Dispelling nutrition myths, ranting, and occasionally, raving


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The glycemic index #realtalk

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I was disappointed to see an article by an RD extolling the virtues of consuming more low glycemic index (GI) foods. I’ve written about the GI before and how glycemic load (GL) is much more relevant when looking at the effects of a specific food on blood sugar. Even so, I don’t think that GL is all that useful (for healthy people) when making food choices in the real world. Sure, you can use it as a tool for selecting foods if you want. There’s certainly no harm in using the GI (or GL), but it’s complicated and frankly, would be a significant pain in the ass to be looking up the GI of every carbohydrate containing food on your grocery list. I mention carbohydrates because the article that prompted this post didn’t, perhaps assuming that everyone is already aware that GI is only relevant to carbohydrate containing foods. Just in case you weren’t, I don’t want anyone walking away with the impression that this is a way to push meat, fat, or a low-carb diet. Although, that would certainly make it whole heck of a lot easier; avoid carbs and thereby avoid high GI foods.

In case you couldn’t be bothered to read the older posts I linked to above. Here’s the gist of it: some high GI foods can be quite healthy (think: watermelon, baked potato, many crackers), and some low GI foods can be quite unhealthy (think: chocolate bars, corn chips, and ice cream). Should we all eat less watermelon and more chocolate bars? Probably not. The other thing about GI is that we don’t generally consume foods in isolation. So, while bread can be high on the GI it’s unusual for most of us to eat bread by itself. Usually we’d have it as part of a sandwich or toasted with peanut butter. Consuming higher GI foods with lower GI foods and fats and proteins helps to mitigate the effect on our blood sugar.

Okay, now that I’ve shat all over the GI what’s an easier way to make healthier choices? And here we go, back to the not so sexy RD style… Choose more whole foods. When choosing processed grains like breads, go for the whole grain options. Try to incorporate two foods groups when you have a snack. For example, cheese and crackers, veggies and hummus, banana and peanut butter, an apple and almonds, snack bars that contain nuts (not just oats and sugar), yoghurt and muesli, you get the idea. Healthy eating doesn’t have to be complicated.


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Eat for your microbes: lose weight fast, gain control of your blood sugar in only one week!

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Photo by Pacific Northwest Laboratory on flickr. Used under a Creative Commons Licence.

I know that I really shouldn’t comment on this research without reading the actual journal article but that hasn’t been published yet and I can’t resist jumping into the fray. Is there a fray? Not really. I just keep seeing people retweeting this and everyone seems all excited about the possibility of these individualized and I need to put a little rain on the parade.

The article starts off sounding great. Who doesn’t want a bespoke diet? Considering the number of people who have asked me as a dietitian to “just tell me what to eat” I think that most people want someone to hand them a nice little meal plan. Of course, most meal plans would be “bespoke” in a sense as any professional worth their credentials is going to tailor the menu to the client. But, I’m not here to quibble about what exactly makes a meal plan bespoke.

So, apparently the researchers looked at how different people react (in terms of blood sugar) to the consumption of different foods. They found a wide range of responses and linked those responses to the types of gut microbes residing in the participants digestive tracts. Then in another study (of only 20 participants) each participants was given a unique diet to control blood sugar and one that was designed to increase blood sugar. Unfortunately, the diets aren’t described in the article so it’s hard to say how much they differed for each participant. There’s also no explanation as to how this ties in to the earlier research looking at the microbiome. In a shocking turn of events, on the diets designed to control blood sugar some (again the article doesn’t indicate how many) participants blood sugar levels returned to normal. On the “bad” diets they had blood sugar spikes that “would be described as glucose intolerant” according to one of the researchers. Essentially, they exhibited diabetes or similar conditions.

The article then goes on to say that this research somehow shows that calories aren’t the only player when it comes to weight loss. What? I thought the research was looking at blood glucose levels. There was no mention of weight change in participants. While I certainly agree that there are many other factors at play, in addition to calorie consumption when it comes to weight management, I fail to see how this research examined this issue at all.

What makes me a little more leery about this study is that the researcher says it’s surprising that ice cream (for example) doesn’t cause huge blood sugar spikes, and that buttered bread has less impact on blood glucose than unbuttered bread. Have these people not heard of glycemic load before? Of course blood glucose responses are going to be mitigated when high carbohydrate foods are consumed with fat or protein. That’s why it’s important to look at how people are consuming foods rather than examining the effect of specific foods in isolation.

I’m trying to withhold full judgement until the research is published. I think that the human microbiome is a fascinating emerging area of research. However, on the basis of this article all I’m envisioning are more scam diet books urging people to eat for their microbes.


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Non-nutritive sweeteners and blood sugar

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I’m starting to think that the sharing of research results is like the telephone game. Researchers publish their articles in journals, slightly (or more so) misleading press releases are issued, news articles are published, these are then shared via social media. Frequently, by the time the information has filtered through these channels, you’re left with a much different message than the original study provided.

