Polyunsaturated fats are fats in which hydrocarbon chain as a constituent acquire two or more carbon–carbon double bonds. Polyunsaturated fatty acids become liquid at room temperature. It is oxidized easily in foods as well as body. These are involved in cholesterol metabolism which is a component of phospholipids in cell membranes and also a precursor of biologically active compounds such as interleukins, prostaglandins and thromboxanes. It has a crucial role in blood clotting, immune response and inflammation. PUFA are obtained from the essential fatty acids linoleic acid (n6 or ω6) and A-linoleic acid (n3 or ω3) and are six divided into omega 3 (ω3) or omega 6 (ω6) groups of PUFA. Essential fatty acids (EFA), docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) are required in neural development of fetus as well as infant. PUFA occur as trans or cis forms which depends on the way hydrogen atoms are arranged. In trans form, hydrogen atoms are on opposite side. In cis formation, hydrogen atoms are boned to either end of double bond on same side.
The n-3 fatty acids include linolenic acid (C18:3,n-3), docosahexanoic acid (DHA) (C22:6,n-3), and eicosapentanoic acid (EPA) (C20:5,n-3). Linolenic acid is high in linseed oil and found in smaller amounts in other vegetable oils. DHA and EPA are enriched in fish oils. For years, linoleic acid was considered to be a unique LDL cholesterol-lowering fatty acid. Recent investigations suggest that earlier findings have overestimated LDL-lowering potential of linoleic acid. Substitute of linoleic acid for oleic acid in diet may lower LDL cholesterol levels in some people. At high intakes, linoleic acid also reduces serum HDL cholesterol concentrations. Moreover, in comparison with oleic acid, it may lower VLDL cholesterol levels in some people. Earlier interest for high intakes of linoleic acid to reduce LDL cholesterol levels has been dampened for several reasons: for example, its LDL-lowering ability does not offset potential disadvantages of HDL lowering, and other concerns include possible untoward side effects such as promoting oxidation of LDL and suppressing cellular immunity to cancer.
The n-3 fatty acids in fish oils (DHA and EPA) are effective in lowering serum VLDL levels. This action results from suppression of the secretion of VLDL by the liver. The exact mechanism for this action is still not known. However, these fatty acids do not reduce LDL cholesterol concentrations relative to oleic acid. They have been used for treatment of some patients with elevated VLDL concentrations, although drug treatment generally is employed when it is necessary to lower serum VLDL levels.
Dietary Sources of Polyunsaturated Fat
|Polyunsaturated Fat (g)
Health Benefits of Polyunsaturated Fat
Let’s take a closer look on the benefits offered by Polyunsaturated fat:
- Cardiovascular health
Polyunsaturated fatty acids affect various physiological processes. Most attention has been given to n-3 PUFAs and its role in preventing and treating cardiovascular problems. Investigations have focused on elucidating pathways and mechanisms for biological activities of n-3 PUFAs. In general, dietary intervention is identified as a key measure in patient therapy and maintaining human health. The review provides summary of various essential clinical trials and exact modes of action of n-3 PUFA are not known.
Evidence has shown that PUFAs urges beneficial cardiovascular effects. An interesting aspect which is concerned for this beneficial action is that it is not achieved through one mechanism of action but is achieved by various effects on heart, blood and vasculature. It makes PUFAs more beneficial as therapeutic modality. Despite of getting information, investigation is still required about health associated benefits of PUFAs.
- Mental health
Omega-3 fatty acids are required for brain function as well as its development. Study in older adults shows link of low blood levels of DHA with mental decline. Likewise, consumption of fish which is rich in DHA helps to prevent mental decline and associated illnesses. Five year study in 200 older men shows that intake of fish was related with less mental decline. Other study in more than 5000 people shows that high consumption of fish resulted 60% low chances of dementia and 70% low chances of Alzheimer’s disease on an average of two years. Dementia is the loss of brain function impairing the ability of the person to think, remember and reason. In older adults, Alzheimer’s disease is regarded as the most common cause of dementia. Several analyses shows that omega-3 fish oil supplements affect brain function in healthy older adults. Research shows that omega-3s promote memory function in older adults.
- Development of infants
Those who consume 8 to 12 ounces of fatty fish per week during pregnancy and breastfeeding have healthier children. A study conducted on children of mothers who consume fish more than twice per week have high language and visual motor skills tests. Other studies conducted on children of mothers who consume 12 ounces of fish per week have lower issues with fine motor, behavioral and communication skills. Pregnant women should avoid fish with high levels of mercury such as marlin, swordfish, orange roughy, king mackerel, tuna and shark.
The body requires fat for production of energy and also other functions. Polyunsaturated fats are considered to be the healthiest choice. Dietary guidelines for Americans recommend consuming not more than 10% of total daily calories from saturated food available in butter, red meat, whole fat dairy products & cheese and trans fats found in processed foods. The intake of total fat should not be more than 25%-30% of daily calories including monounsaturated and polyunsaturated fats. Consumption of too much fat results weight gain.
Health Risks of Overconsumption
- Promote inflammation
Omega-6 and Omega-3 polyunsaturated fatty acids have vital role in inflammation. Generally, omega-3s are anti-inflammatory while omega-6s are pro-inflammatory. Too many consumption of omega-6s and omega-3s helps to enhance inflammation and contribute poor health. Diet high in omega-6-to-omega-3 ratio is related with various inflammatory conditions such as heart disease.
Calories obtained from polyunsaturated fats could add up quickly. One have to be careful, it might exceed calories. If one is intending to eat more polyunsaturated rich foods, it is recommended to eliminate other calories.