Do sharks really not get cancer, and if not why?

Bruce Hamilton B.Hamilton at irl.cri.nz
Sun Feb 23 17:33:18 EST 1997


In article <haifisch-2002971723280001 at heyer.ucsc.edu>
 haifisch at cats.ucsc.edu (Bruce Heyer) writes:

>Squalamine is a high quality lubricant extracted from shark liver, but has
>no special health promotion.  The idea that shark liver extracts are
>medicinal lingers from World War II when the war closed down the North
>Atlantic cod fishery.  Shark liver oil was sold as a replacement for cod
>liver oil for a source of dietary vitamin A.

I find this rather strange. Certainly cod liver oil contains significant
amounts of Vitamins A & D along with the omega 3 fatty acid 
( principally DHA and EPA ) components of the triglycerides - which
make up the vast majority of CLO.

Shark Liver oil composition depends very much on the type of shark, 
the location, the food, and the season, but consists mainly of  hydrocarbons 
( predominantly squalene ( C30 unsaturated ) with some pristane 
( C19 branched )), and diacyl glyceryl ethers, with small amounts 
of triacylglycerides and even smaller amounts of monoglyceryl ether.  

The squalene can vary from 20 - 80 %, pristane from 0.1 - 2%, the 
DAGE can vary from 20 - 60%, and triglycerides from 5-20%.

The squalene is refined and can be used as a lubricant, in hand creams
etc etc, and traditionally it was the squalene that was desired, however it 
is the DAGE that have most of the exotic claimed properties. 

They are claimed to have bacteriostatic action, aid in healing of burns, 
inhibit tumour growth ( B.Boeryd, B.Hallgren, G.Stallberg Brit.J.Exp.Pathol. 
v.52 p221 (1971)), and are intermediates in the synthesis of a platelet 
activating factor ( T.Mauramatsu, N.Totani, H.K.Mangold Chem.Phys.Lipids. 
v29 p121 (1981)) . Industrially, the DAGE are hydrolysed to produce their 
component glyceryl ethers and fatty acids. the glyceryl ethers are used in 
cosmetics and ointments.

>Other sources of vitamin A
>are readily available. Several shark populations impacted by the fishery
>of the 1940's have yet to recover.

I'd like a reference to the use of shark liver oil as an alternative
to cod liver oil, they are completely different compositions, and
serve differing roles. I suspect squalene was sought after, but
not as a substitute for CLO, but because of its own desirable uses.

             Bruce Hamilton




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