A low-carb diet generally keeps your carbohydrate intake between 60 and 90 grams of carbohydrates daily, explains the University of Maryland Medical Center. This means you must limit your intake of foods like cereals, baked goods, sweets and some fruits and vegetables. With some commercial smoothies coming in at around 100 g of carbohydrates, it might seem these treats are off-limits on a low carb diet. You can still enjoy fruit smoothies on a low-carb diet, if you stick to specific ingredients.
Put soy milk into a blender and add whey protein powder. Choose a whey protein powder isolate as it contains no added carbohydrates or fats, says the Whey Protein Institute. Blend briefly.
Add frozen raspberries or strawberries. Both have less than 15 grams of carbohydrate in a 1-cup serving. Blend until smooth, adding a bit more soy milk or water if the mixture is too thick.
Add sweetener to taste. Choose from options like sucralose, aspartame or stevia, which contain no carbohydrates.
Pour into a glass and consume for a total of just 16 to 18 carbs, depending on your chosen ingredients.
For a creamier smoothie, add half a frozen, medium-sized banana for an additional 13 grams of carbohydrates. If you do not drink soy milk, use water, which will result in a lighter smoothie. If you find your smoothie is too thin, add a few ice cubes and blend until smooth.