August 28, 2016
 |
| As a growing child has an extraordinary demand for energy, their taste buds are particularly attuned to sugars and fats – this is obvious from the delight children express whenever ice cream is offered. |
Our lives are profoundly defined by symbols and yet very often, they lie to us.
A symbol could be something like Charlize Theron in the Dior perfume advertisement – she is the symbol of attractive womanhood, invoking romance and glamour, and the suggestion is that puffing J’adore on a woman will somehow confer on her such passion and allure.
But it doesn’t convey the reality of the consequences of ardour – the inevitable disappointment with most partners, not to mention the (extreme) patience and tolerance needed to maintain a relationship. Also, although I find Ms Theron most charming, the scent of J’adore gives me a mild headache.
Why people need symbols is a curious phenomenon, and often it is a two-edged sword. For example, if a woman feels that wearing symbols such as fancy hairdos, expensive handbags and big diamond rings somehow elevates her status above other people, then there are probably many more people who would view such ostentation as charmless, tasteless and offensive, especially if her sources of wealth are questionable.
It reminds me of the odd story of two corrupt politicians who bumped into each other outside a swanky club, and see that they are both wearing exactly the same neckties. One says, “I see you have great taste. How much did you pay for that tie?” The other answers proudly, “$3,000 – it’s the most expensive tie in the shop.” At which point the first guy says, “You idiot! I bought mine for $5,000!”
The irrationality of symbols came to mind when exploring the causes for food addiction – why some people persistently crave to consume certain items even when they know these items actually harm them.
In fairness, sometimes substances are consumed excessively for understandable reasons, such as the reduction of pain due to severe illnesses.
image: http://www1.star2.com/wp-content/uploads/2016/08/star.gif
But normally, an addiction is due to custom, or familiarity of some sort.
There must also be psychological, physiological or chemical reasons for such odd behaviour – and coercion to follow addictive habits (eg. by the marketing media’s use of symbols) does not help the situation.
This series of articles will cover theories of addictions related mostly to food – though there are common factors between all forms of addiction.
There are several definitions for addiction, with strong suggestions of it being both a medical and mental condition.
Addiction for food substances is characterised by several traits, such as:
• Inability to limit oneself to consuming the desired foods in moderation
• Constant craving for desirable foods
• Inability to control normal behaviour in the presence of the desired foods
• Inability to recognise health and behavioural problems related to the overconsumption of desired foods and irrational emotional responses when deprived of such desired items.
It all starts with taste and flavour
People get addicted to selected food substances usually because they simply like the taste and flavour of these foods. There are a very few people who are somehow addicted to food they actually hate eating but this is clearly an abnormal mental problem, probably to do with masochism. So investigating how humans develop their food preferences might be a good basis for understanding how food addiction can arise – and it is rather more complex than you might think.
How our taste senses work and how we enjoy flavours had already been covered in earlier articles so this piece will focus on why certain foods can become addictive.
image: http://www1.star2.com/wp-content/uploads/2016/08/str2_curious2808_jg_5.jpg
The most sought-after durian in Malaysia, the Black Thorn; durian is a fruit you either hate with a vengeance or love with a crazy desire.
Overconsumption – a necessity that is now unnecessary
With humans, there is probably a genetic basis for some of our general predilections for certain foods.
Since we evolved from primitive hunter gatherer tribes, our taste preferences today still remain skewed towards liking foods which can efficiently provide a lot of energy – our Palaeolithic ancestors simply needed energy to hunt and forage and the most energy-laden food substances would be anything with a high sugar content.
This explains why young children instinctively like sweets and cakes – they are conditioned by their genes to prefer high-energy foods which helps them grow, explore and learn.
Following closely behind, and often in parallel with high energy foods, would be a preference for foods with a high nutritional content, such as proteins, minerals, vitamins, etc.
Again this disposition is probably genetic in nature – and humans have made huge strides in rendering food so that it can be consumed and absorbed much more efficiently. This has even affected the physical features of humans – for example, if we had not learnt how to cook with fire, our jaws and mastication muscles would need to be much larger to handle chewing raw meat for long periods of time.
As it is, the jaws of humans are proportionately the smallest of all primates and it has been argued that cooking also permitted humans to develop larger brains as we get so much more energy from cooked food that our brains had consequently been able to evolve to grow larger and plan ever better survival strategies.
It should be noted that the constant availability of food for our Palaeolithic ancestors was very seldom guaranteed.
The simple consequence was starvation when food was scarce, then overeating whenever excess food was around – and the human body had evolved to cope with this by storing excess food (energy) as body fat which would get used up during times when the food supply is limited.
So it can be seen that our own genes can potentially lead humans to food addiction, especially if they cannot control their instincts to consume sugary and high-nutrition foods.
