Background Information

Omega-3s = 1) Alpha-linolenic acid = ALA = 18:3(n-3) precursor to 2) eicosapentaenoic acid= EPA = 20:5n-3 which is precursor to 3) Docosahexaenoic acid = DHA = 22:6(n-3) (the 6 double bonds are at the 4,7,10,13,16,19 carbons). EPA and DPA are synthesized in the liver from ALA or come straight from diet, primarily fish. Humans are unable synthesize fatty acids with double bonds more distal from the carboxyl end of the fatty acid than the ninth carbon atom. The large number is the number of carbons, e.g. ALA has 18 carbons. Linoleic (LA) has two unsaturated carbon-carbon bonds or two "double" bonds with the 1^st from the methyl end of the fatty acid at the sixth carbon atom. Therefore, it is called an omega-6 or n-6 fatty acid. This is elongated and desaturated to yield arachidonic acid or AA (20:4n-6). AA is the usual precursor to the synthesis of eicosanoids, which are oxygenated products of 20-carbon PUFAs (Polyunsaturated fatty acids). Eicosanoids include prostaglandins by means of the cyclooxygenase pathway and leukotrienes by the 5-lipoxygenase pathway. Prostagladins and leukotrienes play major roles in the body’s inflammatory process.

ALA is associated with chloroplasts in green leaves. Only plant chloroplasts can desaturate LA to get ALA. Mosses, ferns, and range-fed nonruminant game animals are sources of EPA and DHA but richest source is marine phytoplankton. Synthesis of EPA and DHA from ALA in humans is slow (Tinoco, Prog Lipid Res ’82;21:1-45) and with aging and certain diseases, a loss of desaturase activity prevents synthesis of EPA and DHA by the human body (W. Lands, Fish and Human Health. Orlando, FL:Academic Press ’86;103-6). Also, n-3 and n-6s compete for desaturase and elongase enzymes (RT Holman. Fed Proc ’64;23:1062-7), so high intake n-6s interferes to some extent with EPA and DHA production. DHA is also high in the testes.

Fish or fish oil is the best proven way of increasing EPA and DHA. Twenty ounces of mackerel over 6 days is equal to the effect of 12 fish oil capsules per day. Over 8 weeks, either results in increasing EPA in platelets or plasma by 12-fold and incr DHA by 2+ fold. (An excellent review in Alexander Leaf and Peter Weber, Harvd & U Munich, New England Journal of Medicine (NEJM 88;318:549-57). Phospholipids make up 60 per cent of the dry weight of the brain. (Phospholipid metabolism and depression: the possible roles of phospholipase A2 and coenzyme A-independent transacylase. Horrobin DF. Hum Psychopharmacol 2001 Jan;16(1):45-52)

Humans have four desaturase enzymes, each with a different specificity: Delta-9, delta-6, delta-5 and delta-4, i.e., they add double bonds or unsaturated bonds at the 9-, 6-, 5-, and 4-carbons form the carboxyl carbon end of fatty acids at least 16 carbons long. 2-carbon elongase enzymes often alternate with the desaturase, making the fatty acid two carbons longer, e.g. linoleic (18:2delta9,12) 6-desatured to gamma-linoleic acid (18:3delta6,9,12) then elongated to dihomo-gamma-linoleic acid (20:3delta 8,11,13) the 5-desaturated arachidonic acid (20:4delta5,8,11,13). The AA is then modified with a lipoxygenase enzyme to make leukotrienes or a cyclooxygenase to make the inflammatory prostaglandins PG2s. The same steps are taken with ALA, i.e., first 6-desaturated to GLA (gamma linoleic acid 18:4n-3), then elongated to stearidonic acid (20:4n-3) then 5-desaturated to eicosapentaenoic acid, i.e. EPA (20:5n-3) which, when further modified, makes prostaglandins PG3s and leukotrienes that are less inflammatory. A third line of prostaglandins PG1s are made from dihomo-gamma-linoleic acid. These PGE1s are vasodialators and increase free fatty acids for use as energy. The enzymes catalyzing the formation of prostaglandins from AA (PGHS-1 and –2) are inhibited by NSAIDs. Anandamide, which binds the cannabinoid receptor, is a metabolite of AA. Epoxyeicosatrienoic acids (EETs) are also synthesized from AA by coronary vasc endothelium and cause vasodilation by opening calcium-activated potassium channels in smooth muscle cells. Some researchers are studying how to block the release of AA from lipoprotein membranes by blocking the phospholipase A2 enzyme that catalyzes AA release. An excess of AA is undesirable.

Sources of ALA: Highest in Flax (57%). Also high in ALA = soybean oil (7%), walnut oil (10%), wheat germ oil (7%), canola oil (11%). Very little in most other oils. Also in pumpkin seeds, mustard oil, dark greens such as kale, and chard. Smart Balance margarine is 6:1 n-6:n-3 which is better than average and its mayonnaise and Super Light margarines are only 2:1 and 2.7:1. Its "Beat Oil" is also 2:1 with 1300 mg. n-3 per serving. There is no EPA or DHA in any of these oils and only a very little in greens.

