(Redirected from Omega 3)
'Omega-3 fatty acids' are a family of
polyunsaturated fatty acids which have in common a carbon-carbon double bond in the ω-3 position. (''See
Nomenclature for terms and discussion of ω (omega) nomenclature.'')
Important nutritional essential omega-3 fatty acids are:
α-linolenic acid (ALA),
eicosapentaenoic acid (EPA), and
docosahexaenoic acid (DHA). For a more complete list see
List of omega-3 fatty acids. The human body cannot synthesize omega-3 fatty acids ''
de novo'', but it can form 20- and 22-carbon unsaturated omega-3 fatty acids from the eighteen-carbon omega-3 fatty acid, α-linolenic acid. These conversions occur competitively with omega-6 fatty acids, which are essential closely related chemical analogues that are derived from linoleic acid. Both the omega-3 α-linolenic acid and omega-6 linoleic acid are
essential nutrients which must be obtained from food. Synthesis of the longer omega-3 fatty acids from linolenic acid within the body is competitively slowed by the omega-6 analogues. Thus accumulation of long-chain omega-3 fatty acids in tissues is more effective when they are obtained directly from food or when competing amounts of omega-6 analogs do not greatly exceed the amounts of omega-3.
Chemistry
:''For detail on omega (ω) nomenclature and numbering, see
EFA Nomenclature.''
The term 'omega-3' (aka "n-3", "ω-3") signifies that the first
double bond exists as the 'third' carbon-carbon bond from the terminal
methyl end (ω) of the
carbon chain.
Omega-3 fatty acids which are important in human nutrition are: α-linolenic acid (18:3, 'ALA'), eicosapentaenoic acid (20:5, 'EPA'), and docosahexaenoic acid (22:6, 'DHA'). These three
polyunsaturates have either 3, 5 or 6 double bonds in a carbon chain of 18, 20 or 22 carbon atoms, respectively. All double bonds are in the ''
cis''-configuration, i.e. the two hydrogen atoms are on the same side of the double bond.
Biological significances
:''The biological effects of the ω-3 fatty acids are largely mediated by their interactions with the ω-6 fatty acids; see
Essential fatty acid interactions for detail.''
A
1992 article by
biochemist William E.M. Lands[W.E.M. Lands (1992). Biochemistry and physiology of n-3 fatty acids. ''FASEB J'' '6': 2530-2536.] provides an overview of the research into omega-3 fatty acids, and is the basis of this section. Extensive details of physiology, metabolism and nutrition are provided in his 2005 book, "Fish, Omega-3 and Human Health". A 2007 book by Evelyn Tribole, "The Ultimate Omega-3 Diet" extends this discussion with food contents and recipies by which people can balance dietary intakes of omega-3 and omega-6 fats.
The 'essential' fatty acids were given their name when researchers found that they were essential to normal growth in young children and animals. (Note that the modern definition of '
essential' is more strict.) A small amount of omega-3 in the diet (~1% of total calories) enabled normal growth, and increasing the amount had little to no additional benefit.
Likewise, researchers found that
omega-6 fatty acids (such as
γ-linolenic acid and
arachidonic acid) play a similar role in normal growth. However, they also found that omega-6 was "better" at supporting
dermal integrity,
renal function, and
parturition. These preliminary findings led researchers to concentrate their studies on omega-6, and it was only in recent decades that omega-3 has become of interest.
In
1963 it was discovered that the omega-6 arachidonic acid was converted by the body into
pro-inflammatory agents called
prostaglandins. By
1979 more of what are now known as
eicosanoids were discovered:
thromboxanes,
prostacyclins and the
leukotrienes. The eicosanoids, which have important biological functions, typically have a short active lifetime in the body, starting with synthesis from fatty acids and ending with metabolism by enzymes. However, if the rate of synthesis exceeds the rate of metabolism, the excess eicosanoids may have deleterious effects. Researchers found that omega-3 is also converted into eicosanoids, but at a much slower rate. Eicosanoids made from omega-3 fats often have opposing functions to those made from omega-6 fats (ie, anti-inflammatory rather than inflammatory). If both omega-3 and omega-6 are present, they will "compete" to be transformed, so the ratio of omega-3:omega-6 directly affects the type of eicosanoids that are produced.
This competition was recognized as important when it was found that
thromboxane is a factor in the clumping of
platelets, which leads to
thrombosis. The
leukotrienes were similarly found to be important in immune/inflammatory-system response, and therefore relevant to
arthritis,
lupus, and
asthma. These discoveries led to greater interest in finding ways to control the synthesis of omega-6 eicosanoids. The simplest way would be by consuming more omega-3 and fewer omega-6 fatty acids.
Health benefits
On
September 8,
2006, the U.S.
