Since the 1970s when scientists discovered that fish-adoring native populations such as the Inuit largely sidestep heart disease despite eating small amounts of fruit and veggies, the research papers proving that omega-3 fatty acids keep your body a well-oiled machine have been piling up faster than snowflakes during an Arctic blizzard. This popularity has prompted a whole industry devoted to pumping everything from eggs to tortillas to mayo with the stuff, all in the name of value-added comestibles. But there is one big caveat: not all omega-3s are as effective at fending off chronic disease.
Forms of Omega-3s
Omega-3 fatty acids are long-chain polyunsaturated fatty acids containing more than one double bond. While the name omega-3 covers a range of fatty acids, there are three in particular that have been obtaining most of the research dollars: eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), which are both found naturally in seafood, and alpha-linolenic acid (ALA), which is found in plant sources. ALA contains 18 carbon atoms, where as EPA and DHA contain 20 and 22, respectively. ALA is considered dietary essential because our bodies lack the enzyme needed to produce this fatty acid from other fats. On the flipside, EPA and DHA are not considered essential because they can be produced through a series of desaturation (addition of double bonds) and elongation (addition of carbon atoms) steps from ALA.
Functions of Omega-3s
Omega-3s are so vital because they are incorporated into the membranes around every cell in our bodies. They are particularly deposited in large amounts in the cell membranes of the brain, retina and nervous system. It’s here where they help control what passes into and out of these cells, as well as how cells reach out and communicate with each other. It’s clear that cells with ample amounts of these fatty acids are more fluid (i.e., more elastic) and work more effectively.
Omega fatty acids also regulate the production of Herculean hormone-like substances called eicosanoids. Those spawned from omega-3s are very effective anti-inflammatory agents that are likely a major reason why these fats have such a strong capability to ward off chronic disease.
Often overlooked is that ALA is not equivalent in it biological effects to longer-chain marine sourced EPA and DHA. Longer molecular chain fats are more efficiently absorbed and used in the body than the shorter chain omega-3s like ALA. Research-speak for they’re more easily incorporated into cells. Because of this, if you were to compare all the studies showing a disease fighting capability of ALA or DHA, it would be DHA winning hand's down. Some experts believe that the only real important function of ALA is to be converted into EPA and, then, DHA and that these fatty acids should also be deemed essential with a specific daily requirement.
The above is very important when you consider that most people just assume that all omega-3s are alike. A notion that is often spurred on by the commonplace headline: “omega-3s fight disease.” While ALA has been found to be an alley in our well being – a good example is it’s ability to regulate heart beat and possibly reduce blood cholesterol and tryiglyceride levels – it’s EPA and, more specifically, DHA that is the real disease arch nemeses. But since the foods and beverages enhanced with omega-3s (i.e., eggs, vegetable oil spreads, cereal, bread, etc) are often fortified with ALA, you don't get the biggest bang from them. Depending on where you live, you can now find DHA fortified items such as milk, yogurt and juice.
The Making of EPA and DHA
Alpha-linolenic Acid (18:3 n-3) -> Stearidonic Acid (18:4 n-3) -> Eicosapentaenoic Acid (20:5 n-3) -> Docosahexaenoic Acid (22:6 n-3)
As mentioned, through a series of biochemical wonders, EPA and DHA can be made from ALA within the human body. However, this conversion is often lackluster at best. While different numbers have floated around it’s likely that this conversion occurs at a rate of only two to 15 percent. So for every gram of ALA consumed you would be lucky if 150 milligrams of it made it down the fatty acid chain to EPA with even less making it one more step to DHA. It’s thought that much of the rest of the ALA is converted into energy via beta-oxidation.
So why such a poor bang for your buck? Well, it’s clear that the conversion of ALA to its long-chain metabolites is affected by dietary factors. Firstly, a diet rich in omega-6 fatty acids such as linoleic acid (18:2 n-6) can significantly inhibit ALA conversion by up to half. Linoleic acid also undergoes a process of elongation and desaturation into other fatty acids such as Arachidonic Acid, which uses the same enzymes like delta-6-desaturase involved in the ALA to DHA train. So it makes sense, more intake of omega-6 means fewer enzymes available to elongate ALA. Unfortunately, diets in the developed world have become skewed towards omega-6s as a result of widespread use of omega-6-rich oils such as soybean and corn in convenience and fast food and the overall reduced consumption of omega-3 rich foods since modern agriculture took hold.
