Milk, whether from a cow or a plant, contains carbohydrates. The total carbohydrate content varies widely depending on the source and processing, but all common forms of milk contribute carbohydrates to the diet. These carbohydrates are typically a naturally occurring sugar, or in the case of many alternatives, starches or added sweeteners.
The Primary Carbohydrate in Milk
The primary carbohydrate found in all true dairy milk is lactose, a disaccharide often referred to as “milk sugar.” This molecule is composed of two smaller, single sugar units chemically bonded together: glucose and galactose. Lactose is unique to milk from mammals, as it is not found naturally in any other type of food.
For the body to use the energy in lactose, it must first be broken down by the digestive enzyme lactase, which is produced in the small intestine. Lactase breaks the bond between the two sugar units, allowing the resulting glucose and galactose to be absorbed into the bloodstream. If a person has a reduced amount of lactase, the lactose passes undigested into the large intestine, causing the digestive discomfort associated with lactose intolerance.
Carbohydrate Content in Cow Milk Varieties
Most fluid cow’s milk, regardless of the fat content, contains a consistent amount of carbohydrates, falling between 12 and 13 grams per standard one-cup (8-ounce) serving. Skim milk, 1% low-fat, 2% reduced-fat, and whole milk all provide similar carbohydrate counts because removing fat does not significantly alter the concentration of the dissolved milk sugar (lactose).
Lactose-free milk is produced by adding the lactase enzyme directly to the milk, breaking the lactose down into glucose and galactose before consumption. This process does not change the total carbohydrate content, but it makes the milk taste noticeably sweeter because glucose and galactose are perceived as sweeter than the intact lactose molecule. Some specialized ultra-filtered milks, however, use a different process that removes some natural milk sugars, resulting in a lower carbohydrate count, sometimes as low as 6 grams per serving.
The carbohydrate content of flavored milks, such as chocolate or strawberry, is substantially higher due to the addition of sweeteners. A cup of flavored milk can easily contain between 24 and 33 grams of total carbohydrates. This significant increase comes from added sugars, which can contribute 10 to 20 grams of sugar on top of the naturally occurring lactose.
Comparing Dairy and Plant Based Milks
The carbohydrate profiles of plant-based milk alternatives vary dramatically from dairy milk and from each other, depending on the source material and whether they are sweetened. Unsweetened almond milk and unsweetened coconut milk are very low in carbohydrates, often containing only 1 gram per cup. This is because the primary ingredients are mostly water and fat, and the nut or coconut extract contributes minimal sugar.
Soy milk, which is nutritionally closer to dairy milk in its protein content, contains a moderate amount of carbohydrates, often around 4 grams per cup for the unsweetened variety. The carbohydrates in soy milk come from the soybean itself, not lactose, and are often a mix of starches and small amounts of naturally occurring sugars.
Oat milk, however, is often significantly higher in carbohydrates, with unsweetened varieties ranging from 8 to 16 grams per cup. The higher carbohydrate count in oat milk is primarily due to the starches naturally present in oats, which are broken down during the manufacturing process.
Many plant-based milks contain added sugars, thickeners, or stabilizers to improve taste and texture, which can drastically increase the final carbohydrate count. This variability means that a direct comparison requires careful examination of the nutritional label for each specific brand and flavor.