Food and Drug Administration gave "qualified health claim" status to eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) omega-3 fatty acids, stating that "supportive but not conclusive research shows that consumption of EPA and DHA omega-3 fatty acids may reduce the risk of
coronary heart disease."
This updated and modified their health risk advice letter of 2001 (see below).
A 2006 report in the
Journal of the American Medical Association concluded that their review of literature covering
cohorts from many countries with a wide variety of demographic characteristics failed to demonstrate a link between omega-3 fatty acids and
cancer prevention.
[ Effects of Omega-3 Fatty Acids on Cancer Risk, Catherine H. MacLean, MD, PhD ''et al'', , , Journal of the American Medical Association, 2006 ] This is similar to the findings of a review by the
British Medical Journal of studies up to February 2002 that failed to find clear effects of long and shorter chain omega-3 fats on total mortality, combined cardiovascular events and cancer.
[ Risks and benefits of omega 3 fats for mortality, cardiovascular disease, and cancer: systematic review, Lee Hooper ''et al'', , , British Medical Journal, 2006 ]
In April 2006, a team led by
Lee Hooper at the
University of East Anglia in
Norwich, UK, published a review of almost 100 separate studies into omega-3 fatty acids, found in abundance in oily fish. It concluded that they do not have a significant protective effect against cardiovascular disease.
[Bijal Trivedi The good, the fad, and the unhealthy ''New Scientist'', 23 September 2006, pp 42-49.] This meta-analysis was controversial and stands in stark contrast with two different reviews also performed in 2006 by the
American Journal of Clinical Nutrition[1] and a second JAMA review
[2] that both indicated decreases in total mortality and cardiovascular incidents (i.e.
myocardial infarctions) associated with the regular consumption of fish and
fish oil supplements.
Several studies published in 2007 have been more positive. In the March 2007 edition of the journal
''Atherosclerosis'', 81
Japanese men with unhealthy
blood sugar levels were randomly assigned to receive 1800 mg daily of eicosapentaenoic acid (EPA - an omega-3 essential fatty acid from fish oil) with the other half being a control group. The thickness of the
carotid arteries and certain measures of blood flow were measured before and after supplementation. This went on for approximately two years. A total of 60 patients (30 in the EPA group and 30 in the control group) completed the study. Those given the EPA had a statistically significant decrease in the thickness of the carotid arteries along with improvement in blood flow. The authors indicated that this was the first demonstration that administration of purified EPA improves the thickness of carotid arteries along with improving blood flow in patients with unhealthy blood sugar levels.
In another study published in the American Journal of Health System Pharmacy March 2007, patients with high triglycerides and poor coronary artery health were given 4 grams a day of a combination of EPA and DHA along with some monounsaturated fatty acids. Those patients with very unhealthy triglyceride levels (above 500 mg/dl) reduced their triglycerides on average 45% and their VLDL cholesterol by more than 50%. VLDL is a bad type of cholesterol and elevated triglycerides can also be deleterious for cardiovascular health.
There was another study published on the benefits of EPA in the prestigious journal ''The Lancet'' in March 2007. This study involved over 18,000 patients with unhealthy cholesterol levels. The patients were randomly assigned to receive either 1,800 mg a day of EPA with a statin drug or a statin drug alone. The trial went on for a total of five years. It was found at the end of the study those patients in the EPA group had superior cardiovascular function. Non-fatal coronary events were also significantly reduced in the EPA group. The authors concluded that EPA is a promising supplement for promoting cardiovascular health.
Another study regarding fish oil was published in the journal ''Nutrition'' in April 2007. Sixty four healthy Danish infants received either cow's milk or infant formula alone or with fish oil from nine to twelve months of age. It was found that those infants supplemented with fish oil had improvement in immune function maturation with no apparent reduction in immune activation.
There was yet another study on omega-3 fatty acids published in the April 2007 ''Journal of NeuroScience''. A group of mice were genetically modified to develop accumulation of amyloid and tau proteins in the brain similar to that seen in people with poor memory. The mice were divided into four groups with one group receiving a typical American diet (with high ratio of omega-6 to omega-3 fatty acids being 10 to 1). The other three groups were given food with a balanced 1 to 1 omega 6 to omega 3 ratio and two additional groups supplemented with DHA plus long chain omega-6 fatty acids. After three months of feeding, all the DHA supplemented groups were noted to have a lower accumulation of beta amyloid and tau protein. It is felt that these abnormal proteins may contribute to the development of memory loss in later years.
