Polyunsaturated Fat — Healthy or Harmful?
Not only that, but medical researchers began recommending the consumption of vegetable oils to obtain large amounts of polyunsaturated fatty acids (PUFA), because these fatty acids reduce cholesterol levels. More recently, to counteract the negative effects of omega-6 PUFA from vegetable oils, many are recommending consuming high amounts of omega-3 PUFA from fish oils. But the need for PUFA is incredibly small and both omega-6 and omega-3 PUFA can contribute to degenerative disease by increasing exposure to "oxidative stress."
How Essential Are the Essential Fatty Acids?
The PUFA Report Part 1: A Critical Review of the Requirement for Polyunsaturated Fatty Acids
By Chris Masterjohn.
Abstract
Current reviews and textbooks call the omega-6 linoleic acid and the omega-3 alpha-linolenic acid "essential fatty acids" (EFA) and cite the EFA requirement as one to four percent of calories. Research suggests, however, that the omega-6 arachidonic acid (AA) and the omega-3 docosahexaenoic acid (DHA) are the only fatty acids that are truly essential. Eicosapentaenoic acid (EPA) occurs in fish products but is probably not a normal constituent of the mammalian body and in excess it interferes with essential AA metabolism. The EFA requirement cited in the scientific literature is inflated by several factors: the use of diets composed mostly of sucrose, glucose, or corn syrup; the use of diets deficient in vitamin B6; the use of purified fatty acids instead of whole foods; the use of questionable biochemical markers rather than verifiable symptoms as an index for EFA deficiency; and the generalization from studies using young, growing animals to adults. The true requirement for EFA during growth and development is less than 0.5 percent of calories when supplied by most animal fats and less than 0.12 percent of calories when supplied by liver. On diets low in heated vegetable oils and sugar and rich in essential minerals, biotin, and vitamin B6, the requirement is likely to be much lower than this. Adults recovering from injury, suffering from degenerative diseases involving oxidative stress, or seeking to build muscle mass mass may have a similar requirement. For women who are seeking to conceive, pregnant, or lactating, the EFA requirement may be as high as one percent of calories. In other healthy adults, however, the requirement is infinitesimal if it exists at all. The best sources of EFAs are liver, butter, and egg yolks, especially from animals raised on pasture. During pregnancy, lactation, and childhood, small amounts of cod liver oil may be useful to provide extra DHA, but otherwise this supplement should be used only when needed to obtain fat-soluble vitamins. Vegetarians or others who eat a diet low in animal fat should consider symptoms such as scaly skin, hair loss or infertility to be signs of EFA deficiency and add B6 or animal fats to their diets. An excess of linoleate from vegetable oil will interfere with the production of DHA while an excess of EPA from fish oil will interfere with the production and utilization of AA. EFA are polyunsaturated fatty acids (PUFA) that contribute to oxidative stress. Vitamin E and other antioxidant nutrients cannot fully protect against oxidative stress induced by dietary PUFA. Therefore, the consumption of EFA should be kept as close to the minimum requirement as is practical while still maintaining an appetizing and nutritious diet.
Arachidonic Acid is Essential to Growth as Well as Healthy Hair and Skin
Moreover, cholesterol-rich foods are the main source of arachidonic acid (AA). While AA is often said to be inflammatory, it is actually the most critically essential fatty acid in the body. Healthy adults only need very little, if any, of it, but growing children, women who are looking to conceive or are pregnant or nursing, and people who are bodybuilding, suffering from degenerative diseases involving oxidative stress, or recovering from injury need to consume AA in the diet. Strict vegans and those who consume lots of omega-3 fats might also require AA in the diet. Signs of deficiency include scaly skin, hair loss, and infertility.
Egg Yolks Contain Essential Fatty Acids DHA and Arachidonic Acid
One important set of nutrients that should not be overlooked is the long-chain essential fatty acids. Egg yolks contain the long-chain omega-3 fatty acid DHA, which is necessary for the brain and proper retinal function in the eye, and the long-chain omega-6 fatty acid arachidonic acid, which is required for the healthy skin, hair, libido, reproduction, growth and response to injury. These fatty acids are primarily needed by young children, pregnant and lactating women, and people with degenerative diseases involving oxidative stress, especially those of the nervous system such as Alzheimer's. While fatty fish and cod liver oil supply DHA in larger amounts, egg yolks have an advantage over these foods because they also contain arachidonic acid and because they do not contain EPA, which interferes with arachidonic acid metabolism.
