Let’s start simple. Sugars (a.k.a. simple carbohydrates) are the most simple type of carbohydrates, and examples include sucrose, glucose (the molecule nearly every cell in your body uses for fuel) and lactose (a type of sugar in milk). Sugars can vary in their chemical arrangement as well as how and where they are digested in the body, but a large amount share a basic formulation similar to the glucose molecule (see my post on sugar). On the average, sugars, like most carbohydrates, yield approximately 4 calories per gram consumed, but as we have already seen, some sugars (fructose, present in a 1:1 ratio with glucose in table sugar, sucrose) cause additional complications and contain “hidden” calories.

Moving up in size, let’s examine complex carbohydrates. These are the kind of carbohydrates found in foods like potatoes, wheat, and corn. Most are essentially sugars (usually glucose, as in the case of starch) linked together into long chains – these are called oligosaccharides or polysaccharides, depending on the number of linked sugars. Compare to simple sugars, known as monosaccharides. We have enzymes in our intestines that are very good at breaking the chains down, and consequently the glycemic index, or a measure of how quickly a food raises blood sugar after consumption, is still relatively high.

Finally, we get to fiber. Fiber is a special type of complex carbohydrates found in fruits, vegetables, and grains. Humans cannot digest fiber, and it  aids with digestion, moderates cholesterol levels and moderates the speed at which glucose enters the bloodstream. Check out my fiber article for more on this.

If you believe the USDA, we should get around 55 percent of our calories from carbohydrates (http://www.health.gov/dietaryguidelines/dga2005/document/html/chapter7.htm). Considering how integral agriculture is to the American image, this isn’t surprising, as the majority of carbohydrate sources in the U.S. do come from grains, legumes, and other starch sources like corn. But let’s take a second to understand what happens when you consume carbohydrates.

When you eat carbohydrates, it ends up dumping glucose into your bloodstream (fiber can mediate and slow down this process, which as we will see momentarily is very important). When you have excess glucose in your blood, it is the job of the hormone Insulin to get it out; high blood sugar is very dangerous. If you’re running a marathon after you eat, then your non-fat cells get the lion’s share of this glucose to provide the energy you need. If not, as is the case 99% of the time, then the glucose gets stored as fat in your fat cells, because we can only burn so much glucose per unit time. This isn’t a problem, because normally, this stored fat gets released slowly after eating, your cells metabolize it, and everything works out.

But, here’s where things go wrong. Your body produces insulin in direct proportion to the amount of glucose in your bloodstream. When you eat a lot of carbohydrates, which dump glucose into your bloodstream, your pancreas has to produce tons of insulin in order to get it out of your blood. Normally, only a little insulin is needed, but repeatedly spiking your blood sugar increases this amount. First of all, you can essentially become diabetic if your pancreas burns out from producing too much insulin. Beyond that, the problem is that your non-fat cells get tolerant to insulin if you produce too much of it too often. Insulin functions as a gatekeeper, allowing glucose into cells, so if your cells are tolerant to insulin, they aren’t letting as much glucose in. And what happens then? If your non-fat cells are taking out a smaller proportion of the glucose in your blood, not only does more of it gets stored as fat, but you end up eating extra calories you don’t need due to the insulin resistance choking your cells of fuel, which your brain then interprets as starvation. What happens when your cells aren’t using as much energy? Even though you’re eating the same amount of calories, due to your fat cells absorbing more energy, your “starving” body does what it has to do: it slows down its metabolism, reducing your energy expenditure and promoting food-seeking behaviors, and you gain weight. As if all this wasn’t enough, according to Dr. Robert Lustig, M.D., insulin acts on certain parts of your hypothalamus to make it less sensitive to leptin, the end result of which is that you get even hungrier. Leptin is your brain’s way of making sure you aren’t starving- the more fat on a person, the more circulating leptin. A drop in perceived leptin due to insulin interference is interpreted as starvation. Some experts attribute the entire obesity epidemic to a western diet rich in insulinogenic foods (those which result in huge blood sugar spikes, i.e. carbohydrates) which essentially train your body to store more of each meal as fat. This set of circumstances renders the usual “cure” for obesity – eating less and exercising more – useless, as we can only exert so much personal control and influence over these extremely powerful biochemical processes. Yikes!

