Oysters: the zinc record holder that carries its own hazard

The strongest human trial on this page is about safety rather than nutrition. In a randomised, double-blinded challenge trial, 44 healthy adults ate oysters deliberately seeded with one strain of norovirus, and high-pressure processing at 600 MPa for 5 minutes left none of them infected, while 400 MPa did not. Zinc is the reason most people look oysters up. The NIH Office of Dietary Supplements says they hold more zinc per serving than any other food. USDA records show how wide the range is: from 16.62 mg per 100 g in raw Pacific oysters to 90.95 mg across nine records of eastern and Pacific oysters, raw, cooked and canned. One raw oyster meat weighs about 15 g in US survey measures, so six Pacific oysters carry about 15 mg, above the 11 mg Daily Value, and six eastern wild oysters could carry about 80 mg, with oyster size varying widely. This page has no card on the upper intake level for zinc, so it cannot say where 80 mg in one sitting stands against it. The one health trial is a 12-week placebo-controlled study of 120 healthy adults in Japan who ate an industry-supplied zinc-rich food product built on oysters. They fell asleep faster and had better sleep efficiency than placebo, and the abstract gives no effect size.

The numbers, per 100 g

How much is actually in it

• In 61 British Columbia oyster growers and their families, recent and long-term oyster intake predicted blood cadmium, and 36% had urinary cadmium above 1 microgram per gram creatinine. — 61 non-smoking oyster growers and family members, mean age 47, British Columbia (n = 61) Evidence C source
  Blood Cd geometric mean 0.83 ug/L, urinary Cd 0.76 ug/g creatinine, 36% above 1 ug/g, oyster intake a positive predictor of blood Cd
• USDA lists zinc from 16.62 mg per 100 g in raw Pacific oysters to 90.95 mg across its 9 oyster records, with vitamin B12 from 8.75 to 28.8 mcg and copper from 0.738 to 5.707 mg, so species and preparation change the numbers several-fold. — USDA SR Legacy, 9 oyster records (eastern wild and farmed, Pacific, raw, cooked, canned), reference record FDC 174219 Pacific raw (n = 9 records) Evidence E source
  Zinc 16.62-90.95 mg, vitamin B12 8.75-28.8 mcg, copper 0.738-5.707 mg per 100 g
• The UK CoFID table gives raw oysters 59.2 mg zinc, 7.5 mg copper, 5.7 mg iron, 17 mcg vitamin B12 and 510 mg sodium per 100 g, against 16.62 mg zinc and 1.576 mg copper in the USDA Pacific record, a gap that reflects species and origin rather than error. — CoFID 2021, Public Health England, record 16-260 Oysters, raw (n = 1 record) Evidence E source
  Zinc 59.2 vs USDA 16.62 mg (72% apart), copper 7.5 vs 1.576 mg (79% apart), B12 17 vs 16 mcg

What a real portion looks like

• One raw oyster meat weighs 15 g in US survey measures and a cup 225 g, so six Pacific oysters (90 g) carry about 15 mg zinc, above the 11 mg Daily Value, and six eastern wild oysters could carry about 80 mg. — US household measures, FNDDS 2021-2023, Oysters, raw, code 26315100 (n = FNDDS 5,432 foods) Evidence E source
  1 oyster 15 g, 1 cup 225 g, unspecified 85 g, zinc recomputed from USDA 100 g values

What your body absorbs

• When 18 men with normal lipids replaced the animal protein in their diet with oysters, VLDL triglycerides, LDL and total cholesterol fell and cholesterol absorption decreased. — 18 normolipidaemic men fed six shellfish diets in turn, protein matched to their usual animal foods (n = 18) Evidence C source
  Oyster diet lowered VLDL triglycerides, VLDL, LDL and total cholesterol, LDL/HDL ratio and cholesterol absorption, raised HDL2
• NIH ODS states that oysters contain more zinc per serving than any other food and that zinc absorption from food ranges from 5% to more than 50% depending on how much phytate-rich plant food is eaten with it, so how much of that zinc is absorbed depends on what is eaten with it. — NIH ODS zinc fact sheet for health professionals Evidence E source
  Oysters highest zinc per serving, absorption 5% to >50% by phytate load, beef gives 20% of US zinc intake

