I was talking to a husband and wife yesterday about what they might do to tidy up their diets a bit in order to improve general levels of energy and vitality. One of the most important things here, I think, is for individuals to ensure that they maintain relatively stable levels of blood sugar throughout the day. If blood sugar levels fall to subnormal levels, energy can stall. And it can also provoke a desire for foods that release sugar briskly into the bloodstream including chocolate and sugary drinks. The consumption of such foods can lead to surges of insulin that can cause low blood sugar levels some time (generally 2-3 hours later), and so the cycle repeats.
This rollercoaster of blood sugar levels can lead some people into what looks like quite compulsive eating. And this may manifest not just as an occasional yen for a chocolate bar in the mid-late afternoon: For some, there is the potential that blood sugar imbalance can lead to food bingeing, and maybe purging too. There is some evidence that the condition bulimia nervosa (characterised by bingeing and purging) can have instability in blood sugar levels at its root (see article ‘A dietary approach to bulimia’ below).
There is no doubt in my mind that some people find themselves struggling to eat healthily because of chemical upset in the body and brain. And the implications of this because ever-more apparent to me when I read this recent report which details some experimental work that appears to prove that sugar has addictive potential in animals. I think this work and the evidence regarding bulimia should serve to remind us that when people find it difficult to control their eating habits, the issue may not be one of a ‘weak will’ or ‘lack of self control’, but one of an awry biochemistry. In other words, the issue can be more physiological than psychological.
Far more common than full-blown bulimia is the syndrome of individuals being drawn almost irresistibly to food they know are not the best for them. For many of us gearing for the festive season, this time of year can be a potential minefield because there is generally more temptation. I am not suggesting for one moment that individuals should not indulge themselves around Christmas and the New Year. However, I also believe that being mindful of a need to keep the body’s blood sugar levels quite stable can help ensure that our eating does not run out of control. For more about this, see the article ‘Getting to grips with sugar cravings’ below.
The benefits of blood sugar stability go beyond this, though, in that as I pointed out to the couple I was talking to yesterday, this may well make their energy levels more predictable. One other potential benefit relates to mood: when blood sugar levels drop, the brain can malfunction, and this may manifest as anxiety, irritability or low mood. Bizarre though this sound, keeping blood sugar levels on an even keel may help individuals maintain a cheerier disposition over the festive season too.
Getting to grips with sugar cravings – 21 April 2002
Most of us will have a pretty good idea of what constitutes a healthy diet. Despite the protestations of the sugar industry, it appears we’ve sussed onto the fact that sugar-charged treats such as chocolate, biscuits and coffee bar patisseries do little for our waistline or well-being. Yet, while we may be sold on sense behind avoiding these sweet treats, for some of us, temptation can be simply too hard to bare. We may know damn well that a crisp green apple would make a fabulously healthy snack after lunch, but it doesn’t necessarily stop us raiding the vending machine or cracking into the chocolate Hob Nobs from time to time.
The traditional view of these dietary indiscretions is that they are the result of a weak will and lack of self-control. Yet, while a ‘sweet tooth’ may seem to be the rooted in some psychological feebleness, my experience tells me otherwise. Mostly, I have found that this issue is the result of an imbalance in body, not mind.
The body, like any well-oiled machine, likes to keep itself in balance. One area that the body puts a lot of time and effort into regulating is the level of sugar in the bloodstream. As blood sugar levels rise after a meal, the body secretes a hormone called insulin which helps bring blood sugar levels back to normal. However, it can happen that blood sugar levels drop lower than normal. The body will want to correct this. One way is to secrete hormones that push blood sugar levels up again. Another way, and this is where the trouble starts, is to stimulate the urge to eat something sweet.
If sugar cravings are a recurrent feature in your life, then balancing your blood sugar is top priority for you. The question is, how? Well, one of the most important strategies in this respect is to make sure you eat – regularly. Skipping breakfast, grabbing a light lunch and eating for Britain in the evening will do nothing to stabilise blood sugar levels. Eating three meals a day (yes, that does mean breakfast), is a central principle in establishing blood sugar stability. For many, eating healthy snacks such as some nuts or fresh fruit in between meals can do wonders to keep blood sugar levels from dropping into the danger zone.
