Oleic and monounsaturated fatty acids [omega-9...] were positively associated with breast cancer risk. The SI [saturation index...] was inversely associated with breast cancer risk [declining with saturation increase]. [...] monounsaturated fats and SI in erythrocyte membranes are predictors of postmenopausal breast cancer. Both of these variables depend on the activity of the enzyme 9-d [delta 9 desaturase].[
Some n?9s are common components of animal fat and vegetable oil. Two n?9 fatty acids important in industry are:
Oleic acid (18:1, n?9), which is a main component of olive oil and other monounsaturated fats
Erucic acid (22:1, n?9), which is found in rapeseed, wallflower seed, and mustard seed. Rapeseed with high erucic acid content is grown for commercial use in paintings and coatings as a drying oil.
Unlike n?3 and n?6 fatty acids, n?9 fatty acids are not classed as essential fatty acids (EFA). This is both because they can be created by the human body from unsaturated fat, and are therefore not essential in the diet, and because the lack of an n?6 double bond keeps them from participating in the reactions that form the eicosanoids.
Under severe conditions of EFA deprivation, mammals will elongate and desaturate oleic acid to make mead acid, (20:3, n?9).[1] This also occurs to a lesser extent in vegetarians and semi-vegetarians.[2]
For an explanation of n and numerical nomenclature (such as n?9 or 18:1), see Nomenclature of fatty acids.Types of fats in food
Unsaturated fat
Monounsaturated fat
Polyunsaturated fat
Trans fat
Omega fatty acids:
??3
??6
??9
Saturated fat
Interesterified fat
See also
Fatty acid
Essential fatty acid Food portal
n?9 fatty acids (popularly referred to as ??9 fatty acids or omega-9 fatty acids) are a family of unsaturated fatty acids which have in common a carbon–carbon double bond in the n?9 position; that is, the ninth bond from the end of the fatty acid.
Four major food oils (palm, soybean, rapeseed and sunflower) provide more than 100 million metric tons annually, providing more than 32 million metric tons of n-6 linoleic acid and 4 million metric tons of n-3 alpha-linolenic acid [18]
poultry
eggs
cereals
whole-grain breads
baked goods
nuts
most vegetable oils
evening primrose oil
borage oil
blackcurrant seed oil
flax/linseed oil
hemp oil
soybean oil
cottonseed oil
sunflower seed oil
corn oil
safflower oil
pumpkin seeds
acai berry
It has been reported that conversion of ALA to EPA and further to DHA in humans is limited, but varies with individuals.[102] Women have higher ALA conversion efficiency than men, probably due to the lower rate of utilization of dietary ALA for beta-oxidation. This suggests that biological engineering of ALA conversion efficiency is possible. In the online book of The Benefits of Omega 3 Fatty Acids found in Seal Oil, as Opposed to Fish and Flaxseed Oils, Dr. Ho listed the several factors that inhibit the ALA conversion,[103] which again indicate that the efficiency of ALA conversion could be adjusted by altering one’s dietary habits, such as rebalancing the ratio of n?3 and n?6 fatty acid intake,[102][104] restraining direct alcohol consumptions, and supplementing vitamins and minerals. However, Goyens et al. argues that it is the absolute amount of ALA, rather than the ratio of n?3 and n?6 fatty acids, which affects the conversion.
Clinical studies[1][90][91][92] indicate that the ingested ratio of n?6 to n?3 (especially Linoleic vs Alpha Linolenic) fatty acids is important to maintaining cardiovascular health. However, two studies[93][94], published in 2005 and 2007, found no such correlations in humans.
Both n?3 and n?6 fatty acids are essential, i.e. humans must consume them in the diet. n?3 and n?6 compete for the same metabolic enzymes, thus the n?6:n?3 ratio will significantly influence the ratio of the ensuing eicosanoids (hormones), (e.g. prostaglandins, leukotrienes, thromboxanes etc.), and will alter the body’s metabolic function.[95] Generally, grass-fed animals accumulate more n?3 than do grain-fed animals which accumulate relatively more n?6. Metabolites of n?6 are significantly more inflammatory (esp. arachidonic acid) than those of n?3. This necessitates that n?3 and n?6 be consumed in a balanced proportion; healthy ratios of n?6:n?3 range from 1:1 to 4:1.[96][97] Studies suggest that the evolutionary human diet, rich in game animals, seafood and other sources of n?3, may have provided such a ratio.[90][98]
Typical Western diets provide ratios of between 10:1 and 30:1 - i.e., dramatically skewed toward n?6.[99] Here are the ratios of n?6 to n?3 fatty acids in some common oils: canola 2:1, soybean 7:1, olive 3–13:1, sunflower (no n?3), flax 1:3,[100] cottonseed (almost no n?3), peanut (no n?3), grapeseed oil (almost no n?3) and corn oil 46 to 1 ratio of n?6 to n?3.[101] It should be noted that olive, peanut and canola oils consist of approximately 80% monounsaturated fatty acids, (i.e. neither n?6 nor n?3) meaning that they contain relatively small amounts of n?3 and n?6 fatty acids. Consequently, the n?6 to n?3 ratios for these oils (i.e. olive, canola and peanut oils) are not as significant as they are for corn, soybean and sunflower oils.
Milk and cheese from grass-fed cows may also be good sources of n?3. One UK study showed that half a pint of milk provides 10% of the recommended daily intake (RDI) of ALA, while a piece of organic cheese the size of a matchbox may provide up to 88%”.[88]
Krill, which are small, shrimp-like zooplankton, also contain the n?3 fatty acids EPA and DHA. One advantage of extracting n?3 fatty acids from krill, as opposed to sources higher in the food chain, is that krill contain fewer heavy metals and PCBs harmful to humans.[citation needed] However, in comparison to higher animals, they also contain fewer n?3 fatty acids per gram.[citation needed]
The microalgae Crypthecodinium cohnii and Schizochytrium are rich sources of DHA (22:6 n?3) and can be produced commercially in bioreactors. Oil from brown algae (kelp) is a source of EPA. Walnuts are one of few nuts that contain appreciable n?3 fat, with approximately a 1:4 ratio of n?3 to n?6.[50] Acai palm fruit also contains n?3 fatty acids.
Omega 3 is also found in softgels in pharmacies and nowadays it is also found in combination with omega 6, omega 9 and shark liver oil [89]
Some vegetables, too, contain a noteworthy amount of n-3, including strawberries and broccoli.
The n?6 to n?3 ratio of grass-fed beef is about 2:1, making it a more useful source of n?3 than grain-fed beef, which usually has a ratio of 4:1.[86]
Commercially available lamb is almost always grass-fed, and subsequently higher in n?3 than other common meat sources.[citation needed]
The omega-3 content of chicken meat may be enhanced by increasing the animals’ dietary intake of grains such as flax, chia, and canola.[
Eggs produced by chickens fed a diet of greens and insects produce higher levels of n?3 fatty acids (mostly ALA) than chickens fed corn or soybeans.[84]In addition to feeding chickens insects and greens, fish oils may be added to their diet to increase the amount of fatty acid concentrations in eggs.[
Six times richer than most fish oils in n?3,[79] Flax (aka linseed) (Linum usitatissimum) and its oil are perhaps the most widely available botanical source of n?3. Flaxseed oil consists of approximately 55% ALA (alpha-linolenic acid). Flax, like chia, contains approximately three times as much n?3 as n?6.
15 grams of flaxseed oil provides ca. 8 grams of ALA, which is converted in the body to EPA and then DHA at an efficiency of 2–15% and 2–5%, respectively.