杏吧原创

MOVE over cows, there鈥檚 a new milk in town. There are many, actually. The old alternatives 鈥� soy, rice and coconut milk 鈥� are now joined on grocery shelves by alt-milks made from almonds, cashews, macadamia nuts, oats, peas, flax, hemp 鈥� the list goes on and on. You can even buy milk made from potatoes or bananas.

Since 2012, , according to market research by Mintel. There is a similar trend in the UK, with plant-milk sales up a third since 2015. More than half of that is almond milk, with soy and coconut milks making up another quarter of the market.

As you might expect for the latest food trend, these milks are mostly bought by millennials, or adults younger than 35. Manufacturers appeal to that generation鈥檚 values by positioning the products as a healthy alternative, both for the body and the planet. But is that really true?

Nutritionally, it depends on which milk replacement you consider. In general, they are made by grinding up plants and soaking them in water, then adding emulsifiers and stabilisers to thicken the liquid and keep it from separating, but they have a lot of variety (see 鈥�What鈥檚 in a name?鈥�).

In terms of protein, soy milk is quite like cow鈥檚 milk, and it contains similar omega-3 fatty acids that are important for heart health. Almond and cashew milks have less than half the calories found in cow鈥檚 milk, but are lower in protein. Coconut and hemp milk have a rich texture owing to their high fat content and they also include a small amount of dietary fibre not found in cow鈥檚 milk. Oat and rice milks are higher in carbohydrates than both cow鈥檚 milk and other plant-based alternatives.

Milks made from legumes, such as peas, soya beans and peanuts, also offer amino acids not found in cereal crops. Each type of alternative milk has its nutritional benefits and limitations. Any one of them can be considered healthy only when combined with a rounded diet, though the same can be said for dairy milk.

鈥淎lmost all of these products are fortified,鈥� says P. K. Newby, a nutrition and sustainability scientist at Harvard University. Many non-dairy milks have vitamin D, vitamin B12 and calcium added to make them more similar to cow鈥檚 milk.

鈥淢ilk alternatives are only healthy if combined with a rounded diet, though the same is true of dairy milk鈥�

Few of them have added iodine, though, which helps make thyroid hormones that regulate our metabolism. A available in the UK found average iodine concentrations of just 1.7 per cent that seen in cow鈥檚 milk. The authors found that only three of 47 alt-milks on the market were fortified with iodine, and the concentration in those was just a bit over half that seen in cow鈥檚 milk.

Still, Newby says people who use milk in their coffee or just for cereal could easily switch to a non-dairy alternative without much dietary impact (see 鈥�Where to start with alt-milk鈥�).

鈥淚t鈥檚 not like most people are drinking this for the nutrients, as such,鈥� she says. 鈥淭hey tend to meet their nutrient needs with other foods.鈥�

Glass half-full

There are some alt-milks it makes little sense to produce in bulk. Rice milk is an option for those with dairy, nut, gluten and soy allergies, but it has far less protein than cow鈥檚 milk and often has significant amounts of sweeteners added to improve the flavour.

It is also one of the most environmentally costly alt-milks to produce. When rice paddies are flooded to stimulate plant growth, submerged biomass decomposes without oxygen, producing the potent greenhouse gas methane.

鈥淩ice has a much greater carbon footprint than other cereals,鈥� says Elin R枚枚s, who studies the environmental impacts of food production at the Swedish University of Agricultural Sciences. 鈥淚t鈥檚 very low in nutrition. I don鈥檛 see why you should use it.鈥�

Of course, cows are notoriously bad for the environment as well. The carbon footprint of producing cow鈥檚 milk varies from place to place, but in Western countries, it is typically around twice as big as that of making plant-based alternatives, says R枚枚s.

A found that the production, packaging and transportation of cow鈥檚 milk emits 4 per cent of all human-caused greenhouse gas emissions.

In fact, lactating cattle are the main source of greenhouse gases among all livestock and poultry. These emissions include methane that builds up in a cow鈥檚 digestive tract and is then burped out or emitted from its manure. Carbon dioxide and nitrous oxide are also released from any land cleared for feed crops. Fertilisers used to grow feed further add to the greenhouse gas emissions.

鈥淵ou need to produce a lot of feed for the animals,鈥� says R枚枚s. 鈥淢ost of the energy in that feed is lost in the process of feeding animals, so in general, all the resource use is much bigger for animal products than for plant-based milks.鈥�

Land management plays a role in the environmental impact of every kind of milk. Some cattle graze on grassland, which stores more carbon than land that has crops turned over each year. But at the University of Oxford found that the carbon sequestered in the soil would only offset up to 11 per cent of the animals鈥� emissions.

Carbon isn鈥檛 the only environmental concern to consider. Nuts are notorious water sinks, with some requiring nearly as much water to produce as cow鈥檚 milk. 鈥淲e made a calculation that came to a water footprint of 917 litres per litre of almond milk, the same order of magnitude as cow milk, 1000 litres per litre,鈥� says Arjen Hoekstra at the University of Twente in the Netherlands.

He also found that producing 1 litre of soy milk requires 297 litres of water. That includes water that ends up in the milk itself, water that evaporates during production and water polluted by those processes. It also accounts for the water used to make the sugars and starches that flavour and stabilise the milk.

In a assessed the water footprint of global food crops. It found that of the plants used for alt-milks, water usage was highest for nuts, flax and soy, and lowest for coconut, oats, rice and hemp.

鈥淵ou also have to take into account the water scarcity situation in a region,鈥� says R枚枚s. There are places where you need to irrigate to produce any crops, so they will have higher water usage. And there are places like Sweden, she says, that rely more on rain stored in the soil 鈥� but that also adds to a water footprint.

On the whole, it is clear that alt-milks are friendlier to the environment than traditional dairy, but their growing popularity may cause problems. As more people jump on the bandwagon, manufacturers are starting to compete to introduce new flavours and new types of plant-based milks. R枚枚s warns that this trend may cause unintended environmental harm.

If demand for coconut milk skyrockets, for example, it will become more profitable to grow coconut trees, which could lead to deforestation as farms expand. To avoid that, it is best to have several non-dairy options to choose from. So maybe the proliferation of alt-milks is a saving grace.

鈥淎lt-milks are better for the environment than dairy, but their growing appeal may cause problems鈥�

All that said, sometimes the impacts on the food system may not be worth the end product, says R枚枚s, as with rice milk. Or take banana milk, which involves blending bananas, usually adding some sugar and spice for flavour, and straining the mixture. Then it must be packaged, stored and transported. 鈥淚s it worth it? Or is it best to just eat the banana?鈥� asks R枚枚s.

This article appeared in print under the headline 鈥淭he white stuff鈥