In 1981, a plain-speaking, unassuming scientist at the University of Toronto published with his colleagues a meticulous list that ranked foods according to the effect they had on blood sugar. The goal was to better understand the role of carbohydrates in managing diabetes. But the effect was more far-reaching than perhaps he ever would have imagined.

Dr. David Jenkins's glycemic index revolutionized the diet industry. His isn't a household name, but the diets his research inspired certainly are: Atkins, The Zone, South Beach, Sugar Busters and the G.I. Diet, to name a few. Along with laying the scientific groundwork for wildly popular lower-carb diets, Jenkins's work on international committees has influenced dietary guidelines issued by the World Health Organization, the U.S. National Academy of Sciences and national diabetes associations around the world. His research demonstrated the statin-like cholesterol-lowering power of what he coined the "Portfolio Diet" and he helped create the President's Choice Blue Menu line of healthier food products in the hopes of reaching even more consumers.

It's fair to say Jenkins has had a profound influence on how and what we eat. And now he wants us to radically rethink our diets once again.

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This time, though, he may meet a little more resistance: If it were up to Jenkins, he would have us all give up meat, fish and dairy and embrace veganism. And not just for our individual health.

Earlier this year, Jenkins – a Canada Research Chair in nutrition, metabolism and vascular biology, a professor in the department of nutritional sciences, faculty of medicine at the University of Toronto, and scientist at the Li Ka Shing Knowledge Institute of St. Michael's Hospital – became the first Canadian recipient of the Bloomberg Manulife Prize for the Promotion of Active Health. In a celebratory public conversation about his research, he shared with the crowd that he follows a vegan diet.

A properly planned plant-based diet – one that avoids all animal products, including meat, poultry, fish, eggs and dairy – is incredibly good for your health.

Studies have shown plant-based eaters are thinner and have lower cholesterol and blood-pressure levels, a reduced risk of coronary heart disease, Type 2 diabetes and lower cancer rates – especially colorectal cancer.

Foods such as beans and lentils, nuts, whole grains, fruits and vegetables offer a wealth of nutrients, fibre and phytochemicals that have favourable health effects. And vegan diets are usually higher in fibre, magnesium, folate, vitamins C and E, iron and phytochemicals, while tending to be lower in calories, saturated fat and cholesterol.

But the individual health benefits are just the beginning. Though he's well aware of the nutritional advantages, it was environmental and humanitarian concerns that pushed Jenkins to drop meat, eggs, fish and dairy from his diet.

FOR THE ENVIRONMENT

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"Human health must be linked to planetary health, and how we feed ourselves has a major impact on the planet," says Jenkins, now 72. It's the positive impact of plant-based eating on the environment, as well as animal welfare, that appeals.

In Canada, more than 700 million animals – 20 times more than our human population – are killed each year for food, a large majority in intensive livestock organizations, or factory farms. The production of large volumes of meat, poultry, eggs and milk – as quickly and as cheaply as possible – is done at a major cost to the environment.

Intensive animal agriculture is one of the leading sources of greenhouse-gas emissions and uses more water than any other human activity. (In Canada it's the single largest consumer of water, according to the 2012 report from the World Society for the Protection of Animals.) Concentrated livestock operations can be major water polluters. Factory farms, as a whole, generate far more manure than can be properly disposed of. Nitrates, phosphates, bacteria and viruses present in manure can seep into groundwater and pollute surface water, killing marine life and threatening public health.

According to Tony Weis, associate professor in the department of geography at the University of Western Ontario and author of The Ecological Hoofprint: The Global Burden of Industrial Livestock, increasing livestock production is a major force in the loss of biodiversity (the number of different species within an ecosystem), the pollution of waterways and climate change.

Within the past 50 years, increased affluence, urbanization and population growth have increased worldwide demand for meat. Our appetite is voracious: It's predicted that by 2050, meat production will nearly double from what it is today.

"This enormous shift [in per capita meat consumption], what I have called the 'meatification' of diets, greatly expands the land, water and resources needed for agriculture and the ensuing pollution burden," Weis says.

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When it comes to advocating for a shift to a vegan diet, Jenkins is hardly alone. In its 2010 Assessing the Environmental Impacts of Consumption and Production report, the United Nations urged a global move to a meat– and dairy-free diet in an effort to curb the environmental impacts of large-scale animal agriculture. And last week the U.S. Dietary Guidelines Advisory Committee announced it will recommend that Americans eat more plant-based foods and less meat, for better individual health and to protect the environment.

FOR ANIMAL WELFARE

Animal-welfare considerations factor in Jenkins's commitment to veganism, too. Animals raised in intensive livestock operations are crammed together in pens, small cages or on feedlots, with minimal or no access to sunlight, fresh air, open pastures or exercise. Many of us are unaware of the industrial methods – from farm to slaughterhouse – that put steak, chicken, pork, eggs and milk on our table.

The 2008 report of the Pew Commission on Industrial Farm Animal Production (a project with the Johns Hopkins Bloomberg School of Public Health) notes that animals raised for human consumption endure stress and pain at some point in their lives even in the best of conditions, and much more in intensive confinement facilities.

"Our children and future generations will be horrified that collectively we paid no attention to these issues," Jenkins contends.

That someone such as Jenkins is advocating for a shift to a plant-based diet is significant: Shortly after receiving the Bloomberg Manulife Prize, he was invested into the Order of Canada for his contributions as a nutrition scientist committed to helping Canadians make informed food choices.

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For years, we've been making dietary decisions based on the calories, fat, fibre or vitamins and minerals foods contain. But, with mounting concerns over freshwater supply, loss of biodiversity and climate change, it's time to make the shift away from animal foods and toward a plant-based diet.

As Jenkins says, "It's easier to follow a healthy diet if you have more reasons to do so."

Leslie Beck, a registered dietitian, is based at the Medisys clinic in Toronto. She is a regular contributor to CTV News Channel.