In neuroscience, food is something we call a “natural reward.” In order for us to survive as a species, things like eating, having sex and nurturing others must be pleasurable to the brain so that these behaviours are reinforced and repeated.
Evolution has resulted in the mesolimbic pathway, a brain system that deciphers these natural rewards for us. When we do something pleasurable, a bundle of neurons called the ventral tegmental area uses the neurotransmitter dopamine to signal to a part of the brain called the nucleus accumbens. The connection between the nucleus accumbens and our prefrontal cortex dictates our motor movement, such as deciding whether or not to taking another bite of that delicious chocolate cake. The prefrontal cortex also activates hormones that tell our body: “Hey, this cake is really good. And I’m going to remember that for the future.”
Not all foods are equally rewarding, of course. Most of us prefer sweets over sour and bitter foods because, evolutionarily, our mesolimbic pathway reinforces that sweet things provide a healthy source of carbohydrates for our bodies. When our ancestors went scavenging for berries, for example, sour meant “not yet ripe,” while bitter meant “alert – poison!”
Fruit is one thing, but modern diets have taken on a life of their own. A decade ago, it was estimated that the average American consumed 22 teaspoons of added sugar per day, amounting to an extra 350 calories; it may well have risen since then. A few months ago, one expert suggested that the average Briton consumes 238 teaspoons of sugar each week.
Today, with convenience more important than ever in our food selections, it’s almost impossible to come across processed and prepared foods that don’t have added sugars for flavour, preservation, or both.
These added sugars are sneaky – and unbeknown to many of us, we’ve become hooked. In ways that drugs of abuse – such as nicotine, cocaine and heroin – hijack the brain’s reward pathway and make users dependent, increasing neuro-chemical and behavioural evidence suggests that sugar is addictive in the same way, too.
The healthy eating trends of 2015
The healthy eating trends of 2015
1/10 Acai bowls are the new green juice
Who ever thought we’d have been ok with adding spinach to our smoothies? Yet even virtuous green juices started to get something of a bad rep, as the ‘juice fast’ backlash grew and it turned out that some shop-bought juices contained as much sugar as a can of fizzy drink. Bring on Acai bowls, the new darlings of Instagram. Like a gloopier smoothie, these are made with antioxidant-rich acai berries (they are hard to come by - search for powdered or dried berries or frozen puree), which are said to aid weight loss. Blend with frozen bananas, berries and a little nut milk and top with whatever you like - seeds, nuts, cacao nibs, goji berries. A picture-perfect purple powerhouse for breakfast.
Ella Grace Denton, www.weneedtolivemore.com
2/10 Bone broth is the new Miso soup
Remember back in the day when the word ‘broth’ would conjure up visions of Dickensian orphanages? Then miso came along, Gwyneth embraced it, and we all followed suit, lauding how filling and protein rich with little wonder broth was. We’ve come full circle now, as bone broth is back on the radar. The glowing-with-health Hemsley sisters seem to use bone broth in most of their recipes, and rave about its nutritional benefits. “Bone broth is a nourishing all rounder packed with vitamins, minerals, collagen and keratin which makes it amazing for skin – including the dreaded cellulite! The healthy fats in the broth help you to assimilate important vitamins including Vit D.” There you go, something to stew over...
Food Loves Writing, Flickr
3/10 Bee pollen is the new Manuka honey
Every health hipster has a jar of manuka honey on their shelves - if they can afford it that is, a jar can cost about £15. But many claim it is worth its weight in gold, due to its unique antibacterial properties. Traditionally it was used on wounds, but many also claim that it performs miracles combatting cholesterol, diabetes, cancer and digestive problems (although the science is limited). Now bee pollen is the latest ‘superfood’ out there - thought to ward off colds, limit food cravings, improve skin tone, ward off allergies like hay fever (although some caution that it may exacerbate them) and, of course, fight cancer. Again, the science behind these claims is dubious - but it certainly adds a nice sweetness to your morning porridge.
4/10 Kelp is the new kale
Last year saw the emergence of an unassuming green leaf that was previously barely used beyond cattle feed. Now, we have kale chips in Pret, kale juices, ‘massaged’ kale salads - it’s even on the menu in fine dining restaurants. Yawn. Introducing kelp. This seaweed is high in iodine, which is said to improve thyroid function and control metabolism. It is also thought to have anti-aging properties for skin and hair. Try it in salads or add to asian-style soups.
