Polyunsaturated fats in food

Where are the polyunsaturated fats?

The polyunsaturated fatty acids ω-3 are the oldest, as they are typical of the aquatic kingdom; as such they are widely represented in algae, marine organisms and the fish that feed on them. Other sources are somewhat widespread: significant concentrations are found in flax seeds and their oil, in hemp and to a lesser extent in canola and soy oils. The nutritional importance of ω-3 polyunsaturated fatty acids is such that today some foods, such as milk and eggs, are fortified with them directly or indirectly (for example by increasing the content of ω-3 in the feed or selecting the cultivars richer).

The precursor of the omega three, alpha-linolenic acid, cannot be synthesized by the body and as such must necessarily be introduced with the diet. Once ingested, the body can transform it into their respective semi-essential fatty acids.

The polyunsaturated fatty acids ω-6 are widespread throughout the vegetable kingdom and are abundant in sunflower oil, in that of peanuts, grape seeds and corn. Despite being an essential nutrient, linoleic acid - the forerunner of ω-6 - is generally consumed in more than sufficient or even excessive amounts.

Presence of essential fatty acids (EFA) and semi-essential acids in foods
Omega series 6	Food
Cis linoleic acid (LA) * Gamma-linolenic acid (GLA) Domo-gamma-linolenic acid (DGLA) Arachidonic acid (AA)	Olive and seed oil Blackcurrant oil, borage oil, evening primrose oil Breast milk Dairy products, meat, human milk, shellfish
Omega 3 Series	Food
Alpha-linolenic acid (ALA or LNA) * Eicosapentenoic acid (EPA) Docosahexaenoic acid (DHA)	Linseed, hemp, soy and canola oil Fish oil, herring, salmon, whale Fish oil, some algae
(*) The fatty acids marked with an asterisk are essential, the others are semi-essential

In polyunsaturated fatty acids the double bonds are not adjacent, but separated by a methylene group (-CH2-).

A special case is given by some polyunsaturated fatty acids with conjugated double bonds, such as the so-called CLA (conjugated linoleic acid). Present in meat and dairy products obtained from ruminants, conjugated linoleic acid has a pair of double bonds separated from a single methylene group (simple bond), hence the adjective "conjugated". Slimming, antioxidant and antitumor properties have been ascribed to this nutrient, but the usefulness of supplementation has been reduced by the possible negative implications that emerged in some studies.

Essential fatty acids in food

FOOD (100 g)	ω-3				ω-6	ω-6: ω-3
	DHA (g)	EPA (g)	LNA (g) *	totals (g)	totals (g)	-
Salmon oil	18.232	13, 023	1, 061	35.311	1, 543	0.04: 1
Liver oil of cod	10, 968	6, 898	0, 935	19.736	0, 935	0.05: 1
Sardine oil	10.656	10, 137	1, 327	24.093	2, 014	0.08: 1
Caviar	3, 801	2, 741	0, 017	6, 789	0.081	0.01: 1
Mackerel	1, 401	0, 898	0	2, 670	0.219	0.08: 1
Coho salmon (wild)	0.656	0, 429	0, 157	1, 474	0.206	0.14: 1
Coho salmon (breeding)	0.821	0, 385	0.075	1, 281	0.349	0.27: 1
Anchovy or alice	0, 911	0.538	0	1, 478	0, 097	0.07: 1
Tuna	0, 890	0.283	0	1, 298	0.053	0.04: 1
Herring	0.862	0.709	0, 103	1, 729	0, 130	0.08: 1
Flax seed	0	0	22.813	22.813	5, 911	0.26: 1
Linseed oil	0	0	53.304	53.304	12, 701	0.24: 1
Walnut oil	0	0	10, 400	10, 040	52.890	5.27: 1
Dried walnuts	0	0	8, 718	8, 718	33.717	3.87: 1
Dried almonds	0	0	0	0	12.648	-
peanuts	0	0	0, 170	0, 170	10.535	61.97: 1
Dry salted pistachios	0	0	0, 263	0, 263	13.636	51.85: 1
Soy lecithin	0	0	5, 135	5, 135	40.178	7.82: 1
Olive oil	0	0	0761	0.761	9, 763	12.83: 1
* LNA = undifferentiated alpha-linolenic acid