Species
a Source: Grangaud (1950).
B. VITAMIN D
While vegetables contain essentially the provitamin D2 (ergosterol) primarily vitamin D3, derived from 7-dehydrocholesterol, is found in fish, associated with small quantities of other D vitamins, some of which are unknown as to their structure or possess a low vitamin efficiency
(vitamin D6) . Vitamin D3 is said to be the real natural vitamin D. Its genesis in fish has been studied. Steenbock and Black (1925) assume that it originates through the solar irradiation of plankton containing provitamins (Drummond and Gunther, 1930-34) or directly by ingestion of the active vitamin as such. Bills (1927) maintains, however, that the antirachitic vitamin is synthesized by fish. He partly proved this by feeding catfish in an aquarium with veal meat which did not contain vitamin D. The oil from the viscera of these experimental fishes showed the same vitamin D content as such fishes caught at sea. Hess et al.
(1929), however, by giving ergosterol per os or by intramuscular injec
tion to cod held captive, did not find the slightest evidence of any conversion into vitamin D.
The distribution of vitamin D follows closely that of vitamin A, liver oils being the richest. A great number of analytical data on vitamin D content are listed in Chapter 13.
In the meat, the distribution is the same for vitamins A and D : both are hardly traceable or wholly absent in the flesh of lean fish. On the other hand, the meat from fatty or semifatty fishes constitutes an
excel-lent source. The amount of vitamin D varies from 500 to 3,000 I.U. per 100 g. The high values for eel should be especially noted.
Canning of fish, independent of the procedure used, does not appre
ciably affect the amount of vitamin D, which furthermore does not diminish during storage (Lunde, 1939). See also Volume II, Chapter 6.
C. VITAMIN Ε
The presence of tocopherols in fish has been discussed for a long time. In flesh it occurs largely as vitamin Ε—α-tocopherol (Harris et al., 1950). A detailed discussion of available data in this respect is found in Chapter 3. Duchesnay (1941), as well as Kringstad and Folkvord (1949), did not find tocopherol in cod liver oil. Smith and Nelson (1931) did report its presence, and Brown (1953) confirmed this and gave the analytical data shown in the tabulation.
Liver oil Tocopherol mg./100 g.
Angler 31.9
Blue rayfish 25.3
Cod 29.3
Haddock 18.0
Ling 27.2
Turbot 45.0
Forty mg. of α-tocopherol per 100 g. of liver oil has been reported from a shark (Eugaleus galeus) (Robeson and Baxter, 1945). Dubouloz and Hedde (1942), however, identified in fish oils, particularly from tuna, other antioxidants than tocopherols.
Kringstad and Folkvord (1949) found rather large quantities of vitamin Ε in the eggs of Gadidae, from 5 to 0.6 mg. per 100 g., calcu
lated on the basis of dry weight; this amount comes close to that for cereal germs.
D. VITAMINS F AND Κ
Vitamin F corresponds to the essential fatty acids (generally indi
cated as E F A ) : linoleic, arachidonic and linolenic. The latter two acids are rare in the lipids of fish which, on the other hand, contain other polyenoic fatty acids (see Section I, C ) . The clupanodonic acid does not seem to exercise a curative or preventive effect upon the syndrome termed Burr and Burr (Tange, 1932). The total methylic esters of cod liver oil have only a very slight curative effect (Hume et al., 1932).
Nevertheless, the methylic ester docosahexanoic acid, a fatty acid of 22
6. ORGANIC CONSTITUENTS OF FISH 185 carbon atoms and 6 double bonds present in cod liver oil, shows a favorable action on the growth of rats on a diet deprived of lipids, but it does not remedy the skin lesions of the Burr and Burr disease (Hume et al., 1938). The body oils (sardines, herring), and the egg lipids (sal
mon) exercise an important curative action in rats deprived of E F A (Bailey, 1943), although less pronounced than that of methyl linoleate.
The presence of antihemorrhagic vitamin Κ in fish has been reported by Fontaine (1945). Fish meal seems to be rather rich in this substance.
E . THIAMINE
Though fish flesh contains less of this substance than pork or even beef (Beveridge, 1947), fish, nevertheless, is a good source of vitamin Bi. Particularly high amounts are found in the flesh of turbot (Rhombus sp.) and that of various codfishes (Gadidae) (Lunde, 1942). The red meat has a higher content than white meat (Braekkan, 1956); the differ
ence can be considerable as in skipjack (Mari et al., 1956). Liver, milt, and eggs are classified for the majority of species as foods richly provided with thiamine. The liver of marine mammals contains more than the liver of domesticated land mammals. The Crustacea and the mollusks also constitute a good source of thiamine. For a further discussion and a listing of analytical data see Chapter 13, this volume.
