Friday, April 11, 2014

Cocoa and Weight: What do mice have to do with it?

I regularly consume cakes and cookies made with pure cocoa powder.  I choose cocoa powder because I understand that it contains substances (e.g., antioxidants, polyphenols, flavanols) that promote health similar to the way fruits and vegetables do.  I also choose it because it adds great flavor - a wonderfully rich chocolate taste - acts like a leavening agent (and therefore must be one, because my cakes and cookies with cocoa are fluffier than those without it), and adds only a small amount of calories.

I do not add cocoa to my foods because I think it will allow me to eat a calorically dense high fat diet without consequence.  In other words, I would never read the headline Eating Chocolate Keeps You Thin and 1) believe it, or 2) start eating a lot of chocolate. So when I saw this actual headline: “Eat Chocolate to Get Thin? Study Touts Cocoa for Weight Loss,” in Forbes magazine, I decided to find and read the actual research. The study was published in the Journal of Agricultural and Food Chemistry.  The study subjects in were not people and they were not given cocoa in the sense that you and I know cocoa.

I have just finished reading – really reading – my first scientific study in which the subjects were animals, mice in this case.  The details on the mice were fascinating: where the mice came from, how they were kept (i.e., the type of cage, the number of mice to a cage, the air temperature, the humidity, and the cage cleaning schedule), how their body composition was measured, how they were fed, tested for glucose and insulin tolerance, and finally euthanized and autopsied.  Well ok, the killing of the mice was not at all fascinating; it sort of broke my heart a little.

As I said, the study was published in a chemistry journal, so I am trying to simplify something I can only begin to grasp.  The scientists in this study (Dorenkott, et al 2014) began by explaining that the chemical properties of cocoa have shown health promoting effects in previous animal studies, but the exact mechanism of effect is not fully understood (e.g., if mice who consumed cocoa had less heart attacks than mice who did not consume cocoa is it because the cocoa reduced plaque buildup? lowered LDL cholesterol? raised HDL?).  In addition, researchers have not identified the specific part of cocoa that is creating the positive outcome.

Cocoa is rich in a compound called flavanol, which researchers believe drives its health promoting or disease inhibiting effects. Flavanol breaks down into several other components and in this study, the researchers wanted to compare cocoa extract and three fractions from the extract: polymer rich, oligomer rich, and monomer rich fractions. The researchers were specifically testing how these 4 substances influenced weight and body fat (i.e., obesity markers); and glucose/insulin tolerance (i.e., diabetes markers).  

This was a feeding study, not a weight loss study and the mice were NOT put on diets.

In order to compare the 4 substances, the researchers fed a group of mice one of six diets.  Each cage of mice was randomly assigned to one of six diets: a low fat diet with no cocoa ‘parts,’ a high fat diet with no cocoa ‘parts,’ a high fat diet with cocoa extract, a high fat diet with a monomer rich fraction, a high fat diet with a polymer rich fraction or a high fat diet with an oligomer rich fraction. Staff prepared and weighed the food before providing it to the mice. At the end of each of 12 weeks, the food was removed (if left over) and weighed again – similar to a plate waste analysis – and fresh food was provided.  The researchers placed the exact same amount of calories in each cage, but the mice on the low fat diets consumed more total grams of food.  I expect this is because the number of calories per gram is higher in a high fat diet. 

What I described sounds like the ideal controlled experiment. The mice could NOT cheat on their diet and were not aware of which study condition they were in.  All the mice lived in the same ‘neighborhood.’  The mice did not self-report their food intake or weight and every mouse was tested with the same calibrated device.  The study lasted 3 months, which is enough time to get an idea of an effect; and because it was an experiment, we can be confident that any difference in the outcomes was due to diet type.

Still, even in this near perfect situation there was an issue regarding the dietary intake.  As already noted, there was more food intake (by weight) in the low fat diet.  In addition, the texture of the diets was different.  Texture can influence diet likability and accuracy of the plate waste measurement.  The low fat diet was a powder-based diet; calories were in the powder and the powder was hard to clean from the feeders.  Some of the powdered feed could have dispensed into the cage uneaten and unnoticed by staff.  So, as a consumer of research, keep in mind this limitation.  It is possible that the low fat mice did eat fewer calories than the high fat mice even though the study was set up so that the calories would be the same. 

The high fat diet mice all ate the same amount of food – across the 5 high fat diets.  This is important because in other studies, one concern has been that the cocoa extract/fraction was making the food less enjoyable, leading the mice to eat less food and therefore gain less weight because they were consuming fewer calories (not because cocoa was limiting their weight gain).  In this study, the researchers are confident that the calorie intake was the same, so any differences in actual body weight, body fat and diabetic markers is attributed to whichever supplemented diet (if any) showed such differences.

I may have a limited understanding of the chemistry of cocoa, but the graphs showed a clear difference in outcomes between any high fat diet and the low fat diet. The mice on the high fat diets gained more weight and increased their body fat more under any of the cocoa conditions than the low fat diet mice.  There were a few subtle differences between the diets on the diabetic markers.  The low fat mice always had the best outcomes (e.g., lower fasting blood glucose), but in some cases one or more of the high fat diets with supplementation was equal to the low fat diet or one of the high fat supplement conditions was better than the high fat diet without any cocoa substance.   The high fat diet without any cocoa substances was always worse than the low fat diet.  Remember when I say diet, I mean meal plan; the mice were fed a high number of calories in order to cause weight gain they were not ‘dieting.’  

The researchers will be following up on the oligomer rich cocoa fraction as it showed the most promise in this study.

An important side that I want to point out is that the researchers justified the study by stating as fact that high fat diets are detrimental to health because they lead to obesity and metabolic dysfunction.  This leaves me wondering why we still debate the pros and cons of a high fat diet and why we are using our resources to find fixes for things we could change.  Is the goal of the research to give people a cocoa extract pill that allows them to eat a high fat diet without jeopardizing their health?  I suppose that makes sense if the high fat diet refuses to die; we will need alternative measures to improve health outcomes. 

The researchers killed and autopsied the mice at the end of the 12 weeks.  I find that the most disturbing part of this study – the headline should be, “Mice die so you can keep eating a high fat diet.’

No comments: