Chicken or tofu: a small cholesterol gap and a big protein gap

Swapping other protein for soy lowers LDL cholesterol, by a small amount. Across 41 trials in adults whose LDL sat between 110 and 201 mg/dL, about 25 g of soy protein a day for a median 6 weeks cut LDL by 4.76 mg/dL (95% CI 2.80 to 6.71), roughly 3 to 4 percent. The proteins soy was compared with were mostly dairy. For muscle, soy protein matched other proteins. Nine trials with 266 people doing resistance training for at least 6 weeks found no difference in strength or lean mass between soy and whey, beef or milk protein, and all of them used protein supplements in place of tofu or chicken meals. The certain gap is density. Raw skinless chicken breast carries 22.5 g of protein per 3.5 oz (100 g) in USDA samples. A single UK record puts steamed tofu at 8.1 g, about a third as much, though firm shop tofu can be denser, and gives it 1.2 mg of iron against 0.35 mg in the chicken. We found no trial that fed chicken against tofu head to head on any health outcome.

How much is actually in it

• Raw skinless chicken breast carries about 22.5 g protein, 0.35 mg iron and 0.35 g saturated fat per 3.5 oz (100 g). — USDA Foundation Foods analytical samples, 6 to 8 per item (n = 6-8 samples) Evidence E source
  Chicken breast skinless raw: protein 22.525 g (21.56-23.38), iron 0.3543 mg (0.304-0.413), saturated fat 0.3488 g (0.19-0.6); breast with skin: zinc 0.6245 mg (0.546-0.813)
• UK data give steamed tofu 8.1 g protein, 4.2 g fat and 1.2 mg iron per 3.5 oz (100 g) at 73 calories, so it has about a third of chicken breast protein by weight but more iron. — UK food composition data, CoFID code 13-570 (n = 1 record) Evidence E source
  Tofu steamed: energy 73 calories, protein 8.1 g, fat 4.2 g, iron 1.20 mg per 3.5 oz (100 g)

What your body absorbs

• In 23 healthy volunteers, 1.8 oz (50 g) of red fermented tofu with 0.096 ug vitamin B12 did not raise blood B12 over 72 hours compared with plain tofu. — 23 healthy university volunteers, one breakfast with 50 g red furu (n=11) or 50 g tofu (n=12) (n = 23) Evidence B source
  No significant change in serum B12; non-significant trend to lower homocysteine

What cooking and storage change

• Frying steamed tofu takes it from 73 to 261 calories and from 4.2 to 17.7 g fat per 3.5 oz (100 g) in UK data. — UK food composition data, CoFID codes 13-570 and 13-571 (n = 2 records) Evidence E source
  Steamed: 73 calories, 4.2 g fat, 8.1 g protein; steamed then fried: 261 calories, 17.7 g fat, 23.5 g protein

What it does to your health

• Across 41 trials, about 25 g soy protein a day for a median 6 weeks lowered LDL cholesterol by 4.76 mg/dL against other proteins. — adults with LDL 110 to 201 mg/dL in the 46 trials named by the FDA, 41 with LDL data (n = 41 trials) Evidence A source
  LDL -4.76 mg/dL (95% CI -6.71 to -2.80), total cholesterol -6.41 mg/dL, about 3-4%
• Across 9 trials with 266 people doing resistance training, soy protein built strength and lean mass as well as whey, beef or milk protein. — 266 participants in 9 resistance training trials of 6 weeks or more (n = 266) Evidence A source
  No between-group difference in bench press, squat or lean body mass (all p >= .38)

Safety, limits and interactions

• Italian data from 48 studies found Campylobacter on 62% of chicken skin samples and 20% of meat samples. — chicken skin, feces and meat samples in Italy, 2003-2023 (n = 48 studies) Evidence C source
  Pooled proportion skin 0.62, feces 0.67, meat 0.20; retail meat about 10%
• USDA FSIS advises cooking whole and ground chicken and other poultry to a safe minimum internal temperature of 165 °F (74 °C), measured with a food thermometer. — consumers cooking poultry, USA Evidence E source
  165 °F for whole and ground poultry
• The FDA label for levothyroxine says soybean flour may bind the drug and cut its absorption from the gut. Tofu is a soy food but the label does not name it. — People taking levothyroxine sodium tablets (n = -) Evidence E source
  Direction only: soybean flour may bind levothyroxine and reduce its absorption; no size, no amount of soy, no timing in this section