In addition, it has recently been found that consumption of trans-fat (i.e., hydrogenated oil) can further decrease conversion via inhibition of the delta-6-desaturase enzyme and thus reduce the amount of omega-3 fat present in cell membranes. A deficiency in any number of vitamin and mineral co-factors (B6, magnesium, zinc) needed for proper functioning of elongation and desaturation enzymes would also negatively affect DHA production. It should also be noted that the activity of delta-6-desaturase can be reduced by normal aging.
So, if you were to take the typical diet of an individual from the developed world (and, increasingly, in developing nations) that is oversaturated with omega-6 and trans-fats and undersaturated with ALA you begin to see why so many in-the-know health professionals and scientists studying the health impacts of EPA and DHA say that it is vital to consume EPA and DHA directly from foods and supplements to bypass any need for conversion. Interestingly, hempseeds are a rare source of stearidonic acid meaning that fewer metabolic steps are needed than from ALA to convert it to DHA.
Some studies suggest that women may possess a greater capacity for ALA conversion than men. Such metabolic capacity may be important for meeting the demands of the fetus and new born child for DHA during pregnancy and lactation.
Dietary sources of the plant-based omega-3 fat (ALA) include vegetable oils (e.g., canola, soybean), flaxseed, salba, walnuts and hempseeds.
As for EPA and DHA, the main source is fish. All fish contain EPA and DHA. However, the quantities vary among species and within a species according to environmental variables such as diet and whether the fish are wild or farm-raised. In general, cold water oily fish such as sardines and salmon tend to have higher levels of EPA and DHA that white fish such as tilapia and catfish.
**These levels can vary depending on season, diet, pollution, canning and cooking methods.
|Natural Sources of ALA
||Natural Sources of EPA and DHA
|Amount of ALA in grams per 100g serving
||EPA+DHA in grams per 100g serving**
||Atlantic Herring 1.6
|English Walnuts 6.8
||Atlantic Salmon 1.0-1.8
||Chinook Salmon 1.4
|Wheat Germ 0.7
||Pink Salmon 1.1
|Purslane (green leafy vegetable) 0.4
||Coho Salmon 0.8
|Pinto Beans 0.3
||Sockeye Salmon 0.7
||Chum Salmon 0.7
||Rainbow Trout 0.5-1.0
||Atlantic Cod 0.3-0.5
||Atlantic White Shrimp 0.4
|Northern Lobster 0.2
|Pacific Cod 0.1-0.3
Because long-chain omega fatty acids are such a prominent player in the membranes of all our cells, it’s little surprise that they have such a wide array of health benefits. In recent times, it has been linked to a reduced risk of cardiovascular disease, vision loss, Parkinson’s disease, lupus, Crohn’s and colitis, cancers like that of the breast and kidney, osteoporosis, arthritis, obesity (yep, you read right. A salmon sandwich may help whittle the middle), diabetes, stroke, depression and cognitive decline. What’s more, a healthy intake of this polyunsaturated fat during pregnancy and lactation improves visual, cognitive and motor development in offspring. That’s the reason why DHA is now added to so many different baby formulas to help mimic what is hopefully naturally present in breast milk.
Official recommendations for EPA and DHA intake are still pending but it’s generally thought that at a minimum we should aim for an average of 500mg per day from direct sources such as fish, fortified foods and supplements. It would be smart to take heed of a Journal of the American Medical Association study that found eating just three to six ounces of fish per week, especially the omega-3 potent kind, can cut the risk of death from heart attack by a whopping 36 percent and total mortality by 17 percent. As discussed, it’s best not to rely on ALA containing foods for all of your EPA and DHA needs.
Because long-chain polyunsaturated fatty acids, specifically arachidonic acid and DHA, accrue rapidly in the grey matter of the brain during development, it’s absolutely vital that pregnant and breast feeding women take in enough DHA (as mentioned, at least 500mg per day) to meet their needs and the needs of their offspring. After birth, both pre-term and full-term babies are capable of converting ALA into EPA and DHA, but the production from this synthesis is likely low. Therefore, it is more appropriate for a fetus or child to receive a direct source from the mother.
There are numerous reasons why taking a regular fish oil supplement could be beneficial. We have already talked about all the healthy outcomes resulting from EPA and DHA intake and the benefits are no different if these fats come from fish or supplements. The vast majority of people are not consuming enough fatty fish to reach the levels of EPA and DHA necessary to achieve desirable health improvements. Taking a fish oil supplement can help close this gap.
Dietary influences such as increasing intake of omega-6 and trans-fats are contributing to lower levels of EPA and DHA within humans as a result of decreasing their formation from plant-derived ALA. By providing the body with a direct source of EPA and DHA, the concerns regarding this conversion are no longer an issue.
