Some like to trumpet the health benefits of a vegan lifestyle, but a new report from the US National Academy of Sciences suggests that if the US were to go full vegan, it would be a disaster.

The study, which was intended to look at the impact of the meat industry on greenhouse gas emissions, asked what would happen if every person in the US fully embraced meat-free living.

The answer, said Robin White, of Virginia Tech, and Mary Beth Hall, of the US Department of Agriculture’s Agricultural Research Service, was disaster for a great many Americans.

Herd the news? Removing livestock from the US would be a nutritional disaster for American people, a new study says, due to an imbalance of nutritional requirements

Not mincing words: Meats are dense with nutrients, which makes it easier to feed a population. Carefully balancing a vegan diet is possible for individuals, but hard to scale up

The initial impact on food would seem positive.

At present we feed huge quantities of food to livestock; without them, the total amount of food available would increase by 23 per cent, not including exports.

But that increase would largely be in the form of the same kinds of grains (of which 77 per cent would be corn) and legumes (92 per cent soybeans and soy flower).

That would in turn mean that the US would have more of some very important nutrients - carbohydrates, magnesium, copper, and cysteine, for example - than they actually need.

It might be suggested that the land used to grow those foods could be transferred to other fruits and vegetables, but the paper's authors have an answer for that.

'Given the tremendous domestic demand for fruits and vegetables, if it was viable to produce more of these high-value crops in the current system, this would already be occurring,' the report said.

'Limitations on increased fruit and vegetable production may reflect suitability of land, climate, and infrastructure to grow these crops.'

Salad daze: Without countrywide access to the right veggies, malnutrition would occur in certain areas. However, the report does note that eating vegetables is important for health

More importantly, it would mean a domestic deficit of many nutrients that people now get from animals, such as calcium, vitamin A, vitamin D, B12, arachidonic, eicosapentaenoic, and docosahexaenoic fatty acids.

The report didn't factor in supplements, only looking at 100 per cent nutritional intake from food.

The report also says that while vegan living on an individual level is possible with a carefully controlled and calibrated supply of rations, it's difficult to scale up to a nationwide level.

That would leave some people in areas with less access to varied plant-based foods malnourished, it said.

But, the report said: 'When animals are allowed to convert some energy-dense, micronutrient-poor crops (e.g., grains) into more micronutrient dense foods (meat, milk, and eggs), the food production system has enhanced capacity to meet the micronutrient requirements of the population.'

One answer, Quartz noted, was lab-grown meat, or 'clean meat', that's created without having to slaughter animals.

Hampton Creek, a San Francisco-based company, says it plans to have lab-grown meat for sale sometime next year.

As for carbon emissions, there's little to be gained there, the scientists concluded.

Without fields of cows breaking wind, agricultural greenhouse gas emissions dropped by 28 per cent.

That may seem impressive, but it's only 2.6 per cent of America's total greenhouse gas emissions - although the exact impact of agriculture on the ozone layer is still a matter of some debate.