by Richard Lunsford.
Often on our forums people ask about, allude to
or otherwise mention thiaminase, typically in discussions about fish in turtle
diets, particularly frozen fish. Let’s talk about what it is, what it does, why
it matters & what you should do about it.
Thiamine is Vitamin B1 – a water-soluble vitamin involved in energy
metabolism - much of what I know about it comes from its importance in thiamine
deficiency in human alcoholics, but there’s a lot more to it than that.
Click to read about it at Nutrition.org. (Note: I saw both ‘thiamine’
& ‘thiamin’ spellings used in online sources).
Chronic, heavy drinking alcoholics may over-rely on alcoholic beverages
as a caloric source & eat poorly, developing a thiamine deficiency over long
This can eventually lead to acute confusional episodes called Wernicke’s
Click here to read about it.
If this condition persists long enough, severely enough, it can lead to
Korsakoff’s Psychosis (covered in the same link given for Wernicke’s
Encephalopathy). K.P. is an anterograde amnestic state rather than a psychotic
state. It can be permanent.
This article at Cornell University states “In humans thiamin deficiency
leads to a disease termed "beri-beri". Symptoms of beri-beri are basically the
same as thiamin deficiency in other non-ruminants - anorexia, cardiac
enlargement, and muscular weakness leading to ataxia. However, the disease has
been divided into the following two forms:
Dry beri-beri - usually without cardiac involvement, this form of
the disease is typified by atrophy of the legs and peripheral neuritis. It
occurs mainly in adults.
Wet beri-beri - the primary sign of this form of the disease is
cardiac enlargement and edema.”
turtles, we turn to the Practical Encyclopedia of Keeping & Breeding
Tortoises & Freshwater Turtles, Page 90, where A. C. Highfield states a
Vitamin B deficiency (he doesn’t break it down, but B1 is clearly covered) can
produce symptoms including muscle tremors, nervous type behavior and anorexia.
7.) Thiaminase (There are 2
types, Type I & Type II) is an enzyme.
Enzymes are biological catalysts made of proteins.
A catalyst is a substance that speeds up a chemical reaction without
being consumed by that reaction. It makes reactions happen faster. Like if a log
rots over 5 years, & you somehow catalyze all the chemical reactions involved &
make it rot in 5 minutes.
Our bodies require enzymes to speed some of the chemical reactions
required in our metabolism.
Thiaminase destroys Thiamine (Vitamin B1).
Regular intake of substantial amounts of food containing thiaminase could
introduce enough thiaminase into the gut to break down the thiamine in food &
render an animal thiamine-deficient.
Some fish contain thiaminase (Type I, not II) & some don’t.
For an in-depth discussion of thiamine’s role in the body, Type I & Type
check out this article at Cornell University.
Nutrient Requirements of Mink and Foxes, Second Revised Edition, 1982, Pages 64
& 65, provides tables of fish reported to contain & not to contain
thiaminase. A sampling from those tables (bold emphasizing fish you might use):
Fish Reported to contain Thiaminase:
White Bass – Morone chrysops
Bowfin – Amia calva
Bream – Abramis brama
(Not the U.S. fish;
see this link).
Buffalofish – Ictiobus
Bullhead catfish –
Ameiurus m. melas
Carp – Cyprinus carpio
Channel Catfish –
Fathead minnow –
Pimephales promelas (the red rosy is a color morph of this fish!)
