Omega-3 fatty acids

Omega-3 fatty acids

Omega-3 fatty acids (also called ω−3 fatty acids or n−3 fatty acids) are fats commonly found in marine and plant oils. They are polyunsaturated fatty acids with a double bond (C=C) starting after the third carbon atom from the end of the carbon chain. The fatty acids have two ends—the acid (-COOH) end and the methyl (-CH3) end. The location of the first double bond is counted from the methyl end, which is also known as the omega (ω) end or the n end.

Common sources of omega–3 fatty acids include fish oils, algal oil, squid oils, and some plant oils such as Sacha Inchi oil, echium oil, flaxseed oil and hemp oil.

Cancer

The evidence linking the consumption of fish to the risk of cancer is poor Supplementation with omega-3 fatty acids does not appear to affect this risk either.

A 2006 report in the Journal of the American Medical Association, in their review of literature covering cohorts from many countries with a wide variety of demographics, concluded that there was no link between omega−3 fatty acids and cancer.

Cardiovascular disease

Omega-3 fatty acids also have mild antihypertensive effects. When subjects consumed omega-3 fatty acids from oily fish on a regular basis, their systolic blood pressure was lowered by about 3.5–5.5 mmHg. The 18 carbon α-linolenic acid (ALA) has not been shown to have the same cardiovascular benefits that DHA or EPA may have. 

Omega-3 fatty acids in algal oil, fish oil, fish and seafood have been shown to lower the risk of heart attacks.

Inflammation

Although not confirmed as an approved health claim, current research suggests that the anti-inflammatory activity of long-chain omega−3 fatty acids may translate into clinical effects. For example, there is evidence that rheumatoid arthritis sufferers taking long-chain omega−3 fatty acids from sources such as fish have reduced pain compared to those receiving standard NSAIDs. Some potential benefits have been reported in conditions such as rheumatoid arthritis.

Developmental disorders

Although not supported by current scientific evidence as a primary treatment for ADHD, autism spectrum disorders, and other developmental differences, omega-3 fatty acids have gained popularity for children with these conditions. 

Omega-3 fatty acids offer a promising complementary approach to standard treatments for ADHD and developmental coordination disorder. Fish oils appear to reduce ADHD-related symptoms in some children. Double blind studies have shown "medium to strong treatment effects of omega 3 fatty acids on symptoms of ADHD".

Psychiatric disorders

Though there is some evidence that omega-3 fatty acids are related to a variety of mental disorders. They may tentatively be useful as an add-on for the treatment of depression associated with bipolar disorder and there is preliminary evidence that EPA supplementation are helpful in cases of depression. There however is a significant risk of bias in the literature.

 

Cognitive aging

Epidemiological studies suggest that consumption of omega-3 fatty acids can reduce the risk of dementia, but evidence of a treatment effect in dementia patients is inconclusive. However, clinical evidence suggests benefits of treatment specifically in patients who show signs of cognitive decline but who are not sufficiently impaired to meet criteria for dementia.

 

List of omega−3 fatty acids

This table lists several different names for the most common omega−3 fatty acids found in nature.

Common name	Lipid name	Chemical name
Hexadecatrienoic acid (HTA)	16:3 (n−3)	all-cis-7,10,13-hexadecatrienoic acid
α-Linolenic acid (ALA)	18:3 (n−3)	all-cis-9,12,15-octadecatrienoic acid
Stearidonic acid (SDA)	18:4 (n−3)	all-cis-6,9,12,15-octadecatetraenoic acid
Eicosatrienoic acid (ETE)	20:3 (n−3)	all-cis-11,14,17-eicosatrienoic acid
Eicosatetraenoic acid (ETA)	20:4 (n−3)	all-cis-8,11,14,17-eicosatetraenoic acid
Eicosapentaenoic acid (EPA)	20:5 (n−3)	all-cis-5,8,11,14,17-eicosapentaenoic acid
Heneicosapentaenoic acid (HPA)	21:5 (n−3)	all-cis-6,9,12,15,18-heneicosapentaenoic acid
Docosapentaenoic acid (DPA), Clupanodonic acid	22:5 (n−3)	all-cis-7,10,13,16,19-docosapentaenoic acid
Docosahexaenoic acid (DHA)	22:6 (n−3)	all-cis-4,7,10,13,16,19-docosahexaenoic acid
Tetracosapentaenoic acid	24:5 (n−3)	all-cis-9,12,15,18,21-tetracosapentaenoic acid
Tetracosahexaenoic acid (Nisinic acid)	24:6 (n−3)	all-cis-6,9,12,15,18,21-tetracosahexaenoic acid

The omega−6 to omega−3 ratio (Most Important)

Some clinical studies indicate that the ingested ratio of omega−6 to omega−3 (especially linoleic vs alpha-linolenic) fatty acids is important to maintaining cardiovascular health. However, two studies published in 2005 and 2007 found that while omega−3 polyunsaturated fatty acids are extremely beneficial in preventing heart disease in humans, the levels of omega−6 polyunsaturated fatty acids (and therefore the ratios) were insignificant. 

Both omega−6 and omega−3 fatty acids are essential; i.e., humans must consume them in the diets. Omega−6 and omega−3 eighteen-carbon polyunsaturated fatty acids compete for the same metabolic enzymes, thus the omega−6:omega−3 ratio of ingested fatty acids has significant influence on the ratio and rate of production of eicosanoids, a group of hormones intimately involved in the body's inflammatory and homeostatic processes which includes the prostaglandins, leukotrienes, and thromboxanes, among others.

This necessitates that omega−6 and omega−3 be consumed in a balanced proportion; healthy ratios of omega−6:omega−3, according to some authors, range from 1:1 to 1:4 (an individual needs more omega−3 than omega−6). Other authors believe that ratio 4:1 (when the amount of omega-6 is only 4 times greater than that of omega-3) is already healthy. Studies suggest the evolutionary human diet, rich in game animals, seafood, and other sources of omega−3, may have provided such a ratio.

Daily values

As macronutrients, fats are not assigned Dietary Reference Intakes. Macronutrients have acceptable intake (AI) levels and acceptable macronutrient distribution ranges (AMDRs) instead of RDAs. The AI for omega−3 is 1.6 grams/day for men and 1.1 grams/day for women, while the AMDR is 0.6% to 1.2% of total energy.

Grams of omega−3 per 3oz (85g) serving
Common name	grams omega−3
Herring, sardines	1.3–2
Mackerel: Spanish/Atlantic/Pacific	1.1–1.7
Salmon	1.1–1.9
Halibut	0.60–1.12
Tuna	0.21–1.1
Swordfish	0.97
Greenshell/lipped mussels	0.95
Tilefish	0.9
Tuna (canned, light)	0.17–0.24
Pollock	0.45
Cod	0.15–0.24
Catfish	0.22–0.3
Flounder	0.48
Grouper	0.23
Mahi mahi	0.13
Orange roughy	0.028
Red snapper	0.29
Shark	0.83
King mackerel	0.36
Hoki (blue grenadier)	0.41
Gemfish	0.40
Blue eye cod	0.31
Sydney rock oysters	0.30
Tuna, canned	0.23
Snapper	0.22
Eggs, large regular	0.109
Barramundi, saltwater	0.100
Giant tiger prawn	0.100
Lean red meat	0.031
Turkey	0.030
Cereals, rice, pasta, etc.	0.00
Fruit	0.00
Milk regular	0.00
Regular bread	0.00
Vegetables	0.00