Tongue: an organ meat without trials, and the tongue that tells on your diet

One word, two questions. People search for tongue either because they are cooking an organ meat and want to know what it gives them, or because their own tongue is sore and they suspect their diet. Neither question has a trial on this cut. The nearest measurement comes from 45 women aged 35 to 45, split across three sub-studies. In one, heme iron eaten alone was absorbed at about 13 percent. In another, heme alone was absorbed at 10.3 percent, beef left that unchanged, and blending the same heme with fish dropped it to 7.1 percent and with chicken to 4.9 percent, in single test meals built from purified heme and red cell concentrate rather than from a whole piece of meat. Take that as a fact about heme iron and the company it keeps, not about tongue. Composition, at least, is measured: US survey tongue gives 282 calories per 3.5 oz (100 g), with 19 g protein, 22 g fat and 3.1 mcg vitamin B12. UK data for stewed ox tongue put sodium at 860 mg per 3.5 oz (100 g), more than twice the US value.

As people eat it, per 3.5 oz (100 g)

How much is actually in it

• UK data for stewed ox tongue give 242 calories, 19.4 g protein and 18.3 g fat per 3.5 oz (100 g), with 4 mcg vitamin B12 and 860 mg sodium, more than twice the sodium in the US survey value. — CoFID 2021, Tongue, ox, meat only, stewed (code 18-426) Evidence E source
  Per 100 g: 242 calories, protein 19.4 g, fat 18.3 g, sodium 860 mg, iron 2.50 mg, zinc 3.8 mg, vitamin B12 4.0 ug, niacin 2.6 mg

What a real portion looks like

• US survey tongue gives 282 calories per 3.5 oz (100 g), with 19 g protein and 22 g fat, 3.1 mcg vitamin B12, 4.1 mg zinc and 2.6 mg iron. The default portion is 85 g. — USDA FNDDS, Tongue (code 25160000, fdc_id 2706160) Evidence E source
  Per 100 g: 282 calories, protein 19.14 g, fat 22.12 g (saturated 8.06 g), cholesterol 131 mg, sodium 372 mg, iron 2.59 mg, zinc 4.06 mg, vitamin B12 3.1 ug, niacin 3.46 mg; default portion 3 oz (85 g)

What your body absorbs

• Heme iron eaten alone was absorbed at about 13% in one sub-study, and in a second sub-study heme alone at 10.3% was unaffected by beef but fell to 7.1% when blended with fish and 4.9% with chicken. — 45 women aged 35 to 45 randomly assigned to three iron absorption sub-studies (n = 45) Evidence B source
  Heme alone about 13.0%; red blood cell concentrate 25.0% and concentrate with beef 21.3%, a 2-fold and 1.6-fold rise, p < 0.05; heme alone 10.3% fell to 7.1% with fish and 4.9% with chicken
• Eating 4 oz (113 g) of beef with an iron supplement every day for 8 weeks improved iron status no more than the same supplement with plant-based meat in 52 iron-deficient women. — 52 nonpregnant women of reproductive age, mean 24 years, serum ferritin below 25 mcg/L, one lunch meal daily for 8 weeks (n = 52) Evidence B source
  Ferritin rose 10.7 +/- 9.6 mcg/L and hemoglobin 0.5 +/- 0.9 g/dL over time in both arms, with no treatment-by-time interaction, P > 0.05 for all indicators
• A diet built around meat and ascorbate let premenopausal women absorb up to 4.5 mg of dietary iron, 30% to 35% of what they ate, while a low bioavailability diet did not. — premenopausal women on a high or low bioavailability diet for 12 weeks, absorption measured at 0 and 10 weeks, diets matched for total iron at 13.1 and 14.8 mg/day nonheme plus 2.0 and 0.3 mg/day heme (n = not stated in abstract) Evidence B source
  Up to 4.5 mg (30 to 35%) of dietary iron absorbed on the high bioavailability diet, and only the high bioavailability diet enabled more absorption in relation to low iron stores