Finally, there was a study published regarding omega-3 supplementation in children with learning and behavioral problems. This study was published in the April 2007 edition of the ''Journal of the Developmental and Behavioral Pediatrics'' (5), where 132 children, between the ages of seven to twelve years old, with poor learning, participated in a randomized, placebo-controlled, double-blinded interventional trial. A total of 104 children completed the trial. For the first fifteen weeks of this study, the children were given polyunsaturated fatty acids (omega-3 and omega-6, 3000 mg a day), polyunsaturated fatty acids plus multi-vitamins and minerals or placebo. After fifteen weeks, all groups crossed over to the polyunsaturated fatty acids (PUFA) plus vitamins and mineral supplement. Parents were asked to rate their children's condition after fifteen and thirty weeks. After thirty weeks, parental ratings of behavior improved significantly in nine out of fourteen scales. The lead author of the study, Dr. Sinn, indicated the present study is the largest PUFA trial to date with children falling in the poor learning and focus range. The results support those of other studies that have found improvement in poor developmental health with essential fatty acid supplementation.
[3]
Research in 2005-06 has suggested that the in-vitro anti-inflammatory activity of omega-3 acids translates into clinical benefits. Cohorts of neck pain patients and of rheumatoid arthritis sufferers have demonstrated benefits comparable to those receiving standard
NSAIDs . Those who follow a Mediterranean-style diet tend to have less heart disease, higher HDL ("good") cholesterol levels
[4] and higher proportions of omega-3 in tissue highly unsaturated fatty acids
[5]. Similar to those who follow a Mediterranean diet, Arctic-dwelling Inuit - who consume high amounts of omega-3 fatty acids from fatty fish - also tend to have higher proportions of omega-3, increased HDL cholesterol and decreased triglycerides (fatty material that circulates in the blood) and less heart disease. Eating
walnuts (which have several-fold more omega-3 ALA than omega-6 LA) was reported to lower total cholesterol by 4% relative to controls when people also ate 27% less cholesterol.
[6]
Health risks
In a letter dated
October 31,
2000 entitled
Letter Regarding Dietary Supplement Health Claim for omega-3 Fatty Acids and Coronary Heart Disease, the United States
Food and Drug Administration Center for Food Safety and Applied Nutrition, Office of Nutritional Products, Labeling, and Dietary Supplements noted that the known or suspected risks of EPA and DHA omega-3 fatty acids may include:
★ There have been reports that increased bleeding can occur if overused (normally over 3 grams per day) by a patient who is also taking aspirin or coumadin (warfarin). However, this is disputed.
[1]
★ The possibility of
hemorrhagic stroke.
★ Oxidation of omega-3 fatty acids forming biologically active oxidation products.
★ Reduced glycemic control among diabetics.
★ Suppression of immune and inflammation responses, and consequently, decreased resistance to infections and increased susceptibility to opportunistic bacteria.
Subsequent advices from the FDA and national counterparts have permitted health claims associated with heart health.
Warning for persons with Congestive Heart Failure (CHF)
Persons with
congestive heart failure, chronic recurrent
angina or evidence that their heart is receiving insufficient blood flow are advised to talk to their doctor before taking omega-3 fatty acids. It may be prudent for such persons to avoid taking omega-3 fatty acids or eating foods that contain them in substantial amounts.
[ This advice has now been updated in favour of omega 3 intake by the UK's medical committee, NICE ( see below ).]
The Dark Side of Good Fats Dean Ornish
In congestive heart failure, cells that are only barely receiving enough blood flow become electrically hyperexcitable. This, in turn, can lead to increased risk of irregular heartbeats, which, in turn, can cause sudden cardiac death. Omega-3 fatty acids seem to stabilize the rhythm of the heart by effectively preventing these hyperexcitable cells from functioning by increasing the blood flow, thereby reducing the likelihood of irregular heartbeats and sudden cardiac death. For most people, this is obviously beneficial and would account for most of the large reduction in the likelihood of sudden cardiac death.
Research frontiers
Autism
According to an Internet survey, approximately 30% of parents use omega-3 supplements as a therapy for children with
autism.
[7] There are currently only a few studies on the effectiveness of essential fatty acid supplementation as a treatment of autism and none of these has been well-controlled.
[8][9][10][11] Bell and colleagues reported that parents of 18 children with autism who had been supplemented with fish oil for six months described improvements in overall health, cognition, sleep patterns, social interaction, and eye contact.
[12] Another case report found that a child with autism given 540 mg of EPA per day over a four week period experienced a complete elimination of his previous anxiety about everyday events as reported by his parents and clinician.
[13]
Low birth weight
In a study of nearly 9,000 pregnant women, researchers found women who ate fish once a week during their first trimester had 3.6 times less risk of low birth weight and premature birth than those who ate no fish. Low consumption of fish was a strong risk factor for preterm delivery and low birth weight.
[14] However, attempts by other groups to reverse this increased risk by encouraging increased pre-natal consumption of fish were unsuccessful.
[15]
Psychological disorders
Omega-3s are known to have membrane-enhancing capabilities in brain cells.