Sources of EPA and DHA: EPA:DHA g/100g of raw edible portion: Mackerel 0.9:1.6=2.5, Herring 0.8:0.8=1.6, Lake Trout 0.5:1.1=1.6, Tuna (albacore) 0.3:1.0=1.3, Whitefish 0.3:1.0=1.3; Salmon 0.3:0.9=1.2, Bluefish 0.4:0.8=1.2, Sardines 0.4:0.6=1.0; Total EPA+DHA from another source: canned sardines 1.7, chinook Salmon 1.4, Atlantic salmon 1.2, tuna, unspecified 0.5, Rainbow trout 0.5, european oyster 0.5, shrimp 0.4, atlantic cod 0.3, swordfish 0.2, lobster 0.2. The fish oil from fish oil capsules comes from fish that are otherwise used for animal or aquaculture feed. Actually, the majority of all fish and fish oil is used as feed. Fish oil margarines, i.e. part fish oil, do exist but are unavailable so far as I know in the U.S.

Oils in General: Percentages in following oils are reported in four categories of oil content: Monosaturated, Linoleic (2 poly-unsat), Linolenic (3 poly-unsat), Saturated: Olive=70%-16-0-14; Canola=58-26-10-6; Peanut=48-34-0-18; Lard=47-11-1-41; Beef Tallow=44-3-1-52; Butter=30-2-2-66; Corn=25-61-1-13; Soy=24-54-7-15; Sunflower=20-69-0-11; Cottonseed=19-78-0-27; Coconut=6-2-0-92; borage oil high in gamma linolenic and perilla oil highin alph-linolenic

The following oil are reported following a different pattern: Palmitic(16:0), stearic(18:0), palmitoleic(16:1n-7), oleic(18:1n-9), linoleic(18:2n-6), linolenic(18:3n-3), saturated total: Avocado oil (like olive)=12-20%, .1-2%, 2-10%, 55-75%, 9-17%, .1-2% linolenic, sat 12-22%; sweet almond nut oil=4-9%, 2.5% max, .6%, 60-86%, 7-30%, .1-1% linolenic, sat 7-11%; peanut oil=7-16%, 6% max, .5% max, 35-72%, 13-43%, .6% max linolenic, arachidic 30% max; safflower=4-9%, 2.5%max, 12-16%, 72-80%, 2.5% max linolenic, sat 5-10%; Sesame oil=7-12%, 3.5-6%, .5%, 35-50%, 35-50%, 1% linolenic. www. 602-869-7720; cis-Vaccenic acid (18:1n-7) is a minor component of most seed oils and a larger component of seafood. Palmitoleic acid is a minor component of animal and veg fats <2%, but more abundant in fish and some nut oils. Eicosenoic (20:1n-9) and erucic (22:1n-9) are found in rapeseed and fish oil.

n-3 & AA: AA (Arachidonic Acid) is metabolized to eicosanoids and is important in hippocampus mossy fibers for memory and elsewhere. AA is considered by some to be "antithetic" to fish oil and n-3 in inflam and lipid metab, i.e. prostaglandins and leukotrienes. Drugs that inhib AA decr intestinal tumors 90%. Inhib of prostaglandin may be one of the actions of fish oil. . Humans compensate for dietary AA by substantially reducing synthesis by the body. Also synthesis of AA fr linoleic is probably sufficiet to meet requirements. Therefore AA in diet not major factor (sic). (This claim makes meat and egg producers happy). Ed Emken, Food quality and Safety Research, Peoria fx 309-681-6679

Walnuts: 70% polyunsat with linoleic and linolenic plus omega-3 fatty acids. 33% U.S. eat fish regularly (1996 US News/CNN). Amer Dietetic Assoc suggest fish or nuts BIW-TIW for omega-3. Loma Linda U study NEJM ’93 walnut-almond-peanuts decr chol and heart disease. Also vit E in nuts.

Cost: Fish oil capsules cost around 5-7 cent each depending on the source. They usually have 30% EPA+DHA. One can of mackerel (15 oz or 425 gm) has 11.25 g. of EPA+DHA, especially DHA which may be most important at least for the nervous system. Thus one can of mackeral contains as much as 37.5 capsules. Mackerel costs between 48 cents and $1.00 depending on the store and the brand vs. $2.60 for the same amount in capsules. Thus, it is clearly the cheapest source of long-chain n-3s. Still, capsules are fairly inexpensive and as cheap as eating most any other type of fish although eating the fish may be more fun and you get proteins, too. Compared to the relatively useless medications given by physicians for cardiac disease prevention, i.e., the statins and the cholesterol lowering medications, fish or fish oil is a super good deal. All brands of canned mackerel do contain varying amounts of salt and the brand with the lowest level of sodium should be chosen. Mackerel also contains the least expensive source of ready to eat animal protein. At least one can a week of Mackerel should be eaten for full effect although less would probably still give very good results. Flax seeds are the cheapest source of ALA although this can also be had by switching to canola oil and consuming walnuts. There is still some question on the effect of baking ALAs. Despite what is reported, whole flax seeds seem well absorbed as best I can tell from my own experience.