Turning vegan: Are there any negative side effects?

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How Many Vegans Are in the UK?

Turning vegan can have a profoundly positive effect on your life, not to mention the benefits it can have for society at large, animals, and the environment. Veganism has received a lot more attention in recent years, probably due to the mounting evidence demonstrating its advantages. Perhaps this is why, according to one survey, the number of vegans in the UK went from approximately half a million people in 2016 to more than 3.5 million in 2018. In contrast, the Vegan Society estimated that the number of vegans only quadrupled between 2014 and 2019, from 150,000 to 600,000.

Is Veganism a Miracle Diet?

Whether or not the above figures are to be trusted, it is clear to see that the vegan diet is growing in popularity. From dedicated vegan menus at popular restaurants to plant-based celebrity ambassadors, countless news stories, scientific papers, and even advertisements on the sides of London buses, veganism is all over the place.

the negative side effects of going vegan

It seems like every day new claims are being made about the impact it has on environmental sustainability, immunity, future pandemics, and health and well-being. Simply take a look on social media and you will see plenty of pictures and stories about how strong, happy, and healthy people are since making the switch.

That being said, is a plant-based diet as remarkable as it’s made out to be? The growing science behind veganism would absolutely suggest that it is. Nevertheless, it’s important to understand that there is no single solution to all of the world’s problems and what’s perfect for one person does not automatically make it suitable for everyone. In fact, a vegan diet can have copious negative side effects if entered into blindly. 

What I Wish I’d Known Before Going Vegan: Negative Side Effects

Not many vegans talk about the negative side effects of their diet, maybe because they are lucky enough not to experience any. Regardless, they do exist. Whether they manifest themselves as nutritional health complications, social difficulties, or lifestyle-based challenges, it’s my opinion that transitioning vegans should be aware of these consequences. By being informed, newcomers will know how to prevent or mitigate negative side effects and, therefore, might not fall off the wagon never to return to veganism ever again.

Below are some of the things I wish I had known before going vegan along with my suggested preventative measures. I hope that they help others to transition without facing the same difficulties as myself and many other vegans I know.

Negative Vegan Side Effect #1: Nutritional Deficiencies

At first glance, a plant-based diet might seem restrictive: we can’t eat meat, fish, eggs, dairy, or honey. Cutting out whole food groups can certainly have its consequences and so it should come as no surprise that some vegans end up with nutritional deficiencies. Nutrients such as omega-3, iron, calcium, iodine, and vitamin B12 are more difficult to obtain from plant-based foods.

Check out these nutritional vegan breakfast, lunch, and dinner recipes for inspiration

For example, although seaweed is often lauded as a great way to increase your iodine intake, it’s actually an incredibly unreliable source due to its variable levels. What’s more, although iodine is present in other plant foods, most contain very low amounts. It’s entirely possible to consume too much and you don’t want too little either as it can lead to conditions such as hypothyroidism.

Another extreme negative side effect that vegans can experience is irreversible nerve damage due to vitamin B12 deficiency! That’s not to say that non-vegans don’t also face these risks if they don’t eat healthily enough but there are certain deficiencies that vegans are more likely to encounter. 


Luckily, these are all avoidable as long as we remain aware of what we are eating and take supplements to replace anything that’s missing from our diets. The majority of important nutrients are easily obtainable as long as we eat lots of healthy plant-based foods including fresh fruit, vegetables, legumes, and whole grains. However, as mentioned above, there are some nutrients that we should acquire through supplements – The Vegan Society makes a fantastic multivitamin formulated specifically for vegans!

I would also recommend making an appointment to get your bloods checked once you have settled in to your new diet. This way you can find out for certain the nutrients you may be lacking.

Negative Vegan Side Effect #2: Weight Loss or Gain

Many vegans experience weight loss (or in my case weight gain) as a negative side effect when they go vegan. Primarily, this is because your body will be adjusting to a completely new diet. However, some people may struggle to get as many calories as they were consuming before making the transition. On the other hand, if you’re like me, then you may get excited by all of the new vegan convenience food products that are being released and eat too many calories as a result. It all comes down to the type of plant-based diet you adopt.

the negative side effects of going vegan


Initial weight fluctuations are to be expected when transitioning to a completely new diet. Nevertheless, you can mitigate and maybe even prevent this altogether by building a healthy and balanced eating routine from the word go and make sure you are consuming everything you need. What’s amazing about the vegan diet is that you can easily adapt it to lose weight, maintain it, or even gain muscle.