What cooking and storage change

• People who eat raw or undercooked meat carry 1.2 to 1.3 times the risk and 1.7 to 3.0 times the odds of Toxoplasma gondii infection compared with those who cook meat through, whatever the animal. — cohort, case-control and cross-sectional studies pooled by random-effects model; seroprevalence across studies ranged from 1.3% to 88.6% (n = not stated in abstract) Evidence C source
  Risk ratio 1.2 to 1.3 and odds ratio 1.7 to 3.0 for raw or undercooked meat versus thoroughly cooked

What it does to your health

• A sore tongue was recorded in 23% of 103 adults diagnosed with pernicious anemia, behind fatigue at 55% and numb limbs at 32%. — 103 adults with a diagnosis of pernicious anemia, symptoms extracted from published case studies (n = 103) Evidence C source
  Sore tongue 23%, fatigue 55%, loss of sensation in limbs 32%, excessive weight loss 27%
• The NIH Office of Dietary Supplements lists glossitis of the tongue among the symptoms vitamin B12 deficiency can cause, alongside fatigue, neurological change and megaloblastic anemia. — general adult population, NIH fact sheet for health professionals Evidence E source
  No effect size; a list of deficiency symptoms compiled by the agency
• The same agency describes folate deficiency as producing soreness and shallow ulcerations on the tongue and oral mucosa. — general adult population, NIH fact sheet for health professionals Evidence E source
  No effect size; a description of the deficiency picture
• In pellagra, severe niacin deficiency, the agency describes a bright red tongue, and WHO treatment is 300 mg of nicotinamide a day in divided doses for 3 to 4 weeks. — people with severe niacin deficiency, mostly in settings of poverty and very limited diets Evidence E source
  Bright red tongue as a described sign; WHO treatment 300 mg/day nicotinamide for 3 to 4 weeks
• In Plummer-Vinson syndrome, built on long-standing iron deficiency anemia, atrophic glossitis was among the common oral findings across the seven case reports that met review criteria. — seven case reports of head and neck cancer in patients with Plummer-Vinson syndrome, selected from 19,183 citations (n = 7 case reports) Evidence C source
  Atrophic glossitis and angular cheilitis common; cancers predominantly at the pharynx and tongue borders

Safety, limits and interactions

• For healthy adults the US upper limit for niacin from supplements is 35 mg a day, and it covers both nicotinic acid and nicotinamide. The limit does not apply to people receiving niacin under medical supervision. — healthy adults aged 19 and over, US Food and Nutrition Board Evidence E source
  UL 35 mg/day of supplemental niacin for adults, both nicotinic acid and nicotinamide; it does not apply to people treated under medical supervision
• Nicotinamide does not cause flushing, but the agency reports nausea, vomiting and signs of liver toxicity at 3,000 mg a day. In small studies of people on hemodialysis, 500 to 1,500 mg a day for several months caused diarrhea and a low platelet count. — people taking nicotinamide supplements, including small studies in hemodialysis patients Evidence E source
  Nausea, vomiting and signs of liver toxicity at 3,000 mg/day; diarrhea and low platelet count at 500 to 1,500 mg/day for months in hemodialysis
• No harm has been reported from the niacin that occurs naturally in food such as tongue. As a supplement, 30 to 50 mg or more of nicotinic acid usually causes flushing, and 1,000 to 3,000 mg a day can cause low blood pressure, impaired glucose tolerance and, over months, liver damage. — general population, niacin from food versus supplements and medication Evidence E source
  No adverse effects from niacin naturally in food; 30 to 50 mg or more of nicotinic acid typically causes flushing; 1,000 to 3,000 mg/day can cause low blood pressure, glucose intolerance and liver damage
• Pellagra is uncommon in industrialized countries and mostly affects people in poverty, such as refugees on very limited diets. The WHO treatment of 300 mg of nicotinamide a day for 3 to 4 weeks is given together with a B-complex product for a diagnosed disease. — people with pellagra, mostly in poverty, refugees and displaced people on very limited diets Evidence E source
  Pellagra uncommon in industrialized populations; WHO treatment 300 mg/day nicotinamide in divided doses for 3 to 4 weeks plus a B-complex or yeast product
• Vitamin B12 deficiency is confirmed with blood tests, not by symptoms. Serum B12 below 200 to 250 pg/mL counts as low, and when it falls between 150 and 399 pg/mL experts suggest checking methylmalonic acid to confirm the diagnosis. — adults assessed for vitamin B12 deficiency Evidence E source
  Serum B12 below 200 or 250 pg/mL subnormal; methylmalonic acid above 0.271 micromol/L suggests deficiency and is checked when B12 is 150 to 399 pg/mL
• In alpha-gal syndrome, an allergy usually set off by tick bites, eating red meat from mammals can cause hives, swelling, gut symptoms or life-threatening anaphylaxis. Cases are reported on six continents and the condition is underdiagnosed. — people sensitized to alpha-gal, mostly after tick bites, on six continents Evidence C source
  Red meat can trigger hives, angioedema, gastrointestinal distress and anaphylaxis in alpha-gal syndrome; underdiagnosed