I recently read this article that stated “artificial sweeteners affect metabolism and insulin levels”. Now, if you go back to the original journal article, you’ll see that this is quite misleading. The authors found that sucralose (not all non-nutritive or “artificial” sweeteners) had an impact on blood sugar levels and blood insulin levels following a glucose challenge.

Seventeen participants who were not regular consumers of non-nutritive beverages, did not have diabetes, and were classified as obese were given a glucose tolerance test following the consumption of water on one occasion and sucralose sweetened water on another. Increased levels of blood sugar and insulin were observed following the glucose challenge given after the sucralose consumption. However, the blood glucose levels were not all that different (4.2 + 0.2 and 4.8 + 0.3 mmol/L). The insulin levels were about 20% higher following the ingestion of sucralose. 

Other things that I would like to note about this study: there were only 17 participants. This is quite a small sample size (although slightly better than the ones Dr Oz was basing his recommendation to consume vinegar to prevent diabetes) which means that we can’t be certain that the results seen were all that meaningful. There is power in numbers and to be sure that a treatment is truly having the effect you’re observing you need lots of participants. In addition, these participants were not regular consumers of sucralose. Perhaps a different result would have been obtained had they tested individuals who regularly consume sucralose sweetened products. Finally, the study only included obese individuals (the average BMI was 42.3). Would the results be the same for healthy or overweight individuals? What would the results be had tests been done on participants who had type 2 diabetes?

Yes, it’s interesting that sucralose may have an effect on blood sugar but this study is not definitive and it’s definitely not reasonable to extrapolate the results to include all non-nutritive sweeteners.


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Something sour: Vinegar and blood sugar control

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I saw this tweet: “Add 4 teaspoons of vinegar to your diet daily to lower your blood sugar. This may help prevent diabetes #OzTip” from Dr Oz the other day and I immediately thought “blog fodder!”

Googling the subject of vinegar and blood sugar and diabetes, I thought maybe there was something to this lower effect of vinegar on blood sugar after all. WebMD said:

The effect of vinegar on blood sugar levels is perhaps the best researched and the most promising of apple cider vinegar’s possible health benefits. Several studies have found that vinegar may help lower glucose levels.

However, they carry on to state that:

a 2007 study of 11 people with type 2 diabetes found that taking two tablespoons of apple cider vinegar before bed lowered glucose levels in the morning by 4%-6%.

Umm… if this is the best evidence they could come up with then I’m not so sure about using vinegar to lower blood sugar. 11 is an extremely small sample size. As it turns out, most of the evidence supporting the use of vinegar for blood sugar control comes from very small studies. I found one study that compared the consumption of vinegar, vinegar pills, and pickles in 27 people (so, only nine in each treatment group). They found that vinegar had a modest (0.16% in HbA1c) lowering effect on the morning blood sugar of participants while those consuming pickles and vinegar pills actually saw a slight increase in HbA1c. The other study I found was even worse. It included only 11 participants (I think that this is the one the WebMD article was referring to). They found that fasting blood sugar was reduced by 2% in the control group and 4% in the group ingesting vinegar at bedtime. I also think it’s interesting to note that this footnote accompanied the study:

The costs of publication of this article were defrayed in part by the payment of page
charges. This article must therefore be hereby marked “advertisement” in accordance
with 18 U.S.C Section 1734 solely to indicate this fact.

Yes, these results are interesting but with such small sample sizes they’re essentially meaningless. Until larger studies are able to produce similar results I don’t think that advising anyone to consume vinegar at bedtime for blood sugar control is prudent.


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Restless sleep and blood sugar

I don’t know how my friend finds these people… Another gem of a quote from a personal trainer posted on facebook and twitter:

A common cause of restless sleep is low blood sugar. To combat this try eating a stalk of celery with some almond butter or a small handful of nuts before bed. The slow digesting good fats will help raise your blood sugar level slowly and induce a restful sleep!

It’s amazing how three sentences can contain so much misinformation. Does low blood sugar cause restless sleep? It seems unlikely. Many things cause poor and restless sleep (1). Your diet can certainly have an impact. However, eating right before bed is a more likely culprit than low blood sugar. In fact, elevated blood sugar (seen in newly diagnosed, and those with uncontrolled, diabetes) may cause restless sleep as it can lead to frequent urination (2). If you’re so hungry that your stomach’s rumbling, that can make it more difficult to fall asleep. However, it’s much more likely that high blood sugar will negatively impact your sleep than will low blood sugar.

Fortunately, celery and nuts will have very little to no impact on your blood sugar levels. The glycemic load of celery is 1 (this is on a scale of 0 to 250). The glycemic load of nuts is zero.

A few better ways to improve your sleep: get some exercise every day (but not right before bed), impose a no screen-time for at least one hour before bedtime rule for yourself, make sure your room is completely dark and as quiet as possible, avoid caffeine late in the day, don’t have a large meal right before bed. Routine is essential. Try to go to bed at approximately the same time every night.