In some fresh fish an enzyme is present which destroys vitamin B i by splitting its two constituent core molecules, thiaminase. It does not occur in all aquatic animals. It is less common among sea-water species than among fresh-water fishes. Clams contain this substance, oysters do not. Sealock et al. (1943), studying its distribution in carp, this spe
cies being particularly rich, showed that the thiaminase was especially localized in the viscera: spleen, liver, pancreas, pyloric caeca, and the gills. The muscle itself contained very little. Thiaminase is thermolabile.
Boiled and smoked fish (Melnick et al., 1945) are not antivitaminic.
However, the existence of this factor should be taken into consideration in fish feeding. It has been amply proved that this antivitamin is respon
sible for the Chastek paralysis observed in fur animals raised on raw fish (Green et al., 1941) (see also Chapter 1 3 ) .
F . RIBOFLAVIN
Fish flesh contains approximately as much riboflavin as beef, i.e., 0.2-0.3 mg. per 100 g. of fresh flesh. It varies somewhat. High values have been encountered in the conger eel. Red flesh has a much higher
content than white muscles (Braekkan, 1956). Liver, eggs, milt, skin, and eyes all carry higher values than flesh. Several values have been listed in Chapter 13.
In the pigment layer of a skin carrying scales, fluorescyanine, a pterine which possesses a vitamin activity analogous to that of riboflavin, has been identified (Fontaine and Busnel, 1937; 1938a, b; Polonovski et al, 1946).
G . NIACIN
Fish flesh is a good source of vitamin PP (niacin). There are no basic differences between sea-water and fresh-water fish (Klocke et al, 1946) nor between red and white flesh (Braekkan, 1956). Salmon (Bailey, 1950) and swordfish (Matas and Fellers, 1948) appear to be particularly rich in this respect, in excess of 9 mg./100 g. of flesh. In liver, eggs, and milt, one may also find high niacin values; see special table in Chapter 13.
H . PANTOTHENIC ACID
Analyzing a great number of samples of various fish species, Neilands et al (1947) found values for pantothenic acid between 0.25 and 0.80 mg. per 100 g. of fresh weight flesh. These results coincide well with the analyses of Ives et al (1945), who found 0.26 to 0.39 mg. per 100 g. of
TABLE XVI
PANTOTHENIC Aero CONTENT ( F L E S H ) Fish or shellfish Μ-g'/g· Flesh Reference Bluefin tuna
red meat 1.2 \
Braekkan et al ( 1 9 5 5 ) light meat 6 . 1 - 9 . 0 ) Braekkan et al ( 1 9 5 5 ) Mackerel 1 0 . 3 Braekkan and Probst ( 1 9 5 3 ) Herring 9 . 5 Braekkan and Probst ( 1 9 5 3 )
Cod 1.1 Hoogland ( 1 9 5 3 )
Haddock 0.9 Hoogland ( 1 9 5 3 )
Carp 7 . 5 Briggs and Deft ( 1 9 5 4 )
Salmon, Pacific 5.8 Neilands et al ( 1 9 4 7 ) Tuna (not specified) 4 . 2 Neilands et al ( 1 9 4 7 ) Crayfish 2 . 3 - 3 . 8 Novak et al ( 1 9 5 6 ) Oyster 1 . 8 - 5 . 4 Fieger ( 1 9 5 6 )
fresh weight (see Table X V I ) . It thus seems that the margin for varia
tion is broader than the one indicated by the first-mentioned authors.
The extremes may be given as 0.12-1.38 mg. per 100 g. of flesh. Red flesh carries appreciably more than white flesh (Braekkan, 1956).
6. ORGANIC CONSTITUENTS OF FISH 187 Livers of a few fishes have been analyzed as to this vitamin and values of around 3 mg. per 100 g. of fresh tissue have been established.
I. PYRIDOXINE
Lunde and Kringstad (1938) reported that flesh, liver, and eggs constitute one of the richest sources for vitamin B6, quite comparable to the best other sources such as beer yeast. Neilands et al. (1947) established much lower values. In any case, there seem to exist appre
ciable differences between various species, although individual varia
tions are minor (Yanase, 1956).
Fresh-water fish are poorer in this vitamin than ocean fish. Pelagic fishes, such as herring, bonito, and mackerel, are very much richer than nonmigrating ones or those living at the bottom, such as the Alaska pollack, the rock cod, and the blanquillo. See further listings of analyti
cal data in Table XVII. These values show that fish matches fresh yeast (about 0.6 mg.) in its content of pyridoxine.
TABLE X V I I