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Repair Windows errors before they cause bigger problemsFix Now →Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →Clear out junk files and repair common Windows errorsFree Scan →Oyster “blood”—more accurately, hemolymph—is being studied as a possible source of antibacterial compounds. In laboratory tests, a protein extract from Sydney Rock Oysters inhibited some disease-causing bacteria and biofilms, and improved the activity of selected antibiotics in combination assays. These are early drug-discovery findings, not evidence that oyster products can treat infections in people or pets.
What is oyster hemolymph?
Oysters do not have blood like mammals. Their circulating fluid, called hemolymph, carries immune cells and soluble factors involved in defense. Scientists study its cells, proteins and peptides to understand how oysters respond to microbes and whether any components could inform future antimicrobial drugs.
The recent Sydney Rock Oyster studies examined collected and processed hemolymph, including cell-free material and protein fractions. That is not the same as edible oyster meat, a store-bought oyster extract, or a supplement.
What did the Sydney Rock Oyster studies find?
Laboratory activity against two Streptococcus species
A 2025 study by Summer and colleagues tested a semi-purified hemolymph protein extract (HPE) from Sydney Rock Oyster (Saccostrea glomerata). The authors reported activity against laboratory and clinical strains of Streptococcus pneumoniae and Streptococcus pyogenes, with antimicrobial and antibiofilm effects observed at 4.4 and 24.1 μg/mL total protein, respectively. Those figures are concentrations used in laboratory assays, not doses for people or animals. Read the 2025 PLOS ONE study.
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- CALCIUM SUPPLEMENT: Major Oyster Shell Calcium 500 mg with Vitamin D3 5 mcg is a calcium supplement. Adequate calcium and vitamin D throughout life, as part of a well-balanced diet, may reduce the risk of osteoporosis.
- ACTIVE INGREDIENTS: Each tablet contains 5 mcg (200 I.U.) of Vitamin D (as cholecalciferol), 500 mg of calcium (as oyster shell), and 6 mg of sodium. These tablets are free from yeast, wheat, gluten, milk, lactose, and artificial flavors.
- HOW TO USE: Do not crush, split, or chew these tablets. Adults, take one tablet twice daily, preferably with a meal. To preserve quality and freshness, keep the bottle tightly closed.
- QUALITY FORMULATION: We maintain high standards of care through strict regulatory compliance to deliver carefully formulated, effective oyster shell calcium with vitamin D3 tablets.
- MAJOR PHARMACEUTICALS: At Major Pharmaceuticals, we believe wellness should be accessible to everyone. We pride ourselves on our legacy of delivering quality OTC and vitamin supplements.
Antibiotic combinations were tested in vitro
In combination assays, the same study reported that HPE improved the effectiveness of ampicillin, gentamicin, trimethoprim and ciprofloxacin by 2 to 32-fold against a range of tested bacteria. The assays used HPE concentrations of 1–12 μg/mL. This result does not show that patients can safely take oyster extract with antibiotics, that an antibiotic dose can be reduced, or that the combination works in a living animal or person.
An earlier study isolated an active fraction
A 2024 study separated Sydney Rock Oyster hemolymph proteins into fractions and found the strongest antibacterial and antibiofilm activity against multidrug-resistant S. pneumoniae in fraction 7. It was bactericidal and inhibited biofilm formation at 42 μg/mL protein in vitro. Proteomic analysis associated the fraction with carbonic anhydrase, cofilin, cystatin B-like and gelsolin-like proteins; it did not establish which molecule caused the activity or that the fraction is a treatment. Read the 2024 Marine Biotechnology study.
Rank #2
- CALCIUM SUPPLEMENT: Major Oyster Shell Calcium 500 mg is a calcium supplement. Adequate calcium throughout life, as part of a well-balanced diet, may reduce the risk of osteoporosis.
- ACTIVE INGREDIENTS: Each tablet contains 500 mg calcium and 5 mg sodium. These oyster shell calcium tablets also contain soy.
- HOW TO USE: Do not crush, split, or chew these tablets. Take one tablet twice a day, preferably with a meal. The tablets are free from gluten, preservatives, yeast, and artificial flavors.
- QUALITY FORMULATION: We maintain high standards of care through strict regulatory compliance to deliver carefully formulated, effective oyster shell calcium 500 mg tablets.
- MAJOR PHARMACEUTICALS: At Major Pharmaceuticals, we believe wellness should be accessible to everyone. We pride ourselves on our legacy of delivering quality OTC and vitamin supplements.
