So, actually how healthy is your vegan lifestyle?
Vegan? Pescatarian? Flexitarian? The term 'plant-based' can cover a broad spectrum of eating and while research shows that consuming more vegetables, legumes, nuts and wholegrains has health benefits, not all plant-based diets are created equal, writes Katy McGuinness
It can be hard to keep up when it comes to deciding what foods we should and should not be eating for the good of the planet, but one thing's for sure - the shift towards plant-based eating shows no sign of abating, with those who eat meat on a daily basis increasingly regarded as some class of evolutionary throwback.
But leaving aside the climate change debate for the moment, what about the impact - for good or ill - a plant-based diet has on individual health? Is it possible to improve our health by turning vegan, for instance, or does our long-term health suffer if we don't include animal protein in our diet?
Dietician Maeve Hanan says that there is no specific definition of a plant-based diet.
"The term refers to a spectrum of ways of eating that covers everything from vegan and vegetarian to flexitarian and pescatarian," she explains.
A new study from Harvard's TH Chan School of Public Health analysing data from over 300,000 participants has concluded that eating a plant-based diet may lower the risk of developing type 2 diabetes, as well as lowering blood pressure, and reducing insulin sensitivity, weight and systemic inflammation.
Unsurprisingly, the greatest benefit was seen in those who consumed a plant-based diet containing low levels of unhealthy foods, implying that following a plant-based diet primarily comprised of unhealthy foods - highly-processed foods and snacks containing high amounts of saturated fat - would do little to reduce an individual's risk.
So, not all plant-based diets are created equal.
Interestingly, Qi Sun, the study's senior author and an associate professor in the Department of Nutrition, said that a healthy plant-based diet could include low or modest amounts of animal products, white flour, sugar and potatoes. Which sounds like being able to have your cake and eat it - just not too big a slice.
The Harvard study coincides with other research that concluded that following a diet low in animal protein might lower the risk of developing cardiovascular disease. A new study from Johns Hopkins Bloomberg School of Public Health examining data from over 12,000 middle-aged people found that eating more vegetables, legumes, nuts, and wholegrains and fewer animal products correlates with a much lower risk of dying of a heart attack or another serious cardiovascular event.
Participants who had the highest intake of plant-based foods were 16% less likely to have a cardiovascular condition - such as a heart attack, stroke or heart failure - when compared with adults who consumed the smallest amount of plant-based foods.
Consumers of large amounts of plant-based food were also 25% less likely to die from any cause and had a 32% lower risk of dying from a cardiovascular condition. Lead researcher, Casey M Rebholz, said that while it was not necessary for people to stop consuming animal products completely, in order to reduce cardiovascular disease risk, people should eat more vegetables, nuts, whole grains, fruits, legumes, and fewer animal-based foods.
The EAT-Lancet report was published last January, coinciding with Veganuary. A consensus report from over 30 scientists from across the globe, it defined what constitutes a healthy diet from a sustainable food system and called for the reduction in consumption of animal protein, highly processed foods and added sugar. It has been criticised for lack of scientific rigour, its negative impact on human health and the livelihoods of farmers, and for the fact that amongst the interests that it promotes are those of global food conglomerates behind the manufacture of highly processed vegan foods.
So it's not all good news when it comes to plant-based diets, with the most questions being raised about restrictive vegan diets.
A number of high-profile vegans have given up the diet on the basis of health issues. Earlier this year, Tim Shieff, YouTuber and athlete, abandoned his vegan diet citing "digestion issues, depression, fatigue, brain fog, lack of energy", and "waking up stiff". Actress Anne Hathaway said that eating a piece of salmon after years of veganism when she felt neither healthy nor good nor strong, made her feel as if her brain was "re-booting".
One vegan-turned-omnivore, speaking anonymously, reported that she lost her hair and suffered from very dry skin when following a vegan diet - and gained weight because she was mainly eating bread, pasta and rice. She has now incorporated meat and fish into her diet and reports an improvement in her skin, while her hair has grown back to cover her bald patches.
Statistically in the UK, most vegans are affluent female millennials who live alone; the vast majority do not have children. Becoming pregnant and having children is a trigger for many vegans to reassess their diet and adopt a less restrictive approach.
"As well as the usual dietary changes that need to be made when pregnant," says Hanan, "those who follow a plant-based diet [especially a vegan diet] need to pay extra attention to getting enough omega-3, iodine, vitamin B12 - all of which are needed for healthy brain development in a foetus. It is also important to get enough iron and calcium, for the health of both baby and mum, and vitamin D supplements are advised."
Hanan says that this advice applies equally to breastfeeding mothers.
"Breastfeeding also increases the requirements for protein and zinc, which can be found in plant-based sources like tofu, lentils, beans, chickpeas, quinoa, nuts and seeds," says Hanan. "Plant-based sources of calcium include fortified plant-based milk alternative drinks and yoghurts, calcium-set tofu, spinach, bok choy, baked beans, Brazil nuts and almonds."
Parents need to be sure that children are getting the nutrition that they need for healthy development. In Belgium, a couple who owned an 'alternative' food shop were convicted of killing their baby by feeding him a nutritionally-deficient diet that left him dehydrated and malnourished, with organs shrunk to half their proper size.
So, with arguments on both sides, is a plant-based diet for everyone?
"It's all about context," says Hanan, "but taking the evidence as a whole, the best diet for health is plant-based and flexitarian, with red meat once a week, some dairy for iodine and oily fish for omega-3." This plant-based flexitarian diet sounds a lot like the Mediterranean diet, already shown to reduce the risk of developing type 2 diabetes, and like a balanced omnivorous diet that includes plenty of plant-based foods alongside the meat and dairy that are an integral part of our food culture.
"If you are making the switch to a more plant-based diet, it's important to get a good variety of plant-based protein for fibre, vitamins and minerals," says Hanan. "Animal proteins are complete, in that they contain all eight amino acids, while the only plant proteins that are complete are soy, hemp and quinoa.
"With other plant proteins you need to combine them to make them complete - so, for instance, if you are having a bean or lentil curry you need to combine it with wholegrain rice to make it complete.
"When it comes to processed plant-based foods, there are some exciting new products emerging that are more nutritionally balanced than their predecessors. Some of the new burgers, Beyond and Impossible for example, are fortified with B12 and contain a good amount of protein, while others, for example those based on jackfruit, contain little to no protein.
"And for good gut health, we should all be aiming to eat a variety of plants, ideally 30 different types each week. People tend to think of plants as fruit and vegetables, but other types of plants are nuts, seeds, wheats, oats, beans, lentils and tofu."
Hanan says that there is a risk for anyone cutting out any food group that they can become deficient in key nutrients, and that vegans in particular need to be careful that they are eating a balanced diet and supplementing if necessary.
"It depends on the diet and what is and is not being included," she says. "Most vegans need to supplement their diet with omega-3 and Vitamin B12, and I have seen cases of iron deficiency and poor bone health in patients following a vegan diet. Another concern with veganism and any other restricted diet is that it can mask disordered eating, and that is becoming more rather than less common."
Hanan says that there is evidence that a well-balanced plant-based diet can improve heart health, help with weight loss and bring other health benefits.
However, she says some vegan processed foods are still high in saturated fat due to containing coconut oil, and it's not healthy to consume them too often.
"We wouldn't advise anyone to eat a processed plant-based burger any more often than we would advise an omnivore to eat a red meat burger. It all depends on balance - a vegan could be eating chips all the time and that's not healthy.
"Coconut oil [contained in many processed vegan foods] has never been promoted by dieticians for health - you can include small amounts in your diet, but I think it's most useful on the skin and as a hair conditioner!"