Dr. Dante Ruskin, diabetologist & intensivist Dr. Dante Ruskin Diabetes & Critical Care Specialist
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Is Tuna (Choorai / Choora) Good for Diabetes?

YES

Yes — tuna is a good fish for diabetes. Fresh choorai carries no carbohydrate at all, about 24 g of protein per 100 g and very little fat (USDA FoodData Central), so it does not raise blood sugar. What it is cooked in — oil, coconut, batter — decides the meal.

Answered by Dr. Dante Ruskin · Diabetologist & Intensivist

Eat it as curry, thoran or avicha meen rather than deep-fried, and keep the plate's rice small — that is where the sugar comes from. One caution: tuna is a large predatory fish, so pregnancy and gestational diabetes call for limited portions, and sardine or ayala beat it for omega-3.

Why tuna earns a yes

Tuna is one of the easier answers in this series, and the reason is arithmetic rather than reputation. Fresh yellowfin carries no carbohydrate at all — USDA FoodData Central puts raw yellowfin at about 109 kcal, 24.4 g protein and 0 g carbohydrate per 100 g, with under a gram of fat. Nothing in that column raises blood glucose. Protein also slows a meal down: fish beside the rice blunts the rise that rice produces alone. Patients still reach my clinic worried that fish is “heaty”. The trouble in a fish meal has always been the rice, the porotta and the frying oil — never the choora.

Choorai, choora, keerai — the fish this coast lands

Kanyakumari lands more marine fish than any other district in Tamil Nadu — roughly a fifth of the state’s catch in 2023 (CMFRI) — and tuna is local here, not an import. The west coast, Cape Comorin up through Colachel and Thengapattanam, is the scombroid stretch: tuna, seerfish and mackerel. Colachel has a seasonal handline fishery for yellowfin of around 30 kg, roughly February to April, and the Thoothoor villages work the Wadge Bank as India’s deep-sea longline cluster. At Vadasery, Thoduvatti or Kaliakkavilai the same fish is soorai on the Nagercoil side and choora on the Marthandam and Kerala-border side; the yellowfin is keerai soorai. Tins marked “light tuna” are usually skipjack, a smaller relative.

The form decides the meal, not the fish

This is where a yes turns into a no on the plate. A meen kuzhambu ground with coconut and tamarind — or the Kerala-border version with kudampuli — leaves the fish carbohydrate-free and the gravy light. Choora thoran, flaked tuna dry-cooked with grated coconut, adds fat rather than sugar, so it moves the calories more than the glucose. Avicha meen, this district’s boiled-fish signature with coconut paste, tamarind and no added oil, is the lightest of them. The evening roadside meen varuval is where the meal turns: batter, reused oil, two porottas alongside. And with kappa, the tapioca — not the tuna — is the glycemic event; the fry-versus-curry page takes that apart in full.

Tinned tuna: brine, oil and the salt line

Tinned tuna is a weekday food here now — hostel rooms, Gulf-returned households, gym-going sons. Read the tin, not the front label. Tuna in spring water or brine, drained, is the closest thing to plain fish: USDA FoodData Central puts light tuna canned in water at about 116 kcal and 25 g protein per 100 g drained. Oil-packed tuna keeps whatever oil clings to it after draining, so calories run higher while sugar stays at zero. The number worth watching is sodium — salt is added to most tins, and with high blood pressure or kidney disease it adds to a diet already carrying karuvadu and pickle.

Mercury, pregnancy and who should hold back

Tuna’s one real caution has nothing to do with sugar. It is a large predatory fish that lives long and eats smaller fish, so it accumulates more methylmercury than sardine, mackerel or anchovy. India publishes no comparable consumer fish list, so the reference most of us use is the US FDA and EPA advice: yellowfin sits in the once-a-week band, small tinned light tuna in the more-often group, and shark (sura, paal sura) and bigeye tuna in the avoid column — worth knowing where sura puttu is a household dish. It matters most in pregnancy and breastfeeding, the group my gestational diabetes page is written for: not “no fish”, but small fish often — chaala, ayala, kozhuva — with choora occasional, and the amount settled with your obstetrician.

What tuna will not do

Set expectations honestly. Tuna does not lower blood sugar, and no fish substitutes for the medicine your doctor adjusts or for the walking that makes insulin work better (exercise for sugar control). It is also not the omega-3 fish its price suggests: yellowfin is lean, well under a gram of fat per 100 g, so that benefit belongs to sardine and ayala. Nor does good protein cancel a large plate — three pieces of fish, a mound of rice and a payasam is still a high-carbohydrate meal with fish in it. Use tuna as the protein that lets you serve yourself less rice, across the district’s whole non-veg spread, with your cholesterol numbers checked on schedule.

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Frequently asked questions

No. Fresh tuna is protein and water with very little fat and no carbohydrate, so on its own it produces essentially no rise in glucose. What rises is the rice, kappa or porotta eaten with it, and the oil it was fried in. Keep the fish, shrink the starch, and the meal behaves.

Brine or spring water, drained — and rinsed if your blood pressure or kidneys need watching, because salt is added to most tins. Oil-packed tuna is the same fish carrying extra fat and calories, since some of the oil stays behind; drain it well if that is what the shop has. Neither tin touches blood sugar directly.

In limited amounts. Tuna is a large predatory fish and carries more mercury than sardine or mackerel; the FDA and EPA fish advice places yellowfin in its once-a-week band and puts shark and bigeye tuna on the avoid list. In pregnancy, favour the small fish and settle your own intake with your obstetrician.

Both are fine; the curry is lighter. Thoran adds grated coconut and a spoon of coconut oil, which is fat rather than sugar, so it moves the calories more than the glucose. A meen kuzhambu with kudampuli, or avicha meen boiled with coconut paste and no added oil, is the everyday version when weight is the target.

For protein they are much the same; for omega-3, sardine and ayala win comfortably, because yellowfin is a lean fish with very little fat. If you eat fish for the heart as much as for the sugar, keep chaala and ayala in the weekly rotation and let choora be the change of taste rather than the whole plan.

Most patients here eat fish four or five days a week, and that is not a problem — it is a steadier habit than the same number of meat meals. A palm-sized 100 to 150 g piece per meal is the sensible portion. The frequency worth watching is fried fish and karuvadu, for the oil and the salt rather than the sugar.