What people call a scallop is one muscle. Scallops swim by clapping their two shells together to jet away from danger. The large adductor muscle that powers the clap is the round white meat sold as a scallop. In the UK and Australia they are often sold with or without the soft roe, called the coral.
A scallop can have up to 200 eyes. Each eye focuses light with a concave mirror of guanine crystals, not with a lens, and the design resembles the mirrors of reflecting telescopes.
Raw scallops are lean: 12.1 g of protein, 0.5 g of fat and 69 calories per 100 g. They also give 59% of the Daily Value of vitamin B12.
What you buy may not match that number. In a German retail check, most frozen scallop products contained added phosphates, and their water content reached up to 89%. Fresh king scallops held 78%. That is the gap behind “wet” and “dry” scallops, covered below.
Health benefits of scallops
The top findings from 14 studies, strongest evidence first
What the stars mean
- Strong. Several randomized trials, pooled in a meta-analysis, point the same way, or regulators (FDA or EFSA) have approved the claim.
- Moderate. Good randomized trials support it, but there are fewer of them, or their results vary.
- Limited. Small, short or single trials, or mixed results. Promising, but it needs confirmation.
Population and lab studies get no stars: they show a link or a mechanism, not proof.
How we rate evidence →- ★Mixed memory results with a scallop fat extractA purified scallop fat (plasmalogens, 1 mg a day) did not improve overall thinking scores in 328 people with mild Alzheimer’s or mild cognitive impairment. In healthy adults with below-average memory, verbal memory scores ended 10.1 points above placebo.
- ★Lower triglycerides with oil from scallop organsIn 70 Japanese adults, 1.2 g a day of oil from scallop organs (not the meat) lowered triglycerides and oxidized LDL over 12 weeks. The effect showed in the group with higher triglycerides.
- ★Less anger and fatigue in young male athletesIn 40 male college athletes, 2 mg a day of scallop plasmalogens for 4 weeks lowered anger and fatigue. The overall mood score gap was only borderline, and the trial was small and short.
- ★Scallop fat blood levels near normal in Parkinson’sIn 10 people with Parkinson’s, 24 weeks of scallop-derived fats (1 mg a day) brought their blood levels of these fats near normal. There was no placebo group, so symptom changes cannot be told apart from chance.
- Population studyRaw scallops linked to a hepatitis A outbreakIn a Hawaii outbreak, 292 people got sick, 74 were hospitalized and 2 died. Of the cases, 94% had eaten at one restaurant chain, and 86% of them reported raw scallops.
All 14 studies, strongest evidence first
Plasmalogens did not improve overall cognition in mild Alzheimer’s or MCI
This multicenter, double-blind trial gave 328 people aged 60 to 85 with mild Alzheimer’s disease or mild cognitive impairment 1 mg a day or placebo. It lasted 24 weeks, and 276 finished; main and secondary scores did not differ from placebo. A memory test improved in subgroups of women and of people under 77 with mild Alzheimer’s disease. The capsule held a purified fat from scallops, not scallop meat, and the paper states that the Japanese Plasmalogen Society funded the trial.
Scallop oil lowered triglycerides and oxidized LDL in people with higher triglycerides
This randomized, double-blind, placebo-controlled trial included 70 Japanese adults with triglycerides of 120 to under 200 mg/dL. They took 1.2 g a day of oil from the internal organs of the Japanese giant scallop, not the meat, for 12 weeks. The daily dose held 376 mg of EPA and 63 mg of DHA, and the effect showed in the higher-triglyceride group. Safety checks found no meaningful changes.
Plasmalogens improved verbal memory in healthy adults with below-average memory
This randomized, double-blind, placebo-controlled trial included 66 healthy Japanese adults aged 40 and over, out of 68 randomized. They took 1 mg a day for 12 weeks, and verbal memory scores ended 10.1 points above placebo, though the range was wide. Blood levels of the growth factor BDNF rose equally in both groups. Two authors are employed by B&S Corporation, one of them as an executive and shareholder.
