Fish and shellfish are very keto-friendly foods. Salmon and other fish are rich in B vitamins, potassium and selenium, but are practically carbohydrate-free (4).
However, the carbohydrates in different types of shellfish vary. For example, while shrimp and most crabs don't contain carbohydrates, other types of shellfish do (5).
While these shellfish can still be included on a ketogenic diet, it is important to consider these carbohydrates when trying to stay within a narrow range.
Here are the carbohydrate numbers for 100 gram servings of some popular shellfish species (6, 7, 8, 9, 10):
Mussels: 5 grams
Mussels: 7 grams
Octopus: 4 grams
Oysters: 4 grams
Squid: 3 grams
Salmon, sardines, mackerel and other fatty fish contain a lot of omega-3 fats that have been found to lower insulin levels and increase insulin sensitivity in overweight and obese people (11 Trusted Source).
In addition, frequent fish intake has been associated with reduced risk of disease and improved mental health (12Trusted Source, 13Trusted Source).
Consume at least two servings of seafood a week.