I don’t mean to demonize carbohydrates, and many nutritionists who are in the know about this recommend about 20% of calories from carbohydrates, but I really enjoy knowing that others know how these things work. The above information describes what happens when you eat lots of carbs – a big soda, a few pieces of bread, a handful of crackers – really fast. “Good” carbohydrates (fruits and vegetables) are those which come packaged with fiber, which reduces the rate at which glucose is absorbed, leading to decreased insulin resistance over time. I don’t like the idea of my biochemistry being hijacked by the low-fat, high-carb western environment I’m in. As an aside, there is a LOT of very interesting history behind this addressing how it is a “perfect storm” of several political winds; it is covered in several of my favorite documentaries. I will make a list of them eventually. Another interesting note is that it is entirely possible to survive completely on a carbohydrate-free diet, as your body can synthesize its own glucose (http://www.ajcn.org/content/75/5/951.2.full). Many of the scientists responsible for providing the evidence which initially demonized fat in the diet (and consequently promoted carbs) happened to be funded by institutions which stood to benefit monetarily from nationwide increase in carbohydrate consumption via decreased food prices, and they would disagree with this, for reasons which by now should be obvious.

The majority of information from this post comes from the documentary “Fat Head” directed by Tom Naughton. His film represents what I want to do with this blog – debunk myths (such as high carbs being healthy) and provide valuable and useful information in an easy to understand way.

-Sugary drinks are, according to the proposal, ”sweetened with sugar or another caloric sweetener that contain more than 25 calories per 8 fluid ounces and contains less than 51 percent milk or milk substitute by volume as an ingredient.” (25 calories per 8 fluid ounces equates to 9.4 grams of sugar in a 12 ounce can-sized beverage; for reference, Coke contains 39 grams of sugar per can) (source: http://www.huffingtonpost.com/2012/05/30/bloomberg-plans-a-ban-on-_n_1557851.html)

-Diet drinks, since most contain no calorie-containing sweeteners, would not be affected by this.

-Alcoholic beverages would not be affected.

-Dairy products (e.g., milkshakes) would not be affected.

-The ban would apply to any establishment that receives grades for food service.

Considering that 58% of adults in New York City are obese, and that the city spends over 4 billion dollars a year for medical care for overweight people (source: http://www.cnn.com/2012/05/31/us/new-york-sugar-drinks/index.html), you might think that I’d be seriously happy about this, considering yesterday’s discussion of sugar! However, despite being heavily biased, there is a kernel of truth in what some opponents of this proposal are saying. McDonald’s restaurants responded that “…public health issues cannot be effectively addressed through a narrowly focused and misguided ban. This is a complex topic, and one that requires a more collaborative and comprehensive approach.” (source: http://www.usatoday.com/news/health/story/2012-05-31/soda-ban-new-york-city/55296248/1) I  know that if people consume less sugar, they will lose weight. Numerous studies have supported this, including several referenced in Dr. Robert Lustig’s presentation (see yesterday’s post). However, based on my psychological knowledge, I believe that Bloomberg is taking the wrong approach here. If people want sodas, they’re going to buy them, and here’s why: there is scientific evidence showing that obese people show the same brain adaptation as drug addicts in the nucleus accumbens (Wang G-J, Volkow ND, Logan J, et al. Brain dopamine and obesity. Lancet 2001; 357: 354-357), a brain area important for reward pathways (the number of dopamine receptors goes down, contributing to the tolerance phenomenon). There is also evidence that consuming palatable foods such as sugar activates mu-opioid receptors in the nucleus accumbens– the same receptors that fire up when a person uses opioid drugs such as cocaine (Taha S.A. et al. Endogenous opioids encode relative taste preference. European Journal of Neuroscience 2006. 24, pp. 1220–1226). That said, it’s no stretch to say that food can become addictive, and that if people are addicted enough to high-sugar foods, by golly, they’re going to get them somehow. I don’t want to compare this to prohibition back in the roaring 20′s, even though alcohol has the exact same effect (Wang G-J et al, 2001), but my intuition tells me they’re similar.

This is a blog about health, not politics, so I won’t dwell on this for long. I simply think that, in a match between a slightly inconveniencing law and brain chemistry, the brain chemistry is going to win. I don’t know what the right approach is– beyond, of course, making every effort to educate people about the detrimental effects of chronic exposure to certain foods, hence this blog– but I believe Bloomberg’s approach isn’t going to help in a significant way. On top of that, it is definitely getting certain people riled up about restriction of freedom, which I can sympathize with. Ideally, I believe it should be up to the individual to make choices for his or herself, however, as we all live in Lustig’s “Toxic Environment,” it is pretty tough to ascribe the entirety of a person’s choice to consume unhealthy food to his own will (this is actually a very well known phenomenon in cognitive psychology called the “misattribution bias,” where people will continually underestimate the extent to which scenario and environment plays a role in others’ decisions).

I encourage you all to think about this issue from all sides. If you were Bloomberg, running NYC, would you feel like your hands were tied? What if he increased the ban, down to 12 ounces? 8? What do you think is the best way to begin down the path towards a healthy nation?