In the distant past, these foods provide comfort and relief in a harsh environment and it is probable that they can still invoke the same feelings today – the only problem is that modern shops and supermarkets have an unlimited supply of food all year round and therefore the instinct to overeat does not serve humans quite so well these days.
Foods that just can’t be left alone
image: http://www1.star2.com/wp-content/uploads/2016/08/str2_curious2808_jg_4.jpg
Lobster is one of Chris Chan’s favourite foods and hard for me to say no to when offered.
Almost everyone has several favourite foods or snacks which are difficult to avoid when offered – my favourites probably include lobster, durian and steak. I had often wondered about how these strong preferences develop and a little investigation turned up some interesting facts.
A foetus in the womb can detect some of the foods ingested by the mother – the flavours are transmitted via the amniotic fluid. As such, some babies immediately after birth can already detect certain flavours eaten by their mothers – they will turn their heads towards familiar smells such as garlic and aniseed.
However, this does not mean that the babies will necessarily develop strong preferences for these foods in later life, although a study on rat pups whose mothers were fed high fat, salt and sugar diets during pregnancy demonstrated stronger than normal preferences for these foods during weaning.
Even more curious is the fact that newly-born babies come equipped with 30,000 taste buds spread throughout the mouth cavity – but they slowly start losing these taste buds as they age until an adult human ends up with only 10,000 taste buds or so, mostly on the tongue.
This means that eating and tasting food is a much more intense experience for babies than for adults. This exuberance of taste buds may explain why many young children dislike their vegetables, simply because they are much more sensitive to the bitter compounds in greens.
As growing infants and children have an extraordinary demand for energy, their taste buds are particularly attuned to sugars and fats – and this is obvious from the delight children express whenever ice cream is offered.
Human breast milk also contains 10 times more glutamate than cow milk, hence breast-feeding may possibly induce a preference for savoury, umami-laden foods in later life – coincidentally, foods with a lot of umami also tend to contain protein, which is needed for muscular development.
It is unlikely that all adult food preferences get established during infanthood as the radical changes in the number and distribution of taste buds would have a significant effect on food choices over time.
In general, as they age, most humans become somewhat desensitised and more habitual about what they eat, although a significant proportion will continue to develop new food preferences throughout their lives.
However, it is not uncommon for the desire for sugar and fats to be retained into adulthood as foods containing sugars and fats also abound with energy, which would have been very advantageous for our adult hunter-gatherer Palaeolithic ancestors.
Of course, that’s really not a good excuse to overeat and become obese – but it is almost understandable as our genes would seem to be pushing us in that direction.
A crazy desire for certain foods
We have all had little episodes when we succumb to a craving for a favourite food, despite our better judgement – but there are some people who have practically no control over their desire for certain foods.
Very often, these extreme desires would be linked to sweet, fatty or savoury foods – and actually, it would usually be food which combines more than one taste sensation.
image: http://www1.star2.com/wp-content/uploads/2016/08/choc.gif
A classic example is chocolate, which combines a lot of sugar with fat – I have yet to meet anyone who can refuse a proper Belgian truffle.
But then, I wouldn’t expect anyone to empty a box of two dozen truffles from the office pantry either – and this has happened more than a few times.
Why the fondness for certain food items becomes an irresistible, almost criminal urge, may have several reasons.
If we can ignore the psychological aspects, an addiction is usually the result of some form of chemical imbalance in the body, which compels a person to desire food beyond a reasonable limit. This desire may compel an addict to do things which would be normally out of character. More on the chemistry of addiction later.
image: http://www1.star2.com/wp-content/uploads/2016/08/raw.gif
Consuming till death comes along
Along with overconsumption of desired food substances, an addict is also able to ignore (or even crave) the blatant consequences of such unrestricted indulgence.
Normally such consequences would be related to health issues or extreme discomfort though some cases may also include financial problems and emotional burdens to other people.
In short, the habits of some serious addicts may be damaging more than their own bodies. A classic case would be alcoholism, where each bout with drunkenness and painful hangovers actually actively reinforces the need to drink even more despite the intense unpleasant consequences.
In a simplistic way, it might be a matter of perception – what one person knows is not necessarily what everyone else understands.
It reminds me of a little joke: An elderly couple attends a church sermon. About halfway through, the wife leans over and says to her husband, “I couldn’t help it – I’ve just let out a huge fart. But at least it was completely silent. What do you think?” He replies, “I think you should put a new battery in your hearing aid.”
http://www.star2.com/food/food-news/2016/08/28/symbols-of-addiction/
Symbols of addiction – Part 2
The latest Pokemon game has gotten many people addicted. Here's a 'Pokeburg' hamburger called 'Peakachu' caught at Down N' Out Burger restaurant in Sydney.
