Several weeks ago, environmental scientist Cara Augustenborg appeared on her regular Newstalk radio slot to discuss her experience with veganism. She had announced her intentions earlier in the year to follow the plant-based diet as an experiment, and as a way of taking part in “Veganuary” – a movement that invites omnivores to become vegan for the month of January.

Her scientific approach to veganism included having a health check at the beginning and the end of the experiment, which lasted roughly 2.5 months.

During that time, she took a vegan cookery course, stayed away from plant-based “junk food” and cooked all of her own meals. When she received her test results at the end of her experiment, she was surprised.

“I saw that my vitamin B12 score had halved – it was still in the normal range, but it went down by half,” she says. “My iron dropped below normal levels to 10%. That was a huge shock to me. I was eating lots of spinach, beans and all the vegan marketing says you can get everything you need from plants – I really believed that.”

Cara didn’t take nutritional supplements during the experiment because she felt, as a healthy adult, she should be getting all of her nutrients and vitamins from her diet.

She originally predicted that the two main areas of positive change would be in her visceral (internal) fat levels and her cholesterol. In fact, neither changed in a positive way.

“Even though my bad cholesterol went down slightly, my good cholesterol also went down,” she says. “As a result, my overall cholesterol score got worse. It went from 2.5 to 2.9 – which is still healthy – but honestly, I expected it to get better, not worse!”

I want to eat what’s best for my body but also do what’s best for the environment

While she continues to limit her intake of animal products, at the time of writing she has brought eggs, milk and chicken back into her diet. She is choosier when it comes to her purchases and now leans toward organic food products – but for environmental reasons, rather than health.

“I want to eat what’s best for my body but also do what’s best for the environment,” she says.

“In the past, I would have advocated for plant-based diets and if you’re advocating something you should try to do these things for yourself. [Now], I will be cautious about how I promote plant-based eating. But maybe it was just how the diet affected my personal health – maybe it would work out better for others.”

Registered dietician and founder of Eatwell.ie Sarah Keogh says that the discussion around diet and nutrition can often be confusing.

“[For example], it’s very difficult to have a vegan diet without supplements,” she says. “There’s a myth that it’s insanely healthy and you can get everything from it nutritionally, and you just can’t.

“There are nutrients that are either very low or absent in a vegan diet, so you need to look at food sources that have been fortified or take the supplements.”

Sarah recommends a vitamin D supplement for everyone in Ireland, but especially for those following a vegan diet. Vegans should also take a vitamin B12 supplement.

You could be ingesting lots of iron but if you don’t have enough B12, you’ll have low levels of haemoglobin

“Vegan sources of B12 will not do the job,” she says. “Seaweed looks like it contains mountains of vitamin B12 when tested in a lab – but when that particular type of B12 is ingested by humans or animals, it doesn’t behave the same way [in the body].”

Those presenting with low iron or anaemia could be fooled into thinking they aren’t eating enough iron-rich foods, but low haemoglobin levels can also be caused by a lack of vitamin B12. We naturally absorb this vitamin through foods like fish, eggs, beef and milk.

“You could be ingesting lots of iron but if you don’t have enough B12, you’ll have low levels of haemoglobin,” Sarah says.

When Cara spoke about her visceral fat (found around your organs) problem, she was confused when she was told it’s often caused by eating unhealthy, highly processed foods.

Simply changing your diet wouldn’t make any difference to visceral fat

“Sure, I probably eat too much food but the kind of food I eat is healthy and from as close to the ground as possible,” she says. “I don’t do processed or frozen foods at all.”

Sarah says that visceral fat usually isn’t an indication of the types of foods we eat, but it can be an indication that we are consuming too many calories.

“Simply changing your diet wouldn’t make any difference to visceral fat. Instead, you usually have to decrease calories or increase exercise.”

As for cholesterol, Sarah says that, often, the biggest benefit of having a plant-based diet is increased heart health.

“You will usually see a reduction in heart disease because [vegans] are usually a healthier weight,” she explains.

“They also, generally, have more fibre, potassium and heart-healthy nutrients in their diet. Changes in cholesterol levels are heavily influenced by what we eat and can change regularly.”

The US Centre for Disease Control recently listed obesity (a body mass index of over 40) as an increased risk factor for developing complications from COVID-19. This follows the results of their study on both global and US-based COVID-19 cases, which showed an increased risk of mortality in obese patients under the age of 65.

The World Health Organization has been promoting a healthy eating campaign amidst the COVID-19 pandemic; maintaining that a balanced diet will keep your immune system strong. While healthy eating habits have a positive effect on your overall health, Sarah reminds us that food itself will not increase immunity.

“There’s nothing that’s going to ‘boost your immune system’,” she says. “Eat the right foods so your immune system can function as normal – plenty of oily fish, nuts, seeds and a vitamin D supplement.”