This Is Why Going Vegan Can Cause Havoc On Your Bowels

Photographed by Kate Anglestein.
Welcome to Bathroom Break, Refinery29’s series all about poo and the complicated relationship we have with our bowels. To see the rest of the articles, click here.
It’s never been easier or more common to be vegan in the UK. The number of vegans in Great Britain quadrupled between 2014 and 2019 and according to Sainsbury’s Future Of Food Report, vegans and vegetarians look set to make up a quarter of the British population in 2025, and flexitarians just under half of all UK consumers. This is reflected not just in population habits but in industry growth: in 2020 every top supermarket and restaurant/food-to-go outlet in the UK has its own vegan range or vegan option. Just the other week Nando’s, the chain best known for its chicken and its "cheeky" appeal, announced The Great Imitator, its new chicken alternative. Whether you’re a lentils-all-the-way purist or you're pursuing a simulated meat and dairy experience, the choices and availability these days make the lifestyle change (whether you're doing it for the environment, the ethics of the food industry or just out of curiosity) a genuinely easy switch.
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While the diet change has a far less dramatic impact on your life in general than even five years ago, perhaps less documented is the initial impact it will have on your gut. When I went vegan a few years ago, it took a long while for my poo schedule to adjust itself. I experienced it all: bloating! Constipation! Diarrhoea! I’d tricked myself into thinking that no longer eating dairy would mean bypassing any dietary bloat and discomfort. This eventually became true but I hadn’t expected the adjustment period to be quite so extreme.
The good news is that this is normal. Basically, any shift in our diet will result in a shift in our gut behaviour. According to registered dietitian Juliette Kellow: "Changing our diets can really have an impact, particularly on how fast food moves through our digestive system, from the absorption of nutrients through the process and also the knock-on effects from changes to your gut bacteria." When it comes to veganism (and broadly vegetarianism too), the greatest change you make is related to your fibre intake.
All the foods that are integral to vegan and vegetarian eating – fruit, vegetables, pulses, legumes, nuts, grains – contain a lot of fibre. If you weren’t eating a lot of those foods before, the subsequent increase in fibre intake can be quite dramatic. Fibre is really good for you and is really important for your gut health (in January I even tried to pitch fibre as this year’s sexy wellness trend, before 2020 got in the way) but when you have a sudden, rapid increase which isn’t matched by an increase in water consumption, you can head into some backed up territory.
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"It's important if you're increasing fibre that you increase your fluid intake as well," Juliette tells R29, "because fibre is a bit like a sponge – if you've got a dry sponge and you put it in water, it absorbs the fluid and becomes heavy and bulky. That's exactly what happens with fibre in our digestive system." If you haven't got much fluid kicking around to be absorbed by the fibre, it becomes really hard and dry, which is really difficult to pass, she adds. "So you can find if you've got a very high fibre intake but you don't increase your fluid at the same time, you end up with really quite hard pellets – it's difficult to go to the loo and it hurts." The advice given is that you must increase your fluid intake and that the best way to avoid this situation is to gradually increase your fibre intake – your digestive system will adapt in time.
It is also possible to eat too much fibre in general. According to Nehal Keshwala, senior specialist dietitian at Princess Grace Hospital, this can result in the opposite problem. "If you're not used to eating fibre and then you go for it and start eating a lot in one go, especially insoluble fibre, you'll find that you’ll run to the toilet straightaway." As well as going gradually, then, you need to be aiming more towards soluble fibre (things like bananas, golden linseeds and oats) instead of loading up on insoluble fibre. "Really fibrous things like celery and clementines, that will just add to the bulk of the stool and that will just make you go more frequently. Whereas soluble fibre will help soften the stool and help you pass more smoothly. That's the aim," says Nehal.
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Potentially tumultuous adjustment period aside, there are many nutritional benefits to be gained from adopting a vegan lifestyle. All the food groups that can make up the bulk of a vegan diet (fruits and vegetables, legumes, beans, pulses, herbs and spices) are really good for you gut-wise. "[Those foods] are really, really good for you," says Nehal, "because it helps boost the diversity of your gut microbes. If you've got more gut microbes it makes your immune system stronger, you can make vitamins and hormones a bit better, it makes your gut barrier strong and it helps balance your blood sugar levels. It's a good protection mechanism." A healthy load of good bacteria in your gut as a result of a high fibre diet will also help regulate your bathroom breaks – when that gut lining is stripped away it can cause constipation, bloating and diarrhoea.
However what you lack in a vegan diet can also, in a roundabout way, make going to the bathroom a problem. Without careful monitoring and inclusion of supplements, Nehal points out that you will be lacking "calcium, iodine, iron, vitamin B12, omega-3 and selenium and zinc". Calcium and iron are particularly important for making you feel good and giving you energy, but the iron supplements that you get to alleviate iron deficiency can make you constipated. Which is not ideal.
The other key factor is that of course not every vegan eats the most nutritionally rich, fibre-dense diet. The sheer volume of meat and dairy alternatives on the market as well as sweets and treats (all of which I love and am very grateful for) show that it is very possible for someone to be technically vegan without even glancing at a carrot. The relative lack of fibre or nutritional value in some alternatives will have the same effect – the diet change will freak your gut out – but in this instance it is not towards a more robust gut lining or more regular trips to the bathroom.
So what’s the solution? The same as it is for so many things: drink more water, listen to your body, work towards balance and do it gradually. Aim for 30 grams of fibre, eat a diverse and relatively balanced range of food, make sure you’re filling any nutritional gaps and you’ll be on your way to knowing if the vegan way of eating is right for you. And if you listen to your body and it isn’t, that’s fine too. For the sake of your comfort and your poo, prioritise what your gut is telling you.

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