Omega-3 fatty acids are a class of polyunsaturated fatty acids that have been shown to have a wide range of biological functions.
The three most nutritionally important omega-3 fatty acids are:
- alpha-linolenic acid (ALA)
- eicosapentaenoic acid (EPA)
- docosahexaenoic acid (DHA)
These fatty acids are not synthesized by the human body and must be obtained through diet or nutritional supplementation. Dietary sources of ALA include flaxseeds, walnuts, soybeans and certain green leafy vegetables. DHA and EPA are breakdown products of ALA. However, these fats can also be derived from cold-water fish including salmon, tuna, halibut and herring as well as from certain types of algae.
Importance of EPA and prostaglandins:
Once ingested, the omega-3 fatty acid, EPA, is metabolized into hormone-like compounds called prostaglandins. Prostaglandins help regulate numerous physiological functions including blood pressure, blood clotting, neuro-transmission and the inflammatory and allergic response. While certain prostaglandins are thought to be beneficial by reducing inflammation and improving blood flow, others have been shown to enhance the inflammatory process, causing constriction of the blood vessels and promoting blood clotting. Prostaglandins derived from EPA have been shown to belong to the latter class thereby protecting individuals against heart attacks, strokes as well as certain inflammatory conditions.
While DHA is not involved in prostaglandin formation, it has been shown to be the major polyunsaturated fatty acid found in the cell membrane of neurons and is believed to be critical for brain development and function.
A growing body of scientific research indicates that omega-3 fatty acids play an important role by promoting cardiovascular health, improving cognitive function and ameliorating inflammatory conditions such as rheumatoid arthritis. In addition, research also supports a role for omega-3 fatty acids in the prevention of certain types of cancer and diabetes.
Omega-3 fatty acids in cardiovascular health and disease
Cardiovascular diseases (CVD) are a class of diseases that affect the heart or blood vessels. Today, they remain the biggest cause of deaths worldwide. Epidemiological studies dating back to the late 1970s noted relatively low cardiovascular mortality in populations such as Eskimos with high fish consumption.
These results could, at least in part, be explained by the relatively high amounts of DHA and EPA contained in fish. Since these initial reports, numerous observational and clinical trials have been conducted to assess the potential benefits of increased omega-3 intake on cardiovascular health. These studies found that fish oil supplementation had a substantial and beneficial effect on cardiovascular fitness by reducing the levels of markers of CVD, such as triglycerides, significantly reducing the risk of all death and protecting against arrhythmia of the heart.
Omega-3 fatty acids in cognitive function and neurological disease
The omega-3 fatty acid, DHA, is a major component of the cell membranes of neurons and is thought to play an important role in the control of neurotransmitter release. Young animals given a diet deficient in omega-3 demonstrated signs of impaired brain development and poor visual acuity, suggesting that omega-3 fatty acids may be crucial for normal brain development and function. Similarly, another study found that maternal fish consumption during the entire course of pregnancy was associated with a lower risk of cerebral palsy, a debilitating neurological condition, in the offspring.
In addition to playing an important role in neuronal development, clinical studies suggest that omega-3 intake may also improve cognitive impairment in later life. For instance, fish intake was strongly associated with a significant reduction in the incidence of Alzheimer’s disease. Another large multi-country study demonstrated a significant correlation between omega-3 fatty acid consumption and depression. Taken together, these data suggest that increased omega-3 fatty acid intake may not only improve brain development in young children but may also protect against cognitive impairment in later life.
Omega-3 fatty acids in inflammatory conditions
Numerous chronic diseases are the result of an excessive inflammatory response resulting in significant tissue damage over time. There is now growing evidence from animal and human studies that omega-3 fatty acids have immunomodulatory properties and could be beneficial in treating such inflammatory conditions. In patients suffering from rheumatoid arthritis (a chronic inflammatory condition of the joints), significant improvement in joint pain, morning stiffness, fatigue and decreased use of pain medication was noted in participants taking EPA and DHA. A similar beneficial effect of omega-3 fatty acids was observed in patients with cystic fibrosis.
Omega-3 fatty acids in skin conditions
Polyunsaturated fatty acids (PUFA) including ALA are important components of the cell membrane of skin cells contributing to their permeability, plasticity and function. Based on the structural and functional requirement of PUFAs, they are thought to affect the properties of skin that are essential for good cutaneous health. One study found that intake of flaxseed oil over a period of 12 weeks significantly enhanced not only skin hydration but also reduced scaling and roughness. Other studies found that deficiency of these essential lipids was involved in cutaneous disorders including psoriasis and atopic dermatitis.