Hannah Zulueta Raw Feeding · Fish & Seafood
Thiamine and Thiaminase: How to Feed Fish Without Losing Vitamin B1
Which fish carry the enzyme, what cooking does to it, and how to handle sardines.
You can feed your dog fish that contains thiaminase. Cook it first, and the enzyme is gone. I feed fish or seafood at every meal, so I looked into what this enzyme actually does to vitamin B1.
The short answer
Can my dog eat fish that contains thiaminase?
Yes. Heat destroys thiaminase. Cook the fish low and slow in a tablespoon or two of water, and the omega-3 fats you wanted from it stay in the fish. Cooking also lowers some of the thiamine in the fish itself, so the meat and organ in the rest of the bowl supply what your dog needs.
- Fish on the thiaminase list: cook before feeding.
- Fish on the no-thiaminase list: feed raw or cooked.
- Freezer: store each fish in its own container. If fish and meat share one prep container, cook the thiaminase fish first.
Start here
What is thiamine?
Thiamine is vitamin B1. It turns the food in your dog’s bowl into the energy he uses on the walk afterward, and it keeps his nerves working.
Thiamine dissolves in water, so the body flushes extra out in urine instead of storing it. Your dog needs a fresh supply every day.
Good sources are pork, beef, beef liver, fish, and seafood. Kibble loses most of its thiamine to manufacturing heat, so companies add a synthetic form back in.
What does thiaminase do to thiamine?
Thiaminase is an enzyme found in some raw fish and shellfish. An enzyme is a protein that cuts or builds other molecules.
Picture kitchen shears. Thiaminase cuts each thiamine molecule in two, and the two halves no longer work as vitamin B1. Your dog can eat plenty of thiamine and still run short.
Why it made the news
Why does kibble need thiamine added back?
Heat destroys thiamine. The meat used for kibble is rendered at over 230 degrees, and the kibble is then cooked again, sometimes several times. Very little of the original vitamin reaches the bag.
AAFCO addressed this in 2008. Processing can destroy up to 90 percent of the thiamine in a diet, so manufacturers are told to add enough to still meet the minimum after processing.
When that step goes wrong, the food gets recalled. Six of the twelve vitamin recalls below, from 2009 to 2017, were for low thiamine. Dr. Conor Brady compiled the list.
Thiamine and vitamin recalls, 2009 to 2017
- 2017 J.M. Smucker Company, twice. Possible low levels of thiamine (vitamin B1).
- 2016 Addiction Pet Foods. Elevated levels of vitamin A.
- 2016 Fromm Family Foods. Elevated levels of vitamin D.
- 2016 Nestlé Purina. Product may not contain the recommended level of vitamins and minerals.
- 2015 Ainsworth Pet Nutrition. Voluntary cat food recall for potentially elevated vitamin D levels.
- 2014 Natura Pet. Cat food recalled for vitamin insufficiency.
- 2013 Premium Edge, Diamond Naturals and 4health dry cat food. Voluntary recall for possible low levels of thiamine.
- 2012 Nestlé Purina. Voluntary recall of therapeutic canned cat food for low thiamine.
- 2011 WellPet LLC. Voluntary recall of canned cat food for less than adequate thiamine, described as an abundance of caution.
- 2010 Blue Buffalo. Dry dog food recalled for possible excess vitamin D after 36 dogs were diagnosed with high vitamin D levels.
- 2010 P&G. Canned cat foods recalled for low thiamine.
- 2009 Diamond Pet Foods. Premium Edge Adult Cat and Hairball Cat Food recalled for the potential to produce thiamine deficiency. Twenty one cases confirmed in cats eating the product.
The sled dogs
Why did sled dogs get thiamine deficiency?
The sled dogs in that report were fed only fish. With nothing else in the bowl, no other food replaced the thiamine the enzyme destroyed.
A raw diet built from several meats and organs supplies thiamine from many sources at once.
No routine blood test catches thiamine deficiency, so it often goes unnoticed. Prevent it instead: cook the thiaminase fish, and feed a variety of foods.
Sardines
Can I overfeed sardines?
Yes. I talk about sardines because they are the fish most people reach for. A conservative amount is 15 to 20 grams a day for a 20 pound dog. Feed less to a smaller dog.
Feeding raw, whole sardines to a small dog above that amount can cause:
- Thiamine loss, from the thiaminase in raw herring-family fish.
- Too much phosphorus, from the bones. This is a concern for dogs with kidney disease.
- Low vitamin E. Fish oil is a fragile fat, and the body uses up vitamin E protecting it.
- Loose stools or pancreatitis, from the rich fat. Small dogs are most at risk.
When sardines crowd out the rest of the bowl, or the fat keeps stools loose, your dog absorbs less of everything. This is called malabsorption. On bloodwork, it can show up as:
- Low cholesterol, even though sardines are rich in fat.
- Low albumin or low total protein.
- Low vitamin B12 (cobalamin), if your vet runs it.
Thiamine and vitamin E do not appear on a routine blood panel. If your dog eats sardines often and any of these numbers come back low, bring your fish amounts to your vet.
Does anything besides thiaminase affect which fish I feed?
Yes. Histamine and sourcing both count.
Oysters carry no thiaminase, so they can go in raw. They come canned, frozen, or fresh, and finding them is hard for many people. Canned foods tend to carry more histamine, the compound behind an allergic dog’s itch, and some dogs react to it.
The reference lists
Which fish contain thiaminase?
Pick a list, then pick a habitat. Species are grouped by family so you can find the fish in front of you at the market.
Cook these before feeding. Low and slow in a tablespoon or two of water.
- Common bream (Abramis brama)
- Central stoneroller (Campostoma anomalum)
- Goldfish (Carassius auratus)
- Common carp (Cyprinus carpio)
- Emerald shiner (Notropis atherinoides)
- Spottail shiner (Notropis hudsonius)
- Rosy red, fathead minnow (Pimephales promelas)
- Olive barb (Puntius sarana)
- Lake whitefish (Coregonus clupeaformis)
- Round whitefish (Prosopium cylindraceum)
- White sucker (Catostomus commersonii)
- Bigmouth buffalo (Ictiobus cyprinellus)
- Brown bullhead catfish (Ameiurus nebulosus)
- Channel catfish (Ictalurus punctatus)
- Bowfin (Amia calva), family Amiidae
- Burbot (Lota lota), family Lotidae
- White bass (Morone chrysops), family Moronidae
- Rainbow smelt (Osmerus mordax), family Osmeridae
- Loach, weatherfish (Misgurnus sp.), family Cobitidae
- Alewife (Alosa pseudoharengus)
- Gizzard shad (Dorosoma cepedianum)
- Sea lamprey (Petromyzon marinus), family Petromyzontidae
- Fourhorn sculpin (Triglopsis quadricornis), family Cottidae
- Salmon, processed and salted, probably Oncorhynchus sp., family Salmonidae
- Broad-striped anchovy (Anchoa hepsetus)
- Californian anchovy (Engraulis mordax)
- Goldspotted grenadier anchovy (Coilia dussumieri)
- Atlantic herring (Clupea harengus)
- Atlantic menhaden (Brevoortia tyrannus)
- Gulf menhaden (Brevoortia patronus)
- Razor belly sardine (Harengula jaguana)
- Chub mackerel (Scomber japonicus)
- Skipjack tuna (Katsuwonus pelamis)
- Yellowfin tuna (Thunnus albacares, listed in older sources as Neothunnus macropterus)
- Green jobfish (Aprion virescens)
- Ruby snapper (Etelis carbunculus)
- Crimson jobfish (Pristipomoides filamentosus)
- Giant trevally (Caranx ignobilis)
- Doublespotted queenfish (Scomberoides lysan)
- Bigeye scad (Selar crumenophthalmus)
- Red Sea goatfish (Mulloidichthys auriflamma)
- Yellowstripe goatfish (Mulloidichthys samoensis)
- Manybar goatfish (Parupeneus multifasciatus)
- American butterfish (Peprilus triacanthus), family Stromateidae
- Southern ocellated moray (Gymnothorax ocellatus), family Muraenidae
- Bonefish (Albula vulpes), family Albulidae
- Milkfish (Chanos chanos), family Chanidae
- Common dolphinfish (Coryphaena hippurus), family Coryphaenidae
- Hawaiian flagtail (Kuhlia sandvicensis), family Kuhliidae
- Black cod, species indeterminate, family Moridae
- Flathead mullet (Mugil cephalus), family Mugilidae
- Sixfinger threadfin (Polydactylus sexfilis), family Polynemidae
- Regal parrot (Scarus dubius), family Scaridae
- Swordfish (Xiphias gladius), family Xiphiidae
No thiaminase. Feed these raw or cooked, whichever suits how you feed.
- Largemouth bass (Micropterus salmoides)
- Northern rock bass (Ambloplites rupestris)
- Northern smallmouth bass (Micropterus dolomieu)
- Blue gill (Lepomis macrochirus)
- Black crappie (Pomoxis nigromaculatus)
- Pumpkinseed (Lepomis gibbosus)
- Yellow perch (Perca flavescens)
- Walleye (Sander vitreus)
- Bloater (Coregonus hoyi)
- Lake trout (Salvelinus namaycush)
- Rainbow trout (Oncorhynchus mykiss)
- Ayu (Plecoglossus altivelis), family Plecoglossidae
- Longnose gar (Lepisosteus osseus), family Lepisosteidae
- Northern pike (Esox lucius), family Esocidae
- Cisco, lake herring (Coregonus artedi). A whitefish, not a true herring.
- Atlantic salmon (Salmo salar)
- Coho salmon (Oncorhynchus kisutch)
- Sea trout (Salmo trutta)
- Common eel (Anguilla anguilla), family Anguillidae
- Pond smelt (Hypomesus olidus), family Osmeridae
- Winter flounder (Pseudopleuronectes americanus)
- Winter flounder, lemon sole (Pseudopleuronectes americanus)
- American plaice (Hippoglossoides platessoides)
- Yellowtail flounder (Limanda ferruginea)
- Atlantic halibut (Hippoglossus hippoglossus)
- European plaice (Pleuronectes platessa)
- Atlantic cod (Gadus morhua)
- Haddock (Melanogrammus aeglefinus)
- Saithe, pollock (Pollachius spp.)
- Atlantic croaker (Micropogonias undulatus)
- Southern kingfish (Menticirrhus americanus)
- Spot croaker (Leiostomus xanthurus)
- Silver seatrout (Cynoscion nothus)
- Sand weakfish (Cynoscion arenarius)
- Greater amberjack (Seriola dumerilii)
- Yellowtail scad (Atule mate)
- Mackerel scad (Decapterus pinnulatus)
- Cunner (Tautogolabrus adspersus)
- Tautog (Tautoga onitis)
- Atlantic mackerel (Scomber scombrus)
- Kawakawa (Euthynnus affinis)
- Tusk (Brosme brosme), family Lotidae
- Largehead hairtail (Trichiurus lepturus), family Trichiuridae
- Piked dogfish (Squalus acanthias), family Squalidae
- Hake (Urophycis spp.), family Phycidae
- Inshore lizardfish (Synodus foetens), family Synodontidae
- Mullet (Mugil spp.), family Mugilidae
- Scup, southern porgy (Stenotomus chrysops), family Sparidae
- Ocean perch, redfish (Sebastes marinus), family Sebastidae
- Black seabass (Centropristis striata), family Serranidae
- Hardhead sea catfish (Ariopsis felis), family Ariidae
- Searobin (Prionotus spp.), family Triglidae
- Silver hake (Merluccius bilinearis), family Merlucciidae
- Eyestripe surgeonfish (Acanthurus dussumieri), family Acanthuridae
- Atlantic blue marlin (Makaira nigricans), family Istiophoridae
- Blotcheye soldierfish (Myripristis berndti), family Holocentridae
- Glasseye (Heteropriacanthus cruentatus), family Priacanthidae
- Great barracuda (Sphyraena barracuda), family Sphyraenidae
- Cockle (Cardium spp.)