Check out these amazing vegan female bodybuilders smashing all the stereotypes!

Negative Vegan Side Effect #3: Fatigue

Some people feel slightly lethargic when they switch to a vegan diet. This negative side effect usually brought on by nutritional deficiencies or not getting enough calories.


Eat a balanced and varied diet to make sure you are getting enough iron, iodine, protein, and calories! Take supplements if required. If you continue to experience fatigue, then make an appointment with a doctor as there may be an underlying condition.

Negative Vegan Side Effect #4: Digestive Issues

The human body is an amazing ecosystem that works tirelessly to keep us alive. The gut, in particular. Is an incredibly complex arrangement that controls the digestion of our food and impacts our nutrition, immunity. And even our mental health. However, it doesn’t work alone. In fact, the gastrointestinal system contains between 300-500 bacterial species that form a coalition with human cells and chemical pathways to regulate bodily functions. This community of bacteria and other microorganisms are known as the gut microbiome.

Each and every one of us has our own unique microbiome which has developed throughout our lifetime. And optimized for whatever we eat most. Therefore, when we change our diets our guts suddenly presented with a whole new range of nutrients. As a result, many vegans will experience negative side effects such as bloating, gas, constipation, and/or diarrhoea.

Moreover, if you are eating plenty of plant-based foods. Then you will probably consuming more fibre than your body used to. Fibre is plant material that feeds our gut microbiome and helps move the waste out of our bodies. Health professionals generally agree that the more fibre you eat the better. Unfortunately, a sudden increase sometimes leads to unpleasant but usually temporary side effects. Some people also experience a heightened sensitivity to gluten after transitioning to veganism and. Whilst this hasn’t been thoroughly researched yet, may something to be aware of.


Some people find that making a slower transition to a vegan diet can help relieve the negative consequences. Alternatively, try increasing your fluid consumption and being more active. If these don’t work then you could investigate which foods trigger your symptoms by keeping a food diary. From the results, you can work out what you need to avoid. As always, if your symptoms persist and are causing you discomfort, then you should contact a doctor or nutritionist.

Negative Vegan Side Effect #5: Social Challenges

Personally, the hardest part of adopting a plant-based diet has been the social challenges. When going out for food with non-vegan friends. It’s common to have no other options than a plate of chips or a salad. Sometimes, even those aren’t available and many of us vegans been left to go hungry. And I’m sure I used to receive more dinner party invitations…but may that’s because I switched to a plant-based deodorant.

the negative side effects of going vegan

To be fair to my friends, they have been incredibly supportive about my diet. And I’m very lucky to have a mainly vegetarian and vegan family. Others are not so lucky and I know of plenty of vegans who have been met with negativity. Freely mocked and taunted. And even had meat products intentionally snuck into their meals. Be warned, people been known to make it their personal mission to catch you out and. There are a few pointless debates that you will find yourself repeating again and again.


This is one of those negative side effects that doesn’t have a perfect solution. Whilst there are things you can do to prevent some social challenges. It’s impossible to control other people’s actions and feelings. For me, it’s good to remember that I also used to eat animal products; it’s a social norm. Most importantly be prepared. Whether that’s eating before you go out with friends, bringing plant-based food-on-the-go, or readying yourself with some well-educated (but peaceful) responses to frequently asked questions. And remember not to give anyone a hard time about their dietary choices as. It usually makes people defensive and will likely just put them off veganism even further.

Positive Side Effects of Going Vegan

There are lots of great reasons to become a vegan and. Depending on your choices, this could bring benefits to your health, conscience, animals, society, food security, the environment, etc. But let’s face it, instinctively, we just know it’s the right thing to do.

Alice Johnson 
Alice Johnson 
Alice Johnson is a freelance writer, keen musician, and co-founder of Vegan Sisters’ Online Community, which offers training courses for content writers. She is passionate about public health, animal rights, sustainable living, plant-based food, travelling, conservation, and rescuing stray animals on her way around the world. Alice has made appearances on BBC News and her work has been published in national scientific journals, print magazines, and on web-based news channels. When she’s not in the kitchen experimenting with cashew cheese, homemade body moisturisers, and vegan kimchi, you probably won’t be able to find her as she will be off gallivanting around the world.