Looking at a bottle of almond milk, it's easy to see why so many people have made the switch.

"Just filtered water, activated almonds, organic brown rice syrup and sea salt."

No wonder juiced nuts are having a moment! It sounds like a magical nutrient wonder potion.

Except that "organic brown rice syrup" is just a fancy way of saying "sugar", and "activated almonds" are just nuts that have been soaked in water.

Not all plant milks are created equal, of course, and there are lots of good reasons why people make the switch to dairy-free.

But how do alternatives like soy, almond and coconut milk stack up nutritionally?

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Milk that's real milk

Before we make the jump to juicing oats, let's first consider the nutritional benefits of dairy.

Cow's milk has been a staple of Western diets for thousands of years and is an excellent source of vitamins and minerals, particularly calcium.

Milk plays an important role in bone health, and drinking it is an easy way to boost your nutrient intake, said Nicole Dynan, an accredited practicing dietitian and spokesperson for the Dietitians Association of Australia.

"Milk gives us a lot of the nutrients that we need in our diet, including calcium, protein, vitamin A, vitamin B12, zinc, magnesium and riboflavin," Ms Dynan said.

The Australian Dietary Guidelines recommend you eat 2.5 servings of "milk, yogurt, cheese and/or their alternatives" per day.

Tim Crowe, a nutrition researcher and accredited practicing dietitian, said although calcium intake was important, it was "a bit of a myth" that people needed to consume dairy.

"There's no reason why anyone has to drink cow's milk … There's nothing inherently special about it that you can't get from other aspects of your diet," he said.

However, Dr Crowe said cow's milk was a "great source of nutrition", and added that any concerns about it having negative impacts on people's health were unfounded.

"If you don't like milk, or if you're intolerant, that's fine, have something else," he said.

"But if you enjoy it, then by all means keep enjoying it — there's no strong reason to change your habit anytime soon."

Soy: the original 'alt-milk'

If you're opting for a dairy-free milk alterative, soy milk is a good place to start. Soy was the first plant-based milk to appear on supermarket shelves and is still the most widely available option.

Soy milk is made from either ground soy beans or soy protein powder, reconstituted with water, and often adjusted with oil (and sugar) to imitate the consistency of cow's milk.

"Soy milk is a good source of protein, and if it's fortified with calcium — which most soy milks are — it really is on a par to cow's milk," Dr Crowe said.

A 2017 study investigating the nutritional differences between cow's milk and almond, soy, rice and coconut milk found soy milk fared the best of the alternative milks — by a long shot.

"It is quite clear that nutritionally soy milk is the best alternative for replacing cow's milk in human diet," the authors wrote.

Soy milk has more protein on average than other plant alternatives, contains fibre, and is a source of "good" fats.

Dr Crowe said that while soy milk was nutritionally superior to other plant-based milks, it always paid to check whether a product was fortified, and preferably unsweetened.

"That's one thing to watch out for — some soy milks have added sugars to try and mimic the natural sweetness of milk, so it always pays to check," he said.

Rice, soy and almond are just three examples of the many milk plant-based alternatives. ( ABC News: Julia Sansone )

Confusion and distrust surrounding soy foods has grown in recent years because of concerns about their effects on hormones.

Soy milk contains large amounts of phytoestrogens — a class of plant chemicals that mimic the body's natural oestrogen — but on a much weaker scale.

Dr Crowe said despite concerns about phytoestrogens causing an increased risk of breast cancer and hyperthyroidism, clinical studies have consistently shown those fears are overstated.

"Studies that have been done in humans do not point to any harmful effects," Dr Crowe said.

On the contrary, there is research to suggest phytoestrogens may have a protective effect against some cancers.

"We know that people in Japan, for example, who have lots of soy foods have lower risk of cancer, particularly breast cancer … but the research is not conclusive," Dr Crowe said.

The only exception is women with existing breast cancer or past breast cancer, who are advised (by the Cancel Council) to "be cautious in consuming large quantities of soy foods or phytoestrogen supplements".

Almond, coconut and rice alternatives

As for trendy new alternatives like almond and coconut milk, Dr Crowe said they're rarely the natural, nutritious milks they're touted to be.

"There's not a lot in them. They're basically just very watery," he said.

"They might be useful to use as substitutes in cooking, but they're not a nutritional substitute for cow's milk."

Some almond milks contain as little as two per cent almonds. ( Pixabay )

Nut milk, such as almond and cashew, is a mix of ground nuts and water, and usually contains added sweeteners and salt. It tends to be low in calories and saturated fat, but isn't always calcium-fortified.

Rice milk is made from milled rice and water, and has comparable calories to cow's milk. It's generally calcium-fortified, but it tends to be low in protein, and high in natural sugars.

Coconut milk is typically low in carbohydrate and protein, high in saturated fat, and whether it's fortified — like other alternatives — depends on the brand.

Dr Crowe said although the plant milks "paled in comparison" to soy milk, almond milk was probably the next best plant-based alternative to soy.

Ms Dynan said she'd put oat milk "marginally above" almond milk, simply because it had some fibre in it, as well as some "vitamins and minerals".

Both dietitians agreed it was important to read the packaging to check closely for sweeteners (look for sugar and syrups) and to always pick calcium-fortified products where possible.

"Especially if you're following a vegan diet, you do need to make sure you're getting B12 — so fortified milks are a good source of that," he said.

The same goes for calcium, he said.

"You just have to be more aware of good calcium sources, because a lot of these substitutes aren't going to give it to you," Dr Crowe said.

"There's no harm in these milks, they're just not adding a lot to your diet," Dr Crowe said.