Vegetarians and vegans are particularly susceptible to low EPA and DHA levels as this diet appears to reduce the production of these fatty acids in the body as evident by studies showing meat-eaters having higher levels of these fats than vegetarians.
In addition, consuming fish is no longer as easy as it used to be. In recent years numerous reports have been published regarding contaminants such as mercury and PCB’s that are present in our fish supply. Regular intake of fish high in these contaminants (e.g. white albacore tuna) maybe harmful. This is especially the case for pregnant women and young children. It has been shown that as maternal fish consumption goes up so do fetal mercury levels. This stresses the importance for pregnant women to consume fish with low mercury levels and/or use contaminant-free fish oil supplements.
Guide to Choosing the Best Supplement
- Choose a fish oil supplement with adequate amounts of EPA and DHA. Since you are looking for at least 500mg of EPA + DHA per day, choose a supplement that has relatively high amounts of these to negate the need to take several pills. It is best to look for a supplement with 200-500mg of DHA and 100-500mg of EPA per serving. These levels should be clearly stated on the label. If they are not, find another supplement. For example, if it just says 1000mg of omega-3 then you have little idea how much DHA and EPA this contains since other fats will make up some of this 1000mg. 1000mg of fish oil does not necessarily mean 1000mg of EPA and DHA. The benefit of liquid fish oil supplement such as cod liver oil is that they tend to be more concentrated than pills and often only require little intake (i.e. one teaspoon) to reach recommended intake levels.
- Always choose a supplement that indicates that contaminants such as mercury and PCBs have been tested for and removed. Purity is very important, especially for pregnant and lactating women. The good news is that laboratory testing has determined that most fish oil supplements have less contaminants than the fish they come from. For example, a person would need to take about 300 capsules to be exposed to the same level of PCB’s as a single serving of farmed salmon. Mercury tends to be found in fish meat (e.g. muscle) and, thus, the relative concentration in oil would be a lot less. If possible, its best to look for supplements derived from small fish such as sardines, anchovy and herring as these are abundantly present in the wild making them a sustainable choice.
- Don’t rely on a supplement with an omega oil blend (e.g., 3-6-9). This will decrease the amount of DHA and EPA in the product. Some of the omega-3 in these supplements maybe derived from flaxseed oil, which contains ALA, and not DHA and EPA. Remember that DHA and EPA are more potent than ALA. Some oil blends, though, add borage or evening primrose oil, which is a good source of a fat known as GLA. Like DHA, GLA is showing promise as a disease fighter. However, you might be best to look for this supplement on its own.
- In winter, consider using cod liver oil. Only cod liver oil naturally contains vitamins A and D as the oil is from the liver of the fish, rather than the body. Vitamin D is a vitamin that can be synthesized in the skin from sunlight. However, for many countries (like my native Canada) sunlight is not adequate during winter months and, thus, many studies have shown that large segments of people in these locations are deficient in vitamin D during the winter. Of note, according to United Kingdom researchers who reviewed several studies on the matter, the risk of later-life type 1 diabetes is significantly reduced in infants who are exposed to vitamin D supplementation. Not surprisingly then, risk for diabetes is reduced in infants who are given cod live oil supplementation.
- Look for antioxidants. When using a liquid fish oil supplement the addition of antioxidants such as vitamin E is very important as they can help prevent the oil from being damaged by free radicals and being oxidized once the bottle is opened. Some supplements will have a listing for mixed tocopherols. This is a vitamin E mixture. Specifically, you should be looking for alpha-tocopherol as tocopherol acetate is useless in preventing food oxidation. Oxidation appears not a problem for capsules.
The importance of having antioxidants present in a liquid fish oil is highlighted by research finding higher urinary malondialdehyde (MDA), an indicator of lipid peroxidation in the diet and in the tissues of human adults consuming a supplement of n-3 fatty acids derived from a pharmaceutical grade of cod liver oil without added antioxidants versus a concentrate of n-3 acids containing vitamin E. The results indicate that consuming unstabilized fish oils as a source of n-3 fatty acids may entail exposure to potentially toxic products of lipid peroxidation.
To also help reduce the oxidation of liquid fish oils a wine saver to create a vacuum can be used to better preserve the fish oil. Simply transfer your fish oil to a bottle that fits the wine saver cap.