Here’s what a molecule of sucrose looks like:

Source: http://cellbiologyolm.stevegallik.org/sites/all/images/sucrose.png

The first thing to notice is that there are two big rings connected by an atom of oxygen. You have an enzyme in your intestines which is really good at breaking that oxygen bond and separating the rings. When they get separated in your intestines, the two rings become two distinct molecules: the one on the left becomes the molecule glucose, and the one on the right becomes the molecule fructose. These molecules get absorbed through your intestines and get transported around your body. As we will see later on, free glucose floating around in your intestines is probably the worst thing you can do for your insulin levels. With fructose, the effect is much more sinister.

When the body gets exposed to certain substances it can’t process– alcohol, for instance– it is the job of the liver to process and eliminate the poison. The hepatic (liver) metabolism of some substances results in harmful byproducts and side effects. Fructose is one such substance. According to Dr. Robert Lustig, M.D., an endocrinologist at UCSF, fructose is a “chronic toxin,” where continued exposure over long periods of time can lead to serious consequences. There are two main consequences.

First, Chronic hepatic metabolism of fructose interferes with Leptin signaling in the ventromedial hypothalamus in the brain. Leptin is a hormone produced in fat cells, and the amount of fat on a person directly correlates with the amount of leptin circulating in their bloodstream. Your brain can measure the amount of leptin circulating about, and uses that measurement to regulate hunger. If it senses that your leptin levels are decreasing, it interprets that you must be starving because your fat stores are dwindling (note: high insulin levels result in this same reduction in leptin sensitivity). In response to this, not only do you become hungrier, but you also enjoy the lovely benefits of decreased sympathetic nervous system activity: decreased energy expenditure and physical activity (you feel like crap and don’t want to exercise). As an aside, this is part of the reason why weight loss is so difficult; decreased leptin due to fat loss is interpreted by your brain as “oh no, my body is starving! I better make this person hungrier,” most often resulting in gaining the weight back, which is extremely common. It’s a brilliant evolutionary mechanism to ensure nutrition- if prehistoric man stumbled across a patch of berries, he would want to consume as much as possible due to the scarcity of the resource. But, this mechanism gets abused nowadays, as our brains have essentially been hijacked due to the wide prevalence of sugar in western diets.

Second, fructose stimulates the production of fat in the liver. Let’s say you consume a spoonful of either glucose or fructose. According to Lustig, when you compare how much of a load of glucose versus a load of fructose ends up as fat, the fructose wins big time: below 5% for glucose and almost 30% for fructose. In other words, when you eat fructose (sugar), you aren’t eating carbs- you’re eating fat. And indeed, studies do show that acute administration of fructose raises triglycerides in the blood. Lustig goes through all the biochemistry in his presentation I mention at the end of this post. At this point I’d like to remind you all of how you’ll always see candies marketed as “low fat” or “fat free.” Well, considering that fructose ends up as fat, that’s simply a blatant lie, which really irritates me. It irritates me that due to a lack of certain knowledge, people are taken advantage of. But I digress.

In summary, eating sugar results in several unpleasant consequences: 1) High insulin levels due the glucose portion of sugar being mainlined into your bloodstream interfere with leptin signaling in the brain, leading your body to not only divert more energy into fat via energy-saving mechanisms spurred by decreases sympathetic nervous system activity, but also make you feel sluggish and starved, and 2) hepatic metabolism of fructose leads to the same decrease in leptin sensitivity.

If you go to an average grocery store in America and look at the ingredients in random products, you’ll find that much more than you think contains extra added sugar. I never thought it would be so difficult to find a brand of bread in my grocery store that didn’t have extra sugar added (note: high fructose corn syrup is metabolically the same as sugar, in case you were wondering). On the surface, it would seem that manufacturers add sugar because it makes their product taste better, and people will buy more of a product if it tastes good. But, armed with the knowledge from above, we realize that adding sugar is a clever, almost insidious way to get people to eat or drink more of the product, as it basically turns down the volume on the hormone responsible for telling you that you’re full. This is where the skeptic in me starts poking his head out, and reminding me why I created this blog. I want people to be aware of 1) the bad things sugar does to you, 2) how your brain gets tricked into eating more when you eat too much of it, and 3) how “big food” companies are highly aware of both these facts and use them to profit at the expense of our health. I urge you to purchase food with no added sugar, if you have the option. It might taste a little worse, but it’s definitely worth it.

The majority of my knowledge about sugar and the facts in this post come from Dr. Robert Lustig’s presentations titled “Sugar: The Bitter Truth,” which can be found here:

http://www.youtube.com/watch?v=0z5X0i92OZQ