One medical explanation is that omega-3s play a role in the fortification of the
myelin sheaths. Not coincidentally, omega-3 fatty acids comprise approximately eight percent of the average human brain according to Dr.
David Horrobin, a pioneer in fatty acid research.
Ralph Holman of the
University of Minnesota, another major researcher in studying essential fatty acids, who gave it the name, surmised how omega-3 components are analogous to the human brain by stating that "DHA is structure, EPA is function."
A benefit of omega-3s is helping the brain to repair damage by promoting neuronal growth.
In a six-month study involving people with
schizophrenia and
Huntington's disease who were treated with EPA or a placebo, the placebo group had clearly lost cerebral tissue, while the patients given the supplements had a significant increase of grey and white matter.
[B. Puri. ''International Review of Psychiatry'', vol 18, p 149, 2006.]
In the
prefrontal cortex (PFC) of the
brain, low brain omega-3s are thought to lower the dopaminergic
neurotransmission in this brain area, possibly contributing to the negative and neurocognitive symptoms in
schizophrenia. This reduction in
dopamine system function in the PFC may lead to an overactivity in dopaminergic function in the
limbic system of the brain which is suppressively controlled by the PFC dopamine system, causing the positive symptoms of
schizophrenia (Ohara, 2007). This mechanism may explain why omega-3 supplementation shows effects against both positive, negative and neurocognitive
symptoms in
schizophrenia.
Consequently, the past decade of omega-3 fatty acid research has procured ''some''
Western interest in omega-3s as being a legitimate 'brain food.' Still, recent claims that one's
intelligence quotient, psychological tests measuring certain cognitive skills, including numerical and verbal reasoning skills, are increased on account of omega-3s consumed by pregnant mothers remain unreliable and controversial. An even more significant focus of research, however, lies in the role of omega-3s as a non-prescription treatment for certain psychiatric and mental diagnoses and has become a topic of much research and speculation.
In 1998, Andrew L. Stoll, MD and his colleagues at
Harvard University conducted a small
double-blind placebo-controlled study in thirty patients diagnosed with
bipolar disorder. Over the course of nine months, he gave 15 subjects capsules containing
olive oil, and another 15 subjects capsules containing nine grams of pharmaceutical-quality EPA and DHA. In doing so, he was able to make the ''general'' distinction between the placebo group failing to improve while the Omega-3 group experienced a noticeable degree of recovery. Though Stoll believes that the 1999 experiment was not as optimal as it could have been and has accordingly pursued further research, the foundation has been laid for more researchers to explore the theoretical association between absorbed omega-3s and signal transduction inhibition in the brain.
[Stoll et al. Omega 3 Fatty Acids in Bipolar Disorder: A Preliminary Double-blind, Placebo-Controlled Trial "Arch Gen Psychiatry". 1999;56:407-412.]
"Several epidemiological studies suggest covariation between seafood consumption and rates of mood disorders. Biological marker studies indicate deficits in omega-3 fatty acids in people with depressive disorders, while several treatment studies indicate therapeutic benefits from omega-3 supplementation. A similar contribution of omega-3 fatty acids to coronary artery disease may explain the well-described links between coronary artery disease and depression. Deficits in omega-3 fatty acids have been identified as a contributing factor to mood disorders and offer a potential rational treatment approach." (American Journal of Psychiatry 163:1098-1100, June 2006)
In 2006, a review of published trials in the American Journal of Clinical Nutrition found that "the evidence available provides little support" for the use of fish or the n–3 long-chain polyunsaturated fatty acids contained in them to improve depressed mood. The study used results of twelve randomized controlled trials in its meta-analysis. The review recommended that "larger trials with adequate power to detect clinically important benefits" be performed.
[American Journal of Clinical Nutrition 84(December):1308-1316 Katherine M Appleton, Robert C Hayward, David Gunnell, Tim J Peters, Peter J Rogers, David Kessler and Andrew R Ness]
Abstract
===
Short bowel syndrome ===
Case reports show that an omega-3 rich emulsion,
Omegaven, reduced
the risk of liver damage in this condition.
Dietary sources
Daily values
As macronutrients, fats are not assigned
recommended daily allowances. Macronutrients have AI (Acceptable Intake) and AMDR (Acceptable Macronutrient Distribution Range) instead of RDAs. The AI for n-3 is 1.6 grams/day for men and 1.1 grams/day for women
[ Dietary Reference Intakes For Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids, Food and Nutrition Board, Institute of Medicine of the National Academies, , , The National Academies Press, , ISBN 0-309-08537-3 ] while the AMDR is 0.6% to 1.2% of total energy.
