This study found that some of the most commonly eaten shellfish, including oysters, crabs, clams, shrimp
and mussels, showed no evidence of raising
cholesterol levels. Crab
and clams actually lowered the LDL levels (bad cholesterol). Mussels and oysters also lowered LDL, while raising HDLs. Fish and seafood contain a small amount of cholesterol, but are also rich in healthy, unsaturated fat and low in saturated fat, the type of fat that tends to raise blood cholesterol..