What people believe that the data does not support

• Across 18 RCTs, soy did not change thyroid hormones and raised TSH by only 0.25 mIU/L. — randomized trials with soy as intervention measuring fT3, fT4 and TSH (n = 18 trials) Evidence A source
  FT3 +0.027 pmol/L (ns), fT4 -0.003 pmol/L (ns), TSH +0.248 mIU/L (95% CI 0.001 to 0.494)
• Observational data link the highest tofu intake with 22% lower odds of breast cancer, and each 10 g a day with 10% lower odds. — 14 studies (2 cohort, 12 case-control) (n = 14 studies) Evidence C source
  OR 0.78 (95% CI 0.69-0.88) highest vs lowest; 10% lower per 10 g/day (95% CI 7%-13%)
• US food labels may still say that 25 g of soy protein a day in a low saturated fat diet may reduce heart disease risk, a claim the FDA proposed to revoke in 2017. — US food labeling regulation Evidence E source
  Authorized model health claim text

Who this works differently for

• In 21 older men lifting weights for 12 weeks, the beef group ended with higher LDL, HDL and total cholesterol than the soy foods group, with equal strength gains. — 21 men aged about 65 on a lacto-ovo-vegetarian base diet, 0.6 g protein/kg/day from beef or soy texturized vegetable protein, 12 weeks of resistance training (n = 21) Evidence B source
  LDL, HDL and total cholesterol higher in the beef group at 12 weeks; strength and power rose equally

The bottom line

Soy carries a reputation that runs ahead of the data in both directions. Across 18 randomized trials, soy did not change the thyroid hormones fT3 or fT4. It raised TSH by 0.25 mIU/L (95% CI 0.001 to 0.494) in trials that mostly used isoflavone or soy protein supplements, and the authors call the clinical meaning of that rise unclear. On breast cancer the data are observational. Across 14 studies, 12 of them case-control and mostly in Asian populations, the highest tofu intake went with 22% lower odds of breast cancer (OR 0.78, 95% CI 0.69 to 0.88). That is an association measured in odds, and it cannot show that tofu caused the difference. US food labels may still say that 25 g of soy protein a day, in a diet low in saturated fat and cholesterol, may reduce the risk of heart disease. The FDA proposed revoking that claim in 2017, and as of October 2026 we found no final rule. One small test of fermented tofu as a vitamin B12 source came up empty. In 23 healthy university volunteers, one breakfast of 1.8 oz (50 g) red fermented tofu carrying 0.096 mcg of B12 did not raise blood B12 over 72 hours against plain tofu, a single meal with a tiny dose. Frying matters for tofu. UK data take steamed tofu from 73 to 261 calories and from 4.2 to 17.7 g of fat per 3.5 oz (100 g), and part of that rise is lost water, which also lifts protein to 23.5 g. In 21 men around 65 who lifted weights for 12 weeks, the group eating beef ended with higher LDL, HDL and total cholesterol than the group eating soy foods, and strength rose equally. That was beef, and the sample was small and old. For chicken the caution is in the kitchen. Italian studies from 2003 to 2023, 48 in all, found Campylobacter on 62% of chicken skin samples and 20% of meat samples, about 10% at retail. Thorough cooking kills it, so the risk is cross-contamination from raw chicken. The thyroid result above is the other safety finding on this page. It measured hormone levels, mostly with supplements, and says nothing about soy and thyroid medicine. We hold no card on that, so people taking thyroid hormone should not read the result as clearance. We have no card on soy or poultry allergy, and that silence says nothing about whether you can eat either.

