Download Understanding Fatty Acids: Omega 3 and Omega 6

Understanding Fatty Acids:
Omega 3 and Omega 6
Stephen Alajajian, Dietetic Intern
Fish and heart health
In the 1970’s it was
discovered that the Inuit
had low rates of
cardiovascular disease
despite eating a high-fat
diet. Their diet consisted
mainly of fatty fish. A
similar phenomenon was
observed among the
Japanese.
Presentation Outline
 Omega-3 Fats: definition, function, benefits, chemical
structure, food sources
 Omega-6 Fats: “
 Ratio of n-6/n-3: importance of, optimal ratio,
distortions in the American diet, limitations
 The bottom line: dietary recommendations
 Choosing fish oil supplements
 Summary
What are omega-3 fats?
 Polyunsaturated fats found primarily in
fatty fish, grass-fed animal products and
some plants
 Essential to proper functioning of the body
 Must be obtained by diet
 Anti-inflammatory
 Beneficial for cardiovascular health
 Also called n-3 fats
 Include ALA, EPA and DHA
What is the function of omega-3 fats?
 Important component of
gray matter in the brain and
of sperm
 Role in vision
 Cell membrane component,
contribute flexibility
 Precursor to messenger
molecules called eicosanoids
which can help to reduce
inflammation
What are eicosanoids?
 Comprised of prostaglandins, leukotrienes and
thromboxanes
 Fatty acids of 20 carbon length
 “Hormone-like” messenger molecules synthesized
and active within a cell
 Perform various functions such as: lowering blood
pressure, gastric secretion, raising body temperature,
constricting bronchi, etc.
Eicosanoids and Omega-3’s
 Omega-3 fatty acids act as precursors to eicosanoids
that decrease inflammation
 For example, the eicosanoids produced lower blood
pressure, decrease body temperature, prevent
platelet aggregation (and thus inhibit blood clotting),
and down-regulate the immune system
 This is what is meant by their “anti-inflammatory”
effects
What are the benefits of omega-3?
 Cardiovascular benefits (hypolipidemic and
antithrombotic)
 Slows progression of rheumatoid arthritis
 Decreases blood pressure
 Beneficial for psoriasis (skin condition)
 Effectiveness in the prevention and treatment
of autoimmune diseases such as lupus and
ulcerative colitis
 Essential for a healthy pregnancy
 Deficiencies correlated with depression
 Potential benefits for cancer, kidney disease
and other conditions
How do omega-3’s prevent
atherosclerosis?
 Antithrombotic (prevent platelets from sticking
together – worsening plaque)
 Lower triglyceride levels
 Lower LDL levels (only at high doses, > 10 g/day)
 Reduce the release of pro-inflammatory cytokines
which are involved in plaque formation
Why are they called “omega-3”?
 A fatty acid is a long chain of carbon atoms bonded to
each other and to hydrogen
 Omega means “end”
 Omega 3 has a double bond on the 3rd carbon from
the end of the chain
 Omega 6 fatty acids have a double bond on the 6th
carbon from the end
Why are they called “omega-3”?
Note: the entire fatty acid is not shown.
What about ALA, EPA and DHA?
 ALA is the plant form of omega-3, made in the
chloroplasts of green plants such as grass and kale
 Animals convert ALA into EPA and DHA which are
found in fish and grass-fed animal products
 Once converted, EPA and DHA play functional roles in
the body as previously discussed
 EPA is the precursor to the omega-3 derived
eicosanoids
ALA, DHA and EPA
Plant
sources
such as: flax
seed and
green leafy
vegetables
Inefficient
conversion in
humans
Marine sources
Eicosanoid
production,
attenuates
inflammation
Marine sources
Component of cell
membranes, gray
matter of brain,
sperm, role in
vision, etc.
Best food sources of EPA and DHA
 BEST FISH SOURCES: salmon,
mackerel, sardines, bluefish, tuna
 GOOD FISH SOURCES: herring,
anchovy, pilchard, butterfish,
rainbow trout
 Range-fed meats, eggs and dairy
(vs. grain fed)
 Wild fish are higher in Omega-3’s
and lower in Omega-6’s
compared to farm-raised fish
(some studies show omega 3
content about 1.5 X greater in
wild fish)
Omega-3’s: Wild vs. cultured fish
Best sources of Omega-3’s: ALA
 Ground flax seed, chia seed,
hemp seed, pumpkin seed, dark
green leafy vegetables such as
kale, collard greens and swiss
chard, spirulina.