[ Dietary Reference Intakes For Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids, Food and Nutrition Board, Institute of Medicine of the National Academies, , , The National Academies Press, , ISBN 0-309-08537-3 ]
"A growing body of literature suggests that higher intakes of α-linolenic acid, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) may afford some degree of protection against
coronary heart disease. Because the physiological potency of EPA and DHA is much greater than that for α-linolenic acid, it is not possible to estimate one AMDR for all n-3 fatty acids. Approximately 10 percent of the AMDR can be consumed as EPA and/or DHA."
There was insufficient evidence as of 2005 to set a UL (upper tolerable limit) for n-3 fatty acids.
Researchers believe the ideal
omega-6 intake should be no more than 4-5 times that of our omega-3 intake. The National Institutes of Health recently published recommended daily intakes of fatty acids, specific recommendations include 650 mg of EPA and DHA, 2.22 g/day of alpha-linolenic acid and 4.44 g/day of linoleic acid.
A perceived risk of fish oil omega-3 supplementation has been
heavy metal poisoning by the body's accumulation of traces of heavy metals, in particular
mercury,
lead,
nickel,
arsenic and
cadmium as well as other contaminants (
PCBs,
furans,
dioxins), which potentially might be found especially in less-refined fish oil supplements.. The fish oil industry has successfully improved the quality of fish oils on the market. An independent test in 2006 of 42 fish oils on the US market by www.consumerlab.com found that all of the products exceeded safety standards for potential contaminants.
[ Product Review: Omega-3 Fatty Acids (EPA and DHA) from Fish/Marine Oils ] The FDA recommends that total dietary intake of omega-3 fatty acids from fish not exceed 3 grams per day, of which no more than 2 grams per day are from nutritional supplements.
[ ]
Historically, the
Council for Responsible Nutrition (CRN) and the
World Health Organization (WHO) have published acceptable standards regarding contaminants in fish oil. The most stringent current standard is the
International Fish Oils Standard (IFOS).
Fish oils that typically make this highest grade are those that are
molecularly distilled under vacuum, and have virtually no measurable level of contaminants (measured parts per billion and parts per trillion).
Omega supplementation in food has been a significant recent trend in food fortification, with global food companies launching omega-3 fortified bread, pizza, yoghurt, orange juice, children's pasta, milk, confections and infant formula.
Fish
Early humans ate inter-tidal shellfish, while living a shoreline existence in Africa.
[16] Now, as then, inter-tidal herbivorous shellfish such as mussels and clams can help people reach a healthy balance of omega-3 and omega-6 fats in their diets.
The most widely available source of
EPA and
DHA is cold water oily fish such as
wild salmon,
herring,
mackerel,
anchovies and
sardines. The oil from these fish have a profile of around seven times as much omega-3 as omega-6. Farmed salmon, being grain fed, have a higher proportion of omega-6 than wild salmon. Other oily fish such as
tuna also contain omega-3 in somewhat lesser amounts. Consumers of oily fish should be aware of the potential presence of
heavy metals and fat-soluble pollutants like
PCBs and
dioxins which may
accumulate up the food chain.
[18] Some supplement manufacturers remove heavy metals and other contaminants from the oil through various means, such as molecular distillation (see above), which increases purity, potency and safety.
Even some forms of fish oil may not be optimally digestible. Of four studies that compare bioavailability of the triglyceride form of fish oil vs. the ester form, two have concluded that the natural triglyceride form is better, and the other two studies did not find a significant difference. No studies have shown the ester form to be superior although it is cheaper to manufacture.
[Lawson LD and Hughes BG. "Absorption of EPA and DHA from fish oil triacylglycerols or fish oil esters co-ingested with a high fat meal." ''Biochem. Biophys Res. Commun.'', 156:960-963, 1988.][Beckermann B, et al. "Comparative bioavailability of EPA and DHA from triglycerides, free fatty acids and ethyl esters in volunteers." ''Arzneimittelforschung'', 40: 700-704, 1990]
Although fish is a dietary source of omega-3 fatty acids, fish do not synthesize them; they obtain them from the
algae in their diet. For this reason, there is often a significant difference in EPA and DHA concentrations in farmed vs wild caught fish.
Flax
Six times richer than most fish oils in omega-3
[ Bartram's Encyclopedia of Herbal Medicine, Thomas Bartram, , , , 1998 ],
Flax (aka linseed) (''Linum usitatissimum'') and its oil are perhaps the most widely available
botanical source of omega-3.
Flaxseed oil consists of ca. 55% ALA (alpha-linolenic acid). Flax, like
chia, contains approximately three times as much omega-3 as omega-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.
[ Vegetarian Society, Information Sheet on Omega 3 fats]
Botanical sources of omega-3 fatty acid
The table lists omega-3 content as the percentage of
ALA in the seed oil, unless otherwise noted.
Eggs
Eggs produced by chickens fed a diet of greens and insects produce higher levels of omega-3 fatty acids than chickens fed corn or soybeans.
