At 9.30 am on May 19, 2015, Kuntal Joisher, a software engineer, stood on top of the world at the summit of Mount Everest after a 12-hour grueling climb. What distinguished Joisher from all climbers before him was that he is a vegan and survives on an entirely plant-based diet.

Most climbers, especially those climbing to peaks higher than 8,000 meters, are prescribed meat and dairy rich foods. Till recently it was considered impossible for a vegan to climb to such high elevations. But Joisher proved the sceptics wrong. Throughout 60 days of his climb was perfectly fit and reported no altitude sickness.

Joisher is no novice. Before climbing Everest, he scaled Mt Elbrus in Russia, which is one of the peaks of the Seven Summit challenge that involves climbing the highest peaks on each continent. He has also climbed Mount Manaslu, another 8,000-meter peak in Nepal and the eighth highest peak in the world.

“My diet has never been an issue," said Joisher. "I’ve been part of over ten serious Himalayan climbing expeditions, and I’ve never had any problems being a vegan, even on this last attempt to climb Everest”

Joisher’s assertion comes shortly after the death of South African mountaineer Maria Strydom on Mount Everest. Strydom, who died just two days after Joisher reached the mountain’s peak, took on this ultimate mountaineering challenge to prove that “vegans can do anything”, said news reports. She and her husband wanted to complete the Seven Summit challenge to dispel the notion that vegans are malnourished and weak.

Strydom made an attempt to climb to the summit of Everest on May 20, but had to turn back because she felt unwell. After spending a night at a camp, she died on her way down the mountain the next day.

Since Strydom’s death, however, questions have arisen about the suitability of veganism for high-altitude mountaineers.

“While diet and altitude does have a connection, it does not mean that one only needs to have meat and eggs to get the necessary amino acids and proteins," said Luke Coutinho, a nutritionist and fitness coach specializing in lifestyle and integrative medicine. "These can be got very much from plant-based foods as well. And being on plant-based food, one can also play a sport, run marathons and do other high intensity sporting activities."

What mountaineers eat

Research indicates that high altitude mountaineers can burn upwards of 6,000 calories per day in the mountains. With excessive stress on their bodies, mountaineers' very survival depends on a diet that includes a variety of foods to provide sufficient carbohydrates, proteins, fats, vitamins and minerals to support them nutritionally during their expedition.

Climbers on Everest feed themselves well until they reach camp 4, which is at 7,950 metres above sea level. A typical Everest-climber’s diet would include protein-rich foods such as eggs, yak cheese and canned tuna. At Everest Base camp, Joisher had other things on his plate. He ate puffed rice (poha), puri bhaji, vegan Tibetan bread and pancakes, dal-rice, vegan pasta and burgers, pav bhaji and even a vegan cake. Once he started climbing he focused on supplying his body with electrolytes and carbohydrates.

“In fact, meat and other proteins take a long time to digest, and your body would be needlessly expending energy to digest this food,” he said.

At higher elevations, exhaustion and low oxygen tend to steal away climbers’ appetites. Once he was above 8,000 meters and into what’s called the Death Zone, Joisher ate only two Oreo biscuits while he made is way from up to the summit and back down to camp 2 at 6,400 metres. He supplemented this with carbohydrate-dense energy gels that long-distance runners sometimes use.

Vegan vs non-vegan climbers

Mainstream research in high altitude physiology concludes that the human body performs best at high altitudes when on a high carbohydrate, moderate fat, low protein diet. A vegan diet is is supposed to put far less stress on the body, which in turn helps acclimatise at high altitudes better.

“I know lots of derogatory comments have been going around about Strydom being a vegan and how she died,” said Joisher. “The truth is that she died because of altitude sickness. Altitude sickness doesn’t discriminate based on dietary choices. Anyone, even the strongest of the mountaineers and Sherpas can get it. Eating meat or not has no bearing.”

Joisher added that another vegan, Paula Leonard from Alaska, also summited Mount Everest on the same day that he did.

According to Rajat Chauhan, a doctor of sports medicine and ultra-marathoner who high-altitude runs in Ladakh: “Diet and high altitude – there is no connection as such. What is important is that your body should get the necessary protein and fat intake which is required for high altitude and that can be got from any diet. For vegetarians and vegans the required amount is got by taking supplements.”

Said Aashish Contractor, head of rehabilitation and sports medicine at HN Reliance Foundation Hospital: “For any kind of high-altitude activity, endurance is important and for that good training with good diet that gives you all the required amount of carbs, proteins and fats is essential."

He added: "Being vegan or a vegetarian or a non-vegetarian has nothing to do with climbing mountains.”

General physician Akshat Chadha advises that a climber have a complete health check-up prior to the climb making sure that her heart, kidney’s and liver support the arduous task. "As a doctor I would also say that the individual should also be well within normal limits on his vitamin D and B12, calcium, iron and other mineral levels," he added.

Climber and the cause

Joisher was a vegetarian born into a Gujarati family and became vegan 13 years ago when he moved to Los Angeles to study and work. “Being vegan is a way of life for me," he said. "I became a vegan to take a stand for animal rights while studying at The University of Southern California. I feel very strongly about this cause and is not going to waver anytime soon.”

Despite arguments from more traditional mountaineers, Joisher believes it is easier and healthier to engage in serious high-altitude mountaineering on a vegan diet. But Joisher is a vegan when it comes to his gear as well. He has replaced his leather boots and gloves with synthetic fibre ones. He has also acquired non-down pants, caps and synthetic sleeping bags.

His one lament is that he hasn’t been able to change his full-body, down-filled suit that mountaineers wear on summit day on Mount Everest to a vegan-friendly version despite having written to six international companies who manufacture mountain suits.

“I even thought of tearing up my synthetic sleeping bag and wearing it on summit day as a body suit," he said. "But what if I died on Mount Everest wearing it? That would be such a bad publicity for the vegan cause.”