Once, not all that long ago, the only choices for milk were variations of cow’s milk: skim, 1 percent, 2 percent or whole.

Once, not all that long ago, the only choices for milk were variations of cow’s milk: skim, 1 percent, 2 percent or whole. Today, there are so many plant-based alternatives to cow’s milk, it can be hard to know what’s best to pour over your cereal.

People choose milk alternatives for a variety of reasons: allergies, intolerances, concern about animal welfare, avoidance of animal products, fear of antibiotic use and a belief that nondairy beverages are healthier. Worldwide, sales of non-dairy milk alternatives more than doubled between 2009 and 2015, according to the medical journal Practical Gastroenterology, and in the past five years, the consumption of cow’s milk dropped 13 percent. Today, 49 percent of the population consumes plant-based milks, either instead of or in addition to cow’s milk.

Plant-based milks are essentially suspensions of dissolved and disintegrated plant material and extracts in water. These drinks use thickeners and stabilizers to visibly resemble cow’s milk. True dairy foods are good sources for important nutrients, including high-quality protein, vitamin D, calcium and phosphorus. Only animal-based milks are a source of natural calcium, supplying about a third of an adult’s daily requirement in just one cup. Many plant-based milks fortify their products with calcium and other nutrients to mimic the nutritional value of cow’s milk, but consumers still need to read the labels carefully.

Added sugar is another variable that can vary widely among plant-based milks. Although there are unsweetened versions, most non-dairy milks are sweetened with some added sugars to make them more palatable. Many sweetened or flavored non-dairy milks contain up to 20 grams of added sugar, compared to 12.5 grams of naturally occurring lactose sugar in cow’s milk.

Consumers also need to be aware of additives used to thicken and stabilize plant-based milks. Some use carrageenan, derived from seaweed, which has recently been linked to some gastrointestinal complications. Others are thickened with various lecithins or gums, to which some people may be sensitive.

Plant-based milks can be cereal-based (oat and rice milks), legume-based (soy and pea milks), vegetable-based (potato milk), seed-based (flax and hemp milks) or nut-based (almond, cashew and coconut milks).

Here’s a look at the pros and cons of several popular milk varieties, starting with cow’s milk, the gold standard. Because most plant-based milks are fortified with vitamin D and calcium, I did not include that information in their listings.

Whole cow’s milk: One cup has about 150 calories, 12 grams of carbs, 8 grams of fat, 8 grams of protein and 300 milligrams of calcium. It also is fortified with vitamins A and D. Reduced-fat versions of cow’s milk have all the same nutrients but with less fat and fewer calories.

Pros: It provides high-quality protein and essential nutrients and is widely available.

Cons: Unless you choose low-fat versions, cow’s milk is high in saturated fat. The protein in cow’s milk is a common allergen, and lactose may be difficult for some people to digest.

Soy milk: One cup of unsweetened soy milk has about 80 calories, 4 grams of carbs, 4 grams of fat and 7 grams of protein.

Pros: It is low in saturated fat and free of lactose. Also, of the plant-based milks, soy milk has the highest amount of protein. It also has omega 3 fats and some fiber. It is the least processed among plant-based milks.

Cons: Soy is a common allergen. It contains phytoestrogens, which may be a concern for some. Too much soy also can be a problem for people with thyroid issues. Avoid sweetened varieties, which can contain up to 19 grams of sugar per cup.

Almond milk: One cup has just 30 to 50 calories, 1 gram of protein, 1 gram of carbs and 3 grams of fat. Nut milks are highly diluted with water, which makes them low in protein.

Pros: It is low-calorie, low-fat, naturally lactose-free and high in vitamin E.

Cons: It is a poor source of protein, essential fatty acids and trace elements. Avoid sweetened versions, which can contain up to 90 calories and 16 grams of sugar per cup.

Rice milk: One cup has about 120 calories, 22 grams of carbs, 2 grams of fat and less than 1 gram of protein.

Pros: It is the most hypoallergenic non-dairy alternative and low in fat.

Cons: It is a poor source of protein, higher in carbs and often sweetened with brown rice syrup.

Oat milk: One cup has 130 calories, 4 grams of protein, 2.5 grams of fat and 24 grams of carbs.

Pros: It contains fiber (1.9 grams) and iron, and is low in calories and saturated fat.

Cons: It is higher in carbs, and added ingredients could contain potential allergens. Coconut milk: One cup has about 70 calories, no protein, 4.5 grams of fat and 8 grams of carbs.

Coconut milk is a diluted version of the coconut cream sold in cans and used for cooking.

Pros: It’s a good source of potassium and contains fiber (1 gram per cup) and some iron.

Cons: It’s low in protein and high in saturated fat.

Hemp milk: One cup has about 100 calories, 2 grams of protein, 7 grams of fat, 8 grams of carbs and 6 grams of sugar. The milk is made from ground hemp seeds.

Pros: It is high in essential fatty acids.

Cons: It is low in protein and high in fat, has an earthier flavor that may be off-putting, and is usually sweetened.

Pea milk: One cup has about 100 calories, 8 grams of protein, 4.5 grams of fat, and 6 grams of carbs. Pea milk is one of the newer dairy alternatives on the market. It is processed so that the protein content is added back.

Pros: It is high in protein and low in carbs, contains unsaturated fat, and has a creamy taste and texture very similar to cow’s milk.

Cons: It is not yet widely available.

Cashew milk: One cup has 60 calories, 1 gram of protein, 2.5 grams of fat and 9 grams of carbs.

Pros: It is high in vitamin E and low in calories, contains no saturated fat, and has a creamy taste and texture.

Cons: It is low in protein.

Flax milk: One cup has 24 calories, 0 protein, 2.5 grams of fat and 1 gram of carbs.

Pros: It is low-calorie and high in essential fatty acids.

Cons: It has no protein and contains a very high amount of phytoestrogens.

The nutritional profile of each type of plant-based milk depends not only on the plant source but also on the manufacturing process and the degree of fortification. Most are fortified to provide an adequate amount of calcium and vitamin D, but other micronutrients are often unknown. Protein and added sugar should be carefully considered when choosing a non-dairy milk substitute. Choose one high in protein, and avoid added sugars altogether, if possible.