bite my words

Dispelling nutrition myths, ranting, and occasionally, raving


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Can yoghurt prevent diabetes?

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A friend of mine recently shared the news of a new study reporting an association between yoghurt consumption and decreased risk of type 2 diabetes.

The study was actually a meta-analysis of three large studies. Meta-analyses always make me a little nervous due to the ease of cherry picking and interpreting the results to yield the desired effect. The results of a meta-analysis can only be as good as the results of the original studies on which they’re based. I’m not saying this was the case here, just that it’s something to bear in mind when reading about meta-analyses. The researchers do have on their side the fact that all three studies had large sample sizes. After examining the results of these three studies, they added an additional 11 prospective-cohort studies for their meta-analysis.

The researchers controlled for a number of potential confounders. However, there’s always a remaining risk that an unaccounted for confounding variable might be the true reason for any observed effect. While the researchers reported a significant decreased risk of type 2 diabetes in regular yoghurt consumers they were also quick to acknowledge that this does not indicate causation. Yes, people who consume yoghurt appear to be less likely to develop type 2 diabetes than people who don’t. However, the studies all relied upon self-reported food frequency questionnaires and they were observational. It is possible that there is some unaccounted for variable that’s reducing the risk of type 2 diabetes in yoghurt consumers other than the yoghurt.

The researchers do make an interesting suggestion that the probiotics in yoghurt may be responsible for the decreased risk of type 2 diabetes. I do wonder about the validity of this as many yoghurts contain limited live bacteria due to their processing. In addition, it’s unlikely that many probiotics in yoghurt survive the acidic stomach environment to make their way to the intestines. Perhaps it’s the by-products of the bacteria in the yoghurt (e.g. vitamins, lactic acid) that are responsible for decreased risk of type 2 diabetes. Just postulating here. I would love to see a study in which participants are prescribed diets containing either yoghurt with live bacteria, yoghurt without live bacteria, and no yoghurt. Yes, it would take a long time to determine if the yoghurt reduced the risk of type 2 diabetes but other effects could be examined as well and it would be interesting to see what the true effects of  regular yoghurt consumption are on health.


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Follow Friday: @americangut

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I’m just finishing up a short course on the human microbiome on coursera. While we’re only just beginning to scrape the surface of our understanding of how microbes affect our health it’s a fascinating subject. Did you know that bacteria that are beneficial in your gut may be harmful if they’re found in another part of your body? Obviously your diet can transform your gut microbiome but what effect does it have on your health? It seems that exercise also affects the composition of your gut microbiome. In turn, your microbiome may impact your hormones and neurotransmitters.

You can get in on the ground floor of human microbiome research by supporting the American Gut Project. By pledging your support you can get a kit to send them samples of your microbes. In turn, you’ll receive an analysis of your microbes and see how they compare to others in the study. Despite the name, citizens of countries other than American are welcomed to participate as this can help to provide a larger picture of the human microbiome. The analysis is not intended to diagnose any medical conditions, it simply shows you the prevalence and variety of microbes in your gut at a given moment in time (and other areas of your body depending how much you pledge). However, you’re contributing to some really exciting research that will hopefully lead to greater insight into what your microbiome may mean for your health and well being.


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Are apples the key to curing obesity?

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A few weeks ago the media was reporting that apples may provide the cure for obesity. I was a little more sceptical. I mean, how many overweight and obese people do you know who eat apples? Probably lots. If apples were capable of curing obesity everyone would be thin.

My first concern was that this research was conducted on mice. That means that it may (likely) is not translatable to humans. A couple of things to consider: these mice were fattened up by being fed a very specific high-fat diet. Obesity is a complex condition with myriad factors. Unless the reason for people being overweight is due to consuming a similar diet to these lab mice, it’s quite likely that they will not respond to this weight loss treatment in the same manner as the mice. I also wondered how much apple the mice were fed. How much apple would humans need to consume to see similar results? Here’s where it gets crazy: the mice did not eat the apples. Yep, that’s right. We have no idea how much apple would be beneficial to humans as we don’t know how much would be beneficial to mice. Rather than feeding the apples to the mice, the researchers made a slurry of apple compounds and mouse faeces. They found increased levels of certain bacteria that are commonly found in the faeces of slim mice in the cultured faeces of obese mice. Their results were not statistically significant. They showed a trend toward increased levels of some bacteria and butyric acid, and decreased levels of other bacteria in the faeces-apple slurries of obese mice but none of the changes (save the decreased bacteria) were large enough to be statistically significant.