- Oysters
- Marine shrimps, species indeterminate, Hawaii
- Portuguese crabs, species indeterminate
- Brief squid, calmar (Lolliguncula brevis)
The gaps
What about sardines and other fish that aren’t on the list?
Sardines are the fish I get asked about most, and the ones you can buy were never tested. The only sardine on the list is the razor belly. The sardines in your market or pantry are usually one of these three:
- Pacific sardine (Sardinops sagax)
- European sardine, or pilchard (Sardina pilchardus)
- Spanish sardine (Sardinella aurita)
All three belong to the herring family, and every herring on either list carries thiaminase. Cook your sardines.
I can also find wild Canadian capelin easily at my local Asian market. The packaging doesn’t say whether it came from fresh water or the ocean. Capelin belongs to the smelt family, which appears on both lists depending on the species.
When in doubt, cook it. Low and slow in a tablespoon or two of water. The omega-3s stay in the fish, and the enzyme is gone.
Sardines and my family
How do I choose fresh sardines?
In the Philippines, and across much of Asia, sardines are how we get our calcium. We eat the small fish whole, bones and all.
My cousin fished sardines on a remote island there, using outriggers, simple nets, and baskets. He bottled the catch in glass instead of cans. He has passed away, and his wife still runs it the same way.
He noticed his catch shrinking after farms up the mountain started using pesticides. The rain washed the runoff into the sea where his sardines lived.
In an Asian market, fish lies on ice or swims in tanks, and we inspect it before we buy. We pass on any fish with cloudy eyes. Sushi chefs hold fish to an even higher standard.
Commercial sardines are caught by the thousands or millions, packed tight in the hold, and can sit for hours before they are chilled. Their oils go rancid quickly, like cooking oil left too long in the back of the pantry. Bacteria also turn the histidine in warm sardine flesh into histamine.
Cooking destroys thiaminase. Histamine and rancid oil survive the pan, so buy the freshest sardines you can find before you cook them.
Check each sardine for:
- Clear, bright eyes. Cloudy eyes mean an older fish.
- Firm flesh that springs back when you press it.
- A clean ocean smell, with nothing sour.
- A source you can trace, such as a fishmonger who knows where it was caught or a brand that names its fishery.
Putting it together
What do I do at home?
My dogs get fish or seafood at every meal. The fish from the thiaminase list goes into a pan with a tablespoon of water before it meets anything else in the bowl.
Is fish going into the bowl because of a health condition?
This article covers one vitamin and one food group. If you are feeding fish for kidney disease, itchy skin, or a sensitive gut, these guides pick up from here.
Work with me
How much fish is right for your dog?
The answer depends on your dog’s size, health, and histamine tolerance, and on where your fish comes from. If your dog has a condition, or you are building a home-cooked or raw diet and want it checked against NRC and AAFCO standards, book a TCM Dietetics consultation and we will go through the whole bowl together.
More reading: what complete and balanced actually means, the nutrition calculators, or the rest of the blog archive.
Sources: AAFCO 2008 nutrient profiles and processing allowance statement. Recall list compiled by Dr. Conor Brady. Thiaminase species lists compiled from published aquatic and comparative nutrition literature.
Hannah Zulueta obtained her Certificate in Canine Nutrition from CASI Institute. She is also studying for her Doctorate in Acupuncture, Traditional Chinese Medicine, and Herbalism from the esteemed Pacific College of Health and Medicine. If you’re as keenly interested in health for yourself, visit her website for human health: Satori Acupuncture and Herbs.
She resides in San Diego with her three dogs, Maggie, Orbit, and Mr. Higgins.
She is available for one on one consultations. She develops evidence-based recipes that meet both NRC and AAFCO nutritional standards while integrating the therapeutic food principles of Traditional Chinese Veterinary Medicine into her formulations.
Additionally, you can find her sharing free content on Instagram.