[19]
Other sources
Krill, which are small, shrimp-like
zooplankton, also contain the omega-3 fatty acids EPA and DHA. One advantage of extracting omega-3s from krill, as opposed to sources higher in the food chain, is that krill contain fewer heavy metals and PCBs harmful to humans. However, in comparison to higher animals, they also contain fewer omega-3 fatty acids per gram.
The omega-6 to omega-3 ratio of
grass-fed beef is about 2:1, making it a more useful source of omega-3 than grain-fed beef, which usually has a ratio of 4:1.
[20] Commercially available
lamb is almost always grass-fed, and subsequently higher in omega-3 than other common meat sources.
Milk and
cheese from grass-fed cows may also be good sources of omega-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%".
[21]
The
microalgae ''Crypthecodinium cohnii'' and ''Schizochytrium'' are rich sources of
DHA (22:6 ω-3) and can be produced commercially in
bioreactors. Oil from
brown algae (kelp) is a source of EPA.
Acai palm fruit also contains omega-3 fatty acids.
Omega-3
capsules are sold in bottles for daily intake as
supplements.
Walnuts are one of few nuts that contain appreciable omega-3 fat, but it has several-fold more omega-6 than omega-3.
The omega-6 to omega-3 ratio
Main articles: Essential fatty acid interactions
Clinical studies
[ Okuyama H. High n-6 to n-3 ratio of dietary fatty acids rather than serum cholesterol as a major risk factor for coronary heart disease. ''Eur J Lipid Sci Technol''. 2001; 103:418-22.] indicate that the ingested ratio of omega-6 to omega-3 (especially Linoleic vs Alpha Linolenic) fatty acids is important to maintaining cardiovascular health.
Both omega-3 and omega-6 fatty acids are essential, i.e. humans must consume them in the diet. Omega-3 and omega-6 compete for the same metabolic enzymes, thus the omega-6:omega-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. Generally, grass-fed animals accumulate more omega 3 than do grain-fed animals which accumulate relatively more omega 6.
Metabolites of omega-6 are significantly more inflammatory (esp.
arachidonic acid) than those of omega-3. This necessitates that omega-3 and omega-6 be consumed in a ''balanced proportion''; healthy ratios of omega-6:omega-3 range from 1:1 to 4:1
[23] recommend daily intakes of three omega-3 forms: 650 mg of
EPA and
DHA, and 2.22
grams of
ALA, and one omega-6 form: 4.44 grams of
LA. This translates to a 3:2 omega-6 to omega-3 ratio. (i.e. 1.5:1)
Typical Western diets provide ratios of between 10:1 and 30:1 - i.e., dramatically skewed toward omega-6
[24] cottonseed (almost no omega-3),
peanut (no omega-3),
grapeseed oil (almost no omega-3) and
corn oil 46 to 1 ratio of omega-6s to omega-3s.
[25] It should be noted that olive, peanut and canola oils consist of approximately 80% monounsaturated fatty acids, (i.e. neither omega-6 nor omega-3) meaning that they contain relatively small amounts of omega (3 & 6) fatty acids. Consequently, the omega-6 to omega-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.
See also
★
List of omega-3 fatty acids
★
Omega-6 fatty acid
★
Omega-9 fatty acid
★
Essential fatty acid
★
Essential fatty acid interactions
★
Grape seed oil
★
Camelina sativa
★
Cod liver oil
★
Fish oil
★
Flax
★
Linseed oil
★
Chia
★
Purslane
★
Resolvins
★
Wakame
Notes and references
1. Wang C, Harris WS, Chung M, et al. n-3 fatty acids from fish or fish-oil supplements but not a-linoleic acid, benefit cardiovascular outcomes in primary and secondary prevention studies: a systematic review. Am J. Clin Nutr 2006;84:5-17
2. Mozaffarian D, & Rimm EB. Fish Intake, Contaminants, and Human Health: Evaluating the Risks and the Benefits. JAMA, October 18, 2006—Vol 296, No. 15
3. 1. MCKENNEY, J. and SICA, D, Prescription omega-3 fatty acids for the treatment of hypertriglyceridemia, American Journal of Health-System Pharmacy. 646:595-605, March 15, 2007
2. Yokoyama M et al., Effects of eicosapentaenoic acid on major coronary events in hypercholesterolemic patients (JELIS): a randomized open-label, blinded endpoint analysis, Lancet 2007
3. Damsgaard C, Lauritzen L, Kjær T, Holm P, Fruekilde M, Michaelsen K and Frøkiær H, Fish Oil Supplementation Modulates Immune Function in Healthy Infants, J. Nutr. 137:1031-1036, April 2007
4. LaFerla F, Martinez-Coria H, Khashwji H, Hall E, Yurko-Mauro K and Ellis L, Journal of Neuroscience, April 18, 2007, Volume 27, Number 16
5. Sinn, N and Bryan, J, Effect of Supplementation with Polyunsaturated Fatty Acids and Micronutrients on Learning and Behavior Problems Associated with Child ADHD, Journal of Developmental & Behavioral Pediatrics. 28(2):82-91, April 2007
6. Lee D, Lee I, Jin S, Steffes M, Jacobs D, Association Between Serum Concentrations of Persistent Organic Pollutants and Insulin Resistance Among Nondiabetic Adults, Diabetes Care 30:622-628, 2007
4. Kris-Etherton P, Eckel RH, Howard BV, St. Jeor S, Bazzare TL. AHA Science Advisory: Lyon Diet Heart Study. Benefits of a Mediterranean-style, National Cholesterol Education Program/American Heart Association Step I Dietary Pattern on Cardiovascular Disease. ''Circulation'' 2001;103:1823
5. Lands WEM. Diets could prevent many diseases. Lipids 2003;38(4): 317-321
6. Zambón D, Sabate J, Munoz S, et al. Substituting walnuts for monounsaturated fat improves the serum lipid profile of hypercholesterolemic men and women. ''Ann Intern Med''. 2000;132:538-546.
