Linoleic acid (LA) is the only essential omega-6 fatty acid and must be obtained from the diet. From Linoleic acid, other omega-6s can be created using elongase and desaturase enzymes.
Linoleic acid contains 18 carbons, with 2 double bonds, the first of which is at the 6th carbon position (18:2n6).
Linoleic acid is found in nuts and vegetable oils (corn, soybean, canola, sunflower, etc.) as well as most meats. When the double bonds of LA are arranged differently, the term conjugated LA (CLA) is used. Although technically CLA can be termed a trans-fat, a natural type of CLA can be obtained in the dietary intake of meat and milk from ruminant animals.
There are many isomers of CLA – some beneficial and others are not as well defined. There is some controversy regarding how much LA is needed from the diet for adequacy. Although LA is needed to synthesize downstream fatty acids, it may lead to increased inflammatory fatty acid production. Several studies show that LA lowers blood cholesterol levels and improves all-cause mortality However, their current role in atherosclerosis and cardiometabolic disease are being revisited.
There is difficulty in differentiating the biological effects of LA from arachidonic acid in health and disease. In fact, it has been shown that
Linoleic acid is the most abundant fatty acid found in LDL and is one of the first fatty acids to oxidize. Studies are showing that LA promotes oxidative stress, oxidized LDL, and may be a major dietary cause of cardiovascular disease, especially when consumed via industrial vegetable oils.
Linoleic acid is by far the most abundant polyunsaturated fatty acid in most human tissues. Linoleic acid is an essential fatty acid, and low levels indicate dietary insufficiency, which can lead to a variety of symptoms, such as:
– Eczema-like skin eruptions
– Loss of hair
– Liver degradation
– Behavorial disturbances
– Kidney degeneration
– Increased thirst
– Frequent infections
– Poor wound healing
– Sterility
– Miscarriage
– Arthralgia (aching or pain in the joints without swelling)
– Cardiovascular disease
– Growth retardation
Some of these symptoms result from lack of Linoleic acid in membranes, where it plays a role in structural integrity. Most, however, are from failure to produce eicosanoids, which are cell regulators. Linoleic acid is the starting point for this pathway. Normal neonatal status of this fatty acid is marginal, if not insufficient. Since dietary sources (especially corn oil) are abundant, however, Linoleic acid may be found above normal. Excessive Linoleic acid can contribute to inflammation.
Supplementation with LA has been shown to increase body weight and essential fatty acid status in patients with cystic fibrosis.
References:
– Steinkamp G, Demmelmair H, Ruhl-Bagheri I, von der Hardt H, and Koletzko B. Energy Supplements Rich in Linoleic Acid Improve Body Weight and Essential Fatty Acid Status of Cystic Fibrosis Patients, J of Pediatr Gastroenterol Nutr, 31(4):418-423 (2000).
– https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5492028/
– https://www.ncbi.nlm.nih.gov/pubmed/26240151
– https://www.ncbi.nlm.nih.gov/pubmed/28752873
– https://www.ncbi.nlm.nih.gov/pubmed/22889633
Linoleic Acid (LA)
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