Meat: what the studies measured, and what they left out

Meat is a category rather than a food, and our data says so on the first line: this cohort holds no USDA record for meat itself, only for the particular animals and cuts inside it. Composition moves with the animal. Across 377 analyses of camel meat, age, breed, species and the breeding system all changed what was in the meat, and animals slaughtered at six years or younger gave meat higher in dry matter, ash and fat. Camel meat is here as a worked example of how wide that spread gets inside one animal, not as a stand-in for beef or pork. The best known statement about meat is a classification rather than a measurement. IARC classifies processed meat as carcinogenic to humans and unprocessed red meat as probably carcinogenic, and that grading says how sure the evidence is, not how large the risk is. The figure of 18 percent per 50 g a day that usually travels with it is IARC summarising other people's cohort studies, and we hold no study card of our own behind it. It sits further down this page as an agency position, not as one of our numbers. Read the rest with two things in mind. Two of the ten evidence cards behind this page are regulations rather than research, and the strongest health finding here tested meat against plant based substitutes rather than testing meat on its own.

How much is actually in it

• Inside a single kind of red meat the composition moves with breed, age and how the animal was kept: camels slaughtered at six years or younger gave meat with more dry matter, ash and fat. — 57 papers from 12 countries published between January 1991 and August 2024, 377 analyses of camel meat (n = 377 analyses) Evidence D source
  Age, breed, species and breeding system all shifted composition; sex did not

What your body absorbs

• Across 19 human intervention studies, plant based meat analogues delivered less usable protein than animal meat, yet muscle protein synthesis and physical performance did not suffer. — 19 human intervention studies in adults substituting animal meat with plant based analogues (n = 19 studies) Evidence A source
  Lower protein bioavailability and a smaller rise in plasma essential amino acids; satiety rose; muscle protein synthesis and performance unchanged
• The European Union allows one health claim about meat, and it is about iron in other foods: meat eaten with them improves how much iron is absorbed. — EU Register on nutrition and health claims, claim POL-HC-6417, substance Meat or fish Evidence E source
  Regulatory decision, no effect size; the register carries no threshold for how much meat is needed

What it does to your health

• Pooling 31 observational studies, higher red meat intake went with 13% more colorectal adenomas, while white meat and seafood went the other way. — 31 observational studies of meat intake and precancerous colorectal lesions, published up to 31 December 2024 (n = 31 studies) Evidence C source
  Red meat RR 1.13 (95% CI 1.05 to 1.21) for adenomas and 1.73 (1.02 to 2.94) for polyps; processed meat 1.65 (1.05 to 2.61) for polyps; white meat 0.79 (0.63 to 0.99) and seafood 0.74 (0.58 to 0.94) for adenomas
• Across the 18 randomised trials that measured it, more red meat raised C-reactive protein by 0.23 mg/L, in mixed or unspecified red meat and in adults who already had cardiometabolic disease, not in unprocessed red meat. — adults in 22 randomised controlled trials totalling 1152 people, of which 18 trials carried the C-reactive protein estimate, plus 10 observational studies in 438925 adults, published through May 2024 (n = 1152 adults across the 22 trials; 18 trials behind the CRP estimate) Evidence A source
  Weighted mean difference in CRP 0.23, 95% CI 0.08 to 0.39; no effect on IL-6, TNF-alpha, leptin or adiponectin, and no association in the observational studies
• IARC states, summarising the cohort studies it reviewed, that each 50 g of processed meat eaten every day raises colorectal cancer risk by 18%, which is a relative rise on a small baseline. — IARC Monographs Volume 114, dose-response data from the reviewed cohort studies Evidence E source
  18% higher relative risk of colorectal cancer per 50 g of processed meat a day

Safety, limits and interactions

• IARC placed processed meat in Group 1, carcinogenic to humans, and unprocessed red meat in Group 2A, probably carcinogenic, in 2015. — IARC Monographs Volume 114 working group, 22 experts from 10 countries reviewing over 800 studies Evidence E source
  Hazard classification, not a risk size: Group 1 says the evidence that it causes colorectal cancer is sufficient, not that the risk is large
• A review of 30 studies found mercury above national limits in poultry products in 12 of 17 countries, with the highest levels in chicken eggs from Colombia. — 30 studies measuring mercury and methylmercury in poultry meat, eggs and liver across 17 countries (n = 30 studies) Evidence C source
  Levels above limits of 0.05 mg/kg (USDA and China) and 0.02 mg/kg (Thailand) in 12 of 17 countries

What people believe that the data does not support

• In the United States the words extra lean on a meat package have a legal meaning: under 5 g of fat, under 2 g of saturated fat and under 95 mg of cholesterol per serving and per 100 g. — 21 CFR 101.62(e), nutrient content claims for fat, fatty acid and cholesterol content of foods Evidence E source
  Regulatory definition, no effect size

What is still unknown

• On meat and depression the reviews contradict each other: of nine that qualified, four found plant predominant eating went with more depression and five found conflicting or no association. — umbrella review of 9 systematic reviews out of 104 screened, searched to January 2025 (n = 9 reviews) Evidence C source
  No consistent direction; the authors name overlapping primary studies and repeated reviews as part of the problem

