Now again I have to remind that in certain circumstances, there is a great difference between assuming a purified vitamin as supplement instead of the natural nutrients...
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Speaking of why giving stinky "cod" instead of specific synthetic substances, let's borrow this note from the anti-oxidant topic of the Forum:
quote:
A quote from the article is "Just because a food with a certain compound in it is beneficial to health, it does not mean a pill with the same compound in is"
That's exactly right. A pill sometimes works better than the original food and viceversa.
Scientists versus Mother Nature and her tricks
In the late '70s researchers opened their enormous freezers where thousands of serum samples from blood donors had been stocked since over 10yrs before. They wanted to test vitamin A concentration (knowing that it is well preserved in frozen samples) and look for a correlation with cancer incidence in those individuals. Experimental data in animals had demonstrated a positive effect of retinoic acid on precancerous lesions.
They found a strong inverse relation between vitamin A concentration and risk of tumor. All the media started reccomending vitamin A to prevent or even fight cancer.
Few years later a proper RCT (randomized clinical trial) was started: a group of nurses and doctors took either a certain dose of vitamin A or a placebo every day for years. The conclusion of the study was disappointing: no difference in cancer incidence with or without vitamin A.
Some clever mind offered an explanation for this: vitamin A had been found increased in blood donors who had lower risk of cancer because it had been eaten together with some other more effective anticancer compounds.
Here we go with all the broccoli, cabbage, cauliflowers and so on...they are rich of vitamin A and probably have other mysterious anticancer factors.
iko
Addendum:
Vitamin A instead of cod liver oil would play the same trick...if you gave vit.A to patients because the ones taking 'cod' had higher levels of retinoic acid in their blood and were doing better (hypothesis!), you could get poor results because you are not giving together Vit.D and a bit of omega-3 fatty acids, the original recipe.
:mudneddA
Vitamin D instead of cod liver oil would play the same trick...if you gave vit.D to patients because the ones taking 'cod' had higher levels of vitamin D3 in their blood and were doing better (hypothesis!), you could get poor results because you are not giving together Vit.A and a bit of omega-3 fatty acids, the original recipe.
"Fishy news" from Norway:
Fish oils EPA & DHA (not Vitamin A & D!)
are better absorbed in the natural way.
Enhanced incorporation of n-3 fatty acids from fish compared with fish oils.
Elvevoll EO, Barstad H, Breimo ES, Brox J, Eilertsen KE, Lund T, Olsen JO, Osterud B.
Norwegian College of Fishery Science, Department of Marine Biotechnology, University of Tromso, Norway. edel.elvevoll@nfh.uit.no
This work was undertaken to study the impact of the source of n-3 FA(Fat Acids) on their incorporation in serum, on blood lipid composition, and on cellular activation. A clinical trial comprising 71 volunteers, divided into five groups, was performed. Three groups were given 400 g smoked salmon (n = 14), cooked salmon (n = 15), or cooked cod (n = 13) per week for 8 wk. A fourth group was given 15 mL/d of cod liver oil (CLO) (n = 15), and a fifth group served as control (n = 14) without supplementation. The serum content of EPA and DHA before and after intervention revealed a higher rise in EPA and DHA in the cooked salmon group (129% rise in EPA and 45% rise in DHA) as compared with CLO (106 and 25%, respectively) despite an intake of EPA and DHA in the CLO group of 3.0 g/d compared with 1.2 g/d in the cooked salmon group. No significant changes were observed in blood lipids, fibrinogen, fibrinolysis, or lipopolysaccharide (LPS)-induced tissue factor (TF) activity, tumor necrosis factor-alpha (TNFalpha), interleukin-8 (IL-8), leukotriene B4 (LTB4), and thromboxane B2 (TxB2) in whole blood. EPA and DHA were negatively correlated with LPS-induced TNFalpha, IL-8, LTB4, TxB2, and TF in whole blood. In conclusion, fish consumption is more effective in increasing serum EPA and DHA than supplementing the diet with fish oil. Since the n-3 FA are predominantly in TAG in fish as well as CLO, it is suggested that the larger uptake from fish than CLO is due to differences in physiochemical structure of the lipids.
Lipids. 2006 Dec;41(12):1109-14.
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