What cooking and storage change

• High-pressure processing at 600 MPa for 5 minutes, but not 400 MPa, completely inactivated Norwalk norovirus in seeded oysters: none of the volunteers who ate the 600 MPa oysters became infected in a 44-person randomised challenge trial. — 44 healthy secretor-positive adults, three phases, randomised to HPP-treated or untreated virus-seeded oysters, USA (n = 44) Evidence B source
  No infection after 600 MPa at 6 C, infection persisted after 400 MPa at 6 C or 25 C
• Across 27 high-quality studies of post-harvest handling of raw oysters published 2004 to 2019, high hydrostatic pressure was consistently the most effective way to reduce Vibrio parahaemolyticus, ahead of cold storage, depuration and disinfectants. — 93 full-text studies, 27 rated high quality and high relevance, oysters from Chesapeake Bay and Puget Sound focus (n = 27 studies) Evidence C source
  High hydrostatic pressure most effective, irradiation and relaying under-studied
• In 61 samples of post-harvest processed oysters collected by the FDA in 2004, mean levels of Vibrio vulnificus and V. parahaemolyticus were 5 to 6 log lower than in raw Gulf Coast oysters. — 61 post-harvest processed oyster samples (mild heat, freezing, high pressure) from processors and retail, USA, June to October 2004 (n = 61) Evidence C source
  5 to 6 log lower Vibrio levels than unprocessed raw Gulf Coast oysters, <10% detection after mild heat

What it does to your health

• In a 12-week placebo-controlled trial of 120 healthy adults, the group eating zinc-rich food built on oysters fell asleep faster and had better actigraphy-measured sleep efficiency than placebo, though the abstract reports no effect size. — 120 healthy adults, four parallel groups, actigraphy for 12 weeks, Japan (n = 120) Evidence B source
  Shorter sleep onset latency and higher sleep efficiency vs placebo, magnitude not in abstract

Safety, limits and interactions

• Of 630 oysters bought at UK points of sale over one year, 79.7% of those collected from October to March carried norovirus RNA against 57.0% from April to September, so the winter season is the riskier one for raw oysters. — 630 raw oyster samples from 21 UK regions, March 2015 to March 2016, randomised sampling of 373 vendors (n = 630) Evidence C source
  Norovirus RNA in 68.7% overall, 79.7% October-March vs 57.0% April-September, p < 0.0001, most at low copy numbers
• Of 359 shellfish-borne viral outbreaks reported worldwide from 1980 to 2012, oysters were the food in 58.4% and norovirus the pathogen in 83.7%. — 359 outbreaks in the literature plus 9 ProMED reports, 1980 to July 2012, six databases (n = 359 outbreaks) Evidence C source
  Oysters 58.4% of outbreaks, norovirus 83.7%, hepatitis A 12.8%, 63.6% of reports from Japan
• CDC puts the death rate of Vibrio vulnificus infection at about 1 in 5, sometimes within a day or two, and notes that although most infections occur in warmer months they are reported year-round, so the 'months with an R' rule is not a guarantee. — CDC public guidance on Vibrio and oysters Evidence E source
  About 1 in 5 die, infections reported year-round
• Across 61 population studies, self-reported shellfish allergy ran from 0% to 10.3% but shellfish allergy confirmed by food challenge only from 0% to 0.9%. — 61 population-based cross-sectional and cohort studies worldwide, all ages (n = 61 studies) Evidence C source
  Shellfish allergy 0-10.3% by any method, 0-0.9% by food challenge

What people believe that the data does not support

• CDC states that hot sauce, lemon juice and alcohol do not kill Vibrio in raw oysters and that a contaminated oyster does not look, smell or taste different, so neither the condiment nor an experienced palate makes a raw oyster safe. — CDC public guidance on Vibrio and oysters Evidence E source
  Myth correction, no number
• In Trinidad, 86.8% of raw oyster cocktail consumers were aware of the belief that oysters are a sexual enhancer against 11.3% of non-consumers. — 300 members of the public, 72 vendors and 200 samples each of oysters, condiments and cocktails, Trinidad and Tobago (n = 300 respondents, 200 samples) Evidence C source
  Aphrodisiac perception 86.8% vs 11.3% (P < 0.03), 57.5% of raw oysters unfit by TAPC standard

Who this works differently for

• Vibrio vulnificus septicaemia after raw oysters kills more than half of those who develop it, and in 16 Los Angeles cases from 1993 to 1996 all had eaten raw oysters 1 to 2 days earlier and 12 of 16 had pre-existing liver disease. — 16 reported cases of V. vulnificus infection in Los Angeles County, April 1993 to May 1996, all septicaemic (n = 16) Evidence C source
  Case-fatality of septicaemia over 50%, 75% with liver disease, 3 deaths in May 1996
• Among 117 Japanese adults with seafood allergy, 22 (18.8%) had food-protein-induced enterocolitis syndrome rather than IgE allergy, and bivalves, especially oysters, were its most common cause. — 117 seafood-avoidant adults interviewed by telephone, retrospective cohort, Japan (n = 117) Evidence C source
  22 of 117 (18.8%) FPIES, oysters the leading trigger, patients tolerated on average 92.6% of other seafood species

