Fish synthesize Vitamins D but Humans can not ?
Is the function of Vitamins D ( preformed ) in fish known ? Is itrelated to bone calcification ? Why is there such a variance in differentspecies of fish ? It is not relvant to bone characteristics as there arefish with hard bone skeletons and those with soft. ie: the example of theSturgeon ( skeletal softness ). Some cartilaginous fishes store more
Vitamins D than those fishes with hard bones.

There is also a variance in the form of Vitamins D. Some fishes havean admixture of
Vitamin D2 and Vitamin D3 ( Tuna Fish ) andothers have been identified as having Vitamin D3 with anotherVitamin D without the sidechain or admixtures of unidentified VitaminsD. The Goldfish, Carassius auratus ( freshwater ) a surface feederhas no Vitamin D in its body oil. ref: unpublishedobservation of C. E. Bills.
A Japanese researcher has shown that there is. I' m not certainof the publication or date,
maybe the mid 1960's. It could be faulty methodology ie: In therearing of the sample fish
in an unnatural environment, were all factors eliminated that allowedfor
exogenous sterols ?

C. E. Bills was an exact researcher. So in finding a fish thathad hardly a trace of Vitamin D in its body oils he must have decided tokeep the research results unpublished . A puzzle to him, what ! or wasit an inside joke. Swallowing Goldfish, anyone ?

" It is true nevertheless, that most fish oils have an efficacy ratioof around 100, the value characteristic of cod liver oil and the activated7-DEHDROCHOLESTEROL
( Vitamin D3 )......................."

" The fact that cod liver oil and many other fish oils exhibit theefficacy ratio of
Vitamin D3 is no proof that this is the one and onlyform of VITAMIN D which these oils contain. It is possible that other formsare present which are equally effective for rats and chicks, or that formsof higher and lower efficacy ratio are present in admixture.
Hickman and Gray, ref: K. C. D. Hickman,Ind. Eng. Chem. 29, 1107 ( 1937 );
K. C. D. Hickman and E. L. Gray, ibid.30 796 ( 1938 ) utilized the technique ofmolecular
distillation in an investigation of the VitaminsD of several fish oils. They found at the
outset that about 70% of the Vitamin D ofCod Liver oil occurs as esters, and so it was necessary to conduct theshort path distillations with saponified material. Cod Liver Oil exhibiteda complex elimination curve indicative of two major, two minor and twotrace forms of Vitamin D. "
Other admixtures are found in other fishes,ie: Tuna Fish.

regards,
Distribution of Vitamins D and A in the LiverOils of Fish
Partial list and Reference:
C. E. Bills, F. G. MacDonald, O. N. Massengale,M. Imboden, H. Hall, W. D. Hergert, and J. C. Wallenmeyer, J. Biol.Chem. 109, Proc. vii ( 1935 ).
Reported more than one assay.
Common Name Of Fish · Scientific
Name · Zoological
Order · Vitamin D,
I.U./g. · Vitamin D,
I.U./g.
Oriental Tuna · Thunnus orientalis · Percomorphi · 45,000 · 170,000
Frigate Mackerel · Auxiz
thazard · Percomorphi · 44,000 · 30,000
California
Bluefin Tuna · Thunnus
saliens · Percomorphi · 42,000 · 65,000
Stripped
Tuna · Katsuwonus pelamis · Percomorphi · 42,000 · 36,000
Sturgeon · Acipenser
fulvescens · Galiniostomi · <1 · 600
Gray Sole · Glyptocephalus
cyanoglossus · Heterosomata · <2 · 8,900
Ratfish · Hydrolagus
colliei · Chimaeroidei · 2 · 180
Atlantic
Dogfish · Squalus
acanthias · Tectospondyli · 3 · 1,700
Basking Shark · Cetorhinus
maximus · Euselachii · 6 · <100
Pacific
Dogfish · Squalus
suckleyi · Tectospondyli · 13 · 13,000
California
Flyingfish · Cypselurus
californicus · Synentognathi · 51 · 35,000
Abura Karei · Hippoglossoides
dubius · Heterosomata · 25 · 5,100
Yellow Sole · Pseudo-
pleuronectes
dignabilis · Heterosomata · 87 · 17,000
Atlantic Cod · Gadus morrhua · Anacanthini · 100 · 1,400
Menuke · Sebastodes
baramenuke · Cataphracti · 100 · 120,000
California
Turbot · Pleuronichtys
decurrens · Heterosomata · 110 · 8,200
Chili-Pepper · Sebastodes
goodei · Cataphracti · 270 · 150,000
Cabrilla · Epinphelus
analogus · Percomorphi · 260 · 160,000
Boston
Mackerel · Scomber
scombrus · Percomorphi · 750 · 31,000
Ling Cod · Ophiodon
elongatus · Cataphracti · 920 · 160,000
Rockfish · Acutomentum
entomelas · Cataphracti · 1,100 · 8,000
Shad · Alosa
sapidissima · Isospondyli · 1,200 · 17,000
Halibut · Hippoglossus
hippoglossus · Heterosomata · 1,200 · 75,000
Pacific Hake · Merluccius
productus · Anacanthini · 1,500 · 50,000
Bocaccio · Sebastodes
paucispinis · Cataphracti · 1,800 · 77,000
Sardine · Sardinia
caerulea · Isospondyli · 2,300 · 16,000
Jack Smelt · Atherinopsis
californiensis · Percomorphi · 2,400 · 96,000
Barracuda · Sphyraena
argentea · Percomorphi · 4,700 · 67,000
Albacore · Thunnus
germo · Percomorphi · 13,000 · 12,000
Red Snapper · Lutianus
campechanus · Percomorphi · 22,000 · 61,000
Bonito · Sarda lineolata · Percomorphi · 35,000 · 57,000
Meji Tuna · Parathunnus
sibi · Percomorphi · 38,000 · 22,000