Mutton: dense in B12, and most trials used lamb

The trial that carries mutton in its name tested a whole diet. In 206 Navajo adults with heart failure, 8 weeks of delivered meals built on traditional Navajo foods lowered hospital or emergency visits from 57.0 to 40.6 percent (relative risk 0.72, 95% CI 0.54 to 0.96), mainly through fewer hospital stays. It was an open-label meal program in one community, and nothing in it isolates the meat. What the meat contains is easier to state. Per 100 g, the single USDA record for roasted Navajo mutton gives 4.44 micrograms vitamin B12, 38 micrograms selenium and 33.4 g protein, with no second sample to check it against. In a systematic review of absorption studies, a 3.0 microgram B12 dose eaten as mutton was 83 percent absorbed. Absorption falls as the dose rises, so that figure reflects the small dose as much as the meat.

The numbers, per 3.5 oz (100 g)

How much is actually in it

• Roasted mutton in the USDA reference table gives 4.44 mcg vitamin B12, 38 mcg selenium and 33.43 g protein per 3.5 oz (100 g). — USDA SR Legacy record, Mutton, cooked, roasted (Navajo) (n = 1 record) Evidence E source
  Per 100 g: vitamin B12 4.44 mcg (185% DV), selenium 38 mcg (69% DV), protein 33.43 g (67% DV)
• In 34 healthy adults eating three portions of lamb a week for 4 weeks, grass-finished lamb raised blood omega-3 levels more than concentrate-finished lamb. — 34 healthy participants, two lamb chop portions and one lamb mince portion weekly for 4 weeks, grass vs concentrate finished (n = 34) Evidence B source
  Higher plasma ALA, EPA and DPA after grass-finished lamb (P < 0.05); about 328 mg per 3.5 oz (100 g) total omega-3 in the grass-finished portions; no difference in blood pressure or lipids

What a real portion looks like

• A cup of lamb or mutton with gravy (244 g) carries about 534 calories, 42 g protein and 876 mg sodium in US survey data. — US household measures, FNDDS (n = 1 food code) Evidence E source
  Per 100 g: energy 219 calories, protein 17.29 g, sodium 359 mg; per cup 244 g: 534.4 calories, 42.2 g, 876.0 mg; per slice with gravy 43 g: 94.2 calories

What your body absorbs

• In a systematic review of vitamin B12 absorption, a 3.0 mcg dose eaten as mutton was absorbed at 83%, against 4.5% for a 38 mcg dose from liver. — pooled absorption studies in healthy adults and elderly, 8 studies with 83 subjects for the dose model (n = 83) Evidence C source
  Absorption from 4.5% (38 mcg from liver) to 83% (3.0 mcg from mutton); absorbed amount rises with dose less than proportionally

What cooking and storage change

• Across case-control studies, eating raw or undercooked sheep meat carried odds of acute toxoplasma infection of 3.85, and the authors advise at-risk groups, including pregnant women, to avoid it. — case-control studies of acute Toxoplasma gondii infection, pooled Evidence C source
  Raw or undercooked sheep meat OR 3.85 (95% CI 1.85 to 8.00); raw or undercooked beef OR 2.22; these are odds rather than risk
• A Dutch risk model attributes 3.7% of predicted meat-borne toxoplasma infections to mutton, against 84% for beef, once salting and heating are accounted for. — quantitative microbial risk assessment for the Dutch population Evidence D source
  Share of predicted infections: beef 84%, pork 12%, mutton 3.7%, lamb 0.2%

What it does to your health

• In 50 Spanish students over two 8-week periods, a lamb-based diet lowered waist circumference, triglycerides and insulin more than a chicken-based one. — 50 healthy students aged about 19 (22 men, 28 women), randomized crossover, normocaloric diets with PGI lamb or chicken (n = 50) Evidence B source
  Suprailiac skinfold, waist circumference, triglycerides and insulin decreased more with lamb than chicken (p < 0.05); no other differences

Safety, limits and interactions

• In England and Wales, people with acute toxoplasmosis had 4.9 times the odds of having eaten lamb or mutton, though only beef stayed significant after adjustment. — 28 cases of acute toxoplasmosis and 27 seronegative controls, England and Wales (n = 55) Evidence C source
  Univariable OR 4.9 for lamb or mutton (P = 0.01); adjusted, only beef remained (OR 5.6)
• Listeria was found in 5.4% of fresh mutton samples in China, the lowest of the raw meats pooled, against 11.4% for fresh pork. — 112 publications on meat samples from 24 Chinese regions, 2000 to 2016 (n = 112 studies) Evidence C source
  Fresh mutton 5.4% (95% CI 2.5% to 11.0%); fresh pork 11.4%; fresh beef 9.1%; raw meats overall 8.5%