Plasmalogens lowered anger and fatigue in male athletes; overall mood borderline
This randomized, double-blind, placebo-controlled trial included 40 Japanese male college athletes aged 18 to 22, 20 on plasmalogens and 20 on placebo. They took 2 mg a day for 4 weeks; the overall mood score gap was only borderline, while anger and fatigue differed clearly. Physical performance and lab measurements did not differ. It was small, short and limited to young athletes.
In 10 Parkinson’s patients, scallop lipids brought blood levels near normal
This preliminary report had no placebo group: ten patients took 1 mg a day of scallop-derived ether phospholipids for 24 weeks. Their blood levels were compared with 39 healthy people of the same age, and blood was checked at 0, 4, 12, 24 and 28 weeks. The authors say some symptoms improved, but without a control group that cannot be told apart from chance or the placebo effect.
Top shellfish eaters had no higher or lower heart disease risk
This cohort (a study that follows people over time) covered 13,355 middle-aged and older US adults in the ARIC study, with 1,382 heart disease events. After adjustment, medium and high shellfish eaters had 0.96 and 0.98 times the risk of low eaters, results that could be chance. It covers shellfish as a group, not scallops alone, and intake was self-reported.
Top fish-and-shellfish protein intake went with 16% higher gout risk
This cohort followed 51,114 Singapore Chinese adults aged 45 to 74 at recruitment, free of gout at the start. By 2010, 2,167 had physician-diagnosed gout; the comparison was the top fourth against the bottom fourth of fish and shellfish protein. Poultry protein showed a similar link (hazard ratio 1.27), while soy foods and other legumes went with a lower risk. Fish and shellfish were combined, so the result is not about scallops alone.
Hawaii hepatitis A outbreak: 292 sick, most had eaten raw imported scallops
This was the second-largest US foodborne hepatitis A outbreak of the vaccine era: 74 people were hospitalized and 2 died. Of the cases, 94% had eaten at one restaurant chain, and 86% of them reported raw scallops. Virus recovered from the scallops matched the patients’ virus. The scallops were traced to one distributor that imported them from the Philippines.
Cadmium in farmed Chinese scallops exceeded the standard in 96% of samples
This study measured three scallop species from 10 sites along the Bohai and Yellow Seas. Metals gathered most in the digestive gland, then the gill, and least in the adductor muscle. The authors estimate a safe amount of whole scallops of 127 g a week for adults and 63 g for children. They advise eating only the adductor muscle, and the study measured shellfish, not people.
Argentine scallops: toxins in whole tissue, none in the adductor muscle
This monitoring covered Patagonian scallops caught between 2012 and 2017. Paralytic shellfish toxins reached 3,985 µg of saxitoxin equivalents per kg in whole tissue, gathered in the digestive tract. So removing the adductor muscle on factory ships gave a product the authors call free of a human health threat. Lipophilic and amnesic toxins stayed under regulatory limits.
Most German frozen scallops had added polyphosphates and up to 89% water
This lab analysis compared frozen king scallop and Atlantic sea scallop meat bought at retail with fresh king scallops, which held 78% water. The moisture-to-protein ratio reached 9 in treated products and stayed under 5 in fresh ones. Sodium was high because of the additives. Labels did not always give the species or the ingredients correctly.
Sea scallops and canned clams had the least cholesterol of six shellfish
This lab analysis tested samples from 12 supermarkets across the US in 2007 and 2008, to update the USDA nutrient database. Raw sea scallops and canned clams held 23.4 to 30.1 mg of cholesterol per 100 g, while shrimp, crab and lobster held more. Non-cholesterol sterols in scallops totaled 46.5 to 75.6 mg per 100 g in five single-location samples and 107 mg in a sixth.
Cod-and-scallop protein cut artery plaque 24% in mice, against chicken
This was a study in mice, not people: 24 female mice prone to atherosclerosis ate a Western-type high-fat diet for 13 weeks. Their protein came from chicken or a mix of cod and scallops. Plaque was 24% lower in the whole aorta, the main artery, and 46% and 56% lower in its thoracic and abdominal parts. The cod-scallop mice also gained less weight and had lower LDL cholesterol and blood sugar.