Who this works differently for

• Four of the ten studies in a review of malnutrition and oral health in people over 60 reported soft tissue signs in malnourished participants, including a red tongue with blisters. — 10 studies, nine cross-sectional and one prospective cohort, in people aged 60 and over, literature from 2000 to May 2020 (n = 10 studies) Evidence C source
  Soft tissue problems reported in four studies; fewer teeth or functional tooth units in three; poorer subjective oral health in six

What is still unknown

• The review of malnutrition and oral health ends by saying the actual association is still not established and that longitudinal cohorts are what is missing. — 10 studies in people aged 60 and over identified by a four-database search (n = 10 studies) Evidence C source
  No causal estimate available; authors name longitudinal cohort studies as the gap

The bottom line

The heme story has a second half that cuts the other way. In 52 nonpregnant women of reproductive age with ferritin below 25 mcg/L, 4 oz (113 g) of beef eaten at lunch every day for 8 weeks moved iron status no further than the same lunch built on plant-based meat. Ferritin rose 10.7 plus or minus 9.6 mcg/L and hemoglobin 0.5 plus or minus 0.9 g/dL in both arms, with no treatment-by-time difference. Both arms also took a 32 mg iron supplement, which can swamp whatever the meat itself contributes. The diet as a whole does more than any one food in it. Premenopausal women on a high bioavailability diet built around meat and ascorbate absorbed up to 4.5 mg of dietary iron, 30 to 35 percent of what they ate, while a low bioavailability diet holding the same total iron did not let them absorb more iron against their low stores. The abstract of that trial does not report how many women took part or how far apart the two diets ended up. Now the other question, the sore tongue. Among 103 adults whose pernicious anemia was written up as a case study, 23 percent had a sore tongue, behind fatigue at 55 percent and loss of sensation in the limbs at 32 percent. Case studies are selected for being worth publishing, so those shares describe the literature rather than the illness. The NIH Office of Dietary Supplements lists glossitis among the things vitamin B12 deficiency can cause and gives no frequency for it. The same agency describes folate deficiency as producing soreness and shallow ulcerations on the tongue and oral mucosa, and notes that isolated folate deficiency is uncommon and usually travels with others, so the sign rarely points at one nutrient. It describes a bright red tongue in pellagra, which WHO treats with 300 mg of nicotinamide a day in divided doses for 3 to 4 weeks. Pellagra is uncommon in industrialized countries and mostly affects people in poverty on very limited diets, so a red tongue there is far more likely to have another cause. That 300 mg is a treatment dose for a diagnosed disease, given together with a B-complex product. It is more than eight times the US upper limit of 35 mg a day for niacin from supplements in healthy adults, a limit that is set aside only for people treated under medical supervision. Nicotinamide does not cause flushing, but the agency reports nausea, vomiting and signs of liver toxicity at 3,000 mg a day, and in small studies of people on hemodialysis 500 to 1,500 mg a day for several months caused diarrhea and a low platelet count. No harm has been reported from the niacin that occurs naturally in food. Long-standing iron deficiency anemia carries the same theme: atrophic glossitis was a common oral finding in the seven Plummer-Vinson case reports that a review pulled from 19,183 citations, which is an association in a rare syndrome rather than a risk you can apply to yourself. In people aged 60 and over, four of the ten studies in a review of malnutrition and oral health reported soft tissue signs in malnourished participants, including a red tongue with blisters, and nine of those ten studies were cross-sectional. Those authors say the actual association is not established and name longitudinal cohorts as what is missing, so a sore tongue is a reason to get tested, not a diagnosis. Vitamin B12 deficiency, for one, is confirmed with blood tests rather than by symptoms: most laboratories call serum B12 below 200 to 250 pg/mL low, and between 150 and 399 pg/mL experts suggest checking methylmalonic acid. On caution, start with cooking. A meta-analysis of observational studies found that people who eat raw or undercooked meat carry 1.2 to 1.3 times the risk and 1.7 to 3.0 times the odds of Toxoplasma gondii infection compared with people who cook meat through, whatever the animal. Those pooled studies were observational, with seroprevalence running from 1.3 percent to 88.6 percent. Odds are odds, and they overstate risk where infection is common. Cooking meat through inactivates the parasite, which suits a cut that is usually simmered for hours anyway. One allergy applies: in alpha-gal syndrome, usually set off by tick bites, red meat from mammals can cause hives, swelling, gut symptoms or life-threatening anaphylaxis. Tongue is mammalian meat, though no study names it, and the condition is underdiagnosed. Beyond that, we found no study on tongue in pregnancy, in children or with medicines. That is an empty shelf in our evidence rather than a clean bill.