Obviously, blood sugar balance doesn’t just depend on when you eat, but what you eat too. The most important thing here to base the diet around foods which give long, slow release of sugar into the bloodstream. Fast releasing foods tend to cause high peaks of blood sugar, which can over-stimulate the body’s regulatory mechanisms, leading to crashes of blood sugar within a few hours. It comes as no surprise that sugar-laden foods such as chocolate, biscuits, sugared breakfast cereals, and soft drinks tend to upset blood sugar balance. What is perhaps more surprising is that many starchy foods, traditionally thought of as being ‘slow releasers’, turn out to be nothing of the sort. White bread, rice, pasta and potatoes all cause relatively rapid rises in blood sugar levels.
The foods which tend to give more sustained blood sugar release include whole rye bread, brown rice, beans, pulses and most fresh fruits and vegetables. Another important dietary element for blood sugar stability is protein. Studies show that including protein (e.g. lean meat, fish, egg, natural yoghurt, tofu) with meals helps regulate the level of sugar in the body. What does all of this mean in practice? Well, instead of your favourite breakfast fayre of honey nut cornflakes, why not try some unsweetened muesli topped with natural yoghurt and raspberries. A chicken Caesar is a much better bet for lunch than a huge baguette. And while pasta may seem like an ideal supper, it doesn’t compare to a piece of fish with vegetables.
A dietary approach to bulimia – 29th February 2004
The National Institute for Clinical Excellence (NICE) here in the UK recently published a report which stressed the role of psychological therapies in the treatment of eating disorders such as bulimia and anorexia nervosa. However, while conventional wisdom has been that these conditions are essentially mental disorders for which a head-first approach should prevail, mounting evidence suggests that disordered eating may be rooted in issues that have more to do with the body, than the brain. In particular, studies suggest that the bingeing of food typically exhibited by sufferers of bulimia may be manifestations of biochemical processes gone awry. Scientific research shows that dietary modification can put pay to the symptoms of bulimia, and is an approach that may be considered to be a no-brainer for those seeking an effective treatment for this condition.
One common cry heard from those suffering from bulimia is that once they start eating, they can struggle to stop. While any food may be the object of a bulimic’s desire, experience shows that most gravitate to carbohydrate-based foods rich in sugar and/or starch. The sort of carb-fest many find themselves engaged in will generally ignite a skyrocketing of blood sugar levels. There is some evidence that this surge in the system has the potential to skew the delicate biochemistry of the brain, and this may have repercussions for both appetite and mood.
In one study published in the journal Biological Psychiatry, an injection of sugar was found to provoke feelings such as depression and anxiety in a group of bulimic women, while a placebo injection did not. Interestingly, women subjected to an influx of real sugar also led to an upsurge in their urge to binge. The precise biochemical mechanism responsible for this phenomenon is unknown. However, the results of this study do at least seem to lend some credence to the common bulimic experience of getting stuck on a roll.
Another hallmark symptom of bulimia is the purging of food from the body, for which induced vomiting and/or laxatives are commonly employed. Interestingly, a study published in the International Journal of Eating Disorders found that purging tends lead to sub-normal levels of blood sugar in the body . The relevance of this is that when blood sugar levels are low, there is a tendency for the body to crave carbohydrate foods, and usually plenty of them too. The available evidence suggests that those suffering from bulimia can be caught in a viscous cycle fuelled by highs and lows of blood sugar.
In practice, I have seen many individuals break this cycle by adopting a diet designed to get blood sugar levels on an even keel. Three meals are day are recommended, and these are best based on relatively slow sugar-releasing foods such as meat, fish, eggs, vegetables and a limited amount of unrefined starch-based foods such as potato, brown rice and wholemeal pasta. Snacks of fresh fruit and/or nuts had between meals can also be useful for keeping blood sugar levels buoyant. Scientific validation for such an approach comes in the form of a study in which 20 bulimic women put on a sugar-stabilising diet . Within three weeks, all 20 of the women had stopped bingeing, and remained free from binges in the long term too. The evidence suggests that a nutritional approach often proves effective for curbing uncontrolled eating, and promises significant benefits for individuals keen to get bulimia out of their system.
1. Johnson WG, et al. Repeated binge/purge cycles in bulimia nervosa: role of glucose and insulin. Int J Eat Disord. 1994;15(4):331-41
2. Dalvit-McPhillips S. A dietary approach to bulimia treatment Physiol Behav. 1984;33(5):769-75
Sugar can be addictive, Princeton scientist says
Posted December 10, 2008; 06:00 a.m.
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by Kitta MacPherson
Animal studies show sugar dependence
A Princeton University scientist will present new evidence today demonstrating that sugar can be an addictive substance, wielding its power over the brains of lab animals in a manner similar to many drugs of abuse.