Scallop plasmalogen aided memory and restored brain blood flow in diseased mice
This was a study in mice, not people, with Alzheimer’s-like disease and poor brain circulation, using a purified plasmalogen from scallops. The mice also showed less amyloid, brain inflammation, oxidative stress and loss of neurons at 12 months of age.
Who should be careful with scallops
Most people can eat scallops freely. Take a little care if one of these applies:
- Shellfish allergy. Scallops are mollusks. In the US, crustacean shellfish such as shrimp are a major allergen on labels, but mollusks such as scallops are not. Most people allergic to one group of shellfish react to others too, so ask your allergist before trying them.
- Raw scallops, and whole ones with the roe. A 2016 hepatitis A outbreak in Hawaii was tied to raw imported scallops. The FDA tells pregnant women, children, older adults and people with weakened immune systems to avoid raw or undercooked shellfish. It also says natural toxins are not a likely hazard when only the adductor muscle is eaten, but whole and roe-on scallops can carry them.
- Gout. A review says shellfish may raise the risk of high uric acid and gout. A Singapore cohort found a 16% higher gout risk with the most fish and shellfish protein. The link is modest, and it matters mainly if you already have gout.
How to choose, store and eat scallops
- Dry or wet: dry scallops have no additives, while wet ones are soaked in a phosphate solution. In a German check, treated frozen products held up to 89% water and extra sodium. Read the ingredient list for phosphates.
- Cooked through: the FDA says scallop flesh turns firm, pearly and opaque when done, at an internal temperature of 145°F (63°C).
- Raw: in the Hawaii outbreak, 86% of the cases who ate at the chain reported raw scallops, so cooking is the safer route.
Fresh scallop flesh should look clear and pearl-like, with little or no odor. Keep it at 40°F (4°C) or below and use it within 2 days of buying, or freeze it. Scallops are on the FDA and EPA (US Environmental Protection Agency) “Best Choices” list, the lowest-mercury group. The FDA suggests 2 to 3 servings a week from that list in pregnancy.
Sources
- Questions and answers regarding food allergens, including the food allergen labeling requirements of the Federal Food, Drug, and Cosmetic Act (Edition 5). FDA. 2025.
- Shellfish. Food Allergy Research & Education.
- Fish and Fishery Products Hazards and Controls Guidance, chapter 6: natural toxins. FDA. 2022.
- Selecting and serving fresh and frozen seafood safely. FDA.
- Advice about eating fish. FDA and EPA. Revised 2021.
- CPG Sec 555.875 Water in food products (ingredient or adulterant). FDA.
- Viray MA, Hofmeister MG, Johnston DI, et al. Public health investigation and response to a hepatitis A outbreak from imported scallops consumed raw, Hawaii, 2016. Epidemiol Infect. 2018.
- Manthey-Karl M, Lehmann I, Ostermeyer U, Rehbein H, Schröder U. Meat composition and quality assessment of king scallops (Pecten maximus) and frozen Atlantic sea scallops (Placopecten magellanicus) on a retail level. Foods. 2015.
- Teng GG, Pan A, Yuan JM, Koh WP. Food sources of protein and risk of incident gout in the Singapore Chinese Health Study. Arthritis Rheumatol. 2015.
- Xu L, Cai J, Gao T, Ma A. Shellfish consumption and health: a comprehensive review of human studies and recommendations for enhanced public policy. Crit Rev Food Sci Nutr. 2022.
- Scallop. Wikipedia.
History of scallops
Scallops belong to the family Pectinidae, which has more than 300 living species. The biggest wild scallop fishery targets the Atlantic sea scallop, Placopecten magellanicus, off the northeastern US and eastern Canada. Most of the rest of the world’s supply comes from Japan and China. Sea scallop stocks are now at historically high levels after recovering from overfishing.
The scallop shell became a pilgrim’s badge. Pilgrims to Santiago de Compostela in Spain first bought real scallop shells at the shrine and wore them. When demand outran supply, metal versions were sold instead.
A London museum notes that 100 licensed badge makers worked in Compostela in the 13th century. It adds that no one is quite sure why the scallop became the badge of St James.
