Hi Dr. Cordain,
I read your book The Paleo Diet several years ago and on page 122 you mention that “Canning also increases the level of oxidized cholesterol in fish, specifically increasing a molecule called 25 hydroxycholesterol that is extremely destructive to the linings of arterial blood vessels. This is so destructive, in fact, that oxidized cholesterol is routinely fed to laboratory animals to accelerate the artery-clogging atherosclerotic process in order to test theories of heart disease. In animal models of atherosclerosis and heart disease, only 0.3 % of the total ingested cholesterol needs to be in the form of oxidized cholesterol to cause premature damage to arterial linings.”
Many health-conscious people eat canned fish for the supposed health benefits and are not aware of the book’s claims. Also noticed you only mention canned tuna but no other species of fish.
Is consuming canned fish really a serious danger to people’s arterial blood vessels and should we avoid eating these products? Appreciate if you could refer me to research studies that confirm the above and if you aware of any recent studies?
Your thoughts are appreciated and I look forward to your reply.
Dr. Cordain’s Response:
Good to hear from you and good question. The bottom line is that we should steer clear from oxidized cholesterol derived from any and all foods in our diet (see references 1-9). Clearly it is an impossible task to completely remove oxidized cholesterol from our diets, given that we are no longer hunter gatherers and that we enjoy cooked meats and fish in 21st century contemporary “Paleo Diets.” In references (10-21) you can see how the canning, smoking and preservation process of fish dilutes its nutritional characteristics and increases the production of oxidized cholesterol which is frequently referred to as oxysterols.
So, I recommend to reduce oxidized cholesterol in your diet. Try to eat meat, fish, poultry and eggs that have been slowly cooked under low heat like steaming, slow cooking crock pots, low heat baking, poaching, and other low temperature cooking techniques, including microwave. Try to avoid foods that have been cooked under high temperatures like frying, broiling, high temperature barbecuing, and searing. Additionally, canned meats and fish are almost always cooked at high heats to prevent botulism, which increases their oxidized cholesterol content. Clearly, canned tuna contains many healthful elements (high protein, high omega 3 long chain fatty acids) and should be part of contemporary Paleo Diets, but fresh tuna and fish is a better option if it is available and you can afford it.
Loren Cordain, Ph.D., Professor Emeritus
1. Emanuel HA, Hassel CA, Addis PB, Bergmann SD, Zavoral JH. Plasma cholesterol oxidation products (oxysterols) in human subjects fed a meal rich in oxysterols. Journal of food science 1991; 56: 843-7.
Hubbard RW, Ono Y, Sanchez A. Atherogenic effect of oxidized products of cholesterol. Prog Food Nutr Sci. 1989;13(1):17-44.
2. Jacobson MS. Cholesterol oxides in Indian ghee: possible cause of unexplained high risk of atherosclerosis in Indian immigrant populations. Lancet 1987;2:656-58.
3. Kumar, N., and O.P. Singhal, Cholesterol Oxides and Atherosclerosis: A Review, J. Sci. Food Agric. 55:497–510 (1991).
4. Kummerow FA. Interaction between sphingomyelin and oxysterols contributes to atherosclerosis and sudden death. Am J Cardiovasc Dis. 2013;3(1):17-26.
5. Otaegui-Arrazola A, Menéndez-Carreño M, Ansorena D, Astiasarán I. Oxysterols: A world to explore. Food Chem Toxicol. 2010 Dec;48(12):3289-303.
6. Pohjantahti-Maaroos H, Palomaki A, Kankkunen P, Laitinen R, Husgafvel S, Oksanen K. Circulating oxidized low-density lipoproteins and arterial elasticity: comparison between men with metabolic syndrome and physically active counterparts. Cardiovasc Diabetol 2010 Aug 20; 9: 41.
7. Staprans I, Pan XM, Rapp JH, Feingold KR. Oxidized Cholesterol in the Diet Accelerates the Development of Aortic Atherosclerosis in Cholesterol- Fed Rabbits. Arterioscler Thromb Vasc Biol 1998 Jun; 18: 977-83.
8. Otaegui-Arrazola A, Menéndez-Carreño M, Ansorena D, Astiasarán I. Oxysterols: A world to explore. Food Chem Toxicol. 2010 Dec;48(12):3289-303.
9. Lordan S, Mackrill JJ, O’Brien NM. Oxysterols and mechanisms of apoptotic signaling: implications in the pathology of degenerative diseases. J Nutr Biochem. 2009 May;20(5):321-36.
10. Aubourg S., Gallardo J.M. and Medina, I. 1997. Changes in lipids during different sterilizing conditions in canning albacore (Thunnus alalunga) in oil. Int. J. Food Sci. Tech. 32, 427-431.
11. Aubourg S., Medina I. and Pérez-Martin R. 1996. Polyunsaturated fatty acids in tuna phospholipids: distribution in the sn-2 location and changes during cooking. J. Agr. Food Chem. 44, 585-589.
12. Boran G., Karacam H. and Boran M. 2006. Changes in the quality of fish oils due to storage temperature and time. Food Chem. 98, 693-698.
13. Maruf F.W., Ledward D.A., Neale R.J. and Poulter R.G. 1990. Chemical and nutritional quality of Indonesian dried-salted mackerel. Int. J. Food Sci. Tech. 25, 66-77.
14. Ohshima, T., N. Li, and C. Koizumi, Oxidative Decomposition of Cholesterol in Fish Products, J. Am. Oil Chem. Soc. 70:595–600 (1993).
15. Oshima T. Formation and Content of Cholesterol Oxidation Products in Seafood and Seafood Products. In: Cholesterol and Phytosterol Oxidation Products Analysis, Occurrence, and Biological Effects, (Eds.), Codony R, Savage GP, Dutta PC , Cuardiola F. AOCS Publishing, 2002.
16. Osada, K., T. Kodama, L. Cui, K. Yamada, and M. Sugano, Levels and Formation of Oxidized Cholesterols in Processed Marine Foods, J. Agric. Food. Chem. 41:1893–1898 (1993).
17. Sebedio J.L., Ratnayake W.M.N. Ackman R.G., and Prevost J. 1993. Stability of polyunsaturated n-3 fatty acids during deep fat frying of Atlantic mackerel (Scomber scombrus L.). Food Res. Int. 26, 163-172.
18. Selmi S, Sadok S. Change in lipids quality and fatty acids profile of two small pelagic fish: sardinella aurita and sardina pilchardus during canning process in olive oil and tomato sauce respectively. Bull. Inst. Natn. Scien. Tech. Mer de Salammbô, Vol. 34, 2007.
19. Stołyhwo A., Kołodziejska I. and Sikorski Z.E. 2006. Long chain polyunsaturated fatty acids in smoked Atlantic mackerel and Baltic sprats. Food Chem. 94, 589-595
20. Tarley R.T.C. Visentainer V.J., Matsushita M. and De-Souza N.E. 2004. Proximate composition, cholesterol and fatty acids profile of canned sardines (Sardinella brasiliensis) in soybean oil and tomato sauce. Food Chem. 88, 1-6.
21. Zunin P, Boggia R, Evangelisti F. Identification and Quantification of Cholesterol Oxidation Products in Canned Tuna. JAOCS. 2001; 78: 1037–1040