7. Green, V.A., K.A. Pituch, J. Itchon, A. Choi, M. O'Reilly, J. Sigafoos, "Internet survey of treatments used by parents of children with autism," Res Dev Disabil, 2006, 27(1):70-84.
8. Young, G., and J. Conquer. 2005. "Omega-3 fatty acids and neuropsychiatric disorders." Reprod.Nutr.Dev 45(1):1-28.
9. Genuis, S.J.a.G.K.S. 2006. "Time for an oil check: the role of essential omega-3 fatty acids in maternal and pediatric health." Journal of Perinatology 26:359-365.
10. Richardson, A.J. 2006. "Omega-3 fatty acids in ADHD and related neurodevelopmental disorders." Int.Rev.Psychiatry 18(2):155-172.
11. Richardson, A.J., and M.A. Ross. 2000. "Fatty acid metabolism in neurodevelopmental disorder: a new perspective on associations between attention-deficit/hyperactivity disorder, dyslexia, dyspraxia and the autistic spectrum." Prostaglandins Leukot.Essent.Fatty Acids 63(1-2):1-9.
12. Bell, J.G., et al. 2004. "Essential fatty acids and phospholipase A2 in autistic spectrum disorders." Prostaglandins Leukot.Essent.Fatty Acids 71(4):201-204.
13. Johnson, S.M., and E. Hollander. 2003. "Evidence that eicosapentaenoic acid is effective in treating autism." J Clin Psychiatry 64(7):848-849.
14. Olsen SF, Secher NJ. Low consumption of seafood in early pregnancy as a risk factor for preterm delivery: prospective cohort study. BMJ 2002; 324: 1–5
15. Odent M, Colson S, De Reu P. Consumption of seafood and preterm delivery. Encouraging pregnant women to eat fish did not show effect. BMJ. 2002 May 25;324(7348):1279
16. Shellfish view of omega-3 and sustainable fisheries
17. Shellfish and Health
18. 'Pollutants found in fish oil capsules'
19. How Omega-6s Usurped Omega-3s In US Diet
20. Omega-3/Omega-6 fatty acid content of Grass Fed Beef:
21. More Omega 3 in Organic Milk
22. Simopoulos AP, Cleland LG (eds): "omega-6/omega-3 Essential Fatty Acid Ratio: The Scientific Evidence." ''World Rev Nutr Diet''. Basel, Karger, 2003, Vol 92.
23. [. Studies suggest that the evolutionary human diet, rich in seafood and other sources of omega-3, may have provided such a ratio.][Simopoulos AP, Leaf A, Salem Jr N. Statement on the essentiality of and recommended dietary intakes for omega-6 and omega-3 fatty acids. Prostaglandins, Leukotrienes and Essential Fatty Acids 2000;63:119-121.]
24. . Here are the ratios of omega-6 to omega-3 fatty acids in some common oils: canola 2:1, soybean 7:1, olive 13:1, sunflower (no omega-3), flax 1:3[Erasmus, Udo, Fats and Oils. 1986. Alive books, Vancouver, ISBN 0-920470-16-5 p. 263 (round-number ratio within ranges given.)]
25. Essential Fats in Food Oils, NIH page - http://efaeducation.nih.gov/sig/esstable.html
Robson, A. 2006. "Shellfish view of omega-3 and sustainable fisheries." Nature 444, 1002
Shellfish in NATURE
Robson, A. 2007. "Preventing the diseases of civilisation: shellfish, the omega-3:6 balance and human health." Shellfish News 23, 25-27
Shellfish and Health
Cunnane SC (2006) "Survival of the fattest: the key to human brain evolution." M S-MEDECINE SCIENCES 22 (6-7): 659-663.
