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PUFA (polyunsaturated fatty acids)
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Polyunsaturated fats (PUFAs) are fatty acids with many double carbon bonds (double bonds link four electrons, versus the usual two). PUFAs contain double bonds because they lack several hydrogen atoms. This is why they are referred to as “unsaturated.” Remember from the last chapter that saturated fatty acids have only single bonds and are fully “saturated” with hydrogen atoms. Double bonds, although stronger, are more reactive to oxygen than single bonds, making them unstable and susceptible to oxidative stress.
Polyunsaturated fatty acids (PUFAs) are fatty acids with many double carbon bonds, resulting from a lack of hydrogen atoms. This characteristic makes them unstable and susceptible to oxidative stress, as oxygen reacts with them to create free radicals .
The immunosuppressive effects of PUFAs are widespread, increasing metabolites that harm the immune system, such as histamine, serotonin, lactate, and nitric oxide . These substances are also involved in tumor development. PUFAs have direct effects on tissues, acting as signals or interfering with signals, and can influence cellular excitability thresholds, potentially leading to anxiety, panic, seizures, senility, and excitotoxicity .
Saturated fatty acids, on the other hand, terminate stress reactions, whereas PUFAs amplify them . The most highly unsaturated fats, including DHA, accumulate with aging and are associated with Alzheimer's disease. Omega-3 fats found in fish oil break down into chemicals that block glucose and oxygen use, and promote metastasis in cancer .
PUFAs are detoxified by attaching glucuronic acid, making them water-soluble and excretable in the urine . However, the fat cells preferentially oxidize saturated fatty acids, leading to an accumulation of unsaturated fats with age. PUFAs are more water-soluble and easier to release from adipose tissue than saturated fats .
The promotion of PUFAs as essential nutrients has led to a reversal of the old theory, where the inhibition of enzymes is taken as evidence of toxicity, but the activity of intrinsic enzymes is taken as evidence of harm . The Mead acid, which has anti-inflammatory effects, is associated with many biological advantages, but research has been misinterpreted to suggest that its presence in tissues is evidence of damage from the absence of PUFAs.
A study in the 1960s tested the "heart protective diet" based on PUFAs on a group of 846 veterans, but found no difference in fatal heart attacks between the control group and the group consuming corn oil . However, there were seven deaths from cancer in the experimental group.
The marketing of PUFAs has undergone several phases, from linoleic acid being "heart protective" to the longer chain omega-3 fatty acids, DHA and EPA, being touted as even better . The highly unsaturated arachidonic acid, which is made from linoleic acid in foods, was initially identified as a "harmful animal fat," but its amount in tissues depends on the amount of linoleic acid in the diet.
The industry has defended the use of added PUFAs by arguing that human milk contains more PUFAs than cow milk, leading to a separate industry promoting supplements of omega-3 fatty acids for babies .
People also ask
- What causes polyunsaturated fatty acids to be unstable and susceptible to oxidative stress?The lack of hydrogen atoms in PUFAs results in many double carbon bonds, making them unstable and susceptible to oxidative stress.
- How do polyunsaturated fatty acids affect the immune system and tumor development?PUFAs increase metabolites that harm the immune system, such as histamine, serotonin, lactate, and nitric oxide, and are involved in tumor development.
- Do polyunsaturated fatty acids have any benefits, or are they entirely detrimental to health?The Mead acid, a type of PUFA, has anti-inflammatory effects and is associated with many biological advantages, suggesting that PUFAs may not be entirely detrimental to health.