It’s impossible to say whether or not eating apples (how many, how frequently) would have similar effects on the fecal microbiomes of mice or humans. We also don’t know if these microbial changes do occur if they would result in weight loss. Without knowing this, it’s a ridiculously huge leap to suggest that consuming apples could be a treatment for obesity. This didn’t stop the authors from concluding that:

These results suggest that dietary fibre and phenolic compounds remaining in apples after IVD might help to prevent metabolic disorders driven by an altered microbiota in obesity, and potentially protect from an obesity-disturbed balance of microbiota.

It also didn’t stop the media from publishing articles with headlines like: “An apple a day could keep obesity away: Granny Smiths promote friendly bacteria helping us feel fuller for longer” and “Granny Smith apples can help prevent the damage of obesity“.

I do think that research into our microbiomes is going to provide insight into many illnesses and conditions. However, our individuals microbiomes are extremely variable. Suggesting that this research using mice will translate to obesity treatments for humans. It’s also extremely unlikely that consuming one healthy food will negate the effects of an overall unhealthy diet. That being said, apples are nutritious and it’s certainly not going to hurt you to have an apple a day.


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Parasites for gluten!

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A friend alerted me to this article last week. Before we look at the actual research study, I need to say this is terrible reporting. The headline proclaims: Gluten allergies may be reduced using hookworms. No. Well, maybe. But probably not, and that’s certainly not what the study was looking at. No wonder people are confused about gluten. The study looked at the effect of hookworms on gluten tolerance in individuals with celiac disease. Which, we know, is not an allergy. Celiac disease is an autoimmune disease in which consumption of gluten results in the destruction of microvilli in the small intestine in sufferers. Gluten allergy is a hypersensitivity of the immune system to the gluten (or one of its component proteins) protein. So… if you are allergic to gluten, don’t go infect yourself with hookworms and eat a sandwich. I wouldn’t recommend doing this if you have celiac disease either.

Looking at the actual study… It was very small (12 people, two of whom withdrew from the study before completion). When a study is so small, it’s impossible to say if the results would extend to the majority of those with celiac disease. Setting aside the fact that I’m doubtful that the majority of celiac disease sufferers would willingly ingest hookworms in order to be able to consume gluten again. That being said, it’s quite interesting that the study participants were able to gradually increase their gluten intake to 3 g of spaghetti a day without experiencing any overt, nor covert (i.e. intestinal damage) symptoms of celiac disease. Of course, that’s not a lot of gluten (about one cup of pasta a day) and the study took place over 12 weeks, with the largest quantity of pasta being consumed over the final two weeks. It would be interesting to see if intestinal damage was visible after an extended period of time or if greater quantities of gluten could be consumed.

Something else that I wondered about when reading the article was any potential complications from the use of hookworms. According to the Centre for Disease Control, most people with hookworms experience no symptoms. However, some many experience gastrointestinal distress and the most serious complication is blood loss leading to anemia, and protein loss.

Essentially, celiac disease leads to nutritional deficiencies when gluten is consumed. Introducing hookworms may allow celiac disease sufferers to consume gluten but may also lead to nutrient deficiencies. Alternatively, celiac disease sufferers can follow a nutritious gluten-free diet.


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Follow Friday: All of the low-carb diet blogs

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When the news about the new “low-carb diet is the best long-term weight loss diet” came out I fleetingly considered writing about it. In the moment that I took to think about it, pretty much everyone else had covered it. So… Rather than reinvent the wheel. Here are some links to posts that say pretty much everything I would have said (and then some):

James Fell on Six Pack Abs: New Study: What is low carb good for

Karmal Patel on Examine.com: Is low-carb really the best weight loss diet?

Yoni Freedhoff on Weighty Matters: What I actually learned by reading that low-carb is best study

Julia Belluz on Vox: The one thing you need to know about weight loss and diet studies

There’s more, but that’s probably more than enough reading for now. I’m off to The Canteen for a sandwich. See you Monday!