Got alt-milk? How plant-based alternatives compare

But despite its winning nutrient profile, cow's milk doesn't always have a place within one's diet. Take vegans, who avoid food from all animals, or people who have an allergy to milk protein. Or the large percentage of individuals who have trouble digesting lactose, the sugar in milk, and prefer something other than dairy milks that may be more easily digested.

Non-dairy milks, including soy, almond, rice and coconut milk, are juices from nuts, seeds, grains and legumes that are often fortified with vitamins and minerals in an attempt to deliver the equivalent nutrient profile and sometimes taste and consistency of cow's milk.

These plant-based "milks" have become increasingly popular and serve as a welcome alternative for those who can't tolerate or choose not to consume cow's milk. According to market research analysis, half of Americans consume these milks, including 68% of parents and 54% of children younger than 18. But how well do these "milks" compare to the real thing?

Nutrients in dairy vs. non-dairy milks

Cow's milk can be considered the nutritional gold standard. It's high in protein; provides a good mix of key nutrients such as calcium, magnesium, potassium, riboflavin, folate and vitamin B12 and is fortified with vitamin D, according to Vandana Sheth, a registered dietitian and spokeswoman for the Academy of Nutrition and Dietetics.

An 8-ounce serving of whole milk provides 8 grams of protein -- that's about 60% of the Recommended Daily Allowance for toddlers and 40% of the RDA for young children. But it's not just quantity that matters when it comes to protein: The quality matters, too. Cow's milk is considered a high-quality protein because it contains all of the essential amino acids required by the human body.

Though non-dairy beverages are often substituted for cow's milk, "they are not able to completely mimic the nutritional profile," Sheth said. For example, rice milk, coconut milk and almond milk provide minimal amounts of protein. And if the dairy alternative is not fortified with vitamins such as calcium, D and B12, you might be missing those, Sheth explained.

So if you can't consume the cow, what's the next best beverage?

Soy milk: The best 'milk' alternative

A study published in the Journal of Food Science and Technology that compared the nutritional content of plant-based milks concluded that "nutritionally soy milk is the best alternative for replacing cow's milk in the human diet."

Based on the study, an 8-ounce glass of soy milk contains 7 to 12 grams of protein, "which is the highest among all the alternate milk options available." Soy milk's calories are also comparable to those in reduced-fat cow's milk and range from 80 to 100 calories per serving for unsweetened versions.

Though soy milk may be a good non-dairy alternative to cow's milk, it's important to "ensure that it is fortified with calcium and vitamins D and B12, especially if you are following a vegan diet," Sheth said.

Almond, rice, coconut and hemp milk

Almond milk is a good source of heart-healthy fats and vitamins E and A. It is also lower in calories than cow or soy milk (unsweetened versions range from 30 to 50 calories per serving, according to the study), which can be helpful if you're watching calories from beverages.

However, fewer calories also means fewer nutrients, including protein, which can be as low as 1 gram for an 8-ounce serving of almond milk. So if you have a soy allergy or you prefer the taste of almond milk, "you will need to plan on getting your protein from other food sources," Sheth noted.

On the flip side, rice milk is rich in carbohydrates, which contribute a higher amount of calories: up to 140 calories per cup. It is naturally sweet and can serve as an option for those allergic to soy and nuts. However, as starch contributes almost all of its calories, rice milk is also low in protein and fats.

It's not uncommon to find high calorie counts coupled with fewer nutrients. But unlike naturally sweet rice milk, oftentimes, sugar is added to improve the taste of milk, without additional nutrients.

"If you have an unsweetened version and sweetened version of almond milk, the sweetened version might not necessarily have more almonds in it. But, for sure, it will have added sugar in it," said Sai Kranthi Kumar Vanga, who authored the study on plant-based milks and is a PhD candidate in the department of bioresource engineering at McGill University.

Unsweetened coconut milk has fewer calories than cow's milk (it ranges from 45 to 60 calories per cup), but sweetened versions might have calories similar to 2% milk's, depending on the sugar content, according to Vanga.

Most of the calories in unsweetened coconut milk come from saturated fat, though at least one study found that saturated fat from coconut milk may not have a detrimental effect on blood cholesterol levels. Coconut milk also lacks protein and has very few carbohydrates.

Hemp milk may be an appealing option for vegans since it is a good source of omega-3 fats, Sheth said; however, "ensure that it is fortified with calcium and vitamins D and B12, and know that it will again not be a good source of protein."

A newer alternative, pea-protein-based ripple milk, is promising, as its nutritional composition is similar to cow's milk, however, "further research is needed to assess the pea protein quality," according to Dr. Sarita Singhal, a pediatric gastroenterologist at the Baystate Medical Center in Springfield, Massachusetts, who has researched the nutritional value of plant-based milk alternatives.

Bioavailability of nutrients in milk

There is also the issue of bioavailability in plant-based milks, which refers to the actual amount of a nutrient that will be absorbed once it enters the body. For example, calcium is often added to plant-based milks to mimic levels present in cow's milk, but that doesn't mean all of it is absorbed and therefore available to be used for its intended purpose.

As something that might impact bioavailability, consider "antinutrients" in soy -- compounds that can combine with proteins or minerals in foods and make them unavailable for absorption. For example, phytic acid in soy can prevent minerals such as calcium, zinc and magnesium from being absorbed, Vanga said. "And unless the human body can absorb a particular compound, you are not benefiting from it."

"Adding calcium to a product does not guarantee nutritional equivalence with other products containing similar amounts of calcium because the bioavailability of calcium varies significantly in fortified beverages," Singhal added.

To optimize your intake of nutrients with plant-based milks, its important to shake the carton well before you pour, since vitamins and minerals may settle at the bottom, Sheth explained.

Infants and toddlers

Until the age of 2, the only suitable milk beverage for ideal growth and development and to prevent nutritional deficiencies in children (other than breastfeeding) is whole cow's milk or formula. If your child is sensitive or allergic to cow's milk, specialized hypoallergenic formulas can be considered, Sheth explained. A plant-based milk should be considered only after the age of 2.

"If you do choose to provide a plant-based milk to your child [and] if over the age of 2, I would suggest soy, as it provides about 6 to 8 grams of protein per cup," she said. "It's also a good idea to consult with a registered dietitian to discuss your child's unique situation and get guidance about the right choice to allow for normal growth and development."

Taste matters

Nutrition aside, the taste of non-dairy milks can vary greatly. Vanga's study noted that the "beany flavor" of soy milk can be problematic for some.

"Soy milk has been on the market for decades, but there have been numerous reports which showed that people are moving away from soy milk primarily because of the taste," Vanga said. Almond milk and other plant-based milks have gained traction and captured the market, as they have a "better flavor profile compared to soy milk."

So if you opt for non-dairy milk, the type you choose will depend on your personal preference and what nutrients you're trying to replace by consuming it. But whichever you pick, be sure to read labels carefully, and seek out other foods for those nutrients that fall short.