Sources

1. hf2-tng-8 · reference dataset
   CoFID 18-426 Tongue, ox, meat only, stewed: Energy 242 kcal | Protein 19.4 g | Fat 18.3 g | Sodium 860 mg | Iron 2.50 mg | Zinc 3.8 mg | Vitamin B12 4.0 µg | Niacin 2.6 mg per 100 g
   CoFID 2021 (Public Health England / OHID), code 18-426 · checked 2026-10-08
2. hf2-tng-7 · reference dataset
   FNDDS 25160000 Tongue (fdc 2706160): Energy 282 kcal | Protein 19.14 g | Total lipid (fat) 22.12 g | Fatty acids, total saturated 8.061 g | Cholesterol 131 mg | Sodium 372 mg | Iron 2.59 mg | Zinc 4.06 mg | Vitamin B-12 3.1 ug | Niacin 3.462 mg per 100 g || 1 oz yields 20 g | Quantity not specified 85 g
   USDA FNDDS 2021-2023 (FoodData Central), code 25160000 · checked 2026-10-08
3. tong-r3-01 · randomized absorption trial
   Study 1: the bioavailability of heme Fe from Hb was similar to heme only (∼13.0%). RBCC (25.0%) and RBCC+beef (21.3%) were found to be increased 2- and 1.6-fold, respectively, when compared with heme alone (p<0.05). Study 2: the bioavailability from heme alone (10.3%) was reduced (p<0.05) when it was blended with fish (7.1%) and chicken (4.9%), however it was unaffected by beef.
   Food Chem, 2016 · checked 2026-09-24
4. tong-r3-02 · randomized parallel trial
   Daily consumption of an iron supplement with a lunch meal for 8 wk improved serum ferritin concentrations (main time effect: +10.7 ± 9.6 μg/L, P < 0.0001), transferrin saturation (main time effect: +5.1% ± 18.7%, P = 0.048), soluble transferrin receptor (main time effect: -0.6 ± 1.0 mg/L, P < 0.001), body iron stores (main time effect: +2.8 ± 3.1 mg/kg, P < 0.0001), and hemoglobin (main time effect: +0.5 ± 0.9 g/dL, P = 0.0002) regardless of whether the meals contained Animal or Plant (treatment-by-time interaction: P > 0.05 for all indicators).
   Am J Clin Nutr, 2025 · checked 2026-09-24
5. tong-r3-03 · randomized factorial trial
   Only the high-bioavailability diet enabled women to absorb more iron in relation to their low iron stores. Women consuming the high-bioavailability diet absorbed up to 4.5 mg (30-35%) dietary iron with minimal influence of the diet consumed during the previous 10 wk.
   Am J Clin Nutr, 2003 · checked 2026-09-24
6. tong-r3-10 · meta-analysis of observational studies
   Our results suggest that individuals who eat raw or undercooked meat have, respectively, 1.2-1.3 times the risk and 1.7-3.0 times the odds of T. gondii infection compared to those who thoroughly cook meat, regardless of the animal species they consume. These results align with the current understanding that adequately cooking meat inactivates the parasite and decreases the risk of transmission.
   Vector Borne Zoonotic Dis, 2021 · checked 2026-09-24
7. tong-r3-04 · systematic review of case reports
   Symptoms were documented for 103 adults with a diagnosis of PA; the most frequent symptoms were fatigue (55%), loss of sensation in limbs (32%), excessive weight loss (27%), and a sore tongue (23%).
   Food Nutr Bull, 2024 · checked 2026-09-24
8. tong-r3-05 · fact sheet