According to NutritionData.Com, one egg yolk contains 75 mg of arachidonic acid (AA), 20 mg of DHA, but no EPA. As I describe in my Special Report, How Essential Are the Essential Fatty Acids?, DHA and AA are the two fatty acids essential to humans and other mammals, while EPA interferes with the body's use of AA and probably does not belong in the mammalian body at all.
Animal foods from animals raised on pasture are likely much richer in DHA. In all eggs, both the DHA and AA are contained in the yolk.
Dus doe niet moeilijk en eet veel rauwe eigeel.
Dus voor de omega-3 pak je de fatty acid DHA die in eigeel zit, en voor de omega-6 pak je de fatty acid arachidonic acid AA die ook in eigeel zit! The omega-6 arachidonic acid (AA) and the omega-3 docosahexaenoic acid (DHA) are the only fatty acids that are truly essential.
http://www.cholesterol-and-health.com/Egg_Yolk.html
En nog iets over lever:
Liver is Rich in EFA — Arachidonic Acid and DHA
In my thoroughly researched and extensively referenced Special Report, How Essential Are the Essential Fatty Acids?, I concluded that the only fatty acids for which there is convincing evidence of essentiality to humans and other mammals are the polyunsaturated fatty acids arachidonic acid and DHA. Arachidonic acid is necessary for growth, proper hydration, healthy skin and hair, gut health, and fertility, while DHA is necessary for learning, intelligence, and visual acuity.
According to NutritionData.Com, liver appears to contain 141 mg of arachidonic acid per serving. Thus, it is an even richer source of this nutrient than egg yolks. High-vitamin cod liver oil (discussed further in the product recommendations section) contains between 70 and 360 mg of DHA. Liver from land animals does not appear to contain significant quantities of DHA, but it probably does when the animals are fed grass, which is higher in omega-3 fatty acids than grain.
As described in my Special Report, the need for these fatty acids is extremely low for healthy adults. The requirement increases during infancy and childhood, pregnancy and lactation, recovery from injury, and diseases involving oxidative stress. Bodybuilders and others interested in building new muscle tissue should probably make sure to get some of these fatty acids.
Cod liver oil and fish oils contain EPA, a fatty acid that is probably not essential to mammals and interferes with arachidonic acid. When the total intake of polyunsaturated fatty acids (PUFA) is low, the EPA should be efficiently converted to DHA. When total PUFA intake or EPA intake is very high, however, the EPA may interfere with arachidonic acid metabolism and contribute to deficiency symtoms such as growth retardation, dehydration, flaky and scaly skin, hair loss, gastrointestinal syndromes, or infertility. Moreover, all of the PUFA contribute to oxidative stress when consumed in high amounts, a phenomenon that contributes to heart disease, cancer, fatty liver, diabetes, brain disease, DNA damage, and ageing. Therefore, it makes sense to obtain these precious fatty acids in small amounts. This means avoiding vegetable oils and excessive supplementation with fish oils and obtaining essential fatty acids from liver, muscle meat, butter, occasional fatty fish and very small amounts of high-vitamin cod liver oil.
A recent review by Darisuh Mozaffarian of Brigham and Women's Hospital and Harvard Medical School, cited in Issue 14 of my free newsletter, concluded that the benefits from fish oils plateau at 250 mg of omega-3 fatty acids per day. This is based on studies of populations consuming far too much total PUFA and a great excess of omega-6 fatty acids, and it still only justifies the consumption of one or two servings of fatty fish per week or one-half teaspoon of high-vitamin cod liver oil per day.
Cod liver oil should thus only be consumed in amounts higher than this in order to obtain the fat-soluble vitamins, and one should only consume these higher amounts within the context of a diet rich in vitamin B6, magnesium, and other minerals, low in total PUFA, and balanced by reasonable quantities of liver, muscle meat, and butter to provide adequate arachidonic acid and prevent EPA-induced deficiency symptoms.