After the success of the first AHSNZ conference in Christchurch we had many people who were unable to make it contact us hungry for more information. In response we have requested that our speakers write a post on their presentation. Reading it on your computer screen pales in comparison to hearing it in person, in a room full of like-minded passionate people, but we felt that these talks were too important. So, without further ado, allow us to present the AHSNZ Conference series of posts. Let us know what you think, which presentations sparked your interest, and what topics you would like to see addressed at our next conference in Wanaka on October 25.
Food for Thought – Nutrition and Brain Health
Technology. Isn’t it amazing? Well, actually – it’s only as amazing as the person using it. And for someone like me – who may be an early adopter of some things, but can’t read instructions or follow intuitive prompts – that limits the capability of the machinery. However, we all have the equipment that is described as the most sophisticated piece of machinery there is. Ourselves. The human body – how amazing is it?In order to maintain that level of amazing, we require our brain to co-ordinate a gazillion functions at the same time in order to function effectively.
That takes quite a bit of energy and it’s no wonder then, that humans have evolved to have an extraordinarily large brain in relation to the body – the adult brain takes approximately 20% of resting energy expenditure (or basal metabolic rate), and around 10% of total energy expenditure. Not bad for an organ that only accounts for 2% of overall body mass. An infant requires even more, with 50-70% of their BMR being used to support their brain function, and up to 9 years of age, their brain requires around 50% more energy than that of an adult brain. Blame the increased number and activity of synapses (the bridge between neurons in the brain, delivering messages) in their grey matter. When measured against our predicted brain mass (predicted against the size of our body) we, humans, punch above our weight.
Given the myriad of functions required by the brain to maintain our most superior standing in the animal kingdom, fuelling the brain is essential.
The brain can effectively run off three different fuel systems. Predominantly – and in most people today – glucose is the preferred fuel source, and can use up to 120g of glucose a day. As you know, this will come from dietary carbohydrate (CHO). However, in times of CHO restriction/depletion – we can provide glucose from stored CHO (glycogen), our protein stores (gluconeogenesis – breakdown of protein), and from glycerol (the CHO backbone of triacylglycerol – a fatty acid). In fact, our evolutionary response to CHO restricted environment is to shut down the delivery system of CHO to other areas in the body and deliver it to the brain (i.e. insulin resistance). This isn’t to say that the brain can’t run on other fuel sources – indeed, if that were the case then we probably wouldn’t have survived the last 3,000,000 years if that was the case. The next main fuel source is from fat – ketone bodies derived either through the diet or through the breakdown of fatty acids in the body. This only really occurs in times of CHO restriction/depletion – this happened at a much more frequent rate throughout evolutionary times when food was scarce, which clearly isn’t the case in today’s modern world. An individual is better to rely on ketone bodies as a fuel source for the brain if they’ve gone through an extended period of carbohydrate restriction and a higher fat diet. The brain can then begin to utilise fat as a fuel source. Those who follow a ketogenic diet (whereby fat makes up 80% of overall caloric intake, with adequate protein and minimal (~5-10% calories) carbohydrate can shift the fuel preference from glucose to ketones. Lastly, the brain can also use lactate as a fuel source, and this is called upon during times of intense exercise when glucose is depleted.
Which fuel source is the best?
The calorie requirements of the brain can be easily met in today’s environment of an abundance of food – however the metabolic consequence of the different fuel sources available can wreak havoc on the brain’s ability to function – both in the short and the long term.
The metabolic breakdown of carbohydrate into glucose to use as a fuel is damaging – and the brain isn’t spared from this. An excessive amount of glucose in the brain can have a neurotoxic effect – increasing the oxidative stress, inflammation, and causing damage at the cellular level. At its worst, it is also associated with more serious neurological disorders such as dementia and Alzheimer’s, stroke and epilepsy. Ketone bodies, on the other hand, are a clean burning fuel – causes less oxidative stress, less inflammation and better neuronal recovery can take place in an environment where ketones are used to fuel the brain. Indeed a ketogenic diet is used as a therapeutic tool for people with epilepsy, Alzheimer’s and to slow the growth of brain tumours.
Vitamins and mineral essential for brain function
In order to convert the calories provided into ATP for the mitochondria to use (energy to be produced), B vitamins, Co-enzyme Q10 and magnesium are required to enable reactions at various stages of the process. Antioxidants (vitamins C and E, and sulphur too) are also required to scavenge free radicals so they do not damage cellular tissue through oxidation. The B vitamins and amino acids are important as neurotransmitters to send messages from the brain to various parts of the body. Magnesium is like a super mineral – involved in over 300 processes in the body – and among other things, acts as a ‘guard at the gate’ if you like, blocking excess calcium and glutamate from entering the cells. Both of these can increase cellular damage due to their excitatory effects in the brain.
Vitamin D has a neuroprotective role, promoting their survival and reducing damage – hence its association with the preservation of cognitive function in the brain. It helps reduce inflammatory factors related to neurological disorders such as multiple sclerosis and there is an association between vit D levels and depression – with receptors for the active form of Vit D found in the hippocampus. Iodine has been found to be particularly important in the development of the brain, and if a pregnant women has an insufficient intake of iodine, their baby may be born with a low birth weight, cognitive impairment and their physical development impaired.
Docohexanoic acid (DHA) is a long chain fatty acid that is found pre-formed in fatty fish such as salmon, sardines and mackerel. It may be the most studied nutrient with regards to the brain and is the most abundant omega 3 fat found in the cell membranes of the brain. Our body is not good at synthesising it and the conversion of it from plant-based sources such as alpha-linoleic acid is poor. It’s important for ensuring membrane fluidity, protects membrane integrity and is involved in the development of synapses.
Calorie restriction vs. nutrient dense diet
So when you do hear ‘a calorie is just a calorie’ as is often touted, particularly in the weight loss arena where the argument of a calorie restricted diet versus the nutrient-focused diet is often played out, you can see that this just isn’t true.
A calorie restricted diet is often too restrictive, not only making fuel availability questionable at certain times, but not focusing on the right macronutrient calories – given that carbohydrate is much less calorie dense than fat. In addition, the focus on calories shifts attention away from the all important micronutrients which are essential for brain functioning and overall mood and wellbeing. Unfortunately when we consider all of the elements that promote and preserve brain health in light of what people are actually buying, then it doesn’t make for a pretty picture. Of the top 10 foods sold by volume in supermarkets in 2009, bananas were the only one that contained any nutrients whatsoever. Coca cola, white bread, canned baked beans…. Are representative of the nutrient devoid foods on the list.
In NZ currently, we have pockets of society who are overrepresented in both the academic achievement rates and the lower socioeconomic sections – these being intrinsically linked. Further, these children tend to have a poorer diet – with less fibre, less calcium, less fruit, cheese and milk than their school-aged peers. As these foods are important contributors to the aforementioned nutrients above, is it any wonder that those most disruptive in class, less likely to achieve academically are less likely to finish high school and change their socioeconomic position by getting further education or training to help support themselves and their future families? There are clear links between diet and hyperactivity, concentration, and even cognitive development – the latter of which has been set up essentially from prenatal. How are these children supposed to further themselves if they don’t have the right start in life?