   Vitamin B12 deficiency can cause a number of symptoms, including fatigue, neurological changes, megaloblastic anemia, glossitis of the tongue, palpitations, and low counts of white and red blood cells.
   NIH Office of Dietary Supplements, Vitamin B12 Fact Sheet for Health Professionals · checked 2026-09-24
9. tong-r3-06 · fact sheet
   Folate deficiency can also produce soreness in and shallow ulcerations on the tongue and oral mucosa; changes in skin, hair, or fingernail pigmentation; gastrointestinal symptoms; and elevated blood concentrations of homocysteine [1,2,4,32].
   NIH Office of Dietary Supplements, Folate Fact Sheet for Health Professionals · checked 2026-09-24
10. tong-r3-07 · fact sheet
    In addition, pellagra can cause a bright red tongue and changes in the digestive tract that lead to vomiting, constipation, or diarrhea...The World Health Organization recommends treating pellagra with 300 mg/day nicotinamide in divided doses for 3–4 weeks along with a B-complex or yeast product to treat likely deficiencies in other B vitamins [21].
    NIH Office of Dietary Supplements, Niacin Fact Sheet for Health Professionals · checked 2026-09-24
11. tong-r3-08 · systematic review of case reports
    Prevalent symptoms included dysphagia and esophageal webs, with atrophic glossitis and angular cheilitis being common oral manifestations. Most patients presented with long-standing iron deficiency anemia.
    Oral Dis, 2025 · checked 2026-09-24
12. hf2-tng-1 · agency fact sheet
    The FNB has established ULs for niacin that apply only to supplemental niacin for healthy infants, children, and adults [2]. These ULs are based on the levels associated with skin flushing. ... The UL, therefore, applies to both forms of supplemental niacin. However, the UL does not apply to individuals who are receiving supplemental niacin under medical supervision [2]. ... 19+ years 35 mg 35 mg 35 mg 35 mg
    Niacin, Fact Sheet for Health Professionals, NIH Office of Dietary Supplements (updated 2022-11-18) · checked 2026-10-08
13. hf2-tng-2 · agency fact sheet
    Nicotinamide does not cause skin flushing and has fewer adverse effects than nicotinic acid, and these effects typically begin with much higher doses [12]. Nausea, vomiting, and signs of liver toxicity can occur with nicotinamide intakes of 3,000 mg/day [2]. In several small studies of participants undergoing hemodialysis, the most common adverse effects from 500–1,500 mg/day nicotinamide supplementation for several months were diarrhea and thrombocytopenia (low platelet count) [36,40-42].
    Niacin, Fact Sheet for Health Professionals, NIH Office of Dietary Supplements (updated 2022-11-18) · checked 2026-10-08
14. hf2-tng-3 · agency fact sheet
