People abandon plant-based eating for any number of reasons, but it’s often because they didn’t feel well as vegans. Some are so convinced that their former diet was damaging to their health that they even become activists against veganism.

If you poke around the internet and read stories of ex-vegans, it becomes pretty clear that at least some of them never wholeheartedly embraced the principles of vegan lifestyle to begin with. In one interview, Rhys Southan, an ex-vegan who blogs about veganism, said, “I’ve come to appreciate ethics as one possible ingredient in a meal, but not a mandatory one.”

Other ex-vegans might believe that, animal suffering notwithstanding, the personal sacrifice involved in being vegan is just not worth it. Ex-vegan Pamela Wilson writes on her blog: “I found the vegan lifestyle, with its emphasis on purity from animal products, emotionally and socially taxing in a way that was incompatible with my maximal well-being in the long term.” 

Quite a few ex-vegans seem to buy into myths about protein and fats—the type of myths that make it impossible for them to believe that a diet free of animal foods can support health. They expect to feel unhealthy and so they do. They also confuse food cravings with nutrient or dietary needs. Health beliefs can have a powerful placebo effect which helps explain why some people feel instantly better when they adopt a vegan diet and some feel instantly worse.

A recurring theme among ex-vegans is that they often felt depressed and their thinking was “fuzzy” when they ate a diet free of all animal foods. Some attribute this to a lack of EPA and DHA (the omega-3 fats in fish oils), among other things. But a study comparing mood among vegetarians and omnivores showed better scores for the vegetarians despite their lower intakes of EPA and DHA. (And even if EPA and DHA are an issue, there are vegan sources of these fats now.) Others suggest that vegans don’t get enough saturated fat in their diet for proper brain function. There is no dietary requirement for saturated fat, though, since the body can make all it needs from unsaturated fats.

Diet can affect mood, but that doesn’t mean it is always the culprit. For one thing, mood may simply change over time for a host of reasons. A new study published in the Proceedings of the National Academy of Sciences suggests that happiness in life follows a U-shaped curve. That is, overall happiness declines as we head toward middle age and then starts climbing again well into our eighties.

It would be interesting to know if vegans are any more likely to be depressed than anyone else. Brain scans suggest that vegans and vegetarians are more empathetic than omnivores. Being empathetic isn’t necessarily always great for mental health. It can be painful to be especially sensitive to the plight of enslaved and abused animals.

But there are certainly dietary factors that can affect overall mood and plenty of things that we vegans can do to protect our mental and emotional health. I’ve written here about some of these. One of the most important factors is vitamin B12. Based on some recent research, Jack Norris has updated his recommendation for this nutrient. Take a look at his post and make sure you are getting enough B12—either from fortified foods or a chewable or sublingual supplement.