5/10 Matcha is the new green tea
Yes, yes, yes, green tea, weightloss, yadda yadda yadda, boosts metabolism, etc etc. For 2015, though, it’s not about just any old green tea - this is matcha green tea. Made from finely milled high-grade matcha leaves, which are grown in the shade, matcha boasts 130 times more anti-oxidants than your bog standard green tea and is supposed to boost energy levels, lower stress, improve your mood and aid metabolism. It can be consumed as a regular tea, added to steamed milk for a matcha latte or even used to add a pleasant green shade and flavour to ice-cream.
6/10 Whole 30 is the new Paleo diet
Thought you were a culinary champ with your caveman-style eating plan? Well, think again, paleo is for wimps! Ok, not quite, but while people on the paleo plan cut out grains, legumes, sugar and processed foods, there is an increasing trend to paleo-fy your treats, with almond-flour pancakes, banana bread and a lot of brownies. The Whole 30 plan is a purer, stricter version of Paleo and really takes you back to basics when it comes to eating natural foods. The 30-day plan bans scales as well as sugar and alcohol, so that you can concentrate on nourishment rather than weight.
7/10 Fermenting is the new sprouting
Just when we thought we were ahead of the game by starting to sprout our own seeds and with sprouted flours creeping on to the market, the health set had to kick it up a notch. Now it’s all about making your own kombucha (fermented tea), sauerkraut or kimchi (both kinds of pickled cabbage). Fermented foods are said to aid digestion thanks to the creation of enzymes and probiotics in the process. Plus they tend to be high in B-vitamins and Omega-3 fatty acids. Think of it as the new jam-making, and break out those mason jars.
8/10 Banana flour is the new coconut flour
Coconut flour was one of the coolest baking ingredients of the year, beloved by Paleo fans. Its highly absorbent qualities mean you only need a tiny bit for baking, keeping your creations low carb but resulting in the odd dry-crumbly-mess baking fail. Banana flour is the next flour to experiment with. Made from green bananas (and no, not banana-flavoured), it is gluten free and light in texture, so ideal for baking. High in resistant starch, which is effective against colon cancer, obesity, and diabetes, it is already being lauded for its nutritional benefits in Africa and South America, and will surely start to become much more visible on health-food shop shelves in the near future.
9/10 Bulletproof coffee is the new soy latte
Nowadays it is possible to walk into almost any cafe and order a soy latte without being eyeballed as a lunatic by the person behind the counter. But would you have the guts to request a stick of butter in your morning brew? Well, some coffee shops are offering exactly that. Bulletproof coffee is a paleo-friendly invention which involves a black coffee with a dollop of coconut oil or butter. Bleurgh. But advocates say it gives you more slow-release energy, sharpens your brain and helps you to focus - and even that it is delicious. Now the theory has been expanded into a whole ‘Bulletproof’ diet plan, rich in fat. Who wants to bet on when Starbucks will give it a shot?
10/10 Tiger nuts are the new almonds
2014 was a good year for almonds. Gym-goers and raw foodists alike carried around a stash for healthy, protein-rich snacking, almond-milk lattes were quaffed, and almond flour featured in so many paleo and gluten-free treats. Now tiger nuts, or ‘earth almonds’ (yes, really), are about to vie for snacking superiority. Tiger nuts are not nuts, but the tubers of the sedge plant. Originally a key food source for Paleolithic Indians, they have until recently been used as animal feed or a side dish in South America, Africa and the Middle East, or in Hispanic companies made into a sweet, milky drink called horchata. But now the hipsters have got their hands on it, drying, roasting and flavouring with the likes of sweet chilli for an on-the-go snack. High in healthy fats, protein and natural sugar, it is rich in energy content, and thought to help prevent heart disease and improve circulation.
Sugar addiction is real
Anyone who knows me also knows that I have a huge sweet tooth. I always have. My friend and fellow graduate student Andrew is equally afflicted, and living in Hershey, Pennsylvania – the “Chocolate Capital of the World” – doesn’t help either of us. But Andrew is braver than I am. Last year, he gave up sweets for Lent. “The first few days are a little rough,” Andrew told me. “It almost feels like you’re detoxing from drugs. I found myself eating a lot of carbs to compensate for the lack of sugar.”