Vegetarians and/or Vegans
Those who do not consume any fish and wish to supplement with omega-3 fat but choose not to use products derived from sea critters can now purchase supplements with DHA sourced from the algae that the fish eat. These are produced under controlled conditions and are free of contaminants, taste and odour. Only algae sources of omega-3 fatty acids are used in infant formulas. One study found that those who supplement with DHA from algae significantly increased DHA levels in the body. Even though these supplements often do not contain EPA, supplementing with just DHA should increase EPA levels as DHA can be converted back to EPA in the body.
- Look at food labels to see which form of omega-3 food has been added to the product.
- Get a good mix of ALA and EPA/DHA in your diet.
- Consider supplementation if you feel your diet is coming up short.
- Consume low contaminant, high omega-3 fish such as wild salmon, sardines, mackerel and herring more often.
- If you are a female of child-bearing age take a good, hard look at your diet to ensure you are consuming a direct source of DHA.
- Barre, D.E. The role of consumption of alpha-linolenic, eicosapentaenoic and docosahexaenoic acids in human metabolic syndrome and type 2 diabetes--a mini-review. J Oleo Sci. 2007;56(7):319-25.
- Brouwer, I.A. et al. Dietary alpha-linolenic acid is associated with reduced risk of fatal coronary heart disease, but increased prostate cancer risk: a meta-analysis. J Nutr. 2004 Apr;134(4):919-22.
- Clarke, S.D. (2000) Polyunsaturated fatty acid regulation of gene transcription: a mechanism to improve energy balance and insulin resistance. Br J Nutr. Mar;83 Suppl 1:S59-66.
- Conquer JA et al. (1996) Supplementation with an algae source of docosahexaenoic acid increases (n-3) fatty acid status and alters selected risk factors for heart disease in vegetarian subjects. J Nutr.Dec;126(12):3032-9.
- Gester, H. et al. (1998) Can adults adequately convert alpha-linolenic acid (18:n-3) to eicosapentoaenoic acid (20:5n-3) and docosahexaenoic acid (22:6n-3)? Int J Vitam Nutr Res. 68(3): 159-73.
- Ghadimi, R et al. Serum concentrations of Fatty acids and colorectal adenoma risk: a case-control study in Japan. Asian Pac J Cancer Prev. 2008 Jan-Mar;9(1):111-8.
- Harper, CR et al. (2001) The fats of life: The role of omega-3 fatty acids in the prevention of coronary heart disease. Arch Intern Med. 161: 2185-2192.
- He, K. et al. Fish consumption and incidence of stroke: a meta-analysis of cohort studies. Stroke. 2004 Jul;35(7):1538-42. Epub 2004 May 20.
- Hill, H.M. et al. Combining fish-oil supplements with regular aerobic exercise improves body composition and cardiovascular disease risk factors. American Journal of Clinical Nutrition, Vol. 85, No. 5, 1267-1274, May 2007
- Holguin, F. et al. Cardiac Autonomic Changes Associated With Fish Oil vs Soy Oil Supplementation in the Elderly. Chest. 2005 Apr;127(4):1102-7.
- Hu, FB et al. (2002) Fish and omega-3 fatty acid intake and risk of coronary heart disease in women. JAMA Apr 10; 287(14): 1815-21.
Innis, S.M. et al. Essential n–3 fatty acids in pregnant women and early visual acuity maturation in term infants. American Journal of Clinical Nutrition, Vol. 87, No. 3, 548-557, March 2008
- Jacobson, J. L. et al. Beneficial effects of a polyunsaturated fatty acid on infant development: evidence from the inuit of arctic Quebec. J Pediatr. 2008 Mar;152(3):356-64. Epub 2007 Oct 22.
- Jensen, C.L. et al. Effects of maternal docosahexaenoic acid intake on visual function and neurodevelopment in breastfed term infants. Am J Clin Nutr. 2005 Jul;82(1):125-32.
- Johnson, E.J. et al. Potential role of dietary n-3 fatty acids in the prevention of dementia and macular degeneration. Am J Clin Nutr. 2006 Jun;83(6 Suppl):1494S-1498S.
- Kris-Etherton, PM et al. (2002) Fish consumption, fish oil, omega-3 fatty acids, and cardiovascular disease. Circulation. 106:2747-2757.
- Weiss, L.A. et al. Ratio of n–6 to n–3 fatty acids and bone mineral density in older adults: the Rancho Bernardo Study. American Journal of Clinical Nutrition, Vol. 81, No. 4, 934-938, April 2005
- Magnusson A et al. (2000) Lack of seasonal mood change in the Icelandic population: results of a cross-sectional study. Am J Psychiatry. Feb;157(2):234-8.
