Soy Milk vs Whole Milk: Nutrition Compared

Of all the plant-based milk alternatives, soy milk is the one that most closely resembles cow's milk nutritionally. If you are switching from dairy for ethical or health reasons and want to minimise the nutritional trade-off, soy milk is the most logical starting point. Here is how the two compare in detail.

This is part of our Milk Alternatives Complete Guide. See also Oat Milk vs Whole Milk and Highest Protein Milk Alternative.

Calories: Soy Milk Is Lower

Soy milk contains approximately 80 calories per cup unsweetened, compared to whole milk's 149 calories. Switching from whole milk to soy milk saves around 69 calories per cup — a meaningful reduction for daily users. That said, choosing semi-skimmed or skimmed dairy milk instead of whole milk also reduces calories significantly, so the comparison is most relevant for those specifically choosing between whole dairy and plant-based alternatives.

Protein: Soy Milk Is the Closest Plant Match

This is where soy milk stands apart from every other plant milk. Soy milk provides approximately 7g of protein per cup — nearly matching whole milk's 8g. This makes soy milk the only plant-based milk that can genuinely substitute for dairy milk on protein grounds. The protein in soy milk is also complete protein, containing all nine essential amino acids, which is unusual for a plant food.

Fat: Whole Milk Is Higher, Especially in Saturated Fat

Whole milk contains around 8g of fat per cup with approximately 5g saturated. Soy milk contains around 4g of fat per cup with very little saturated fat. For anyone managing cardiovascular risk factors or reducing saturated fat intake, soy milk is the better choice. The overall fat content of soy milk is more comparable to semi-skimmed dairy milk than whole milk.

Carbohydrates: Soy Milk Is Lower

Whole milk contains around 12g of carbohydrates per cup as lactose. Soy milk contains around 4g. This makes soy milk suitable for people who are lactose intolerant or managing blood sugar, who cannot tolerate dairy milk's lactose content.

Calcium and Vitamins

Whole milk is naturally rich in calcium, vitamin D, and B vitamins. Soy milk does not naturally match these levels but is widely fortified to comparable amounts. When choosing a fortified soy milk, calcium and vitamin D levels are typically similar to dairy milk. B12 is naturally absent from soy milk and needs to come from fortification — check the label.

Which Should You Choose?

Choose soy milk if: you are switching from dairy for ethical, environmental, or health reasons and want to maintain protein intake, reduce saturated fat, or avoid lactose.

Choose whole milk if: you prefer dairy, want the highest natural nutrient density, or are not concerned about saturated fat intake.

Use our Daily Calorie Needs Calculator to set your daily targets.