It was omega-3, that magical ingredient, that transformed us from the knuckle-dragging apes we were into the intelligent Homo sapiens we are today. Well, if you believe in the theory of evolution that is. Thousands of years ago in the cradle of man-kind, the enormous fresh water lakes of the great Rift Valley provided an important addition to our diet that was a turning point in history. Fish. This fuelled a sudden increase in relative brain size and a peak in intelligence.
Lubrication of the mind
Omega-3, found primarily in seafood sources, is just as important for our brains today. The long-chain omega-3 fatty acids, EPA and DHA, in particular are key in the efficient functioning of our neurons and are found in abundance in the brain. They allow our cell membranes, those dynamic structures that manage the majority of life processes, to be fluid and flexible.
Saturated fatty acids (which have no double bonds) are rigid and pack together tightly to form a solid membrane. Omega-3 fatty acids are poly-unsaturated, meaning they have more than one double bond in their carbon chain. DHA, which is highly unsaturated, has six. The double bonds effectively introduce 'kinks' into the chain so they are unable to pack together tightly, giving it a highly flexible structure.
The more fluid a membrane is, the more efficient it can function. Molecular messengers can glide easily through and neurotransmitters can leap-frog with less resistance from one synapse to another.
DHA itself can act as a signalling molecule. When liberated from the cell membrane it can travel down the anti-inflammatory pathway or be transformed into neuroprotectin D1. A molecule that does just that, protects neurons by switching off programmed cell death in conditions of severe stress.
EPA too has a second beneficial power under it's belt. It encourages blood circulation providing your brain with the nourishment it needs for optimal function.
Feeding a developing brain
During childhood brain development there is a great need for the omega-3 fatty acids. In the last trimester of pregnancy there is a sudden growth spurt where brain tissue dramatically swells in size and DHA is rapidly accrued. These essential nutrients are provided by a mothers placenta and after birth by her breast milk. Given the importance of DHA in early brain development it seems logical that a deficiency would effect the developing babies cognitive abilities. However, strong evidence is still a bit on the thin side in humans.
A review which collated evidence of prematurely born babies, found that DHA supplementation was beneficial for the first four months after birth but no momentous benefit was seen there after.
Another review, which took into account eight studies on full term babies, did not find a significant benefit on general development but there was a hint of possibility that supplemented babies were better able to process information.
Feeding a plastic brain
Over our lifetime our brains remain highly plastic organs. They are forever renewing cells, changing their structure and ultimately their function. The synapses between each neuron can turn-over as many as 350 times per year in mammals. A beautifully simple example of plasticity is a tiny worm called C. elegans. Admittedly not a mammal but still translatable to a degree. It's basic nervous system has a grand total of 302 cells. When there is a physical change in it's nervous system, a correlating behavioural change is often seen. This can be a change in learning, memory, recovery or maturation. And one factor, among a myriad of others, known to support changes in brain tissue plasticity (and therefore function) is diet.
Omega-3 fatty acids directly influence the structure and therefore the function of cell membranes in the brain.
Sharpen your mind
Cognitive decline in middle age can make you more vulnerable to dementia in later life. Dementia describes a set of symptoms that includes forgetfulness, confusion, difficulties with problem solving and with language. The cause of dementia can be attributed to a wide range of diseases and conditions including the most common form Alzheimer's (where abnormal protein build-up damages brain structure), vascular dementia (where narrowing arteries reduces oxygen supply to the brain) and frontotemporal dementia (where abnormal protein build-up damages neurons specific to the frontal and temporal lobes of the brain).
Evidence is accumulating to suggest that omega-3 deficiency may contribute to cognitive decline. Many studies have found a link between dementia and abnormally low DHA levels in the blood. Patients with Alzheimer's disease have also been found to have abnormally low levels of DHA in the membranes of the grey matter in the brain. Grey matter consists mainly of neuron cell bodies and is responsible for processing information received from sensory organs and other areas of the brain.
Food for the brain
Supplementation or including more DHA food sources into your diet could correct the deficiency in the cell membranes of your brain. Additionally many of the dementia related diseases do have some sort of inflammation process associated with them too. Both EPA and DHA could help curb the inflammation that contributes to neuron damage.
Despite the evidence of abnormally low blood and brain levels of DHA and EPA and a lower incidence of dementia in fish eaters, trials which have looked at supplementation for dementia are relatively inconclusive. This could be due to the fact that currently we are unsure what dosage of omega-3 would show a benefit. Varying amounts of omega-3 and different ratio's of EPA to DHA have been used in the past in supplementation trials.
Despite these inconsistencies a few positive results have managed to emerge from the framework. In 2006, a group of researchers from Stockholm's Karolinska University hospital found in a group of patients with mild cognitive decline, supplementation did have a positive action. It slowed progression of cognitive decline.
The Food chain: enter omega-3
Omega-3 is given the title of 'essential' as we mammals cannot synthesise it from scratch. We must obtain it from our diet. As we have come to learn the omega-3 fats with the most benefit are the long chain omega-3's; EPA and DHA. The metabolic pathway of an omega-3 starts with the parent, ALA. Carbon atoms and double bonds are added one by one until EPA and then DHA, with the longest carbon chains and the most double bonds are formed last in line.
ALA can be found in chia seeds, flax seeds and walnuts among other sources. But the sluggish conversion to the final product, DHA, means we need to eat it in its preformed state to reap the full benefits.
Omega-3 enters the food chain via marine algae who are able to synthesise the parent ALA and readily convert it to DHA. Here it steadily moves up the food chain through small marine crustaceans, to larger fish until it lands on our plate.
The current evidence for DHA and EPA in brain function is relatively small compared to the evidence for cardiovascular benefits. However, the weight of the evidence there is does strongly support the essential role of omega-3 in brain development, mental performance and prevention of cognitive decline. The fundamentals of their super powers lies in their abundant presence in neuron cell membranes as well as their secondary anti-inflammatory role.