Studies shine light on health effects of vegetarian and vegan diets
With winter courses and exams coming to an end, Naomi found herself with a lot of extra time on her hands. She spent much of that free time watching documentaries related to nutrition and the environmental impact of food consumption on the planet.
The result? After seeing a few videos from the People for Ethical Treatment of Animals (PETA) website, she decided to become a devout vegetarian. After breaking the news to her family, the first questions from her Alberta parents related to the health effects of following that path.
Vegetarian and vegan diets have become increasingly popular in recent years, and for a variety of reasons, including religious convictions, environmental impact, animal welfare, the use of antibiotics and hormones in livestock and the common view that this is a healthier way to eat. Thanks to the year-round availability of fresh produce in the grocery store and more dining options, becoming a vegan or vegetarian has also become easier than it used to be.
Omnivores are those who eat all types of food, including meats, fish and animal products. A vegetarian is someone who eliminates all animal flesh, including fish and poultry, from what they eat. In a vegan diet, all animalbased products are also avoided, including dairy products and eggs.
In the past, some have argued that vegetarian and vegan diets would lead to protein deficiency as a result of avoiding meats, or in the case of vegans, weak bones from not drinking enough milk. But how true are these claims? Does a vegetarian or vegan lifestyle mean a deficiency in certain important nutrients?
Studies have suggested that those on vegetarian and vegan diets do have healthy bones and even higher blood protein levels than omnivores. Studies are confirming that vegetarian and vegan diets, when properly balanced, not only provide the necessary nutrients for life, but may also provide health benefits in the prevention of certain diseases.
The research on this question is extensive but also somewhat messy; we’ll elaborate on that later.
Recently, investigators in Florence, Italy, published a systematic review of the evidence on the association between vegetarian and vegan diets and a variety of critical health outcomes, such as your chances of dying from any cause, having a heart attack and getting cancer.
The most compelling and favourable findings were that vegetarian diets reduce your risk of cancer by eight per cent and your chances of getting heart disease by 25 per cent. Vegans are far less well studied but seem to enjoy a 15 per cent reduced risk of developing cancer.
Just to be clear on the numbers and using veganism as the example, if you had a 20 per cent chance of developing cancer in your lifetime, that would fall by three per cent (15 per cent of 20 per cent) if you were a vegan. In other words, your risk of developing cancer would go from 20 per cent to 17 per cent.
Despite tens of thousands of participants in all these studies, there was no convincing benefit with regards to overall death rates or mortality. There was also no clear sign that your chance of actually dying from cancer was any less if you were a vegetarian or vegan. Similarly, no specific cancers occurred less frequently for those following meat-free diets. Lastly, the likelihood of dying from a heart attack or stroke was not convincingly reduced with vegetarianism.
This raises an intriguing but unanswered question: If vegetarians are not at a lower risk of dying from the major killers in western society, i.e. heart disease and cancer, then what explains an overall rate of death that seems to be similar to the omnivores? If you are wondering about things like obesity, blood sugar and cholesterol levels, meat-free diets lead to clear improvements, although these improvements don’t consistently translate into living disease-free and longer.
It is important, however, to appreciate the limitations of all this research: the messy part. The only scientifically unequivocal way to determine the health benefits of vegetarian and vegan diets is to randomize large groups of people to one diet or another; something that is generally not feasible for the time period required to see an impact on lifespan. The studies we have follow vegetarians and vegans and either collect information on them on the spot or follow them for many years. That’s anywhere from four to 21 years in the Italian systematic review papers, which may still not be long enough for health benefits to become apparent.
While these studies did their best to measure other important factors, such as diet, smoking and exercise, it is unlikely that all of the potentially important lifestyle factors were accounted and corrected for. If vegans and vegetarians have healthier lifestyles than omnivores, the reduced risk of developing cancer and heart attacks may be the result of something else.
It is important to note that the benefits of a vegetarian diet only exist if recommended guidance on nutrition, fat consumption, and weight control are followed. For example, although a diet that consists strictly of chips and soda may be vegetarian, it will not yield any benefits. A healthy vegetarian diet is mostly plant based and includes a wide variety of fruits, vegetables, whole grains and fats, like those found in olive oil and avocados. And, just as with any diet, it is important to practise moderation of all foods consumed and engage in physical activity.
For guidelines on foods that must be included for a healthy vegetarian diet, visit myhealth. alberta.ca and search vegetarian or vegan diet to find helpful advice and information.