- McCann, J.C. & Ames, B. N. Is docosahexaenoic acid, an n-3 long-chain polyunsaturated fatty acid, required for development of normal brain function? An overview of evidence from cognitive and behavioral tests in humans and animals. Am J Clin Nutr 2005;82 281-295.
- Mozaffarian, D. et al. Fish Intake, Contaminants, and Human Health. JAMA. 2006;296:1885-1899.
- Myhre, A.M. et al. Water-miscible, emulsified, and solid forms of retinol supplements are more toxic than oil-based preparations. Am J Clin Nutr. 2003 Dec;78(6):1152-9.
- McGrath-Hanna NK et al. (2003) Diet and mental health in the Arctic: is diet an important risk factor for mental health in circumpolar peoples?--a review. Int J Circumpolar Health. Sep;62(3):228-41.
- Oddy WH et al. (2004) Ratio of omega-6 to omega-3 fatty acids and childhood asthma. J Asthma. 41(3):319-26.
- Price PT et al. (2000) Omega-3 polyunsaturated fatty acid regulation of gene expression. Curr Opin Lipidol. Feb;11(1):3-7.
- Rahman, M.M. et al. Docosahexaenoic acid is more potent inhibitor of osteoclast differentiation in RAW 264.7 cells than eicosapentaenoic acid. J Cell Physiol. 2008 Jan;214(1):201-9
- Rasic-Milutinovic, Z. et al. Effects of N-3 PUFAs supplementation on insulin resistance and inflammatory biomarkers in hemodialysis patients. Ren Fail. 2007;29(3):321-9.
- Rogers I et al. (2004) Maternal fish intake in late pregnancy and the frequency of low birth weight and intrauterine growth retardation in a cohort of British infants. J Epidemiol Community Health. Jun;58(6):486-92.
- Rosell, M.S. et al. Long-chain n-3 polyunsaturated fatty acids in plasma in British meat-eating, vegetarian, and vegan men. Am J Clin Nutr. 2005 Aug;82(2):327-34.
- Sakamoto M et al. (2004) Maternal and fetal mercury and n-3 polyunsaturated fatty acids as a risk and benefit of fish consumption to fetus. Environ Sci Technol. Jul 15;38(14):3860-3.
- SanGiovanni, J.P. et al. The role of omega-3 long-chain polyunsaturated fatty acids in health and disease of the retina. Prog Retin Eye Res. 2005 Jan;24(1):87-138.
- Shaefer, E.J. et al. Plasma phosphatidylcholine docosahexaenoic acid content and risk of dementia and Alzheimer disease: the Framingham Heart Study. Arch Neurol. 2006 Nov;63(11):1545-50.
- Simopoulos AP. (2002) Omega-3 fatty acids in inflammation and autoimmune diseases. J Am Coll Nutr. Dec;21(6):495-505.
- Stene LC et al. (2003) Use of cod liver oil during the first year of life is associated with lower risk of childhood-onset type 1 diabetes: a large, population-based, case-control study. Am J Clin Nutr.Dec;78(6):1128-34.
Sun D. et al. Dietary n-3 fatty acids decrease osteoclastogenesis and loss of bone mass in ovariectomized mice. J Bone Miner Res. 2003 Jul;18(7):1206-16.
- Sun, H. et al. Peroxisome proliferator-activated receptor gamma-mediated up-regulation of syndecan-1 by n-3 fatty acids promotes apoptosis of human breast cancer cells. Cancer Res. 2008 Apr 15;68(8):2912-9
- Thorsdottir I et al. (2004) Association of Fish and Fish Liver Oil Intake in Pregnancy with Infant Size at Birth among Women of Normal Weight before Pregnancy in a Fishing Community. Am J Epidem. Sep 1;160(5):460-5.
- Virtanen, J.K. et al. Mercury, fish oils, and risk of acute coronary events and cardiovascular disease, coronary heart disease, and all-cause mortality in men in eastern Finland. Arterioscler Thromb Vasc Biol. 2005 Jan;25(1):228-33. Epub 2004 Nov 11.
- Whalley, L.J. et al. Cognitive aging, childhood intelligence, and the use of food supplements: possible involvement of n-3 fatty acids. Am J Clin Nutr. 2004 Dec;80(6):1650-7.
- Wolk, A. et al. Long-term fatty fish consumption and renal cell carcinoma incidence in women. JAMA. 2006 Sep 20;296(11):1371-6.
- Zhang, J. et al. Dietary fat intake is associated with psychosocial and cognitive functioning of school-aged children in the United States. J Nutr. 2005 Aug;135(8):1967-73.