What people believe that the data does not support

• In 36 women eating lean lamb or chicken three times a week for 5 weeks each, blood cholesterol and triglycerides did not differ, against the rule that red meat must give way to white. — 36 nuns living in convents, open-label randomized crossover, lamb or chicken three times weekly for 5-week periods (n = 36) Evidence B source
  No between-diet difference and no change from baseline in total cholesterol, LDL cholesterol or triglycerides

Who this works differently for

• In 206 Navajo adults with heart failure, 8 weeks of meals built on traditional Navajo foods (the trial is named after mutton) cut hospital or emergency visits from 57.0% to 40.6%. — 206 adults with heart failure at 2 Indian Health Service sites in rural Navajo Nation, mean age 65.8, randomized to 8 weeks of culturally and medically tailored meals or usual advice (n = 206) Evidence B source
  All-cause hospitalization or emergency visit 40.6% vs 57.0%, relative risk 0.72 (95% CI 0.54 to 0.96); hospitalizations 12.3% vs 26.0%
• Among 37 Turkish children with red meat allergy, 64% had anaphylaxis on exposure and most were sensitized to both mutton and beef. — 43 patients with red meat allergy, 37 of them children with median age 10, one Turkish center (n = 43) Evidence C source
  Anaphylaxis in 64% of children; 75% of children with other allergic diseases sensitive to both mutton and beef on prick-to-prick test
• In over 127,000 allergy tests at a Shanghai children's hospital, sensitization to beef and mutton rose with age. — 127,310 serum specific IgE tests in children aged 0 to 18, Shanghai Children's Hospital, 2020 to 2024 (n = 127310) Evidence C source
  Beef and mutton positive rates increased significantly with age

What is still unknown

• Genetic analysis links higher genetically predicted lamb or mutton intake to intracranial aneurysm risk, a signal the authors say still needs confirming. — two-sample Mendelian randomization on GWAS summary data Evidence C source
  Positive association of lamb/mutton intake with intracranial aneurysm (IVW p < 0.05), no effect size given in abstract

The bottom line

A cup of lamb or mutton with gravy, 244 g, carries about 534 calories, 42 g protein and 876 mg sodium in US survey data, and that recipe does not separate lamb from mutton. The controlled trials on health used lamb. The rule that red meat must give way to white was tested in 36 women living in convents, who ate lean lamb or chicken three times a week for 5 weeks each. Total cholesterol, LDL cholesterol and triglycerides did not differ between the diets. In 50 Spanish students over two 8-week periods, a lamb-based diet cut waist circumference, triglycerides and insulin significantly more than a chicken-based one. The abstract gives no sizes, the lamb came from one protected breed, and the product was industry-linked. In 34 healthy adults eating lamb three times a week for 4 weeks, grass-finished lamb raised blood omega-3 fats more than concentrate-finished lamb. Whether mutton relates to brain aneurysm is unresolved. A Mendelian randomization study linked genetically predicted lamb or mutton intake with intracranial aneurysm, with no effect size in the abstract, a genetic proxy that may carry other effects, and authors who call for validation. Who should be careful. Pooled case-control studies found odds of acute toxoplasma infection 3.85 times higher after raw or undercooked sheep meat (95% CI 1.85 to 8.00), and the authors advise at-risk groups, pregnant women included, to avoid it. In a small study in England and Wales the odds for lamb or mutton were 4.9 before adjustment, and only beef stayed significant after it. A Dutch risk model puts mutton at 3.7 percent of predicted meat-borne toxoplasma infections, against 84 percent for beef. In China listeria turned up in 5.4 percent of fresh mutton samples, the lowest share among the raw meats pooled. Children can be allergic to red meat. At one Turkish center, 64 percent of 37 children with red meat allergy had anaphylaxis on exposure, and 75 percent of those with other allergic diseases reacted to both mutton and beef on skin tests. In a Shanghai children's hospital, IgE sensitization to beef and mutton rose with age across more than 127,000 tests.

