T Nation

Negative Effects of Fish Oil


Direct excerpt:

"For most people, fish oil should come from fish, and omega-3 fatty acids should come from foods, not from supplements. Routine supplementation is not recommended for a number of reasons. Perhaps most importantly, high intakes of omega-3 polyunsaturated fatty acids may increase bleeding time, interfere with wound healing, raise LDL cholesterol, and suppress immune function. Fish oil supplements are made from fish skins and livers, which may contain environmental contaminants. Some fish oils also naturally contain large amounts of the two most potentially toxic vitamins, A and D. Lastly, supplements are expensive; money is better spent on foods that can provide a full array of nutrients. People with heart disease, however, may benefit from doses greater than can be achieved through diet alone; they should consult a physician about including supplements as part of their treatment plan."




I say it's over thinking it, I have never heard of anyone have a negative effect from Fish oils.


Interesting, however it'd be nice to know where they got their info from and what the authors credentials are.


The authors are correct, although the dose required to encounter these negative effects is higher than I've ever seen recommended. It's irresponsible of them not to list the dosage levels at which these things become an issue. Like many effective substances, too much can have adverse effects.

Choosing a molecularly distilled fish oil supplement will eliminate the risk of contamination.


I'm mostly concerned about the LDL cholesterol raising and suppressed immune function. Anyone know of any studies to prove or disprove this?


"money is better spent on foods that can provide a full array of nutrients"

That's about the only decent thing in there, everything else seems kinda ludicrous.


Can you post where you read that? What is the recommended dose? Ive heard one gram of EPA/DHA is all that one should have. I usually have 9 grams of fish oil a day so my EPA/DHA is much higher than 1 gram.


So what IS the dosage required to trigger the negative side effects? I'm taking 8 capsules a day of the Carlson's super DHA.


The book should list its sources (if it's any good). Are there any?


Oh. And I was going to say that about the only negative effects I've experienced are a slight fishy taste if I burp within a few hours of taking them. :slight_smile:


to be honest, I read the original quote online and don't actually own the book


I am a nutritional science major. Everything in the field of nutrition is controversial. I have never encountered ANY hard facts. Bottom line, nutrition and supplementation will effect everybody differently. Know your body and how it will react to different foods and supplements.

Nothing is set in stone. Also, please site her research sources.


this is just more FDA garbage, from the same people who no doubt espouse the virtues of high carb/ low protein/ low fat diets and enjoy injecting high fructose corn syrup in anything because it's "natural, ya' know like sugar!"


These paragraphs seem to mix studied findings on fish oil supplementation with conjecture. For instance, I have never found a study indicating anything but the result of fish oil supplementation to lower LDL cholesterol, while this book states that fish oil will raise it.

Let us remember that for many studies, researchers do not use whole food sources, but rather supplements containing the nutrient in question.

The "truth" of this paragraph is that fish oil does slow blood clotting, due to its blood thinning effects. Patients known to supplement with omega 3s are often asked to discontinue use days before surgery. However, this blood thinning effect is one reason fish oil lowers risk of heart attack and stroke.

Again, contrary to the author's claims, I have read literature supporting the hypothesis that fish oil decreases healing time for wounds, even though clotting may take longer.

The long and the short of it is: This author is either confused, or (less likely) has access to data that no one else has.


I'm not a big FDA fan, but your comment reveals a lot of ignorance.


As others have said, in general to get any of the 'negative' effects (eg increased stroke risk) the dose has to be mighty large. Dosages that high HAVE been recommended on this site in the past however (30g+ anyone?), but if you stick to (for example) 4 flameouts per day I'd suggest that you'd be more than fine.


Anyone have any direct studies that they can post that'll disprove my quote? Not that I don't trust you guys, but I'd like to see some solid studies, Ive read a bunch of articles about fish oil, but none addressing the potential ill effects of it.


first you should find a direct study that supports your quote!
fish oil thins the blood, so yes you will bleed more


I know that fish oil will thin the blood and make you slower to clot, and Ive noticed this before.

Im not claiming that fish oil is bad for you, I really don't want this to be true. I still take 9 grams a day, but I read this and wanted to consult with people who know much more than I do. So far, I like the responses Im getting lol


Claim #1: Fish oil raises LDL

Fish oil attenuates the cholesterol induced rise in lipoprotein cholesterol
PJ Nestel American Journal of Clinical Nutrition, Vol 43, 752-757, Copyright © 1986 by The American Society for Clinical Nutrition, Inc

Suppression by diets rich in fish oil of very low density lipoprotein production in man.
P J Nestel, W E Connor, M F Reardon, S Connor, S Wong, and R Boston

Comment: One study I encountered showed an increase of 2.5% over a one year period. Many believe the affect on LDL is inconclusive. However, we should recall that while LDL is one marker, a more significant one in triglyceride level, which has been consistantly shown to be reduced by fish oil.

Claim #2: Decreases immune function
Counter: Modulation of postoperative immune response by enteral nutrition with a diet enriched with arginine, RNA, and omega-3 fatty acids in patients with upper gastrointestinal cancer.
Senkal M, Kemen M, Homann HH, Eickhoff U, Baier J, Zumtobel V.

Dietary omega-3 polyunsaturated fatty acids plus vitamin E restore immunodeficiency and prolong survival for severely ill patients with generalized malignancy
A randomized control trial
Charalambos A. Gogos, M.D. 1 *, Panayiotis Ginopoulos, M.D. 1, Bassilis Salsa, B.Sc. 1, Euterpi Apostolidou, M.D. 1, Nikolas C. Zoumbos, M.D. 1, Fotis Kalfarentzos, M.D. 2

Comments: This claim holds no water when looking to the available research.

Claim #3: Toxic Vitamin A and D


Evidence of a role for retinoic acid (vitamin A-acid) in the maintenance of testosterone production in male rats.

Role of Vitamin D in Skeletal Muscle Function*

Effects of a Combination of Beta Carotene and Vitamin A on Lung Cancer and Cardiovascular Disease
Gilbert S. Omenn, M.D., Ph.D., Gary E. Goodman, M.D., M.S., Mark D. Thornquist, Ph.D., John Balmes, M.D., Mark R. Cullen, M.D., Andrew Glass, M.D., James P. Keogh, M.D., Frank L. Meyskens, M.D., Barbara Valanis, Dr.P.H., James H. Williams, M.D., Scott Barnhart, M.D., M.P.H., and Samuel Hammar, M.D

Vitamin A supplementation for preventing morbidity and mortality in very low birthweight infants.
Darlow BA, Graham PJ.

Benefits and requirements of vitamin D for optimal health: a review
WB Grant, MF Holick

Comments: While only applying to Cod liver oil, this claim is so false it drove me half mad. Vitamin A and D CAN be toxic, but it takes more than some cod liver oil to do it. While staying under toxic doses, they have a myriad of benefits, including ones directly applying to bodybuilding/ weightlifting (see the top of my counter).

So, are you happy? Is this enough to counter your un-cited excerpt of a book? I hope this clears fish oil from these unfounded allegations.