Dr. Dante Ruskin, diabetologist & intensivist Dr. Dante Ruskin Diabetes & Critical Care Specialist
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Is Dried Fish (Karuvadu / Unakka Meen) Good for Diabetes?

IN MODERATION

In moderation. Karuvadu is almost pure protein and carries no meaningful carbohydrate, so it will not raise your blood sugar on its own. The catch is salt: dried fish is preserved with salt, and salted dried fish carries sodium in grams, not milligrams. For most patients that means once or twice a week, soaked before cooking.

Answered by Dr. Dante Ruskin · Diabetologist & Intensivist

Karuvadu is not a sugar problem; it is a blood-pressure and kidney problem waiting for the wrong patient. If you already carry hypertension, or protein has shown up in your urine, the salt matters far more than the fish does. Soak it, discard that water, cook it with vegetables — and count the rice beside it.

The verdict is about salt, not sugar

Karuvadu worries most of my patients for the wrong reason. Dried fish carries essentially no carbohydrate — it is protein, fat, minerals and salt — so it does not push a two-hour reading anywhere. The rice underneath it does. If you have been avoiding nethili karuvadu because somebody said it “raises sugar”, that warning was aimed at the wrong item on the plate; look at the sadam beside it instead. What karuvadu genuinely brings into a diabetic household is sodium, and sodium is no small matter here. High blood pressure travels with diabetes far more often than not, and together they damage kidneys, eyes and arteries faster than either does alone. That is why this page says moderation, not yes.

What the salt actually costs

Salt is not an additive in karuvadu; salt is the preservation. The closest published figure for salted dried fish comes from USDA FoodData Central’s entry for dried salted cod: roughly 7,000 mg of sodium per 100 g, alongside about 63 g of protein. Indian food tables publish no nethili- or mathi-karuvadu sodium value I could retrieve, so read that as an order of magnitude, not a label reading. Set it against the target: the WHO and ICMR-NIN both ask adults to stay under about 5 g of salt — roughly 2 g of sodium — a day. One 30 g piece of heavily salted karuvadu can spend that whole allowance before the kuzhambu’s own salt goes in, before the pickle, before the appalam. Salting varies widely from seller to seller and nobody weighs it at home, so assume the higher end.

Soak it, squeeze it, throw that water away

Every kitchen here already knows this step. Diabetes makes it non-optional. Break the karuvadu into pieces, soak them in plenty of warm water for fifteen to thirty minutes, squeeze, and change the water once or twice. Published desalting work on salted dried fish shows repeated soaking removes much of the salt — enough to change the dish honestly, not enough to make it a low-salt food. Then comes the step where most homes hand the benefit straight back: the usual spoon of salt on top. Taste first, salt last, if at all. Properly soaked fish seasons the pot by itself, and the soaking water goes down the drain.

Kuzhambu, varuval, thokku — the form decides the day

Karuvattu kuzhambu made the Nanjil way — tamarind, ground coconut, and a good weight of brinjal, drumstick or raw mango — is the form worth keeping: the salt spreads across a pot the whole family eats from, and the vegetables bring fibre to a plate that otherwise has none. Varuval is the harder one — shallow-fried in oil already used several times, and nobody stops at one piece. Thokku and unakka meen chammanthi concentrate salt, oil and appetite at once, and exist to make more rice disappear. On the Kerala side of this border the standing pair is kappa and dried fish, putting a high-starch tuber directly under the saltiest thing in the kitchen; read the tapioca answer before that becomes a weekly plate. The kanthari crushed alongside adds heat, not protection.

Who should be stricter than once or twice a week

Coastal households here eat dried fish once or twice a week, and that is a fair ceiling for most people with diabetes. Some of you should sit below it. If your blood pressure is not at target, salt is the lever your doctor is already pulling, and karuvadu works against it. If protein has appeared in your urine, dried fish moves into the occasional column — a kidney damaged by diabetes clears sodium poorly, and your doctor adjusts the rest. Gout is the third group: anchovy and sardine are high-purine fish, drying concentrates them, and frequent karuvadu can bring on an attack. And paal sura — milk-shark karuvadu, still traded around Colachel and Kadiapattinam and on into the Kaliakkavilai border market — is shark, which means mercury: best left alone in pregnancy and while breastfeeding.

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Frequently asked questions

Not directly. Dried fish is protein, fat and salt with essentially no carbohydrate, so it has no glycemic index and does not move a two-hour reading by itself. What moves it is the rice, kappa or kanji beside it — and karuvadu's salty taste is very good at pulling an extra ladle of sadam onto the plate. Watch that, not the fish.

Once or twice a week suits most patients, which is close to what coastal households on this border already do. Keep the piece small — roughly 25 to 30 g dry — soak it before cooking, and skip the usual spoon of salt in the pot. If your blood pressure or kidney function is a concern, go below that.

It removes a useful share of it, not all of it. Break the pieces, soak them in warm water for fifteen to thirty minutes, squeeze, and change the water once or twice — desalting work on salted dried fish shows repeated soaking pulls out much of the sodium. Then skip the salt you would normally add afterwards.

Kuzhambu, clearly. It spreads the salt across a pot the whole family shares and lets you load in brinjal, drumstick or raw mango, so the plate gains fibre it would not otherwise have. Varuval is shallow-fried, often in oil that has already been used, and it gets eaten piece after piece. Keep varuval occasional.

Be stricter than once or twice a week, and raise it with the doctor managing your pressure. Salt is the main lever in both conditions, and a kidney already injured by diabetes clears sodium poorly. Karuvadu becomes an occasional dish rather than a weekly one — always soaked, never with added salt.

Leave shark karuvadu out during pregnancy and breastfeeding. Paal sura is a shark, and sharks concentrate mercury — a reason to avoid a fish rather than merely limit it. Nethili or mathi karuvadu, soaked and used lightly, is the safer choice; gestational diabetes needs the rice portion watched more closely than the fish.