It is virtually impossible to be protein deficient without being calorie deficient as well, according to Colin Campbell, author of the China Study.
An article in the Guardian in May reported the results from the most comprehensive analysis to date of the damage farming does to the planet, and their conclusion was that a vegan diet was probably the single biggest way to reduce the environmental impact on Earth.
Joseph Poore, from Britain's Oxford University, led the research.
"It is far bigger than cutting down on your flights or buying an electric car," he said, as these only cut greenhouse gas emissions.
Agriculture is among the greatest contributors to global warming, responsible for more greenhouse gases than all of our cars, trucks, trains and airplanes combined. It comes largely from methane released by cattle and rice farms, nitrous oxide from fertilised fields, and carbon dioxide from the cutting of rainforests to grow crops or feed livestock.
Farming is our thirstiest user of precious water supplies and a major polluter, as runoff from fertilisers and manure disrupts fragile lakes, rivers and coastal ecosystems across the globe. Agriculture also accelerates the loss of biodiversity.
Research shows that without meat and dairy consumption, global farmland use could be cut more than 75 per cent and still feed the world.
While meat and dairy provide just 18 per cent of calories and 37 per cent of protein, they use 83 per cent of farmland and produce 60 per cent of agriculture's greenhouse gas emissions.
An American study by the NPD Group, a global information company, found in-home consumption of plant proteins were showing a 24 per cent increase since 2015. The study revealed 14 per cent of Americans, equivalent to 43 million consumers, regularly choose plant-based alternatives to animal protein.
There are governments that value the health of their people.
After World War II, the Finns joined the rest of the Western world in increased consumption of meat, eggs and dairy. By the 1970s, the mortality rate for Finnish men was the highest in the world.
They decided to do something about it, and the strategy was to reduce the intake of saturated fat, with amended national dietary guidelines to reflect this.
The government also devised a project to help dairy farmers switch to berry farming. The population were invited to participate in a cholesterol-lowering competition to demonstrate the feasibility of changing diet and lifestyle and achieving measurable and positive outcomes.
The results were an 80 per cent drop in cardiac mortality and the death rate from all causes dropped by about 45 per cent, leading to an increased life expectancy of around seven years for men and six years for women.
So as well as reducing the environmental impact of the way we produce our food, there will be significant tangible health outcomes, saving the billions of dollars poured into a health system that treats the symptoms and not the cause of ill health.
The environmental challenges posed by agriculture are huge, and they'll only become more pressing as we try to meet the growing need for food worldwide.
But sheer population growth isn't the only reason we'll need more food. The spread of prosperity across the world is driving an increased demand for meat, eggs, and dairy, boosting pressure to grow more corn and soybeans to feed more cattle, pigs and chickens.
If these trends continue, they will require us to roughly double the amount of crops we grow by 2050, according to Dr Jonathan Foley, executive director of the California Academy of Sciences.
It is all fairly simple - 43 million Americans (and a few Kiwis) can't all be wrong.