Goldfish – Carassius
Moray Eel – Gymnothorax
ocellatus (since someone recently asked about keeping the brackish water
species with turtles…)
Gizzard Shad –
Spottail Shiner –
Buckeye shiner –
Central Stoneroller –
Campostoma anomalum pullum
Common White Sucker –
Lake Whitefish – Coregonus clupeiformis
Fish Reported to not contain Thiaminase:
Largemouth Bass – Huro
salmoides (I think that’s actually now Micropterus salmoides)
Rock Bass –
Smallmouth Bass –
Bluegill – Lepomis
Chub (Bloater) – Coregonus
Cod – Gadus morhua
Crappie – Pomoxis
Eel – Anguilla rostrata
Northern Longnose Gar –
Lepisosteus osseus oxyurus
Northern Pike – Esox lucius
Pumpkinseed – Lepomis
Salmon – Salmo salar
Brown Trout – Salmo trutta
Lake Trout – Salvelinus
Rainbow Trout –
Note: Be aware that fish are
acquired from pet stores, bait stores, traditional rod & reel or cane poll fish
& netting (dip net, casting net, seine). So you may get such fish as shad… Since
bluegill & pumpkinseed don’t contain thiaminase, I suspect the sunfish generally
won’t (but that’s an assumption…).
It widely rumored that frozen fish is prone to contain more thiaminase
than fish that has not been frozen. But why would this be so? Is it because
thiaminase-containing fish are amongst species offered frozen, or because
thiaminase is formed when some fish are frozen &/or thawed?
It makes no sense to me that something as complex as an enzyme would
‘accidentally happen’ (be made) when fish is frozen & thawed. However, if
thiaminase were contained in the fishes’ cells, when those cells ruptured this
might release thiaminase, making it easier to measure. I would expect digestion
to rupture all the cells in a prey item, anyway.
However, in Practical Encyclopedia of Keeping & Breeding Tortoises &
Freshwater Turtles, on Page 90 A. C. Highfield states that the enzyme
thiaminase forms in fish after death. I have no idea where he got such info. &
can neither prove nor disprove it. He also states that aquatic turtles with a
diet including fish should always be provided a concurrent vitamin B1
Thiaminase is of greatest concern to people feeding animals a fish-heavy
diet, which while inappropriate for most species (i.e.: RES, stinkpots, etc…)
may be needful in some (Chitra softshells & Mata Mata turtles).
Occasional feedings should be irrelevant, but frequent feeding could in theory
keep enough thiaminase in the gut to degrade thiamine.
Some Commercial Turtle Foods listing Thiamine on the label –
(for aquatic turtles, newts & frogs), Wardley®
Reptile Sticks, Jurassi·Diet™ Aquatic Turtle Food, Jurassi·Diet™
Reptile Food, Nature Zone Aquatic Turtle Bites, T-Rex®
Tortoise Dry Formula,
Mazuri® Fresh Water Turtle Diet,
Mazuri® Tortoise Diet.
Options to combat thiaminase deficiencies include:
Oral supplementation of thiamine – I ‘m not up on this. Most won’t
need to explore it but if you keep a Mata Mata, Chitra softshell or other
animal with a high-fish (in some cases only fish) diet you’d better look
Avoiding fish known to contain thiaminase – no red rosies or
feeder goldfish! And who knows whether guppies or platys contain it or not?
Don’t feed fish over once per week on an ongoing basis – ensuring
the turtle eats nutritious food likely to contain thiamine (like reputable
commercial turtle foods) when they’ve had no fish for a few days should help
ensure the body gets to absorb thiamine.
that Cornell article points out that “Thiaminases are denatured by heat,
therefore subjecting any of the sources of thiaminases to cooking or other heat
treatment will render the thiaminases inactive.” Unfortunately, it doesn’t tell
us how much or how long to heat it. Perhaps slow baking or broiling? In this
case ‘denature’ refers to the breakdown of a protein under heat.
Dictionary.com’s entry includes a number of definitions of ‘Denature,’
including “To cause the tertiary structure of (a protein) to unfold, as with
heat, alkali, or acid, so that some of its original properties, especially its
biological activity, are diminished or eliminated.”
Appendix of Useful Online Resources:
Nutrition.org’s Thiamine Info. Page.
Cornell University’s Thiaminase Article.
Fish Base – an online relational
database global info. system on fish claiming to have
28500 Species, 193900 Common names,
36700 Pictures, 33700 References, 1110 Collaborators & 11 million Hits/month.
Their search page is useful to pulling up info. on wild fish species.
Dictionary.com – self-explanatory.