What is still unknown

• USDA retention factors have no oyster-specific entry, only the finfish and shellfish group, where frozen fish fried or heated keeps 100% of zinc and copper and 95% of vitamin B12, so losses on cooking oysters are inferred from fish, not measured. — USDA Table of Nutrient Retention Factors, Release 6 (2007), group 15 Finfish and Shellfish Products Evidence E source
  Zinc 100%, copper 100%, vitamin B12 95% for FINFISH (FROZEN), FRIED and HEATED

The bottom line

Oysters are the food most often named in shellfish-borne viral outbreaks: 58.4% of 359 outbreaks reported worldwide from 1980 to 2012, with norovirus the pathogen in 83.7%, though outbreak counts are not incidence and 63.6% of the reports came from Japan. Of 630 raw oysters bought at UK points of sale over one year, 79.7% of those collected from October to March carried norovirus RNA against 57.0% from April to September, and that was RNA detection rather than proof of infectivity, mostly at low copy numbers. Vibrio is the other hazard. The CDC puts the death rate of Vibrio vulnificus infection at about 1 in 5, with no denominator on the page, and says infections are reported year-round, so the months-with-an-R rule is not a guarantee. In 16 septicaemic cases in Los Angeles County from 1993 to 1996, all had eaten raw oysters 1 to 2 days earlier and 12 of 16 had liver disease, and that 1996 surveillance report puts the case-fatality of septicaemia above 50%. Hot sauce, lemon juice and alcohol do not kill Vibrio, and a contaminated oyster does not look, smell or taste different. Post-harvest processing does change the odds. In 61 processed oyster samples the FDA collected in one 2004 season, with methods pooled, mean Vibrio levels were 5 to 6 log lower than in raw Gulf Coast oysters. Across 27 high-quality studies high hydrostatic pressure was the most effective treatment, with no pooled estimate. Cooking losses have never been measured for oysters: USDA retention factors offer only a fish group, which keeps 100% of zinc and copper and 95% of vitamin B12. The UK CoFID table gives raw oysters 59.2 mg zinc per 100 g against 16.62 mg in the USDA Pacific record, and pairing those two records is a hypothesis about species and origin. On cholesterol, a 1990 feeding study of 18 men with normal lipids found that an oyster diet lowered LDL and total cholesterol, with no randomisation stated and no effect size in the abstract. Who should be careful. If you have liver disease, the Los Angeles series above is the fact to hold on to. Shellfish allergy confirmed by food challenge runs from 0% to 0.9% across 61 population studies, against 0% to 10.3% by self-report, and those studies did not separate molluscs from crustaceans. Among 117 Japanese adults avoiding seafood, 22 had food-protein-induced enterocolitis, a delayed vomiting reaction that is not IgE allergy, and bivalves, especially oysters, were its most common trigger, by telephone interview. In 61 non-smoking oyster growers and their families in British Columbia, a high-consumption group, recent and long-term oyster intake predicted blood cadmium and 36% had urinary cadmium above 1 microgram per gram creatinine. We found no study of oysters in pregnancy and none on drug interactions, so this page says nothing about either. The aphrodisiac story has been measured only as a belief: 86.8% of raw oyster cocktail consumers in Trinidad knew of it against 11.3% of non-consumers.