    No adverse effects have been reported from the consumption of naturally occurring niacin in foods [2]. However, high intakes of both nicotinic acid and nicotinamide taken as a dietary supplement or medication can cause adverse effects, although their toxicity profiles are not the same. Thirty to 50 mg or more nicotinic acid typically causes flushing; ... When taken in pharmacologic doses of 1,000 to 3,000 mg/day, nicotinic acid can also cause more serious adverse effects [2,4,12,36]. ... These adverse effects can include hypotension severe enough to increase the risk of falls; fatigue; impaired glucose tolerance and insulin resistance; ... High doses of nicotinic acid taken over months or years can also be hepatotoxic;
    Niacin, Fact Sheet for Health Professionals, NIH Office of Dietary Supplements (updated 2022-11-18) · checked 2026-10-08
15. hf2-tng-4 · agency fact sheet
    Pellagra is uncommon in industrialized populations and is mostly limited to people living in poverty, such as refugees and displaced people who eat very limited diets low in niacin and protein [21,22]. ... The World Health Organization recommends treating pellagra with 300 mg/day nicotinamide in divided doses for 3–4 weeks along with a B-complex or yeast product to treat likely deficiencies in other B vitamins [21].
    Niacin, Fact Sheet for Health Professionals, NIH Office of Dietary Supplements (updated 2022-11-18) · checked 2026-10-08
16. hf2-tng-5 · agency fact sheet
    Vitamin B12 status is typically assessed by measurements of serum or plasma vitamin B12 levels. The cutoff between normal vitamin B12 levels and deficiency varies by method and laboratory, but most laboratories define subnormal serum or plasma values as those lower than 200 or 250 picograms per milliliter (pg/mL) (148 or 185 picomols per liter [pmol/L]) [2]. ... Experts suggest that if a patient’s serum vitamin B12 level is between 150 to 399 pg/mL (111 to 294 pmol/L), the patient’s serum MMA levels should be checked to help confirm a diagnosis of vitamin B12 deficiency [7,9].
    Vitamin B12, Fact Sheet for Health Professionals, NIH Office of Dietary Supplements · checked 2026-10-08
17. hf2-tng-6 · scoping review
    Alpha-gal syndrome (AGS) is a tick-associated, IgE-mediated allergy to galactose-α-1,3-galactose (alpha-gal), an oligosaccharide found on non-primate mammalian cells expressed by various bacteria and parasites, including ticks. ... Subsequent exposure to alpha-gal, typically through red meat consumption, can cause severe allergic reactions, including hives, angioedema, gastrointestinal distress, and life-threatening anaphylaxis. Alpha-gal syndrome is a global phenomenon, with cases reported on six continents.
    J Med Entomol, 2026 · checked 2026-10-08
18. tong-r3-09 · systematic review of observational studies
    Four studies reported soft tissue problems in malnourished participants, including red tongue with blisters, and dry or cracked lips.
    Nutrients, 2021 · checked 2026-09-24
19. tong-r3-11 · systematic review of observational studies
    Future research should be focused on longitudinal cohort studies with proper determination of malnutrition and oral health assessments, in order to evaluate the actual association between malnutrition and oral health in older people.
    Nutrients, 2021 · checked 2026-09-24