The Claim
“My friend tried veganism, felt worse, and quit — so vegan diets must be unhealthy.”
They tried veganism and blamed the diet
Quick Answer
Some people do try veganism, feel worse, and quit — but the cause is almost always execution, not plant-based eating: no B12 supplement, too few calories, a sudden fibre jump, or a diet of chips and pasta. Meanwhile the population evidence runs the other way: plant-based diets are associated with roughly 14-15% lower all-cause mortality, about 25% less ischaemic heart disease (in vegetarians), ~23% lower type 2 diabetes risk, and lower cancer incidence — and every major dietetics body affirms a well-planned vegan diet is adequate for all life stages. A loud anecdote from someone who did it badly doesn't outweigh that.
Supported by 4 cited sources
Key Points
- 1Most 'it made me sick' stories are execution failures, not the diet. In the largest survey of former vegetarians and vegans (Faunalytics, 2014), people mostly quit over food satisfaction, social friction, and convenience; only about a quarter cited health, and the complaints reported are the kind you'd expect from the two most common mistakes — skipping B12 and simply undereating (plant foods are less calorie-dense) — rather than from plant-based eating itself. (See [I tried veganism and it didn't work](/faq/i-tried-veganism-didnt-work) and [ex-vegans and health failures](/faq/ex-vegans-and-health-failures).)
- 2The 'friend who went vegan and got sick' is amplified far out of proportion to the evidence. A vivid personal anecdote is not data, and it doesn't override large cohort studies or the formal positions of national dietetics associations. Someone doing a diet badly tells you about their execution, not about the diet.
- 3The actual health evidence runs the other way. Vegetarian diets are associated with roughly 25% lower ischaemic heart disease, and both vegetarian and vegan diets with lower total cancer incidence — about 8% and 15% respectively (Dinu et al., 2017); higher adherence to plant-based dietary patterns is associated with about 23% lower type 2 diabetes risk (Qian et al., 2019). Pooled analyses also associate higher plant-based adherence with roughly 14-15% lower all-cause mortality (see [longevity and mortality](/faq/longevity-all-cause-mortality)).
- 4Every major dietetics body affirms adequacy. The Academy of Nutrition and Dietetics states that appropriately planned vegetarian and vegan diets are healthful, nutritionally adequate, and appropriate for all stages of the life cycle (Melina et al., 2016), a position reaffirmed for adults in 2025 with noted cardiometabolic benefits (Raj et al., 2025).
- 5Diet QUALITY matters more than the vegan label. A vegan diet of white bread, chips, and sugar is not health food — 'unhealthful' plant-based patterns are associated with worse outcomes, while the benefits above come from whole plant foods (vegetables, legumes, whole grains, nuts). The people who 'tried veganism and it didn't work' very often tried the junk-food version and skipped B12 — a reason to do it properly, not a reason to write off the diet.
Evidence Summary
The Faunalytics (2014) survey of 11,000+ current and former vegetarians/vegans found the leading reasons for quitting were dissatisfaction with food, social difficulty, and inconvenience, with only about 26% citing health — complaints consistent with the two common mistakes (inadequate B12 or insufficient calories) rather than plant-based eating itself. Against this, Dinu et al. (2017, Critical Reviews in Food Science and Nutrition) meta-analysed 96 studies and found vegetarian diets associated
Most of this evidence is observational and carries healthy-user confounding — plant-based eaters tend to exercise more and smoke less. Many mortality analyses measure a 'plant-based diet index' rather than strict veganism, so the strongest claim is 'more whole plant foods, fewer animal products' rather than 'zero animal products is uniquely optimal.' The benefits attach to whole-food plant-based patterns, not to processed 'junk-food vegan' diets. And none of this removes the real, easy requirements to supplement B12 and eat enough — the point is precisely that individual failures reflect planning, not the diet.
Supporting Evidence
The Faunalytics (2014) survey of 11,000+ found people mostly quit for non-health reasons; only ~26% cited health, and the complaints reported are consistent with the two classic mistakes — no B12 and inadequate calories — rather than plant-based eating itself.
Caveats: Attrition is real and worth addressing; the point is that the cause is fixable planning, not an inherent flaw of plant-based diets.
Dinu et al. (2017) meta-analysed 96 observational studies and found vegetarian diets associated with about a 25% reduction in ischaemic heart disease (RR 0.75, 95% CI 0.68-0.82) and a reduction in total cancer incidence of ~8% for vegetarians and ~15% for vegans.
Caveats: Observational data with healthy-user confounding; associations, not proof of causation.
Qian et al. (2019, JAMA Internal Medicine) pooled nine cohorts (307,099 people, 23,544 diabetes cases) and found greater plant-based-diet adherence associated with a 23% lower risk of type 2 diabetes (RR 0.77, 95% CI 0.71-0.84), stronger for healthful plant-based patterns.
Caveats: Observational; effect is strongest for whole-food (healthful) plant-based patterns, not processed ones.
The Academy of Nutrition and Dietetics states appropriately planned vegetarian/vegan diets are healthful and adequate for all stages of the life cycle (Melina et al., 2016), reaffirmed for adults in 2025 with noted cardiometabolic benefits (Raj et al., 2025).
Caveats: "Appropriately planned" is load-bearing — it means a reliable B12 source and adequate energy, which is straightforward.
The Bottom Line
The person who 'tried veganism and got sick' almost always tried a poorly planned version — no B12, too few calories, or a diet of processed junk. Done properly, a plant-based diet isn't just adequate; it's associated with lower rates of the diseases that kill most people and with lower overall mortality, and every major dietetics body says it works for all life stages. One friend's bad experience is an anecdote; the population data is the evidence — and it favours the plants.
Practical Takeaways
If someone 'tried veganism and it didn't work,' check the usual four before blaming the diet: (1) Were they supplementing B12? (2) Were they eating enough calories (plant foods are less calorie-dense)? (3) Did they get protein from legumes, tofu, tempeh, and soy — or just pasta and salad? (4) Did they ramp up fibre gradually? Fixing these resolves the large majority of 'it made me feel bad' cases. Build the diet on whole plant foods, not processed vegan junk — that's where the benefits live. More detail: I tried veganism and it didn't work.
Sources & Evidence
4 sources cited across 4 claims
Most vegan "failures" are execution (no B12, too few calories), not the diet being unhealthy.
ObservationalVegetarian diets: ~25% less ischaemic heart disease; vegan diets ~15% lower cancer incidence (Dinu 2017).
Meta-AnalysisHigher plant-based adherence: ~23% lower type 2 diabetes risk (Qian 2019).
Meta-AnalysisDietetics bodies affirm well-planned vegan diets are adequate for all life stages.
Guideline