Calories in Oyster: Nutritional facts for Oyster Types

A 100g serving of raw Eastern oysters contains 81 calories. A 100g serving of breaded and fried Eastern oysters contains 188 calories.

One kilogram (1000g) of raw Eastern oysters contains 810 calories. One kilogram of breaded and fried Eastern oysters contains 1880 calories.

One dozen medium raw Eastern oysters (168g) contains 136 calories. One dozen medium breaded and fried Eastern oysters (176g) contains 331 calories.

One medium raw Eastern oyster (14g) contains 11 calories. One medium breaded and fried Eastern oyster (14.7g) contains 28 calories.

The nutritional benefits of oysters offer a unique concentration of micronutrients that provide several health advantages. The table below details some of the key health advantages of consuming oysters.

• Boosts Immune Function. Oysters are the world's best dietary source of zinc, a mineral that is essential for the proper function of the immune system. Zinc is crucial for the development and activation of T-lymphocytes, a type of white blood cell that helps fight infection. A study by Prasad, A. S. (2008), titled "Zinc in Human Health: Effect of Zinc on Immune Cells," concluded that zinc is critical for modulating immune responses and that deficiency impairs immune function.
• Supports Neurological Health. The high concentration of vitamin B12 in oysters is vital for maintaining healthy nerve cells and for the production of DNA and RNA. Oysters also contain omega-3 fatty acids, which are important structural components of the brain. Research from O'Leary, F., & Samman, S. (2010), "Vitamin B12 in Health and Disease," details the essential role of vitamin B12 in preventing neurological disorders.
• Enhances Iron Levels and Energy. Oysters are an excellent source of heme iron, a form of iron that is more easily absorbed by the body than the non-heme iron found in plants. Iron is a critical component of hemoglobin, the protein in red blood cells that transports oxygen throughout the body, making the mineral essential for energy production. A review by Abbaspour, N., et al. (2014), "Review on iron and its importance for human health," confirms the high bioavailability of heme iron from animal sources and its importance in preventing anemia.
• Provides High-Quality Protein. Oysters contain a complete protein profile, providing all nine essential amino acids. These amino acids are the building blocks for creating and repairing muscle tissue, producing enzymes, and supporting overall metabolic function.
• Source of Unique Antioxidants. Oysters contain a recently discovered antioxidant called 3,5-Dihydroxy-4-methoxybenzyl alcohol (DHMBA). This compound has shown potent antioxidant effects. A study by Walton, J. R., et al. (2017), "The novel antioxidant 3,5-dihydroxy-4-methoxybenzyl alcohol (DHMBA), from the Pacific oyster (Crassostrea gigas), protects human intestinal Caco-2 cells from H2O2-induced oxidative stress," demonstrated that DHMBA protects cells from oxidative damage.

Oysters are a nutritious food, but potential downsides exist, related to bacterial contamination in raw oysters and the accumulation of heavy metals. The table below shows some of these disadvantages.

• Risk of Bacterial Infection. Raw or undercooked oysters can harbor harmful bacteria, most notably Vibrio vulnificus and Vibrio parahaemolyticus. These bacteria thrive in the coastal waters where oysters grow and can cause serious illness, especially in individuals with compromised immune systems or liver disease. A report from the Centers for Disease Control and Prevention (CDC) titled "Vibrio Illness (Vibriosis)" states that consuming raw or undercooked seafood is the primary cause of infection. A safe alternative is to eat oysters that have been thoroughly cooked. The suggested amount for raw oyster consumption carries inherent risk, but this risk is minimized when sourcing from reputable suppliers who follow strict harvesting and handling protocols.
• Accumulation of Heavy Metals. As filter feeders, oysters can accumulate heavy metals like cadmium, lead, and mercury from the water. Chronic exposure to these metals can be toxic. A study by Jović, M., & Stanković, S. (2014), "Human exposure to trace metals and possible health risk assessment in a Serbian community," discusses how bivalve mollusks can accumulate high levels of contaminants, posing a potential health risk to consumers.
• High in Cholesterol. Oysters contain a moderate amount of cholesterol. While dietary cholesterol has less impact on blood cholesterol for most people than once believed, individuals with certain health conditions may need to monitor intake.

Yes, oysters are a good food choice because the shellfish is one of the most nutrient-dense foods available, offering exceptional levels of zinc, vitamin B12, copper, and selenium. For immune health, the unparalleled concentration of zinc in oysters directly supports the body's ability to fight off pathogens. A meta-analysis by Hemilä, H., et al. (2017), "Zinc lozenges and the common cold: a meta-analysis comparing zinc acetate and zinc gluconate, and assessing the clinical importance of zinc dosage," found strong evidence that zinc can reduce the duration of the common cold, demonstrating its direct role in immune response. Regarding metabolic and thyroid health, oysters are a premier source of selenium and iodine, two minerals essential for the production of thyroid hormones that regulate metabolism. 

Research from Schomburg, L. (2011), "Selenium, selenoproteins and the thyroid gland: interactions in health and disease," confirms the critical role of selenium in thyroid function. For neurological health, the high levels of vitamin B12 and omega-3 fatty acids support brain function and protect nerve cells. A study by Zhang, Y., et al. (2016), "Intakes of fish and omega-3 fatty acids and risk of stroke: a dose-response meta-analysis of prospective cohort studies," found that higher consumption of omega-3s from fish is associated with a lower risk of stroke.

The calorie content of oysters shows minimal change between the different species. A 100g serving of raw Pacific, Atlantic, or European Flat oysters all contain between 80 and 81 calories. Smaller species like Kumamoto and Olympia oysters have a slightly lower calorie count per 100g, around 70-75 calories, but this difference is small. The most dramatic change in calories comes from the preparation method. The lowest calorie option is raw oysters, at 81 calories per 100g. The highest calorie option is breaded and fried oysters, which contain 188 calories per 100g. This substantial increase is due to the addition of carbohydrates from the breading and a large amount of fat absorbed from the oil during the frying process.

The origin of oysters as a human food source is ancient, with archeological evidence showing consumption by coastal populations for thousands of years. In North America, massive shell middens left by Native American tribes attest to the oyster's importance as a food source long before European arrival. The Romans were famous for oyster aquaculture, engineering oyster beds and prizing the mollusks as a luxury food. The modern culinary history of oysters in the United States began in the 19th century with the rise of oyster cellars and bars in cities like New York and New Orleans, where oysters were an abundant and inexpensive food for all social classes. This accessibility fueled the creation of iconic American oyster dishes. Oysters Rockefeller was invented in 1889 at Antoine's Restaurant in New Orleans as a decadent baked dish with a rich green sauce of herbs and breadcrumbs. The Oyster Po' Boy sandwich also originated in New Orleans during a 1929 streetcar strike, created as a hearty and affordable meal for the striking workers. In contrast, the French tradition of eating raw oysters with a simple mignonette sauce of shallots and vinegar reflects a long-standing preference for preparations that showcase the oyster's natural, unadorned flavor.