Whether due to an allergy, environmental concerns or a vegan diet, some people don't drink cow's milk. Fortunately, there's a large and growing number of plant-based alternatives to choose from.

Most milk alternatives, or alt-milks, are made from oats, almonds or soybeans, with coconut and rice also a common choice. How should you choose among them – aside from the taste, that is?

The drinks have different nutrients, so your best choice depends on your eating habits, says the consumer advice center in the German state of North Rhine-Westphalia (NRW).

If your diet is mainly or entirely vegan, you should choose a plant-based milk high in natural protein, such as soy milk. The exact protein content of the various drinks is included on the nutrition label.

Getting sufficient calcium is important for healthy bones and teeth, and cow's milk is a natural source of calcium. So if you forgo cow's milk in favor of a plant-based alternative, make sure it's enriched with calcium. The calcium content is also included on the nutrition label.

If you want to froth the plant milk barista-style, its fat and protein content is key. Soy milk almost always froths well, even if it lacks a "barista" designation. The barista versions of oat milk are augmented with soy, canola oil or sunflower oil so that they froth better.

The description "without added sugar" or "unsweetened" may attract you to certain plant milks, but keep in mind that those made from oats or rice, for example, naturally contain sugar. Almond and soy milk without added sugar, on the other hand, can truly have little or no sugar.

"Natural" is another attribute sometimes found on alt-milk labels. The term isn't defined though, and its use isn't regulated. So to know what's in the drink, or what's not, you've got to check the nutrition label.

Some eco-minded consumers wonder whether they indirectly contribute to rainforest destruction by purchasing soy milk. Only a fraction of the worldwide soybean harvest is processed into food products, most of it going into animal feed, the NRW consumer advice center points out.

But if you want an absolutely clear conscience, buy soy milk made from soybeans grown in Europe.

Almond milk will have a significantly lower carbon footprint than cow milk, but the amount of water required to make a liter of almond milk is far greater compared to that of oat or soy milk.