Sources

1. chtf-r2-01 · reference dataset
   Foundation: Chicken, breast, boneless, skinless, raw Protein 22.525 g/100 g (21.5625-23.375) · Iron 0.3543 mg (0.304-0.413, 8 samples) · Fatty acids, total saturated 0.3488 g (0.19-0.6, 8) · Chicken, breast, meat and skin, raw Zinc 0.6245 mg (0.546-0.813, 6)
   USDA FoodData Central, Foundation Foods, release 2026-04-30 · checked 2026-10-02
2. chtf-r2-02 · reference dataset
   CoFID 13-570 Tofu, soya bean, steamed: Energy 73 kcal · Fat 4.2 g · Protein 8.1 g · Iron 1.20 mg per 100 g
   CoFID 2021, Public Health England · checked 2026-10-02
3. chtf-r2-10 · randomized controlled trial
   A breakfast meal with 50 g of red furu containing 0.096 μg of B-12 did not increase serum B-12 in healthy volunteers.
   Asia Pac J Clin Nutr, 2020 · checked 2026-10-02
4. chtf-r2-03 · reference dataset
   CoFID 13-570 Tofu, soya bean, steamed: Energy 73 kcal, Fat 4.2 g, Protein 8.1 g · CoFID 13-571 Tofu, soya bean, steamed, fried: Energy 261 kcal, Fat 17.7 g, Protein 23.5 g
   CoFID 2021, Public Health England · checked 2026-10-02
5. chtf-r2-04 · meta-analysis of RCTs
   Soy protein at a median dose of 25 g/d during a median follow-up of 6 wk decreased LDL cholesterol by 4.76 mg/dL (95% CI: -6.71, -2.80 mg/dL, P < 0.0001; I2 = 55%, P < 0.0001) and decreased TC by 6.41 mg/dL (95% CI: -9.30, -3.52 mg/dL, P < 0.0001; I2 = 74%, P < 0.0001) compared with non-soy protein controls.
   J Nutr, 2019 · checked 2026-10-02
6. chtf-r2-05 · meta-analysis of RCTs
   Strength and LBM both increased significantly in the "other protein" and the soy groups (n = 9), but there were no between-group differences (bench: χ2 = 0.02, p = .88; squat: χ2 = 0.78, p = .38; and LBM: χ2 = 0.06, p = .80).
   Int J Sport Nutr Exerc Metab, 2018 · checked 2026-10-02
7. chtf-r2-09 · meta-analysis of prevalence studies
   Higher Campylobacter spp. prevalence rate was observed in faeces (67%) and skin (62%) compared to the meat matrix (20%), suggesting frequent cross-contamination events during slaughtering, processing and handling.
   Vet Med Sci, 2026 · checked 2026-10-02
8. sf-fsis-9 · agency advice
   FSIS recommends cooking whole poultry to a safe minimum internal temperature of 165 °F as measured using a food thermometer...Cook ground poultry to a safe minimum internal temperature of 165 °F as measured with a food thermometer.
   USDA FSIS, Doneness Versus Safety · checked 2026-10-08
9. sf-soylev-r5-1 · agency advice
   Soybean flour, cottonseed meal, walnuts, and dietary fiber may bind and decrease the absorption of levothyroxine sodium from the gastrointestinal tract.
   Levothyroxine sodium tablets, FDA-approved label, section 7.9, effective 2026-03-24 · checked 2026-10-08
10. chtf-r2-06 · meta-analysis of RCTs
    Soy supplementation has no effect on the thyroid hormones and only very modestly raises TSH levels, the clinical significance, if any, of the rise in TSH is unclear.
    Sci Rep, 2019 · checked 2026-10-02
11. chtf-r2-08 · meta-analysis of observational studies
    The overall OR of breast cancer for highest vs lowest intake of tofu was 0.78 (95% CI 0.69-0.88), with moderate heterogeneity (P = 0.011, I2 = 49.7%).
    PLoS One, 2020 · checked 2026-10-02
12. chtf-r2-11 · regulation
    (1) 25 grams of soy protein a day, as part of a diet low in saturated fat and cholesterol, may reduce the risk of heart disease. A serving of [name of food] supplies ____ grams of soy protein.
    21 CFR 101.82, Health claims: Soy protein and risk of coronary heart disease · checked 2026-10-02
13. chtf-r2-07 · randomized controlled trial
    At POST, the concentrations of HDL-C, LDL-C, and CHOL were greater in the BEEF group compared with the VEG group.
    Metabolism, 2005 · checked 2026-10-02