Sources

1. oyst-v1-12 · cross-sectional survey
   Thirty-six percent of participants had urinary Cd levels above 1mug/g creatinine and 5% were above 2mug/g creatinine. Recent (last 12 months) and long-term oyster consumptions were positive predictors of blood Cd but did not directly predict urinary Cd.
   Environ Res, 2008 · checked 2026-09-23
2. oyst-v1-16 · reference dataset
   FDC 174219 Mollusks, oyster, Pacific, raw: Zinc 16.62 mg · Vitamin B12 16 mcg · Copper 1.576 mg per 100 g · across 9 USDA oyster records: Zinc 16.62-90.95 mg · Vitamin B12 8.75-28.8 mcg · Copper 0.738-5.707 mg
   USDA FoodData Central SR Legacy · checked 2026-09-23
3. oyst-v1-17 · reference dataset
   CoFID 16-260 Oysters, raw: Energy 65 kcal · Protein 10.8 g · Zinc 59.2 mg · Copper 7.50 mg · Iron 5.70 mg · Vitamin B12 17.0 mcg · Sodium 510 mg per 100 g
   CoFID 2021, Public Health England, Open Government Licence v3.0 · checked 2026-09-23
4. oyst-v1-18 · reference dataset
   FNDDS 2706351 Oysters, raw: 1 oyster 15 g · 1 cup 225 g · Quantity not specified 85 g
   USDA FNDDS 2021-2023 · checked 2026-09-23
5. oyst-v1-13 · controlled feeding trial
   Oyster, clam, crab, and mussel diets, low in cholesterol and high in n-3 fatty acids, lowered VLDL triglycerides and cholesterol and, except for the mussel diet, LDL and total cholesterol...Cholesterol absorption was decreased on the oyster, clam, and mussel diets.
   Am J Clin Nutr, 1990 · checked 2026-09-23
6. oyst-v1-14 · NIH ODS fact sheet
   Oysters contain more zinc per serving than any other food, but beef contributes 20% of zinc intakes from food in the United States because it is commonly consumed [7]...The amount of zinc absorbed from food ranges from 5% to more than 50%, depending on the amount of plant-based foods (and thus of phytate) in the diet [3].
   NIH Office of Dietary Supplements, Zinc fact sheet for health professionals · checked 2026-09-23
7. oyst-v1-02 · randomised controlled trial
   HPP at 600 MPa, but not 400 MPa (at 6° or 25°C), completely inactivated HuNoV in seeded oysters and resulted in no HuNoV infection among these subjects, as determined by reverse transcription-PCR detection of HuNoV RNA in subjects' stool or vomitus samples.
   Appl Environ Microbiol, 2011 · checked 2026-09-23
8. oyst-v1-03 · systematic review
   Twenty-seven studies were found to be high quality and high relevance, including studies on cold storage, high hydrostatic pressure, depuration, and disinfectant, and other PHPs. High hydrostatic pressure consistently emerged as the most effective PHP in reducing abundance of V. parahaemolyticus.
   Sci Total Environ, 2020 · checked 2026-09-23
9. oyst-v1-06 · survey
   The mean levels of either organism in PHP oysters observed in the present study were 5 to 6 log less than in unprocessed raw Gulf Coast oysters.
   J Food Prot, 2009 · checked 2026-09-23
10. oyst-v1-01 · randomised controlled trial
    Compared with the placebo group, the zinc-rich food group efficiently decreased the time necessary to fall asleep and improved sleep efficiency, whereas the group that ingested zinc-enriched yeast and astaxanthin oil significantly improved the sleep onset latency.
    Mol Nutr Food Res, 2017 · checked 2026-09-23
11. oyst-v1-04 · cross-sectional survey
    A clear seasonality was observed with 79.7% of samples collected in the months October–March positive compared with 57.0% in the months April–September.
    Food Environ Virol, 2018 · checked 2026-09-23
12. oyst-v1-05 · systematic review
    The most common viral pathogens involved were norovirus (83.7 %) and hepatitis A virus (12.8 %). The most frequent type of consumed shellfish which was involved in outbreaks was oysters (58.4 %).
    Food Environ Virol, 2013 · checked 2026-09-23
13. oyst-v1-09 · agency fact sheet
    About 1 in 5 people with this infection die, sometimes within a day or two of becoming ill...Although most Vibrio infections occur during warmer months of the year, infections have been reported year-round.
    CDC, Vibrio and Oysters · checked 2026-09-23
14. oyst-v1-11 · systematic review
    The prevalence of fish allergy ranged from 0% to 7% and the prevalence of shellfish allergy from 0% to 10.3%, depending on the method of diagnosis. Where food challenges were used, the prevalence for fish allergy was found to be 0% to 0.3% and for shellfish allergy was 0% to 0.9%.
    Ann Allergy Asthma Immunol, 2016 · checked 2026-09-23
15. oyst-v1-08 · agency fact sheet
    Hot sauce and lemon juice don't kill Vibrio. Drinking alcohol while eating oysters doesn't kill Vibrio either...An oyster that contains harmful germs doesn't look, smell, or even taste different from any other oyster.
    CDC, Vibrio and Oysters · checked 2026-09-23
16. oyst-v1-15 · cross-sectional survey
    and in individuals who were aware that raw oysters are considered to be a sexual enhancer (86.8%) as compared to those who did not have this perception (11.3%) (P < 0.03).
    Int J Food Microbiol, 2000 · checked 2026-09-23
17. oyst-v1-07 · case series
    the case-fatality rate for V. vulnificus septicemia exceeds 50%...12 (75%) had preexisting liver disease (associated with alcohol use or viral hepatitis), all were septicemic, and all had eaten raw oysters 1-2 days before onset of symptoms.
    MMWR Morb Mortal Wkly Rep, 1996 · checked 2026-09-23
18. oyst-v1-10 · retrospective cohort
    Twenty-two (18.8 %) of 117 adults with seafood-allergy were diagnosed with FPIES...Bivalves, especially oysters, were the most common cause of FPIES.
    Allergol Int, 2024 · checked 2026-09-23
19. oyst-v1-19 · reference dataset
    R6 group 15 Finfish and Shellfish Products: FINFISH(FROZEN),FRIED vitamin B12 95% copper 100% zinc 100% · FINFISH(FROZEN),HEATED vitamin B12 95% copper 100% zinc 100%
    USDA Table of Nutrient Retention Factors, Release 6, 2007 · checked 2026-09-23