Professor Bart Hoebel and his team in the Department of Psychology and the Princeton Neuroscience Institute have been studying signs of sugar addiction in rats for years. Until now, the rats under study have met two of the three elements of addiction. They have demonstrated a behavioral pattern of increased intake and then showed signs of withdrawal. His current experiments captured craving and relapse to complete the picture.
“If bingeing on sugar is really a form of addiction, there should be long-lasting effects in the brains of sugar addicts,” Hoebel said. “Craving and relapse are critical components of addiction, and we have been able to demonstrate these behaviors in sugar-bingeing rats in a number of ways.”
At the annual meeting of the American College of Neuropsychopharmacology in Scottsdale, Ariz., Hoebel will report on profound behavioral changes in rats that, through experimental conditions, have been trained to become dependent on high doses of sugar.
“We have the first set of comprehensive studies showing the strong suggestion of sugar addiction in rats and a mechanism that might underlie it,” Hoebel said. The findings eventually could have implications for the treatment of humans with eating disorders, he said.
Lab animals, in Hoebel’s experiments, that were denied sugar for a prolonged period after learning to binge worked harder to get it when it was reintroduced to them. They consumed more sugar than they ever had before, suggesting craving and relapse behavior. Their motivation for sugar had grown. “In this case, abstinence makes the heart grow fonder,” Hoebel said.
The rats drank more alcohol than normal after their sugar supply was cut off, showing that the bingeing behavior had forged changes in brain function. These functions served as “gateways” to other paths of destructive behavior, such as increased alcohol intake. And, after receiving a dose of amphetamine normally so minimal it has no effect, they became significantly hyperactive. The increased sensitivity to the psychostimulant is a long-lasting brain effect that can be a component of addiction, Hoebel said.
The data to be presented by Hoebel is contained in a research paper that has been submitted to The Journal of Nutrition. Visiting researchers Nicole Avena, who earned her Ph.D. from Princeton in 2006, and Pedro Rada from the University of Los Andes in Venezuela wrote the paper with Hoebel.
Hoebel has been interested in the brain mechanisms that control appetite and body weight since he was an undergraduate at Harvard University studying with the renowned behaviorist B.F. Skinner. On the Princeton faculty since 1963, he has pioneered studies into the mental rewards of eating. Over the past decade, Hoebel has led work that has now completed an animal model of sugar addiction.
Hoebel has shown that rats eating large amounts of sugar when hungry, a phenomenon he describes as sugar-bingeing, undergo neurochemical changes in the brain that appear to mimic those produced by substances of abuse, including cocaine, morphine and nicotine. Sugar induces behavioral changes, too. “In certain models, sugar-bingeing causes long-lasting effects in the brain and increases the inclination to take other drugs of abuse, such as alcohol,” Hoebel said.
Hoebel and his team also have found that a chemical known as dopamine is released in a region of the brain known as the nucleus accumbens when hungry rats drink a sugar solution. This chemical signal is thought to trigger motivation and, eventually with repetition, addiction.
The researchers conducted the studies by restricting rats of their food while the rats slept and for four hours after waking. “It’s a little bit like missing breakfast,” Hoebel said. “As a result, they quickly eat some chow and drink a lot of sugar water.” And, he added, “That’s what is called binge eating — when you eat a lot all at once — in this case they are bingeing on a 10 percent sucrose solution, which is like a soft drink.”
Hungry rats that binge on sugar provoke a surge of dopamine in their brains. After a month, the structure of the brains of these rats adapts to increased dopamine levels, showing fewer of a certain type of dopamine receptor than they used to have and more opioid receptors. These dopamine and opioid systems are involved in motivation and reward, systems that control wanting and liking something. Similar changes also are seen in the brains of rats on cocaine and heroin.
In experiments, the researchers have been able to induce signs of withdrawal in the lab animals by taking away their sugar supply. The rats’ brain levels of dopamine dropped and, as a result, they exhibited anxiety as a sign of withdrawal. The rats’ teeth chattered, and the creatures were unwilling to venture forth into the open arm of their maze, preferring to stay in a tunnel area. Normally rats like to explore their environment, but the rats in sugar withdrawal were too anxious to explore.
The findings are exciting, Hoebel said, but more research is needed to understand the implications for people. The most obvious application for humans would be in the field of eating disorders.
“It seems possible that the brain adaptations and behavioral signs seen in rats may occur in some individuals with binge-eating disorder or bulimia,” Hoebel said. “Our work provides links between the traditionally defined substance-use disorders, such as drug addiction, and the development of abnormal desires for natural substances. This knowledge might help us to devise new ways of diagnosing and treating addictions in people.”