propionic acid [a\u00a0preservative and mould inhibitor] which is then separated from its growth medium \u2013 flour and water, say \u2013 food law deems propionic acid to\u00a0be an additive and it must be listed on the label by name or the code E280,\u201d Young says. \u201cBut if the propionic acid is not separated from the flour and water, food law does not consider it an\u00a0additive, so a manufacturer can list it as \u2018fermented wheat flour\u2019, leading some people to believe it\u2019s a normal part of any breadmaking process.\u201d<\/p>\n Water in your chicken<\/p>\n Legally, the packet has to say if water has been added to meat or fish to make it seem juicier (or heavier) and the water makes up more than 5% of the product\u2019s weight. But even when it\u2019s on the packet, we often don\u2019t notice. A\u00a0quick check in my local supermarket showed that sausages, bacon, pat\u00e9 and several roast chicken products (especially budget options) all had water listed as the second or third ingredient. We don\u2019t have current data, but in 2013 British consumers were found to be paying about 65p a kilo of meat for added water<\/a>.<\/p>\n Peat in your portobellos<\/p>\n Peat bogs are carbon sinks, and digging them up is environmentally ill\u2011advised, so there\u2019s been a big push to move gardeners away from peat\u2011based compost in the last few years. But most supermarket mushrooms and some herbs and salad are still grown on beds of peat, meaning when you brush the soil off your punnet of portobellos, it could easily contain flecks of 7,000-year-old bog. A company called Monaghan<\/a> has developed a peat-free base for mushrooms to grow on, using sterilised manure, straw and gypsum, but as most growers still rely on peat, the industry is responsible for about a\u00a0ninth of all peat lost in the UK each year, and has released about 31m\u00a0tonnes of carbon dioxide since 1990 (that\u2019s still a lot less than the meat industry). The government is funding a\u00a0research project<\/a> looking at alternatives made from coir, a byproduct of the coconut industry, bark or grasses.<\/p>\n Seaweed in your ice-cream<\/p>\n No, not the kind you find wrapped around your maki rolls; carrageenan invisibly and tastelessly acts as a\u00a0stabiliser, thickener and emulsifier. Made from red seaweed, it is used in non-dairy milks, ice-cream, cheeses, sauces and puddings. \u201c\u200aDo\u00a0we really need emulsifiers so we can buy chocolate milk that doesn\u2019t separate, though?\u201d Smith asks. \u201cIs it too much for us to shake a bottle of sauce or chocolate milk before we use it? People think there\u2019s something wrong with a\u00a0food where the solids have sunk and the liquid is at the top of the jar or bottle, so emulsifiers are added to make sure foods have the same consistency all the way through. Sometimes they\u2019re also preservatives, or are there to add bulk to foods that have had other ingredients taken out.\u201d There is a small amount of evidence that carrageenan might worsen existing gut inflammation<\/a>. Sodium alginate is made from brown seaweed and used in cheese sauces, baked goods and frozen desserts, and to make vegetarian sausage casings and sometimes the bubbles in boba tea. Kelp is used to make vegan caviar.<\/p>\n Arsenic in your rice<\/p>\n \u201cPlants don\u2019t just take up nutrients from soil; they can also take up trace contaminants, some of which are natural,\u201d says Prof Jack Gilbert, microbiome scientist and faculty director of the UC San Diego Soil Health Center. \u201cRice is the standout example because flooded paddy soils can make inorganic arsenic more available to the plant, which is why UK advice is that rice drinks shouldn\u2019t be used as a milk substitute for under\u2011fives.\u201d Other potential toxins in soil are there because of us<\/a>: cadmium is a poisonous but natural part of some soils, but fertilisers, pollution and sewage push levels higher in some areas; highly toxic lead can linger in soils near busy roads due to vehicle exhaust, and both can end up in the plants and vegetables we eat.<\/p>\n Cotton in your crisps Photograph: Dan Matthews\/The Guardian<\/p>\n Some of the leftovers from cotton processing are used to make methyl cellulose, but the main cotton industry byproduct used by the food industry is cottonseed oil, which the US brand Crisco first transformed into vegetable shortening in 1911. In the UK, cottonseed oil is mostly used in industrial deep-fat fryers to cook fast food, but it\u2019s sometimes used to make crisps as part of a blend of vegetable oils. As it\u2019s not a common allergen, it doesn\u2019t have to be named on food labels. Emulsifiers such as mono- and diglycerides and polyglycerol esters are sometimes made from cottonseed, too. \u201cThe idea of the food chain containing industrially processed ingredients made from other industries\u2019 non-edible byproducts seems environmentally sound, but should give us pause,\u201d Smith says. \u201cOur physiology did not evolve to digest anomalous ingredients.\u201d<\/p>\n This article was amended on 18 April 2026 to correct a temperature conversion error. In an earlier version we gave a freezing temperature of -20C as 68F, when it should have said -4F. A temperature of 68F is the equivalent of 20C, or a pleasantly warm day.<\/p>\n","protected":false},"excerpt":{"rendered":"Microbial slime and a side helping of sand doesn\u2019t sound like much of a meal, but a startling…\n","protected":false},"author":2,"featured_media":538367,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3],"tags":[59,57,58,50,56,54,55],"class_list":{"0":"post-538366","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-united-kingdom","8":"tag-gb","9":"tag-great-britain","10":"tag-greatbritain","11":"tag-news","12":"tag-uk","13":"tag-united-kingdom","14":"tag-unitedkingdom"},"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/posts\/538366","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/comments?post=538366"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/posts\/538366\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/media\/538367"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/media?parent=538366"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/categories?post=538366"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/tags?post=538366"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}