Tofu: the label America wrote and then took back

In 1999 the Food and Drug Administration let food packages say that soy protein helps your heart. In 2017 it proposed to take that permission away, because the newer trials it reviewed gave, in its own words, varied and inconsistent findings. Nine years later the proposal is still open and the claim is still legal, so a carton of tofu can carry a promise the agency that granted it no longer believes. Meanwhile the observational picture has not moved: people who eat more tofu have about a fifth less breast cancer, a fifth less cancer overall, and around a sixth less cardiovascular disease, with the dose sitting near 27 to 60 grams a day. Those are populations, not experiments, and the one trial that fed people tofu itself found its cholesterol improvements happening in the control group too.

The numbers, per 100 g

How much is actually in it

• Tofu and soymilk carried lower total cancer risk in pooled observational data, while fermented soy products carried none. — 52 studies, of which 17 were cohort studies and 35 were case-control studies (n = 52 studies) Evidence C source
  Total soy products RR 0.69 (0.60-0.80), tofu RR 0.78 (0.70-0.86), soymilk RR 0.75 (0.60-0.93); fermented soy RR 1.18 (0.95-1.47), soy paste RR 1.00, miso soup RR 0.99 and natto RR 0.96 showed no association; 61 g a day more tofu corresponded to 12% lower risk

What a real portion looks like

• About 27 grams of tofu a day, roughly a tenth of a standard block, was the amount tied to lower cardiovascular risk in pooled cohorts. — 29 articles covering 16521 type 2 diabetes events and 54213 cardiovascular events (n = 16521 diabetes and 54213 cardiovascular events) Evidence C source
  Highest against lowest soy intake gave type 2 diabetes RR 0.83 (0.74-0.93), cardiovascular disease RR 0.87 (0.81-0.94), coronary heart disease RR 0.79 (0.71-0.88) and stroke RR 0.88 (0.79-0.99); 26.7 g of tofu a day corresponded to 18% lower cardiovascular risk
• American labels may tie soy protein to heart disease only from 25 grams a day, which is about 145 grams of firm tofu. — — Evidence E source
  The rule sets 25 g or more of soy protein a day as the level associated with reduced risk of coronary heart disease, and requires the label to state how much one serving contributes to it

What your body absorbs

• Ten weeks of soy foods in place of meat left iron and zinc status unchanged in young women, despite the phytate. — 63 nonsmoking women aged 18 to 28 without chronic disease, anaemia, pregnancy or irregular cycles, randomised to soy foods (n=31) or animal foods (n=32) (n = 63) Evidence B source
  No significant change in haemoglobin, transferrin saturation, serum iron, ferritin or transferrin receptor; plasma zinc fell by 0.8 micromol/L in both arms equally; bone-specific alkaline phosphatase rose 1.5 U/L on soy against a fall of 0.7 U/L on animal foods; TSH and free thyroxine unchanged

What it does to your health

• Women who ate the most tofu had about a fifth lower odds of breast cancer, and the association tracked the amount eaten. — 14 studies, of which 2 were cohort studies and 12 were case-control studies (n = 14 studies) Evidence C source
  Odds ratio 0.78 (95% CI 0.69-0.88) for highest against lowest tofu intake, and a 10% lower risk for each additional 10 g a day in the dose-response analysis of 5 case-control studies

Safety, limits and interactions

• Soy left the active thyroid hormones unchanged across eighteen randomised trials, and raised TSH by an amount the authors call of unclear meaning. — 18 articles, contributing 21 to 26 treatment arms depending on the hormone, in men and women including two studies in subclinical hypothyroidism (n = 18 trials) Evidence A source
  Free T3 weighted mean difference 0.027 pmol/L (95% CI -0.052 to 0.107, p = 0.499), free T4 -0.003 pmol/L (-0.018 to 0.011, p = 0.656), TSH +0.248 mIU/L (0.001 to 0.494, p = 0.049); no publication bias found
• The thyroid trials used isoflavone supplements of 40 to 200 milligrams a day, against the 25 to 50 milligrams older Japanese adults get from food. — 18 trials whose interventions were mainly supplements of soy isoflavones, soy extract, soy protein, daidzein-rich isoflavones or genistein alone (n = 18 trials) Evidence A source
  Doses ranged from 40 to 200 mg a day, compared with roughly 25 to 50 mg of isoflavones a day in a survey of older Japanese adults cited by the authors

What people believe that the data does not support

• FDA proposed in 2017 to withdraw its own soy and heart disease claim, and nine years later the proposal is still open. — — Evidence E source
  FDA proposes to revoke 21 CFR 101.82, saying its review of the totality of publicly available evidence no longer supports significant scientific agreement, and that newer trials yielded varied and inconsistent findings