Why oyster defenses are more than a single antimicrobial
Oyster immunity involves interactions among hemocytes, antimicrobial proteins and peptides, and microbes that live in the hemolymph. In a 2013 study, researchers purified four active compounds from oyster hemolymph and screened supernatants from 224 resident bacterial isolates collected from 60 oysters against 10 target bacteria. Five strains—about 2% of those tested—showed antimicrobial activity. These results describe that study’s samples, not all oysters or all their resident microbes. See the 2013 study record.
Other studies show why the biology needs careful interpretation. Work on Pacific oysters (Crassostrea gigas) describes antimicrobial proteins with different patterns of expression in tissues and hemocytes. A 2020 study found that some hemolymph microbes could bind an oyster immune receptor and dampen parts of the hemocyte antimicrobial response. These are distinct species and experiments; neither establishes the mechanism behind the Sydney Rock Oyster extract’s activity. 2012 study record · 2020 study record.
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- The package dimension of the product is 3.3cmL x 3.3cmW x 10.2cmH
- The package weight of the product is 6.6 ounces
- Country of origin is United States
- 500 mg tablets
A separate 2021 study of Hong Kong oyster (Crassostrea hongkongensis) plasma identified a peptide candidate after bacterial challenge and reported activity in laboratory assays, including against foodborne pathogens. It broadens the research context but is not evidence for the Sydney Rock Oyster extract or a human infection treatment. Read the 2021 study.
What the findings do—and do not—mean for infection treatment
The tested strains included clinical isolates, but the experiments were laboratory assays, not clinical trials. The 2025 study also tested the extract on A549 human lung cells and reported no toxicity up to its tested upper concentration. A cell-culture result cannot establish safety in a person or pet, and the cited studies do not establish an effective dose, route of administration, clinical benefit, or approved oyster-derived antimicrobial medicine.
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- OYSTER SHELL CALCIUM TABLETS - Sourced from oyster shells, this 500 mg daily calcium supplement provides a source of calcium to help support bone density and joint health. Making it a quality option for those seeking a mineral supplement.
- DAILY BONE HEALTH SUPPORT - This calcium supplement may help support bone density in individuals with low calcium intake or aging adults. By maintaining strong bones, it also contributes to overall mobility and an active lifestyle.
- CONVENIENT 4-MONTH SUPPLY - Each bottle contains 1000 tablets, providing a generous 16-week supply when taken as directed–one tablet twice daily, with a meal. This makes it easy to maintain your daily routine without frequent reordering.
- QUALITY FORMULATION - Carefully formulated without gluten, yeasts, animal by-products, or artificial flavors, this joint supplement for women and men supports mindful wellness for various dietary considerations.
- MAJOR PHARMACEUTICALS - At Major Pharmaceuticals, we believe wellness should be accessible to everyone. We pride ourselves on our legacy of delivering affordable, high-quality OTC and vitamin calcium supplements, trusted by healthcare professionals and pharmacies across 50+ therapeutic categories.
- Not a treatment recommendation: the studies do not show that eating oysters, taking an oyster supplement, or using whole hemolymph prevents or treats infection.
- Not evidence for pets: these results do not demonstrate safety or effectiveness in dogs, cats, or other animals.
- Not a reason to change antibiotics: combination effects in a dish do not justify starting, stopping, or changing prescribed antibiotics.
What researchers need to establish next
The results identify possible leads for drug discovery, not a ready-to-use medicine. Further work would need to determine which components drive the effects, assess safety and activity in living systems, and establish whether any candidate can be developed into a reliable treatment. Until those questions are answered, oyster hemolymph belongs in the research laboratory—not in a home infection remedy.
Quick Recap
Best Value
- CALCIUM WITH VITAMIN D3 TABLETS - Each dose delivers 500 mg of calcium and 200 IU (5 mcg) of Vitamin D3 to support bone strength and aid calcium absorption. This daily supplement is sourced from natural oyster shells.
- DAILY BONE HEALTH SUPPORT - This calcium supplement may help support bone density in individuals with low calcium intake or aging adults. Adequate calcium and vitamin D throughout life, as part of a balanced diet, may reduce the risk of osteoporosis.
- HELPS ABSORB CALCIUM MORE EFFECTIVELY - Vitamin D3 may help your body absorb and use calcium more efficiently, promoting better bone and tooth health with every dose—great for long-term wellness. For optimal use, take one tablet twice daily with a meal.
- QUALITY FORMULATION - Carefully formulated without gluten, yeast, wheat, milk or milk derivatives, lactose, or artificial flavors, this supplement for women and men supports mindful wellness for various dietary considerations.
- MAJOR PHARMACEUTICALS - At Major Pharmaceuticals, we believe wellness should be accessible to everyone. We pride ourselves on our legacy of delivering affordable, high-quality OTC and vitamin calcium supplements, trusted by healthcare professionals and pharmacies across 50+ therapeutic categories.
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