The bottom line

The randomised evidence on this page is about inflammation, and the effect is small. Across the 18 randomised trials that measured it, more red meat raised C-reactive protein by 0.23 mg/L. The review places that rise in mixed or unspecified red meat and in adults who already had cardiometabolic disease, and it did not appear for unprocessed red meat, so it is not a finding about a healthy person eating a steak. Everything else the same review measured stayed put: IL-6, TNF-alpha, leptin and adiponectin did not move, and the observational data pooled alongside those trials showed no association at all. The colorectal findings are observational, which means they can show a pattern and cannot show a cause. Pooling 31 studies, higher red meat intake went with 13 percent more colorectal adenomas and 73 percent more polyps, processed meat with 65 percent more polyps, while white meat and seafood went the other way, 0.79 and 0.74 for adenomas. Total meat, charred meat and unprocessed red meat showed no association at all in the same pooling, which is the part usually left out. The confidence interval on the red meat polyp figure runs from 1.02 to 2.94, so the direction is steadier than the size. The 18 percent per 50 g a day that IARC prints belongs in this paragraph too: it is the agency summarising cohorts, and the primary numbers we hold are about adenomas and polyps rather than about cancer. If you are cutting back, somebody has tested the swap. Across 19 human intervention studies in adults, plant based meat analogues delivered less usable protein than animal meat and produced a smaller rise in plasma essential amino acids, and muscle protein synthesis and physical performance held up anyway, with fullness going up. Those were short trials with different products, there are no long- term data, and the whole thing is grade A evidence about substituting that says nothing about meat eaten by itself. Two familiar statements about meat turn out to be law rather than biology. On an American package, extra lean is a defined term: under 5 g of fat, under 2 g of saturated fat and under 95 mg of cholesterol per serving and per 100 g. The one health claim the European Union permits around meat concerns iron in other foods, because meat eaten with them improves how much iron gets absorbed. The register attaches no effect size and names no amount of meat. On contamination, a review of 30 studies measuring poultry meat, eggs and liver found mercury above national limits in 12 of 17 countries, and the highest levels were in chicken eggs from Colombia rather than in meat. The limits it compared against were 0.05 mg/kg in the United States and China and 0.02 mg/kg in Thailand. That is a finding about supply chains in those countries, and it tells you nothing about the bird you bought this week. Meat and mood stays unsettled, and we will not tidy it up. An umbrella review of nine systematic reviews found four reporting that plant predominant eating went with more depression and five reporting conflicting or no association. The authors put part of the blame on overlapping primary studies and reviews repeating each other. Nobody should change what they eat on the strength of that. What is missing matters as much as what is here. We hold no card on what cooking does to meat, so frying, grilling, roasting and the losses that come with them are unanswered on this page. We hold no card on portion size in real meals, which leaves the 50 g figure a number rather than a slice you can picture. And we hold nothing on who is different: pregnancy, children, older people, kidney disease, anyone on medication. The safety findings above describe populations. If your question is about you, ask the person treating you.

Sources

1. meat-r2-09 · meta-analysis of meat composition studies
   Camels slaughtered at ≤6 years of age were characterized by higher dry matter, ash, and fat contents, but lower sarcomere length, lightness, redness, and cobalt content.
   Meat Sci, 2026 · checked 2026-09-23
2. meat-r2-03 · systematic review of human intervention trials
   PBMAs generally resulted in lower protein bioavailability and a smaller increase in plasma essential amino acids in comparison to AM.
   Nutrients, 2024 · checked 2026-09-23
3. meat-r2-04 · EU health claim register entry
   POL-HC-6417 Meat or fish Meat or fish contributes to the improvement of iron absorption when eaten with other foods containing iron Authorised
   EU Register on nutrition and health claims, claim POL-HC-6417, snapshot 2026-09-21 · checked 2026-09-23
4. meat-r2-01 · meta-analysis of observational studies
   The results positively linked red meat intake to the risk of colorectal adenomas (RR: 1.13; 95% CI: 1.05, 1.21), colorectal polyps (1.73; 1.02, 2.94), and distal colon adenomas (1.19; 1.02, 1.40).
   Nutr Rev, 2026 · checked 2026-09-23
5. meat-r2-02 · meta-analysis of randomised trials in adults
   Overall, greater total RMI led to higher CRP across 18 RCTs (weighted mean difference 0.23, 95% CI 0.08-0.39).
   Crit Rev Food Sci Nutr, 2026 · checked 2026-09-23
6. meat-r2-07 · IARC Monographs working group statement
   each 50 gram portion of processed meat eaten daily increases the risk of colorectal cancer by 18%
   IARC press release 240, 2015 · checked 2026-09-23
7. meat-r2-06 · IARC Monographs working group classification
   Processed meat was classified as carcinogenic to humans (Group 1), based on sufficient evidence in humans that the consumption of processed meat causes colorectal cancer.
   IARC press release 240, 2015 · checked 2026-09-23
8. meat-r2-08 · systematic review of food contamination surveys
   Levels above those permitted by regulatory organizations such as the United States Department of Agriculture (USDA), China's National Health Commission (NHC), and Thailand's Ministry of Public Health - set at 0.05, 0.05, and 0.02 mg.kg-1 respectively - were observed in 12 of the 17 countries, with the highest concentrations detected in chicken eggs from Colombia.
   Biol Trace Elem Res, 2026 · checked 2026-09-23
9. meat-r2-05 · 21 CFR nutrient content claim rule
   the food is a discrete seafood or game meat product and as packaged contains less than 5 g total fat, less than 2 g saturated fat, and less than 95 mg cholesterol per reference amount customarily consumed and per 100 g
   21 CFR 101.62, Nutrient content claims for fat, fatty acid, and cholesterol content of foods · checked 2026-09-23
10. meat-r2-10 · umbrella review of systematic reviews
    Five articles reported associations between plant- and meat-predominant dietary patterns and depression, 4 reported that plant-predominant dietary patterns increased depression, and 5 found conflicting or no associations.
    Nutr Rev, 2026 · checked 2026-09-23