From the Berkeley Wellness Letter, here's some info about various types of non-dairy beverages that can make good substitutes for plain old milk.
Cow’s milk is a good source of protein, calcium, potassium, and vitamin D. But if you are lactose intolerant or just don’t like regular milk, there are other “milks” you can try.
Nondairy beverages—made from soy, nuts, rice, even oats and hemp—are not nutritionally equivalent to milk. Each has something to offer, though.
Soy milk: Made by soaking, crushing, cooking, and straining soybeans, some soy milks provide as much protein as cow’s milk, often some fiber (dairy milk has none), a range of nutrients (including B vitamins and potassium), and isoflavones (potentially healthful plant compounds).
Nut milk: Often made from ground almonds or hazelnuts, nut milks have little protein, but are relatively low in calories and provide vitamin E, manganese, magnesium, copper, and other nutrients from nuts.
Rice milk: Consisting mostly of carbohydrates, rice milk is low in protein and fat (some have added vegetable oil). Though usually made from brown rice, the “milk” has no fiber and is thin in consistency. Rice milk is naturally sweeter than other nondairy beverages and least likely to cause allergies.
Oat milk: Made from oat groats (oats that have been cleaned, toasted, and hulled), oat milk contains about half the protein of cow’s milk. Oat bran may be added as a source of fiber. It’s slightly sweet with a thin consistency, similar to skim or 1% milk.
Hemp milk: From the seeds of the industrial hemp plant (varieties of Cannabis sativa grown for food and textile uses), hemp milk supplies protein, omega-3 fats similar to those in flaxseeds, and other healthful unsaturated fats. Unlike the Cannabis plant that produces marijuana, foods made from hemp contain only trace amounts, if any, of the psychoactive compound.
Keep in mind:
• If you drink nondairy beverages in place of cow’s milk, look for ones with added calcium and vitamin D. Many are also fortified with vitamin B12 (an advantage for vegans who don’t get much B12 in their diets) and other nutrients.
• Most nondairy beverages are sweetened with sugar (such as evaporated cane juice, rice syrup, or barley malt), which increases calories. Chocolate and other flavored beverages have even more added sugar than “plain” or “original” ones—as much as five teaspoons a cup—and up to 170 calories. Unsweetened versions have as few as 35 calories a cup.
• Though the unsaturated fat in these beverages is heart-healthy, nonfat versions have fewer calories.
• Nondairy beverages, including soy milk, are not a replacement for infant formula.