That Diet Coke isn’t so diet anymore

While everyone is working on their New Year’s resolutions for 2012, either making them or not breaking them, I thought it would be a good time to write about a trio of articles on sugar and artificial sweeteners and their respective health consequences.

A piece published in New York Times magazine several months ago raised the alarm on the extreme health detriments of our sugar habits. Author Gary Taubes cited Dr. Robert Lustig, a researcher in pediatric obesity and hormone deficiencies, as promoting the idea that sugar, not fat, is the main cause for the dramatic rise in type 2 diabetes, hypertension and other “western diet” diseases seen in the last 30 years. These particular detriments stem from the way our bodies metabolize fructose (which makes up half of the refined sugar molecule sucrose), as opposed to pure glucose, which makes up the other half and is found in foods such as potatoes and white bread.

Glucose is metabolized by all cells in the body, whereas fructose is primarily processed by the liver. If the liver cannot adequately break down the sugar (both fructose and glucose) it receives into energy, it is converted into fat. This is more likely to occur if the liver becomes overloaded by the fructose in sucrose solutions, such as in high fructose corn syrup which has a greater concentration of fructose to glucose. The more and faster the body receives the fructose the more likely this is to happen. Therefore, drinking a sugary beverage, such as soda or even fruit juice, results in an even greater spike in fructose as it reaches the liver much more quickly. These drinks place a greater strain on the body than a raw piece of fruit, a “pure” form of fructose, which contains fiber and is digested much more slowly. This failure to break down sugar and the subsequent rise in liver fat is believed to be at the root of insulin resistance, the main underlying deficiency in metabolic disorders such as type 2 diabetes and heart disease.

It is undeniable that as our sugar consumption increases, so do our rates of obesity, diabetes and heart disease. Currently the average American consumes roughly 90 pounds of added sugar a year, and recently non-sugar sweeteners have been proposed as an alternative to sugar and high-fructose corn syrup to help reduce these rates. However two studies from the University of Texas: San Antonio presented at the American Diabetes Association’s Scientific Sessions suggest that these changes might not provide any real benefit.

The first, a longitudinal health study, measured participants’ waist circumference over a ten-year period. They discovered that diet soda drinkers had an almost 70% increase in waist circumference over this time, and those who reported drinking more than two diet soft drinks every day had waist circumference increases 500% greater than individuals who did not consume any diet drinks. These results remained even after controlling for variables such as starting circumference, diabetes, age, sex, smoking status, physical activity levels, and neighborhood of residence.

The second study assessed the effect of aspartame on a high fat diet in mice. One group received food chow with added corn oil and aspartame, the other just the additional corn oil. The group that consumed the extra aspartame had significantly higher glucose levels, but similar insulin levels than the mice who only received the high fat diet. This signifies severe consequences of a fake sweetener diet on diabetes, as blood sugar levels were elevated but insulin (which lowers blood sugar) was not compensatorily raised. This suggests that diet sodas and other foods made with fake sugar could actually lead to an increased risk for developing type 2 diabetes compared to a high fat diet alone.

So if anyone is still looking for a resolution this New Year, perhaps try cutting back on your soda consumption, both regular and diet. Your liver will thank you.

The healing power of the brain-gut connection

Anyone who’s ever tried to cure the blues with Ben and Jerry’s knows that there is a link between our stomachs and our moods. Foods high in fat or sugar release pleasure chemicals into the brain in much the same way that drugs do, and chocolate in particular is frequently touted as a mood-elevating treat. Now research from a team of pharmacologists in Ireland provides new support for this brain-gut connection, showing that probiotic bacteria, like those found in many strains of yogurt, can elevate mood and reduce anxiety.

Formally referred to as the microbiome-gut-brain axis, this system has been implicated in stress responding, with gut microflora affecting the HPA (hypothalamic-pituitary-adrenal) axis and altering stress and anxiety responses. In the current study, researchers gave mice Lactobacillus rhamnosus and then subjected them to various stress-inducing tests. Mice who had been fed the probiotic solution demonstrated less freezing or fear-response behaviors compared to those who were given plain broth. They were also more likely to explore exposed novel environments in an elevated maze, an indication of security and lack of anxiety. Finally, on a depression assessment, mice were placed in a forced swim test (also called the behavioral despair test), where they were submerged in water and had to struggle to stay afloat. Lack of effort and time not spent attempting to swim are seen as indicators of depression and hopelessness, and probiotic-fed mice had less immobility time than broth-fed mice. Corroborating these behavioral results, test mice also had lower levels of corticosterone after being stressed than control mice.

This interaction between the brain and the gut is facilitated by the vagus nerve, a cranial nerve that transmits sensory information from internal organs to the brain. When this nerve was cut the effects of the probiotics disappeared, and test mice had decreased exploratory behavior and greater periods of immobility, similar to the broth-fed mice.

The anxiolytic effects of L. rhamnosus seem to be tied to GABA, an inhibitory neurotransmitter involved in anxiety. Probiotic administration altered levels of GABA mRNA expression in regions of the brain, including the amygdala, hippocampus, and prefrontal cortex. In depressed individuals, GABA levels in the frontal cortex are shown to be reduced, but in the probiotic-fed animals, cortical GABA levels were elevated. This led the researchers to theorize that L. rhamnosus might help to protect against stressful or anxiety-producing events. GABA levels in the amygdala are also commonly elevated in depressed individuals, and GABA antagonists (which reduce the levels of the neurotransmitter in the brain) are sometimes used as antidepressants. In the current study, lower levels of GABA were found in the hippocampus and amygdala after probiotic consumption, suggesting an interaction between L. rhamnosus and the memory and emotional centers of the brain, potentially increasing associative learning and memory consolidation and decreasing fear responding to stressful events.

The connection between diet and behavior doesn’t just apply to stress. Certain highly specified restrictive diets have also been used to help treat and control a variety of neurological disorders, most notably epilepsy. First pioneered in the 1920s at John’s Hopkins Children’s Hospital, extreme high-fat/low-carbohydrate diets are gaining support as a possible alternative for drug-resistant epilepsy, though some physicians are still skeptical. The diet works by invoking ketosis, a process in which the body burns fat stores rather than carbohydrates for fuel. This typically occurs when the body is in a starvation state and is the premise on which low-carb diets are based. However, ketogenic diets also appear to have an antiepileptic effect, particularly in cases of severe pediatric epilepsy. Doctors are not sure why the treatment works, but one theory is that the ketone bodies produced by the liver when the body burns fat protect neurons from damage, though how or why this happens is still unknown.

A keystone paper from University College London published in 2008 was the first to empirically report the efficacy of the ketogenic diet, and a recent provocative profile in the New York Times of a family dealing with epilepsy, “keto,” and the trials it brings has brought this treatment to national attention. The diet itself is strictly regimented and incredibly difficult to follow. It requires exact caloric measurements and proportions of protein, carbohydrates, and fats, with roughly a 3-to-1 fat to carb/protein ratio. This relates to a diet of roughly 90% fat, which can be dangerous, potentially triggering kidney problems and malnutrition. However, the effectiveness of the treatment is gaining recognition, and patients who are on the ketogenic diet (mostly children) are carefully monitored for cholesterol levels and cardiovascular health.

The ketogenic diet is now being looked at to potentially treat other serious medical disorders, such as Parkinson’s disease and cancerous tumors. It is important to note, though, that individuals being treated with a prescribed diet are also frequently on concomitant medication. Diet alone will not be able to cure all ailments, but the connection between diet and mental and physical health cannot be denied, and in the very least it is a good place to start keeping yourself well and taking preventative action.