There are four major components of addiction: bingeing, withdrawal, craving, and cross-sensitisation (the notion that one addictive substance predisposes someone to becoming addicted to another). All of these components have been observed in animal models of addiction – for sugar, as well as drugs of abuse.
A typical experiment goes like this: rats are deprived of food for 12 hours each day, then given 12 hours of access to a sugary solution and regular chow. After a month of following this daily pattern, rats display behaviours similar to those on drugs of abuse. They’ll binge on the sugar solution in a short period of time, much more than their regular food. They also show signs of anxiety and depression during the food deprivation period. Many sugar-treated rats who are later exposed to drugs, such as cocaine and opiates, demonstrate dependent behaviours towards the drugs compared to rats who did not consume sugar beforehand.
Like drugs, sugar spikes dopamine release in the nucleus accumbens. Over the long term, regular sugar consumption actually changes the gene expression and availability of dopamine receptors in both the midbrain and frontal cortex. Specifically, sugar increases the concentration of a type of excitatory receptor called D1, but decreases another receptor type called D2, which is inhibitory. Regular sugar consumption also inhibits the action of the dopamine transporter, a protein which pumps dopamine out of the synapse and back into the neuron after firing.
In short, this means that repeated access to sugar over time leads to prolonged dopamine signalling, greater excitation of the brain’s reward pathways and a need for even more sugar to activate all of the midbrain dopamine receptors like before. The brain becomes tolerant to sugar – and more is needed to attain the same “sugar high.”
Sugar withdrawal is also real
Although these studies were conducted in rodents, it’s not far-fetched to say that the same primitive processes are occurring in the human brain, too. “The cravings never stopped, [but that was] probably psychological,” Andrew told me. “But it got easier after the first week or so.”
In a 2002 study by Carlo Colantuoni and colleagues of Princeton University, rats who had undergone a typical sugar dependence protocol then underwent “sugar withdrawal.” This was facilitated by either food deprivation or treatment with naloxone, a drug used for treating opiate addiction which binds to receptors in the brain’s reward system. Both withdrawal methods led to physical problems, including teeth chattering, paw tremors, and head shaking. Naloxone treatment also appeared to make the rats more anxious, as they spent less time on an elevated apparatus that lacked walls on either side.
Similar withdrawal experiments by others also report behaviour similar to depression in tasks such as the forced swim test. Rats in sugar withdrawal are more likely to show passive behaviours (like floating) than active behaviours (like trying to escape) when placed in water, suggesting feelings of helplessness.
A new study published by Victor Mangabeira and colleagues in this month’s Physiology & Behavior reports that sugar withdrawal is also linked to impulsive behaviour. Initially, rats were trained to receive water by pushing a lever. After training, the animals returned to their home cages and had access to a sugar solution and water, or just water alone. After 30 days, when rats were again given the opportunity to press a lever for water, those who had become dependent on sugar pressed the lever significantly more times than control animals, suggesting impulsive behaviour.
These are extreme experiments, of course. We humans aren’t depriving ourselves of food for 12 hours and then allowing ourselves to binge on soda and doughnuts at the end of the day. But these rodent studies certainly give us insight into the neuro-chemical underpinnings of sugar dependence, withdrawal, and behaviour.
Through decades of diet programmes and best-selling books, we’ve toyed with the notion of “sugar addiction” for a long time. There are accounts of those in “sugar withdrawal” describing food cravings, which can trigger relapse and impulsive eating. There are also countless articles and books about the boundless energy and new-found happiness in those who have sworn off sugar for good. But despite the ubiquity of sugar in our diets, the notion of sugar addiction is still a rather taboo topic.
Are you still motivated to give up sugar? You might wonder how long it will take until you’re free of cravings and side-effects, but there’s no answer – everyone is different and no human studies have been done on this. But after 40 days, it’s clear that Andrew had overcome the worst, likely even reversing some of his altered dopamine signalling. “I remember eating my first sweet and thinking it was too sweet,” he said. “I had to rebuild my tolerance.”
And as regulars of a local bakery in Hershey – I can assure you, readers, that he has done just that.
Jordan Gaines Lewis is a Neuroscience Doctoral Candidate at Penn State College of Medicine