Evolutionary Aspects of Diet: The Omega-6/Omega-3 Ratio and the Brain Molecular Neurobiology

Artemis P. Simopoulos
This article has 116 references
LA = linoleic acid (plant derived omega-6 fatty acid)
ALA = alpha linolenic acid (plant derived omega-3 fatty acid

From Abstract

 

:dropcap_open:S:dropcap_close:everal sources of information suggest that human beings evolved on a diet that had a ratio of omega-6 to omega-3 fatty acids (FA) of about 1/1. Today, Western diets have a ratio of 10/1 to 20–25/1, indicating that Western diets are deficient in omega-3 FA compared with the diet on which humans evolved and their genetic patterns were established. Docosahexaenoic acid (DHA) is essential for the normal functional development of the brain and retina, particularly in premature infants. DHA accounts for 40% of the membrane phospholipid FA in the brain. The balance of omega-6 and omega-3 FA is important for homeostasis and normal development throughout the life cycle.

 

1. Nutrition is an environmental factor that influences gene expression.
2. Major changes have taken place in our diet over the past 10,000 years since the beginning of the Agricultural Revolution, but our genes have not changed. 
3. “Our genes today are very similar to the genes of our ancestors during the Paleolithic period 40,000 years ago, at which time our genetic profile was established.”
4. “Humans today live in a nutritional environment that differs from that for which our genetic constitution was selected.”
5. “The increase in trans-fatty acids is detrimental to health.”
6. “The beneficial health effects of omega-3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were described first in the Greenland Eskimos who consumed a high seafood diet and had low rates of coronary heart disease, asthma, type 1 diabetes mellitus, and multiple sclerosis. Since that observation, the beneficial health effects of omega-3 fatty acids have been extended to include benefits related to cancer, inflammatory bowel disease, rheumatoid arthritis, psoriasis, and mental health.”
7. The change of omega-6/omega-3 ratio in the food supply of Western societies has occurred over the last 150 years. 
8. “During evolution, omega-3 fatty acids were found in all foods consumed: meat, wild plants, eggs, fish, nuts, and berries.”
9. Today in Western societies the omega-6/omega-3 ratio is very high due to the high intake of soybean oil, corn oil, sunflower, safflower, and linseed oil. 
10. The conversion of ALA to EPA and DHA “appears to be limited and variable.” 
11. The omega-6/omega-3 ratio is associated with normal “growth and development, as well as in the outcome of hypertension, cancer, arthritis, mental health, allergies and other autoimmune diseases,” as well as the “pathophysiology of atherosclerosis, inflammation, and aging.”
12.  “DHA is found in high amounts in the membranes of the brain and retina and is critical for proper neurogenesis, neurotransmitter metabolism, neuroprotection and vision. The consumption of high amounts of DHA has been associated with multiple health benefits including brain and retinal development, aging, memory formation, synaptic membrane function, photoreceptor biogenesis and function, and neuroprotection. DHA is essential for pre-natal brain development.”
13. Omega-3s cause apoptotic death in cancer cells whereas omega-6s allow cancer cells to continue to proliferate.
14. Psychologic stress in humans causes an overproduction of proinflammatory cytokines, which are minimized with adequate levels of omega-3s.
15. Diets with a high omega-6/omega-3 ratio may enhance the risk for both depression and inflammatory diseases.
16.  “LA more than any other nutrient is associated with shorter telomeres and shorter telomeres are associated with aging, cancer and coronary heart disease.”
17.  Cognitive performance improves with omega-3s.
18.  “Positive effects of omega-3s on dementia, schizophrenia, and other central nervous system diseases have been reported.”
19.  Omega-3s can affect not only cognitive functions, but also mood and emotional states and may act as a mood stabilizer. Omega-3s have beneficial effects in some neurological diseases in addition to the chronic fatigue syndrome.
20.  Omega-3 deficiency in childhood delays brain development and produces irreversible effects, while the same deficiency in aging accelerates the deterioration of brain function.
21.  Omega-3 intake from ALA does not provide adequate intakes of EPA and DHA. 
22.  Daily administration of 3 g of omega-3s for 3 months significantly decreased feelings of anger, anxiety and aggression.
23.  “Western diets are characterized by high omega-6 and low omega-3 fatty acid intake, whereas during the Paleolithic period when human’s genetic profile was established, there was a balance between omega-6 and omega-3 fatty acids. Therefore, humans today live in a nutritional environment that differs from that for which our genetic constitution was selected.”
24.  “The balance of omega-6/omega-3 fatty acids is an important determinant in maintaining homeostasis, normal development, and mental health throughout the life cycle.”
25.  “A low AA/EPA ratio has been proposed as an index of the beneficial effects of omega-3s which have been shown in animal and clinical experiments.”
26.  Omega-3 deficiency in the brain is associated with “decreased learning ability, with a lower synaptic vesicle density in the hippocampus; whereas, chronic administration of omega-3s improves reference memory-related learning probably due to increased neuroplasticity of the neural membranes.”
27.  Omega-3 fatty acids have positive effects in patients with dementia, schizophrenia, depression and other central nervous systems diseases.
28.  Omega-3 fatty acid supplementation could play a role in [reduced] hostility and violence.
29.  “In humans, the brain is the most outstanding organ in biological development: it follows that the priority is brain growth and development, and in the brain the balance between omega-6 and omega-3 PUFA metabolites is close to 1:1. This ratio should be the target for human nutrition.”
30. “In Western diets, the omega-6/omega-3 ratio has increased to between 10:1 and 20:1. This high omega-6 proportion is largely made up by LA, is far from optimal and is highly inappropriate for normal growth and development.” 
31.  “The ratio of omega-6/omega-3 fatty acids in the brain between 1:1 and 2:1 is in agreement with the data from the evolutionary aspects of diet and genetics.” 
32.  “A ratio of 1:1 to 2:1 omega-6/omega-3 fatty acids should be the target ratio for health.”