The link lives on in language. The French name is coquille Saint-Jacques and the German name is Jakobsmuschel. Scallop shells also appear with Venus in many paintings, including Botticelli’s The Birth of Venus. The Shell oil company uses a scallop as its emblem.
Farming scallops began to pay off in Japan. According to an FAO review, scallop culture grew a great deal after the 1950s. Growers had learned to collect wild baby scallops, called spat, on hanging collectors. The first collectors were cedar leaves, scallop shells and nylon mesh.
A fisherman in Mutsu Bay fastened a small-mesh onion bag around the cedar leaves to keep the spat that settled. Synthetic materials came into use as collectors from the 1960s.
Sources
- Scallop. Wikipedia.
- St James of Santiago de Compostela. London Museum, collections.
- Status of scallop farming: a review of techniques, section 3.1, spat collection. FAO.
- Palmer BA, Taylor GJ, Brumfeld V, et al. The image-forming mirror in the eye of the scallop. Science. 2017.
- Tremblay I, Guderley HE, Himmelman JH. Swimming away or clamming up: the use of phasic and tonic adductor muscles during escape responses varies with shell morphology in scallops. J Exp Biol. 2012.
Frequently asked questions about scallops
Are scallops good for you?
For most people, yes. Raw scallops have 12.1 g of protein and only 0.5 g of fat per 100 g. They give 59% of the Daily Value of vitamin B12.
In the USDA data they also hold 392 mg of sodium per 100 g, 17% of the Daily Value. No trial has tested eating scallops, and the studies above do not reach moderate or strong evidence.
How many calories and how much protein are in scallops?
Raw scallops have 69 calories and 12.1 g of protein per 100 g. A 3 oz (85 g) serving has 59 calories and 10.3 g. About 74% of the calories come from protein.
Two large or five small scallops have 21 calories and 18% of the Daily Value of vitamin B12. These are raw values, and treated “wet” scallops hold more water and sodium.
Are scallops high in cholesterol?
No, scallops are low among shellfish, with 24 mg per 100 g (8% of the Daily Value). In a lab analysis of US supermarket samples, sea scallops and clams had the least cholesterol of six shellfish. They held 23.4 to 30.1 mg per 100 g. In a cohort of 13,355 adults, shellfish intake was not linked to heart disease risk, though that study covered shellfish as a group.
Are scallops high in mercury?
No. The FDA and EPA list scallops among the “Best Choices,” the lowest-mercury group. For pregnancy and breastfeeding the advice is 2 to 3 servings a week from that list, with a serving being 4 ounces. For children it is 2 servings a week, with serving size set by age.
What is the difference between wet and dry scallops?
Dry scallops have no additives, while wet scallops are soaked in a phosphate solution, usually sodium tripolyphosphate, so they absorb water. In a German retail check, most frozen products had added polyphosphates and up to 89% water, against 78% in fresh king scallops. Sodium was high from the additives. The FDA’s compliance policy says scallops with added water are considered adulterated, so read the ingredient list for phosphates.
Can you eat scallops raw?
Raw scallops are eaten as sashimi, but cooking is safer. A 2016 hepatitis A outbreak in Hawaii sickened 292 people. Of the cases who ate at the implicated chain, 86% reported raw scallops. The FDA advises pregnant women, children, older adults and people with weakened immune systems to avoid raw or undercooked shellfish.
Can you eat scallops with a shrimp or shellfish allergy?
Ask your allergist first. Shrimp are crustaceans and scallops are mollusks, but FARE says most people allergic to one group of shellfish are allergic to other types. Allergists usually advise avoiding all kinds unless testing shows otherwise. In the US, mollusks are not a major allergen on labels, so they may be present without a “Contains” warning.
What part of the scallop do you eat?
The adductor muscle, the round white meat that the scallop uses to clap its shell shut. The FDA says natural toxins are not a likely hazard when only the adductor muscle is eaten. Whole and roe-on scallops can carry them.
In studies, paralytic shellfish toxins were absent from the adductor muscle of Argentine scallops. Cadmium also built up least in the adductor muscle of farmed Chinese scallops.