 Advantage: fewer contaminants
 Disadvantage: less efficient
conversion to EPA and DHA
Omega-6 fatty acids
 Like Omega-3’s, absolutely essential in the diet for
physiological functioning
 Like Omega-3’s, polyunsaturated (multiple double bonds)
 Also a component of cell membranes
 Also a precursor to eicosanoids
 Found ubiquitously in the American diet in the form of
vegetable oils, also found in virtually all nuts and seeds
Comparison of oils
NOTE: Every fat or oil contains some of each kind of fat. Olive oil is not pure
monounsaturated fat. Butter is not pure saturated fat. Flax is not pure n-3 fat.
Why does the ratio of n-6/n-3 matter?
 Linoleic and arachidonic acid (n-6) are converted into
eicosanoids that promote inflammation by gearing up
the immune system
 NSAIDS (Aspirin and Ibuprofen) suppress these
eicosanoids
 Too much omega-6 compared to omega-3 causes
inflammatory eicosanoids to predominate
 Cell membranes reflect dietary intake. Too much n-6
and too little n-3 leads to rigid, inflexible membranes.
What should the n-6/n-3 ratio be?
 Highly speculative
 Hunter-gatherer estimates: between 3:1 to 1:1
 Some recent research suggests 4:1 may be an effective ratio
for promoting health
 4:1  prevention of cardiovascular disease
 2-3:1  suppressed inflammation in rheumatoid arthritis
 5:1  beneficial effect on asthma
What is the n-6/n-3 ratio in the US?
Population
n-6/n-3 Ratio
Paleolithic
0.79:1
Greece prior to 1960
1.00-2.00:1
Japan
4.00:1
Rural India
5-6.1:1
United Kingdom and
northern Europe
15.00:1
United States
16.74:1
Urban India
38-50:1
Source: Simopoulos AP. The importance of the ratio of omega-6/omega-3 essential
fatty acids. Biomed Pharmacother. 2008;56(8):365-79.
Why is the American ratio so high?
 Ubiquitous use of vegetable oil (cottonseed oil,
soybean oil, corn oil, sunflower oil) in processed
foods
 Grain-fed animal products contain significant amounts
of arachidonic acid (an omega-6)
 Low intakes of fish, leafy green vegetables and grassfed animal products
 Production-driven agricultural practices
What are some limitations of the
n-6/n-3 ratio?
 Unclear what the optimal ratio should be
 Difficult to measure in an individual (food labeling
does not specify, oils contain some of each and the
ratios vary)
 Critics contend that the ratio is of little use and has
not been conclusively shown to correlate with
inflammatory markers
 May encourage people to avoid healthful foods that
contain omega-6
Omega-6 fats are not bad
 Have been shown to lower LDL
cholesterol (the “bad
cholesterol”)
 Linoleic acid converts to gammalinoleic acid (GLA) before it
converts to arachidonic acid and
GLA is a precursor to a class of
eicosanoids which are antiinflammatory
 Not black and white
The bottom line
 American diet is out of balance (n-6 to n-3) which may shift
the body towards a state of inflammation
 Increase intake of fatty fish (DHA and EPA) and plant
sources of omega-3’s (ALA)
 Choose grass-fed, free range animal products when
possible
 Continue eating healthful whole food sources of omega-6
including whole nuts, seeds and avocado
 Decrease total omega-6 intake by minimizing processed
foods made with vegetable oils, including margarine and
fried restaurant food
Omega 3’s: How much is enough?
 No RDA for omega-3’s or omega-6’s
 AHA: eat fatty fish 3.5 oz 2x/week OR up to 3g/day in
supplements
 WHO: 0.3-0.5g/day
 European Food Safety Authority: 2-4g/day to lower
triglycerides, 3g/day to lower BP
 Estimated US intake: 0.1-0.2g/day (2011) vs. Japan (2g/day)
 Anyone taking anticoagulants or with a vitamin K deficiency
should exercise caution
Choosing a supplement
In summary
 Omega-3’s have many health benefits
 Best sources are fatty fish, grass fed animal products,
ground flax seeds and leafy greens
 Too many n-6’s compared to n-3’s may tilt the body towards
a state of inflammation
 Increase low-mercury fatty fish in the diet for n-3’s and
choose grass-fed animal products
 Choose whole food sources of n-6’s like nuts and seeds
instead of vegetable oils
 Consider an omega-3 supplement
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