Plant-based eating has moved from the margin of the supermarket to the middle of it, and with it a question that used to belong to dietitians: where does vitamin B12 come from when the animal foods step aside? A paper published on 13 October in the European Journal of Nutrition puts numbers to that question using eleven years of British national diet survey data, and its most interesting finding is not that a gap exists. It is that a gap remained in the group using the most supplements.
What the survey actually measured
The authors pooled the UK National Diet and Nutrition Survey across 2008 to 2019 — eleven years of a rolling programme whose yearly samples are independent, so these are pooled survey years rather than repeat measurements of the same women — and restricted the sample to non-pregnant women aged 18 to 45 with at least four days of food-diary data and usable blood biomarkers. The analytic sample was 2,299 women, of whom 2,204 were omnivores and 89 vegetarians. Intake of B12 and folate was calculated from food and from supplements separately, and status was read from serum B12, holotranscobalamin (the fraction of B12 available to tissues), homocysteine — which rises when B12 is short — and red-cell and serum folate.
It is a cross-sectional analysis of a survey, not a trial, and the vegetarian subgroup is small. Both facts shape everything below.
The intake gap, in micrograms
Mean dietary B12 intake was 4.3 micrograms a day among omnivores (95% CI 4.2–4.5) and 2.9 micrograms among vegetarians (2.5–3.3). Against the European Food Safety Authority’s adequate intake of 4 micrograms a day, 51.7% of omnivores and 78.2% of vegetarians fell short on diet alone.
Then the authors added supplements into the total. The share below 4 micrograms a day moved to 49.2% of omnivores and 65.9% of vegetarians — a real narrowing, but not a closure. Their reading of that residual is blunt: supplementation in this group appears either inconsistent or dosed too low. Which dose and for how long, the data cannot say.
What the blood work showed
Serum B12 averaged 271.3 pmol/L in omnivores and 231.0 pmol/L in vegetarians, a difference the analysis did not find statistically significant (p = 0.1). The tissue-availability marker behaved differently: holotranscobalamin was 63.1 pmol/L versus 39.8 pmol/L (p < 0.001), and total homocysteine was 8.49 versus 11.22 micromoles per litre (p = 0.009). The vegetarian difference in holotranscobalamin barely moved after adjustment for confounders, which the authors take as a sign it reflects the dietary pattern rather than demographics.
Prevalence figures come with wide uncertainty in the vegetarian group, and the paper prints confidence intervals whose lower bounds dip below zero — a symptom of 89 people, not a subtlety to smooth over. With that caveat stated: 29.2% of vegetarians (95% CI 8.1–50.3) and 15.7% of omnivores (12.6–18.8) had serum B12 below 180 pmol/L, one common threshold for deficiency. Under the looser 258 pmol/L cut-off for possible deficiency, the shares were 79.2% and 53.4%.
Those looser thresholds are worth handling carefully. When 66.4% of omnivores and 94.3% of vegetarians sit below the holotranscobalamin cut-off for possible deficiency, the category is describing a broad band of suboptimal status rather than a diagnosis for most of the people in it.
Three reference values, three different answers
Part of the confusion in this field is definitional. The U.S. recommended dietary allowance is 2.4 micrograms a day for adults 14 and older, 2.6 during pregnancy and 2.8 while breastfeeding, as MedlinePlus sets out. The UK’s reference intake is 1.5 micrograms a day, a figure last revised in 1996 and built around preventing megaloblastic anaemia. The EFSA adequate intake is 4 micrograms.
The authors argue the higher end is closer to what the biology needs: serum B12 and holotranscobalamin, they note, plateau only at intakes somewhere around 4 to 7 micrograms a day, and they propose that UK guidance move to at least 4 micrograms, particularly for women of childbearing age and those eating vegetarian diets. That is a recommendation about population guidance, offered by three researchers on the basis of cross-sectional data. It is not a personal prescription, and it has not been adopted by any agency.
Where federal guidance already agrees
None of this is a discovery that plant-based diets are dangerous. It is a rediscovery of something the current U.S. Dietary Guidelines state plainly. In its section for vegetarians and vegans, the 2025–2030 edition tells readers to “pay careful attention to potential nutrient gaps,” notes that vegan diets in particular show broader shortfalls that include vitamin B12, and advises monitoring nutrient status periodically — “especially for iron, vitamin B12, vitamin D, calcium, and iodine” — with targeted supplementation named as the route to avoiding those gaps.
MedlinePlus makes the same practical point from the consumer side. Vitamin B12 is “naturally found in animal foods such as fish, meat, poultry, eggs, milk, and milk products,” it notes, and “is not present in plant foods unless fortified.” Fortified breakfast cereals are listed as a readily available source for vegetarians, and some nutritional yeast products contain it too. Its list of groups most likely to be short includes people over 50, those following vegetarian or vegan diets, people who have had stomach or intestinal surgery, those with digestive conditions such as celiac disease or Crohn’s, and people with pernicious anaemia.
That last list is the reason the supplement question is not a lifestyle debate. For some of those groups, absorption is the problem rather than intake, and a food-first argument does not address it.
What the study cannot tell you
Three limits deserve more weight than the prevalence figures. The design is cross-sectional, so it can describe a snapshot but cannot establish that lower intake produced lower status or that supplements would fix it. The vegetarian group is 89 women in one country, which is why the intervals are so wide. Diet was self-reported in four-day diaries, and unmeasured factors — medication, genetic variation in B12 and folate metabolism, two B vitamins the analysis did not include — cannot be ruled out.
There is also a selection question the data cannot answer. People who already suspect a gap may be the ones buying supplements, which would make supplement use a marker of concern rather than a measure of it.
What this changes for a shopping list
For anyone eating little or no animal food, B12 is the nutrient where “get it from food” stops being self-evident, and where a fortified food or a supplement is the ordinary, unglamorous solution rather than a shortcut. The open questions — dose, form, how often — are the ones a clinician or registered dietitian is positioned to answer, especially during pregnancy or when planning one, and especially for anyone on the absorption-problem list above.
What the paper does not support is the larger claims that tend to attach themselves to nutrient-of-the-moment coverage. It says nothing about energy, cognition or “detox” in this population. It does not show that a supplement resolves a deficiency on its own, and it does not turn B12 into a thing to take pre-emptively at high dose. It shows a persistent difference between two dietary patterns in one national survey, and a supplement habit that was not, on its own, enough to erase it.
That is a narrower claim than the wellness aisle makes, and a more useful one. For the parallel case of a nutrient where most people fall short and the supplement aisle oversells the fix, our look at the fiber gap covers the same terrain. As always, this is reporting on published research rather than medical advice — the medical disclaimer explains the difference, and symptoms such as fatigue, tingling in the hands and feet, or memory changes are a reason to talk to a healthcare professional rather than to adjust supplements alone.