Bell, J.G., et al. 2004. "Essential fatty acids and phospholipase A2 in autistic spectrum disorders." Prostaglandins Leukot.Essent.Fatty Acids 71(4):201-204.
Bartram, Thomas, 1998, Bartram's Encyclopedia of Herbal Medicine, p.271.
Genuis, S.J.a.G.K.S. 2006. "Time for an oil check: the role of essential omega-3 fatty acids in maternal and pediatric health." Journal of Perinatology 26:359-365.
Green, V.A., K.A. Pituch, J. Itchon, A. Choi, M. O'Reilly, J. Sigafoos, "Internet survey of treatments used by parents of children with autism," Res Dev Disabil, 2006, 27(1):70-84.
Johnson, S.M., and E. Hollander. 2003. "Evidence that eicosapentaenoic acid is effective in treating autism." J Clin Psychiatry 64(7):848-849.
Ohara, K. "The n-3 polyunsaturated fatty acid/dopamine hypothesis of schizophrenia." Prog Neuropsychopharmacol Biol Psychiatry. 2007 Mar 30;31(2):469-74.
Richardson, A.J. 2006. "Omega-3 fatty acids in ADHD and related neurodevelopmental disorders." Int.Rev.Psychiatry 18(2):155-172.
Richardson, A.J., and M.A. Ross. 2000. "Fatty acid metabolism in neurodevelopmental disorder: a new perspective on associations between attention-deficit/hyperactivity disorder, dyslexia, dyspraxia and the autistic spectrum." Prostaglandins Leukot.Essent.Fatty Acids 63(1-2):1-9.
Young, G., and J. Conquer. 2005. "Omega-3 fatty acids and neuropsychiatric disorders." Reprod.Nutr.Dev 45(1):1-28.
Hibbeln JR, Nieminen LR, Blasbalg TL, Riggs JA, Lands WE. Healthy intakes of n-3 and n-6 fatty acids: estimations considering worldwide diversity. Am J Clin Nutr. 2006 Jun;83(6 Suppl):1483S-1493S.
Further reading
★ Allport, Susan.
Queen of Fats: Why Omega-3s Were Removed from the Western Diet and What We Can Do to Replace Them''. University of California Press, September 2006. ISBN 978-0-520-24282-1.
★ Chow, Ching Kuang.
''Fatty Acids in Foods and Their Health Implications''. Routledge Publishing. New York, New York. 2001.
★ Clover, Charles.
''The End of the Line: How overfishing is changing the world and what we eat''. Ebury Press, London 2004. ISBN 0-09-189780-7
★ Stoll, Andrew L.
Omega-3 Connection''. Simon & Schuster 2001. ISBN 0-684-87138-6, ISBN 0-684-87139-4 (paperback).
★
Erasmus, Udo.
''Fats That Heal, Fats That Kill''. 3rd ed. Burnaby (BC): Alive Books; 1993.
★ Boyd, Hillary & Basant, Puri K.
Natural Way to Beat Depression: the groundbreaking discovery of EPA to change your life.'' London. Hodder and Stoughton. 2004. ISBN 0-340-82497-2
★ Tribole, Evelyn. "The Ultimate Omega-3 Diet" New York. McGraw-Hill. 2007 ISBN 13:978-0-07-146986-9
★ Lands, William E.M. "Fish, Omega-3 and Human Health" Champaign. AOCS Press. 2005 ISBN 1-893997-81-2
External links
★
American Heart Assoc "Fish & Omega-3 Fatty Acids"
★ Further topics and latest scientific research:
DHA/EPA Omega-3 Institute
★ BBC News report:
Oily fish helps cut inflammation,
March 12,
2005.
★ University of Maryland Medical Center,
omega-3 Fatty Acids
★
Durham Research: Using Fatty Acids for Enhancing Classroom Achievement Website for the Durham Schools Trial, a double blind, placebo controlled trial on the effects of fatty acids with children who were under performing in class. Funded by the Durham City Council and Oxford University. Their
initial results (also available on
durhamtrial.org) were published in May of 2005.
★ Read criticism of the above mentioned Durham 'trial' by a columnist for the Guardian at
badscience.net September 2006
★ Essential (Omega-3 and Omega-6) Fatty Acids:
The Linus Pauling Institute Micronutrient Information Center
★ Simopoulos, AP
The importance of the ratio of omega-6/omega-3 essential fatty acids.
★
Letter Responding to a Request to Reconsider the Qualified Claim for a Dietary Supplement Health Claim for Omega-3 Fatty Acids and Coronary Heart Disease
★ MedlinePlus Herbs and Supplements:
Omega-3 fatty acids, fish oil, alpha-linolenic acid
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