--- title: 'Milk, Lemon, Sugar: What Additives Do to Tea' url: 'https://howtotea.me/science/water-and-extraction/additives' markdown: 'https://howtotea.me/science/water-and-extraction/additives.md' lang: en date: '2026-10-25' description: 'What happens in the cup when tea meets milk, lemon, sugar or salt: polyphenol binding, color shifts, suppressed bitterness, and what remains disputed.' --- # Milk, Lemon, Sugar: What Additives Do to Tea Editors · October 25, 2026 · 9 min read Milk proteins bind [polyphenols](https://howtotea.me/science/chemistry/polyphenols) and soften astringency, lemon lightens the liquor by shifting its pH, and sugar and salt mute bitterness on the tongue rather than in the cup. Whether milk cancels the health benefits of tea is unsettled: one study says it does, three others found no difference. ![A cup of tea with milk, a milk jug and a slice of lemon](https://howtotea.me/images/c/o/v/e/r/cover-f749034a.webp) Illustration Additives Milk: caseins bind catechins, astringency drops Lemon: acid shifts pH, the liquor lightens Sugar: astringency down 30–40%, via sweetness Salt: sodium suppresses bitterness (model solutions) Milk first or last: ISO 3103 and RSC: first Health with milk: disputed: 1 study against 3 Pour three identical cups of [black tea](https://howtotea.me/teas/black) and add milk to one, lemon to another and sugar to the third. They will look and smell different, and the difference goes beyond taste. Milk reacts with compounds from the leaf, lemon changes the color, and sugar never touches the chemistry of the cup at all: it acts on the tongue. In each case some things are well established and others only sound convincing. Tea's astringency and bitterness come from [polyphenols](https://howtotea.me/science/chemistry/polyphenols), and each additive dulls them in its own way. ## Milk: proteins against polyphenols Tea polyphenols and milk proteins combine without strong chemical bonds, through hydrogen bonding and hydrophobic interactions[1](#fn:1). [Caseins](https://howtotea.me/science/chemistry/polyphenols) bind them most tightly. The resulting complexes pull catechins out of solution, so fewer of them reach the mouth. In a Japanese experiment, a catechin solution was mixed one to one with whole milk, skim milk and cream. Astringency fell by 46–58% according to the Japanese abstract and by 58–65% according to the English one, so it is too early to quote a single figure. Skim milk removed about 95% of the free catechins, while lactose and whey proteins removed far less, 5–25%. At equal molar concentrations, β-casein bound the most, roughly 35%. The effect is stronger in black tea, whose large polyphenols, reviews suggest, bind to casein more readily. The classic pairing of black tea and milk is no accident: milk really does tame the throat-scratching edge of a strong Assam. ISO 3103 describes a milk test for black tea only. ### Does milk cancel the benefit of tea? This is where the argument starts. In 2007 Lorenz's group gave 16 women 500 ml of tea, in some trials with 10% skim milk, and measured dilation of the brachial artery two hours later. With milk the effect of the tea disappeared completely, and chromatography showed catechins forming complexes with caseins the moment the two were mixed. Still, that is one study, one measure and a small group. Three studies point the other way. In a 1998 study of 12 people, the area under the blood catechin curve was 0.53 with milk and 0.60 without, a difference that was not significant. In 2007 Kyle and colleagues found that 400 ml of black tea raised plasma antioxidant capacity by 10%, phenols by 20% and catechins by 32% within 80 minutes, and milk made no difference. A laboratory digestion model showed that protein-polyphenol complexes break apart in the gut. A study in 24 women muddies the picture further. Milk and caseinate lowered absorption of [green tea](https://howtotea.me/teas/green)'s galloylated catechins (EGCG down to 68% of control) but raised that of the non-galloylated ones (EGC at 134%). So milk does change how catechins behave in the blood, but no study has shown that it "destroys the benefit" of tea. For the compounds themselves, see the article on polyphenols. ## Order and temperature: milk first or last ISO 3103 has the taster pour milk into the bowl before the liquor: 5 ml for a large bowl, 2.5 ml for a small one, with 2 g of leaf per 100 ml of water. The standard itself allows "after" if the liquor has cooled to 65–80 °C. In 2003 the Royal Society of Chemistry explained why. Milk proteins denature above 75 °C, so a drop of milk falling into freshly boiled tea spoils. With milk in the cup first, the tea cools as it mixes, and the milk does not heat up so abruptly. The society's recipe: a warmed pot, about 2 g of leaf per cup, boiling water, 3–4 minutes, and drink at 60–65 °C. UHT milk is the worst choice, since its proteins are already denatured. In her book *Steeped* (2024), Francl recommends the reverse for bagged tea: warm milk, added after, so it does not curdle. The sources disagree, but neither is wrong. The standard is written for a professional taster, the book for someone making a cup in the kitchen. How people actually drink it Tea with milk takes many forms, from a British cup to Tibetan butter tea. For the customs, see [tea in Britain](https://howtotea.me/traditions/europe-and-russia/british-tea), [Tibetan butter tea](https://howtotea.me/traditions/south-and-southeast-asia/tibet), [steppe milk tea](https://howtotea.me/traditions/middle-east-and-central-asia/steppe), [South Asia](https://howtotea.me/traditions/south-and-southeast-asia/south-asia) and [Asian milk teas](https://howtotea.me/traditions/south-and-southeast-asia/asian-milk-teas). This page sticks to chemistry. ## Lemon: color, acid and film The color of black tea comes from two families of pigments. Theaflavins are red-orange and barely respond to acidity. The red-brown [thearubigins](https://howtotea.me/science/chemistry/polyphenols) behave like an indicator. They make up 10–20% of the dry leaf and up to 60% of the dissolved solids in the liquor, so they set the color of the cup. That is why tea turns darker in hard, alkaline water and lighter