Water, coffee, tea, infusions and other drinks: composition, preparation, storage and everyday consumption.
Caffeine can have a mild diuretic effect, especially at high doses, but the water in coffee normally outweighs that effect and the drink still contributes to hydration.
The FDA cites 400 mg per day as an amount not generally associated with negative effects for most adults, but individual sensitivity and serving size can change what is too much for you.
Espresso is more concentrated, but a normal mug of filter coffee usually contains more total caffeine because the serving is much larger.
Robusta beans commonly contain close to twice as much caffeine as arabica by dry weight, although the caffeine in a finished cup also depends on the recipe.
Cold brew is defined by a cool, long extraction; iced coffee is usually hot-brewed coffee that is chilled. Cold brew often tastes smoother and less sour or bitter, but it is not automatically higher in caffeine: coffee-to-water ratio, concentrate strength, dilution, and serving size decide that.
Hot coffee extracts rapidly at high temperature; cold brew trades heat for hours of contact. That changes the balance of acids and aroma compounds and often gives cold brew a smoother profile. Caffeine does not follow a simple hot-versus-cold rule because recipe strength and dilution can outweigh temperature.
If protein is the priority, soy is usually the most consistent choice at roughly 7–9 g per cup, while some pea-protein beverages are around 7–8 g. Oat milk often provides 2–4 g, almond milk 1–2 g, and rice milk about 0–1 g, although brands vary widely.
The phrase plant milk covers products with very different nutrient profiles. Fortification can make calcium look similar to cow’s milk while protein remains far lower. The most useful comparison is the exact carton versus the dairy milk it may replace.
There is no permanent category winner because formulas change, but current U.S. examples show the trade-off clearly: Silk Unsweet Almondmilk has 30 calories and 0 g sugar per cup, Oatly Unsweetened Oatmilk has 40 calories per cup, and Silk Unsweet Soymilk has 80 calories but 8 g protein and less than 1 g sugar. Lowest calorie and most nutritionally similar to milk are different questions.
Calcium in many plant milks is added during manufacturing rather than coming mainly from the diluted almond, oat or soy itself. Current Silk examples range from 300 mg calcium per cup in unsweet soy to 470 mg in unsweet almond. Fortification can make calcium substantial, but it does not make every other nutrient equivalent to dairy milk.
Using current unsweetened products, Silk soy milk provides 8 g protein per cup while Oatly Unsweetened lists 0 g. Fortification can make calcium and vitamin D look similar despite very different macros.
In current unsweetened examples, Silk almond milk has 30 calories and 1 g protein per cup; Oatly Unsweetened has 40 calories and 0 g. Much of the calcium comes from fortification.