Sources

1. mttn-r7-01 · reference dataset
   SR Legacy 167634 Mutton, cooked, roasted (Navajo): Vitamin B-12 4.44 ug/100 g · Selenium 38 ug/100 g · Protein 33.43 g/100 g
   USDA SR Legacy, Mutton, cooked, roasted (Navajo), fdc_id 167634 · checked 2026-09-30
2. mttn-r7-05 · RCT
   Greater levels of ω-3 PUFA, namely C18:3 ω-3, eicosapentaenoic acid (C20:5 ω-3) and docosapentaenoic acid (C22:5 ω-3), were detected in total blood plasma from participants who consumed grass finished lamb (P < 0.05), while consuming concentrate finished lamb higher levels of linoleic acid (C18:2 ω-6) in plasma PL (P < 0.01).
   Eur J Nutr, 2025 · checked 2026-09-30
3. mttn-r7-02 · reference dataset
   FNDDS 2706413 Lamb or mutton with gravy (food code 27130010): Energy 219 kcal/100 g, 1 cup 244 g 534.4 kcal · Protein 17.29 g/100 g, 1 cup 42.2 g · Sodium 359 mg/100 g, 1 cup 876.0 mg
   USDA FNDDS 2021-2023 · checked 2026-09-30
4. mttn-r7-03 · systematic review
   Absorption of vitamin B12 ranged from 4.5 (dose of 38 µg from consumption of liver) to 83% (dose of 3.0 µg from consumption of mutton meat).
   Ann Nutr Metab, 2013 · checked 2026-09-30
5. mttn-r7-08 · meta-analysis, case-control
   consumption of raw/undercooked beef, OR 2.22 (1.57-3.12), and consumption of raw/undercooked sheep meat, OR 3.85 (1.85-8.00)...Their consumption should be avoided in order to prevent toxoplasmosis, particularly by those in at-risk categories, including pregnant women.
   Crit Rev Food Sci Nutr, 2018 · checked 2026-09-30
6. mttn-r7-10 · risk model
   Results show that beef remains the most important source, as it contributed 84% of the total number of predicted infections in the Dutch population, followed by pork (12%), mutton (3.7%), lamb (0.2%) pork/beef mixed products (0.1%), and veal (0.01%).
   Int J Food Microbiol, 2020 · checked 2026-09-30
7. mttn-r7-07 · RCT, crossover
   Suprailiac skinfold thickness and waist circumference significantly decreased (p < 0.05) in the lamb-consumption group compared to the chicken based diet group...Tryacilglicerol and insulin serum concentrations significantly decreased (p < 0.05) in the lamb-consumption group compared to the chicken based diet group.
   Nutr Hosp, 2013 · checked 2026-09-30
8. mttn-r7-09 · case-control
   Univariable analysis showed that the odds of eating beef (OR 10·7, P < 0·001), poultry (OR 6·4, P = 0·01) or lamb/mutton (OR 4·9, P = 0·01) was higher for cases than controls.
   Epidemiol Infect, 2017 · checked 2026-09-30
9. mttn-r7-11 · meta-analysis, prevalence
   The prevalence differed from high to low among raw meats including prefabricated raw meats 12.6% (95% CI: 6.9%-21.7%), fresh pork 11.4% (95% CI: 8.6%-14.9%), fresh beef 9.1% (95% CI: 6.3%-13.0%), fresh poultry 7.2% (95% CI:4.9%-10.4%), frozen raw meats 7.2% (95% CI: 5.7%-9.0%), and fresh mutton 5.4% (95% CI: 2.5%-11.0%).
   Int J Food Microbiol, 2020 · checked 2026-09-30
10. mttn-r7-06 · RCT, crossover
    These recommendations are usually oversimplified by considering that all red meats should be limited and replaced by white meats...The results showed neither between-diet differences in lipid responses nor differences from baseline in total cholesterol, LDL-cholesterol or TAG for any diet period.
    Br J Nutr, 2012 · checked 2026-09-30
11. mttn-r7-04 · RCT, pragmatic
    The primary outcome was significantly less frequent in the intervention arm (43 [40.6%] vs 57 [57.0%]; relative risk, 0.72; 95% CI, 0.54-0.96; P = .02), which was driven mainly by reduced hospitalizations (13 [12.3%] vs 26 [26.0%]).
    JAMA Intern Med, 2026 · checked 2026-09-30
12. mttn-r7-12 · case series
    All of the children had dermatologic manifestations, 51% had respiratory symptoms, and 64% had anaphylaxis upon exposure to red meat...A total of 63% children had additional allergic diseases, and 75% of them were sensitive to both mutton and beef in prickto- prick tests.
    Turk J Pediatr, 2021 · checked 2026-09-30
13. mttn-r7-13 · retrospective cohort
    and food allergens such as beef and mutton increased significantly with age
    Zhonghua Yu Fang Yi Xue Za Zhi, 2025 · checked 2026-09-30
14. mttn-r7-14 · Mendelian randomization
    The findings of the study indicate a positive correlation between the intake of alcohol, lamb/mutton, and pork with the risk of IAs (IVW all p < 0.05)...Additional research is necessary to validate these outcomes and elucidate the underlying mechanisms.
    Nutr Neurosci, 2025 · checked 2026-09-30