What is still unknown

• The one trial that fed people tofu itself found its cholesterol improvements happened in the control group too. — 45 adults aged 40 to 70 with mildly elevated cholesterol (n = 45) Evidence B source
  Total, LDL and HDL cholesterol, HbA1c, fructosamine and systolic blood pressure all fell within the tofu period, and many of the same changes appeared in the control period; only adiponectin differed between treatments, and it did not change significantly within either
• The most recent overview of all the soy meta-analyses calls the evidence more beneficial than harmful, and singles out fermented soy as unresolved. — 23 meta-analyses of observational research covering 39 unique health outcomes, plus one meta-analysis of randomised controlled trials covering four outcomes (n = 24 meta-analyses) Evidence C source
  The balance of evidence favours soy foods in cancer and cardiometabolic disease, while the benefits of fermented soy products are called inconclusive with some studies suggesting possible adverse effects

The bottom line

If you eat tofu because you like it, nothing here should stop you. If you are eating it as medicine, the honest summary is that the associations are real and the causation is unproven. Two specific worries can be set down. Soy does not wreck your thyroid. Across 18 randomised trials the active thyroid hormones did not move at all. The small rise in TSH came from supplements delivering 40 to 200 mg of isoflavones a day, against the 25 to 50 mg older Japanese adults get from food. Soy does not drain your iron and zinc either: ten weeks of soy foods in place of meat left both unchanged in young women. What we could not find is anything on calcium absorption from calcium-set tofu, which is the reason most people buy it. One search, one record, and that record is about lead.

Sources

1. tof-dr-02 · systematic review and meta-analysis of observational studies
   High consumption of total soy products (RR: 0.69; 95% CI: 0.60, 0.80), tofu (RR: 0.78; 95% CI: 0.70, 0.86), and soymilk (RR: 0.75; 95% CI: 0.60, 0.93) were associated with reduced total cancer risk...a 61 g per day increment of tofu reduced cancer risk by 12%
   Nutrients, 2024 · checked 2026-09-22
2. tof-dr-03 · systematic review and meta-analysis of prospective cohort studies
   A daily intake of 26.7 g of tofu reduced CVDs risk by 18% (TRR = 0.82, 95% CI: 0.74-0.92) and 11.1 g of natto lowered the risk of CVDs by 17% (TRR = 0.83, 95% CI: 0.78-0.89), especially stroke.
   Nutrients, 2023 · checked 2026-09-22
3. tof-dr-08 · federal regulation, requirement
   The daily dietary intake level of soy protein that has been associated with reduced risk of coronary heart disease is 25 grams (g) or more per day of soy protein.
   21 CFR 101.82, Health claims: Soy protein and risk of coronary heart disease · checked 2026-09-22
4. tof-dr-06 · randomised controlled feeding trial
   Incorporating ∼19 g soy protein from soy foods for 10 weeks had no significant effect on iron or zinc status, bone resorption or formation, or thyroid hormone status in premenopausal women.
   J Womens Health (Larchmt), 2011 · checked 2026-09-22
5. tof-dr-01 · dose-response 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%)...each 10 g/d increase in tofu intake was associated with 10% reduction in the risk of breast cancer (95% CI 7%-13%, P = 0.037, I2 = 40.8%)
   PLoS One, 2020 · checked 2026-09-22
6. tof-dr-04 · systematic review and meta-analysis of randomised controlled trials
   The meta-analysis showed no significant changes in fT3 (WMD: 0.027 pmol/L, 95% CI: -0.052, 0.107, p = 0.499; I2: 55.58%), fT4 (WMD: -0.003 pmol/L, 95% CI: -0.018, 0.011, p = 0.656; I2: 87.58%) while an elevation in TSH levels was observed (WMD: 0.248 mIU/L, 95% CI: 0.001, 0.494, p = 0.049; I2: 80.31%) levels with soy supplementation.
   Sci Rep, 2019 · checked 2026-09-22
7. tof-dr-05 · systematic review and meta-analysis of randomised controlled trials
   The interventions used in the studies were mainly food supplements containing soy isoflavones, soy extract, soy protein, daidzein-rich isoflavones and genistein alone. The doses used in the studies ranged from 40-200 mg/day.
   Sci Rep, 2019 · checked 2026-09-22
8. tof-dr-10 · regulatory proposed rule
   We are taking this action based on our review of the totality of publicly available scientific evidence currently available and our tentative conclusion that such evidence does not support our previous determination that there is significant scientific agreement (SSA) among qualified experts for a health claim regarding the relationship between soy protein and reduced risk of coronary heart disease.
   FDA proposed rule, Food Labeling: Health Claims; Soy Protein and Coronary Heart Disease, 82 FR 50324, 31 October 2017 · checked 2026-09-22
9. tof-dr-07 · randomised controlled cross-over trial
   Due to the lack of significant effects as compared to control, there is, however, currently no substantiating evidence to claim that Kori-tofu has beneficial effects on cardiometabolic health.
   Nutrients, 2022 · checked 2026-09-22
10. tof-dr-09 · umbrella review of meta-analyses
    Generally, dietary soy food consumption is more beneficial than harmful, especially in cancer and cardiometabolic diseases. However, it is important to note that the benefits of fermented soy products were inconclusive, and even some studies indicated their possible adverse effects.
    Mol Nutr Food Res, 2026 · checked 2026-09-22