Positron Emission Tomography (PET) measurements using [11C] Raclopride to estimate availability of D2 dopamine receptors in brain. Significantly reduced levels of available D2 receptors of dopamine (a neurotransmitter responsible for modulating neural circuits for reward and motivation) in Methamphetamine users and obese individuals compared

Positron Emission Tomography (PET) measurements using [11C] Raclopride to estimate availability of D2 dopamine receptors in brain. Significantly reduced levels of available D2 receptors of dopamine (a neurotransmitter responsible for modulating neural circuits for reward and motivation) in Methamphetamine users and obese individuals compared to control subjects [1, 2].

What do sugar and cocaine have in common? No, you don’t have to literally taste both to know the answer, and I would definitely not encourage you to do so (for the latter, at least). But if your answer was to yell “feel-good sensation!” (maybe?), you guessed correctly! That rewarding feeling we get while munching on chocolate-dipped strawberries (as I am doing now) develops positive reinforcement, just like an addictive drug like cocaine. The result is that we wish to indulge in sweet-tasting, savory foods more and more. Recent fMRI (Functional Magnetic Resonance Imaging) studies that measured brain activity suggest that both sugar and cocaine activate similar areas of the brain. Such overlap in brain activity is due to a sharing of the D2/D3 dopamine (neurotransmitter) receptors by both food cues and cocaine. Believe it or not, studies also suggest a shared reward-related neural circuit between compulsive overeating and addiction to sugar. No doubt, this creates a great of health risk!

But the question is: why do we ‘like’ to eat sugar? The above paragraph explains ‘how’ our brain processes a signal of positive reinforcement to eat more sugar, but the answer to ‘why’ may actually have an evolutionary origin. One hypothesis could be that periodic food shortages in the past led our ancestors to consume plenty of sugar-rich diets when available to meet their energy requirements. Toxic build-up of excess dietary sugar was negatively selected and as a result sugar was converted mainly to fat. This was not an issue for our ancestors because they were very active, and thus a nice balance between low food-availability, high sugar intake, and fat metabolism was positively reinforced in the population. Contrarily, in modern times, with a plethora of sugary food options available, our innate craving for sugar can be easily satisfied. But the problem lies elsewhere. A mostly sedentary lifestyle has tipped the energy balance towards fat storage, leading to a spectrum of debilitating diseases ranging from type 2 diabetes to CVD. Interestingly, studies also suggest that an individual’s innate preference to sweetness could be exacerbated by early childhood exposure to sweetened beverages. Therefore, this ‘sweet-love’ in our daily life has deeper roots than we can actually imagine.

Needless to say, the rapid growth of the fast food industries, who fuel our sugar affection, has spiked the incidence of obesity and type 2 diabetes more over the last three or four decades than ever before. To support this, a 2005 study published in The Lancet clearly showed a significant positive co-relation between fast food consumption and insulin resistance. In addition to fast-food, barbecued food prepared quickly with dry heat could be a source of potentially damaging and highly reactive compounds called Advance Glycation End products (AGEs). AGEs are essentially a heterogeneous group of reactive sugar derivatives formed through non-enzymatic reactions. Precursors of AGEs form covalent cross-links with certain amino acids of proteins and, being highly reactive, have the potential to modify other macromolecules such as lipids and nucleic acids. The formation of AGEs (products of Maillard reaction, or the browning on cooked food) has been implicated as key players in a wide variety of disease pathologies. Believe it or not, increased accumulation of AGEs in our body could lead to accelerated damage in collagen and elastin, two major structural components of our tissues, such as skin. Therefore, more AGEs can cause more wrinkles and faster aging! To look at the other side of the coin, slow cooking at low heat and prior marination of meat in acid, such as lemon juice or vinegar, has been suggested as a way to bring down the AGE content in cooked meals. Additionally, antioxidant-rich vegetables (such as a salad) on the side could also balance a potentially AGE-rich diet.

Our life choice to eat a sugar-rich diet is therefore a constant innate response of deep evolutionary origin, and our goal of achieving healthy living is a daily battle to overcome this strong inner urge. Nevertheless, to end on a positive tone, satisfying this urge is definitely still a choice, and one not too difficult to ignore with the ultimate reward of a better future and a disease-free life.