when acidified. ![Tea with milk and tea with lemon, which turns the liquor lighter](https://howtotea.me/images/m/o/l/o/k/moloko-i-limon-8a867efc.webp)Illustration In a Japanese experiment, liquor buffered between pH 2.2 and 8.0 was bright orange at low pH and red-brown at high pH. Acetic, lactic, oxalic, malic, citric and other acids at equal doses all had the same effect; only ascorbic acid added a yellow tone. The authors concluded that lemon changes the color through the drop in pH and through its own ascorbic acid. A few drops are enough. Green tea also lightens with lemon, and by more than dilution alone would explain. Lemon has a practical upside too. The film on the surface of tea is made of polyphenols bound together by calcium and magnesium ions and bicarbonate, and it does not form in distilled water. Lemon lowers the pH and citrate binds calcium and magnesium, so the film weakens. Sugar also reduces it. With milk the film is thicker and there is more of it, though its makeup is different. For the role of hard water, see [water chemistry](https://howtotea.me/science/water-and-extraction/water-chemistry). Claims about lemon's health benefits call for more caution. In a laboratory digestion model, about 80% of green tea catechins survived with lemon juice, against under 20% with no additives; the more-than-fivefold gain was measured for citrus juices. But that is a test tube, not a body, the share of juice in the drink is not given, and the authors of an overview in The Conversation consider the effect of lemon in a real cup to be small. These data do not support the idea that "lemon makes tea many times healthier." ## Sugar and salt: the tongue does the work Sugar does not bind polyphenols. In Hofmann's work it was the sweetness of sucrose, not its viscosity as many assume, that reduced astringency. A Czech study of 9 black and 10 green teas found that sucrose cut astringency by 30–40%. The abstract does not give the concentrations, so the figure is no recipe. Salt is more interesting. In Breslin and Beauchamp's 1997 experiment, sodium acetate suppressed the bitterness of urea more than the sweetness of sucrose, and sweetness in the mixture even increased. These were model solutions, not tea, and there are no doses for a cup. Francl recommends a pinch too small to taste and likens its effect to a lump of sugar. The mechanisms differ: sodium acts on bitterness, sugar through the perception of sweetness. Salting tea is nothing new. In the *Classic of Tea* (around 760–780), Lu Yu tells you to salt the water at the first boil, when "fish eyes" rise to the surface. He does not say why, and modern chemists can only guess: salting out proteins, protection against microbes, pH stabilization. In the 11th century Su Shi rejected salt in tea and praised ginger. The argument is older than any trend. ## Soda, butter and other extremes Kashmiri noon chai shows how much the color depends on pH. The tea is boiled with baking soda for about an hour: the polyphenols ionize and the liquor turns red, like phenol red in alkali. Adding milk turns the red to pink. [White tea](https://howtotea.me/teas/white) will not work, as it has too few polyphenols and the brew comes out light brown. Tea bags are not recommended either, because the color will not develop. The idea that chlorophyll turning into pheophytin makes the pink appears only on a blog, not in research. Butter tea works differently: it is an emulsion of fat in a strong brew of brick tea. It is churned and warmed but not boiled, because at a boil the butter and the brew separate again. There are no primary studies of the physics of this emulsion, only descriptions and a recipe for the powder: 0.2–0.6 g of salt and 0.5–1.5 g of butter per 100 ml. According to Hofmann's thesis, fat reduces friction in the mouth, but 10% fat does no better than 5%. ## Myths around additives [Caffeine](https://howtotea.me/science/chemistry/caffeine) does not build up with longer steeping: during [extraction](https://howtotea.me/science/water-and-extraction/extraction) nearly all of it comes out in the first minute, and after that the share of large, bitter polyphenols grows. No additive makes up for poor brewing: if the tea is bitter from boiling water, lemon and sugar will not save it. If you want to experiment, start with milk in a strong black tea and a drop of lemon in a green one. The difference is obvious at once, and there is no risk. Save salt and soda for when you are making noon chai or butter tea from a recipe. ## Common questions Milk in first or last? The ISO 3103 tasting standard and the Royal Society of Chemistry (2003) both put the milk in first: drops of milk landing in hot tea heat past 75 °C and their proteins denature, while tea poured onto milk cools below that mark sooner. Chemist Michelle Francl suggests the opposite for bagged tea, adding warm milk afterwards. ISO allows "after" if the liquor has cooled to 65–80 °C. There is no clear winner; it mostly comes down to taste and habit. Does milk really take the benefit out of tea? Nobody knows yet. In a 2007 study at Charité, milk completely blocked the widening of blood vessels that tea produced in 16 women. Yet three studies of catechin and flavonol absorption, two of them in humans, found no difference in the blood. A single study of a single measure does not make tea with milk useless. Why put salt in tea? Sodium suppresses bitterness at the receptor level, and according to the literature sweetness even comes through more strongly. But the convincing experiments used model solutions, not tea, and there are no doses for a cup. A pinch too small to taste is a cook's trick, not a proven improvement. Notes 1. Miura T., Akuzawa R. Suppression of catechin astringency by milk components. Milk Science 59(1), 2014. J-STAGE: [https://www.jstage.jst.go.jp/article/milk/59/1/59\_1/\_article/-char/ja](https://www.jstage.jst.go.jp/article/milk/59/1/59_1/_article/-char/ja) [↩](#fnref1:1) --- ## Navigation - Parent: [Water and extraction](https://howtotea.me/science/water-and-extraction.md) - Previous: [The Chemistry of Water for Tea: Hardness, Alkalinity, Chlorine](https://howtotea.me/science/water-and-extraction/water-chemistry.md)