The answers depend on the composition of the milk substitute, whether it helps you meet your nutritional needs and if you have an underlying medical condition.
Dozens of varieties of milk substitutes are available. In addition to soy milk, there are nut-based products (almond, cashew, coconut, hazelnut and macadamia milks). Some substitutes use grains or seeds, such as flax, hemp, oat, rice and quinoa, as their base. There are also blends made from various nuts, grains and seeds.
Key nutrients that milk and milk products provide are calcium, vitamin D, phosphorus and, to some extent, potassium. It can be difficult to get adequate amounts of these nutrients from other foods, which is why the Dietary Guidelines for Americans recommends three servings a day for most adults.
Not all milk substitutes are fortified with similar amounts of these nutrients. The Dietary Guidelines for Americans mentions only soy milk as an equivalent choice. Read labels to ensure you choose a substitute that contains similar amounts of calcium (30 percent of the Daily Value) and vitamin D (25 percent of the Daily Value) as milk does.
Here are a few conditions where milk substitutes are helpful and where the choice you make is important.
A person with lactose intolerance is partially or completely unable to digest the natural sugar in cow’s milk (lactose). Some people are born with lactose intolerance. Others may develop it after an illness or after surgery of the bowel, or with certain diseases of the small intestine, such as Crohn’s disease or celiac disease.
If you have lactose intolerance, you may be able to tolerate lactose in small amounts spaced throughout the day. If not, you may need to opt for a milk substitute that’s fortified with calcium and vitamin D.
One of the most common food allergies in children, milk allergy is caused when the immune system triggers a response to the proteins casein and whey in cow’s milk. Sheep, goat and buffalo milk also may trigger a reaction.
Avoiding cow’s milk (and possibly other animal milk) and products that contain it is the primary treatment. Although you might think that any plant-based milk substitute would be safe, it’s important to know that about 30 percent of children with allergies have multiple food allergies.
Allergies to tree nuts — including but not limited to walnut, almond, hazelnut, cashew, pistachio and Brazil nuts — peanuts and soy are common. Many milk substitutes are made from these common allergens. So it’s essential to seek advice from an allergist or dietitian.
Chronic kidney disease
Kidneys regulate many nutrient levels in your body. As kidney function declines, dietary restrictions are often placed on food sources of protein, phosphorus, sodium and potassium. Vitamin D and calcium must be monitored too.
Because milk substitutes contain these nutrients, an uninformed choice could be dangerous. Fortunately when people are diagnosed with chronic kidney disease, blood levels are routinely monitored, and individuals get expert dietary advice.
The role of dairy products and various cancers is mixed. Milk from cows may lower the risk of colorectal and bladder cancer, and it doesn’t seem to be associated with breast or ovarian cancer. However, there is limited evidence that milk — and diets high in calcium — may increase the risk of prostate cancer.
The effects of soy milk on cancer risk aren’t clear. However, moderate consumption of soy foods (not supplements) appears safe for breast cancer survivors and may lower breast cancer risk in the general population.
The bottom line: If you have a medical condition, talk with your doctor or dietitian before trying a milk substitute. Don’t risk your health by making an uninformed choice.