Addiction is always irrational – and one little story about irrationality involves a man who turns in exasperation to his girlfriend one day and says, “You’re like the square root of 2.” Puzzled, she asks, “Why?” And he replies, “Because you’re completely irrational.” If you don’t get it, then I won’t bore you further with an explanation – but you might like to search for “irrational numbers” if you’re curious.
The brain pathways
Back to addiction: Although psychological factors often have a bearing on many forms of addiction, there is also a chemical basis for practically all forms of addictive behaviour. It is a very interesting story how the body succumbs to addiction – and it starts with the dopaminergic pathways in the brain. These are neural pathways which shift a neurotransmitter called dopamine around various regions of the brain – the pathways most commonly associated with addiction are the mesolimbic pathway, the nigrostriatal pathway, and to a lesser degree, the mesocortical pathway.
As an aside, dopamine is also involved in the tuberoinfundibular pathway – and problems with this pathway are associated with hyperprolactinaemia, a condition which affects menstruation in women and sexual dysfunction in men, among other things. As explaining each pathway would involve long discourses into the neurobiology of the brain, we will restrict ourselves to only discussing elements mainly involved with the mesolimbic pathway (MLP), which probably drives the most common forms of addictive behaviour.
The MLP is often referred to as the Reward Pathway for this brain pathway directly influences the fuzzy, warm, pleasant responses we feel when something satisfies our urges. As such, the MLP is a crucial component of what motivates and incentivise us to follow our goals. Why nature has developed a system of controlling behaviour via a rewards system is actually very interesting because of its general efficiency, unless of course, it becomes a detrimental syndrome – more on this a little later.
The MLP is located right in the middle of the brain and it connects the Ventral Tegmental Area (VTA) to the Nucleus Accumbens (NAc), via a series of complex connections that also involves the hypothalamus, amygdala and hippocampus. There are also some interactions with the main frontal cortex, the dorsal raphe, the locus coeruleus and significantly, the amygdala – don’t worry, all will be clear (or at least, clearer) in a little while.
image: http://www1.star2.com/wp-content/uploads/2016/09/str2_curious1109_jg_1~1.jpg
Locations of VTA and NAc in the human brain.
Note that the use of dopamine pathways is not a new development and it is certainly not exclusive to humans or even mammals – based on research on fossils many millions of years older than mammals, it was found that dopamine-activated neurons had been controlling behavioural responses in primitive worms and insects even then. As it is such a primitive, compelling piece of circuitry in the brain, the dopamine pathways probably also affect some of the other primal responses in humans, such as lust, jealousy, revenge and greed.
The main chemicals in focus in the MLP are dopamine, gamma-aminobutyric acid (GABA) and a curious amino acid called glutamic acid (often presented as glutamate, where a mineral ion is attached; eg. monosodium glutamate). Dopamine is synthesised from phenylalanine or tyrosine, which are amino acids found in proteins – if present, phenylalanine is converted into tyrosine via the enzyme phenylalanine hydroxylase and tyrosine is next converted into levodopa (L-dopa) by the action of the enzyme tyrosine hydroxylase.
L-dopa is then converted into dopamine by a versatile enzyme called aromatic L-amino acid decarboxylase (AADC) via a process called decarboxylation, which can be summarised as the removal of a COOH molecular sequence from a target compound. Note that these series of reactions will become more significant later on when discussing noradrenaline and the amygdala. The participation of glutamate is interesting: it can act as a neurotransmitter in its own right or it can involve a glutamate enzyme which acts as a precursor for the synthesis of GABA from glutamate, leaving some CO2 (carbon dioxide) as a residue – this reaction is catalysed by glutamic acid decarboxylase (GAD) which appears to be expressed solely by those neurons that reacts to GABA.
image: http://www1.star2.com/wp-content/uploads/2016/09/str2_curious1109_jg_2-e1473548400243.jpg
Our addiction to beer and coffee and other stuff has a psychological basis but there is also a chemical basis for practically all forms of addictive behaviour.
As an aside, GAD is also produced in the pancreas and it has been observed that people with Type 1 diabetes also tend to have antibodies against GAD – these antibodies disrupt the function of the pancreas and hence interfere with the production of insulin.
And regarding glutamates, the glutamates we get from food normally cannot cross the Blood-Brain Barrier so that feeling of drowsiness from eating too much savoury food cannot be attributed to the effect of food glutamate on the brain – the tiredness after overeating is simply due to gluttony overloading the digestive system. The brain isn’t that simple as there are other compounds which interact directly or indirectly with the MLP, such as noradrenaline, serotonin, anandamide, various endogenous opioid neuropeptides (collectively known as endorphins) and so on – the full list is quite extensive and still quite possibly incomplete as it stands today.
In case you’re wondering how the brain can produce these chemicals so quickly, the answer is that certain amounts of several neurotransmitters are actually manufactured in advance, then transported by a protein called the vesicular monoamine transporter (VMAT) for storage in the synaptic vesicles near the synapses, ready for instant use. Once the vesicles are depleted, the brain produces more neurotransmitters as required to keep the required reaction going.
