Comparing dairy milk with “plant milk” as one category hides enormous differences among soy, oat, almond and rice beverages. Fortified soy is the plant option that most closely matches dairy milk for protein and several key nutrients, which makes it the useful comparison here.
Protein is surprisingly close
The closest comparison is between cow’s milk and an unsweetened, fortified soy beverage, not every product sold in the plant-milk aisle. Soy naturally supplies substantially more protein than almond, rice, or many oat drinks, which is why it can resemble dairy milk more closely in a meal. Even then, brands differ. Reading the protein line, calcium line, vitamin D, vitamin B12, and added-sugar entry is more informative than assuming every carton labeled ‘soy’ has the same nutritional profile.
A USDA reference for 2% milk provides about 3.3 g protein per 100 g, or roughly 8 g in a cup. The FDA’s example Nutrition Facts panel for a fortified plant beverage provides 7 g protein per 240 mL cup.
That is far closer than many other plant beverages, which can contain only a small fraction of dairy milk’s protein. Still, soy brands differ, so check the label rather than assuming every carton supplies 7–8 g.
Calcium depends on fortification
Calcium fortification also has a practical detail: added minerals can settle. If the carton says to shake well, doing so matters because calcium left at the bottom does not reach the glass. Dairy calcium is naturally present, whereas soy beverages often rely on fortification to reach a similar amount. That does not make fortified calcium irrelevant; it simply means the label and handling instructions are part of the comparison. The same idea applies to vitamin D and B12, whose amounts vary widely by brand and market.
Dairy milk naturally contains calcium: the 2% reference has around 120 mg per 100 g, about 290 mg per cup. The FDA’s fortified beverage example lists 300 mg per cup.
The important difference is origin. Much of soy beverage’s calcium is added during manufacturing, and unfortified products can contain substantially less. Minerals can also settle, so shake the carton when the label recommends it.
Total fat can be similar while saturated fat differs
The 2% dairy reference contains about 2 g total fat per 100 g. The FDA soy-style example contains 4 g per cup, about 1.7 g/100 mL, but only 0.5 g saturated fat in the whole cup.
Soy fat is predominantly unsaturated and contains no cholesterol. Dairy fat changes dramatically with the product: whole, 2%, 1% and skim milk should not be treated as nutritionally identical.
Lactose and added sugar are different questions
Fat quality can differ even when total fat looks similar. Cow’s milk contains more saturated fat unless a lower-fat version is chosen, while soy tends to provide more unsaturated fat. The practical importance depends on the rest of the diet and on which dairy milk is being compared. Whole milk versus soy gives a different answer from skim milk versus soy. Looking only at the word ‘milk’ or ‘plant-based’ therefore hides the choices that actually change calories, fat, and protein.
Dairy milk naturally contains lactose, contributing roughly 12 g total sugar per cup. Unsweetened soy can contain very little sugar, while flavored soy beverages may contain significant added sugar.
That makes the Added Sugars line especially useful when comparing U.S. labels.
Why fortified soy is different from most plant beverages
Cooking use is another reason the products are not perfectly interchangeable. Both can work in cereal, smoothies, sauces, and baking, but sweetened or flavored soy can alter recipes and some products behave differently when heated or acidified. For someone replacing dairy routinely, an unsweetened fortified soy drink with useful protein is generally the most nutritionally similar plant option. For someone using a small splash in coffee, taste and tolerance may matter more than matching every nutrient exactly.
The FDA notes that fortified soy beverages are the plant-based alternative currently included with dairy in federal dietary guidance because their key nutrient profile is similar enough to milk. Almond, oat and rice beverages are not automatically nutritionally equivalent.
Neither choice wins every criterion. Dairy milk offers naturally occurring protein and micronutrients; fortified soy offers comparable protein and calcium with less saturated fat and no lactose. The specific carton still matters.
Sources
- FDA — Using the Nutrition Facts Label to Choose Milk and Plant-Based Beverages — Fortified plant-beverage example and federal guidance on protein, calcium, vitamin D, saturated fat and added sugars.
- USDA FoodData Central — Milk, reduced fat, fluid, 2% milkfat — Reference composition for 2% dairy milk.