Fish oil contains high amounts of EPA and DHA, two omega-3 fatty acids that are very important for cell function, brain health, and immune modulation.
For this discussion, fats = fatty acids.
Omega-3 vs. Omega-6 in Food
Omega-3 fatty acids include primarily EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid), and less so, ALA and very little DPA. Fish oil provides high concentrations of EPA and DHA. On a typical supplemental fish oil label, you will see the concentrations of each of these. For example, 524 mg of EPA and 375 mg of DHA per serving, with most capsules being around 900- 1,000mg or 1 gram.
Natural non-fish animal sources of meat have a 1:1 omega-6/omega-3 ratio of omega-6 to omega-3 fatty acids. In the last 150 years, the ratio has risen in all foods in Western societies. The ratio increases in favor of omega-6s when the meat source is fed an unnatural diet, such as grain-fed versus natural grass-fed. A ratio of 25:1 is seen with highly processed diets. Currently, NIH recommends a daily intake omega-6/omega-3 ratio of 11:1. When reading about ratios in foods, it is often reported omega-3:omega-6, for example, 1:11 instead of 11:1. Just remember the higher number will always be omega-6.
Plants have only one omega-3, ALA (alpha-linolenic acid). The problem with ALA is that it is at the top of the pathway to create first EPA and then DHA. The body only converts about 10% of ALA to EPA and DHA, which is not enough. There are a few algae supplements on the market that contain DHA only.
Omega-6s tend to be too high in our diets, and although we need some of them, we don't need as much as is often consumed in processed foods. Omega-6s are more inflammatory and tend to stiffen cell and mitochondria membranes, while omega-3s help to keep them pliable.
The best foods to consume to get EPA and DHA include cold-water fish, wild game, grass-fed red meat, and eggs. Eggs that are farm/pasture-raised will have the best nutrition due to the chicken's bug-filled diet. Omega-6s are still needed, but there is no need to focus on them or supplement them because you will get more than enough from most foods. High sources of omega-6s include sunflower, safflower, peanut, most vegetable oils, animal fat (especially grain-fed), dairy, shellfish, borage, black currant seed, and evening primrose.
Depletion of Omega-3s
Unfortunately, worldwide, omega-3 deficiency is prevalent and linked to our high-processed diets. Most people have an average intake of <100mg/d.
Medication can further deplete omega-3s. In the case of statin cholesterol drugs, this is one of the many nutrients that are prone to becoming deficient.
Any medication that binds to fats or blocks their absorption can contribute to a deficiency. Orlistat is an example. Further medications that may speed up intestinal transit time (or digestion) may result in poor absorption of omega-3s.
Any condition of the GI tract that affects fat digestion may also increase the risk of fatty acid deficiency. Pancreatitis, pancreatic insufficiency, gallbladder disease, celiac disease, and Crohn's disease are just a few examples.
The many benefits of Omega-3s
Cardiometabolic health: Fish oil has been shown to lower triglycerides, small density LDL (or sdLDL -- very bad LDL), HDL, and increased LDL.1, 2 There are two main types of LDL: large buoyant LDL and small dense LDL. The large buoyant LDL is a neutral cardiovascular risk factor, while the sdLDL increases risk. Simply, the very small, dense particles tend to get stuck in the blood vessels\ membrane wall while the large particles float on by. Although you do not want your HDL to lower, it will lower, but it will increase large HDL particles. Just like with LDL, HDL can be very small or large particles. Large particles are better as they have more room to grab and hold inflammatory lipid particles, and they are much better at cleaning off the blood vessel walls. As with large LDL, large HDL is less likely to get stuck in the walls.
Studies show fish oil reduces the risk of heart disease by 30%. Further, EPA-only omega-3 supplementation has been shown to reverse plaque in people who have the ApoE4 SNP, as found in the Berkley Heart Study.
(The ASCEND trial, REDUCE-IT, and the VITAL study are a few studies that show CVD benefits.)
Fatty liver: Fish oil has been shown to lower several inflammatory blood markers in people with fatty liver disease, including triglycerides, uric acid, CRP, ferritin, and homocysteine. Studies have shown that this benefit also occurs in rats and mice fed beef tallow. (Recall from above that omega-3s are in all animals.)
Immune system and anti-oxidant effects: Fish oil has amazing effects, including downregulation of inflammatory cytokines and inducing counter-regulatory inflammatory pathways.
One study in people with rheumatoid arthritis found fish oil to be highly anti-inflammatory and as effective as Humira for reducing pain. The most benefits occur when the omega-6/omega-3 ratio is 2-3/1 in persons with RA.3
Asthmatics were found to benefit from fish oil supplementation if their omega-6/omega-3 ratio was 5/1. 3
Cognitive effects: EPA/DHA has been found to reduce the risk of cognitive decline by 50%. In a study with DHA supplementation in people who were ApoE4 carriers, the benefit was found to start prior to the development of dementia. It appears there is increased delivery of DHA to the brain due to increased activation of phospholipase. We must also remember that the brain is made out of DHA. The brain will convert EPA to DHA.
Other conditions: Further benefits of omega-2 supplementation have been shown in CKD, polycystic kidney disease, neurodegenerative disease, and mood disorders, including depression and schizophrenia, dysmenorrhea, and cancer cachexia.
In colorectal cancer a omega-6/omega-3 ratio of 2.5:1 reduced rectal cell proliferation.
Krill Oil vs Fish Oil
Both of these oils will provide you with an abundance of omega-3s. There are several differences; the first is the cost, with krill oil costing significantly more. Part of the reason for this is that it is more expensive to harvest and not as readily available as fish oil, which is a byproduct of anchovies, sardines, mackerel, tilapia, salmon, cod, and/or herring. Krill oil is also not as sustainable to procure. There are significant concerns about food chain disruption. To produce krill oil, large vessels vacuum the north and south arctic waters.
Short studies over only a few days have found that krill oil may be better absorbed, resulting in higher blood levels of omega-3 with the same doses of EPA and DHA. The difference in absorption is due to the omega-3s of krill oil being in a phospholipid form, while in fish oil, it is a triglyceride. Despite this difference, both are absorbed to a high degree, and with digestion, almost no fat comes out in the stools. Krill oil is also marked as a non-fish burp product. 4
References
1. Manson JE, Bassuk SS, Lee IM, Cook NR, Albert MA, Gordon D, Zaharris E, Macfadyen JG, Danielson E, Lin J, Zhang SM, Buring JE. The VITamin D and OmegA-3 TriaL (VITAL): rationale and design of a large randomized controlled trial of vitamin D and marine omega-3 fatty acid supplements for the primary prevention of cancer and cardiovascular disease. Contemp Clin Trials. 2012 Jan;33(1):159-71. doi: 10.1016/j.cct.2011.09.009. Epub 2011 Oct 2. PMID: 21986389; PMCID: PMC3253961.
2. Bowman L, Mafham M, Stevens W, Haynes R, Aung T, Chen F, Buck G, Collins R, Armitage J; ASCEND Study Collaborative Group. ASCEND: A Study of Cardiovascular Events iN Diabetes: Characteristics of a randomized trial of aspirin and of omega-3 fatty acid supplementation in 15,480 people with diabetes. Am Heart J. 2018 Apr;198:135-144. doi: 10.1016/j.ahj.2017.12.006. Epub 2017 Dec 24. PMID: 29653635; PMCID: PMC5971211.
3. Simopoulos AP. The importance of the ratio of omega-6/omega-3 essential fatty acids. Biomed Pharmacother. 2002 Oct;56(8):365-79. doi: 10.1016/s0753-3322(02)00253-6. PMID: 12442909.
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