Why the brain uses rewards
What is rather fascinating and also somewhat infuriating about the brain is that we know much more about how it works rather than why it works the way it does. For example, there is a good theory about how the use of rewards is much more efficient than the alternative, which would require the brain to store all responses to all the foods we have ever eaten – the good foods would get good scores and the bad foods would get bad scores.
If we did not have a reward system, it would mean that every new food we come across has to be evaluated, digested and scored – if the food is poisonous, then life would end there and then and we would not be able to prevent the poisoning because we would have had no previous experience of the poison. But by having a reward system which makes us “feel good” or “feel bad” in some fuzzy way about new food substances, probably based on foods with analogous tastes, then the brain simplifies hugely the whole process of determining between good or bad without having to go through a huge list of previous encounters.
image: http://www1.star2.com/wp-content/uploads/2016/09/Copyofstr2_curious1109_jg_1.jpg
Sweet and fatty foods ‘taste good’ and bitter and sour stuff simply ‘taste bad’ – and this ability to generally distinguish between good and bad food using ‘fuzzy logic’ significantly enhanced many species’ chances of survival. Photo: The Star
So in general, sweet and fatty foods “taste good” and bitter and sour stuff simply “taste bad” – and this ability to generally distinguish between good and bad food using “fuzzy logic” significantly enhanced many species’ chances of survival, including our own. Of course, this reward system also applies to behaviours other than eating – whether it is the comfort of finding shelter from inclement weather, or the pride of a hunting success, or perhaps the vindication of killing an enemy. Rewards do not always end with positive results for everyone involved.
That is currently the best theory about why we have a reward system in our brains – and it is quite a compelling doctrine called the Anhedonia Hypothesis (AH) devised by Roy Wise in 1982 which directly links dopamine with behaviours driven by rewards – and such behaviours can lead to addictions further down the line. But in truth, the function of dopamine isn’t exactly so simple and straightforward either – else it wouldn’t be so interesting. For one, although the VTA produces and sends dopamine to the NAc as a stimulatory, positive response to a food substance which is attractive and pleasurable, the levels of dopamine actually drop after extended exposure to the same food – in short, the sense of a worthy reward fades over time.
This is why food cravings die off after some time, else we would be compelled to eat the same foods every single day – a classic subjective example may be sushi, which can be seriously enjoyed several times in a row but after that, some other kinds of hot food suddenly become more desirable. There may be an evolutionary basis for why dopamine levels change like this – it might be a signal to diversify and consume different foods so as to maximise the nutritional intake.
Glutamate in the brain is an excitatory chemical causing the brain neurons to fire and become more receptive to other neurotransmitters during any brain activity – and its action can sometimes be akin to setting off a chain of fireworks. Therefore, the actions of glutamate (and other neurotransmitters) have to be modulated to prevent over-activity and this regulation is done by GABA, which damps down and controls the signalling between brain neurons. As mentioned earlier, GABA is produced by the neurons themselves when glutamate is catalysed by GAD and this appears to be a self-moderating function in neural signalling.
As an aside, it has been shown that glutamate is actually toxic, more specifically it is an excitotoxin – too much glutamate in the brain causes excitotoxicity which results in brain cell death via a process called apoptosis, which might be a glorified term to describe the suicide of brain cells after having too much stimulation.
image: http://www1.star2.com/wp-content/uploads/2016/09/str2_curious1109_jg_3.jpg
Many people are addicted to Ipoh’s famous ‘mixed rice’ at the Yong Suan coffee shop on Jalan Kalsom, here complete with ayam merah, fish roe curry, sotong curry, coconut sambal, salted egg and a secret gravy. Photo: The Star
However, from the story so far, it seems unlikely that any food addictive behaviour can come about purely as a result of dopamine – even after being initially thrilled and immensely rewarded by interesting foods, the brain damps down by itself the production of dopamine after any extended exposure to the foods and GABA moderates the neural excitement promoted by glutamate. The theory therefore is that addictive behaviour arises from the interplay of other factors which interact with the MLP, and some of these factors may be rather surprising, though always interesting – and it isn’t always what you might assume.
It reminds me of a little story about an old man who visits a doctor with his wife for his medical examination. After looking over the old gentleman, the doctor tells him, “I need to take some samples of your stools, urine and blood.” The old man leans over, hard of hearing, and asks, “What?” So the doctor repeats more loudly, “I need samples of your stools, urine and blood now.” The old man asks again, “What did you just say?”
At this point, the wife gets up and shouts in his ear, “The doctor wants your underwear!”
http://www.star2.com/food/food-news/2016/09/11/symbols-addiction-part-2/
