bite my words

Dispelling nutrition myths, ranting, and occasionally, raving


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Will an avocado a day keep the doctor away?

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Avocado photo by Paree on Flickr. Used under a Creative Commons Licence.

Last week everyone was all excited about new research touting the health benefits of avocados. The gist of it being that everyone should eat an avocado a day to lower improve their cholesterol profile. Now, I love avocados, but I still had to take a look at the study myself.

The first thing I noticed was that the research was “supported by a grant from the Hass Avocado Board” and that the lead author, Dr Kris‐Etherton, is a member of the Avocado Nutrition Science Advisory. According to one of the news items I heard, she insisted that she still would have published the research if it had not shown avocados to impart special benefits on cholesterol levels. Despite this, it’s still a significant red flag to me that the research was supported by the Avocado Board.

This was also a rather small study, looking at 45 individuals over five weeks. While the results were interesting, a larger study would be needed to draw any definitive conclusions. What were these interesting results? Bearing in mind that dietary adherence was self-reported, 90% allegedly stuck to their prescribed diets, and all participants maintained their starting weights. Participants were assigned to one of three treatment diets: low-fat, moderate-fat, or avocado. All three diets were found to lower LDL-C and total cholesterol. However, the avocado diet decreased both (LDL-C and TC) significantly more than the low- and moderate-fat diets. The avocado diet was also the only diet found to decrease the number of small, dense LDL particles (the really bad guys).

Okay, so avocados may impart health benefits. Does this mean we should all exponentially increase our grocery bills and start eating an avocado a day? Probably not. The participants in the study were predominantly white, overweight and obese, healthy Americans. If you’re not part of that group, the results may not apply to you. The study also only ran for five weeks and did not incorporate other life style changes such as exercise and weight loss. We can’t say if eating an avocado a day would impart the same health benefits to someone of a lower weight, different ethnicity, or disease state. We also don’t know if the benefits would continue beyond five weeks or if eating an avocado every day would be more beneficial than increasing exercise and/or losing weight. What about the effects of all three of these together?

Avocados are delicious and full of good nutrients. I don’t want to discourage anyone from eating them if they enjoy them. However, they are expensive, and their use in the treatment of conditions such as elevated cholesterol needs further investigation before we start prescribing an avocado a day.


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Supplements: Should I take truBrain drinks?

I guess promoted tweets do come in handy every now and again. Blog fodder. This tweet appeared in my feed last week:

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Naturally, my response was: that sounds like complete and utter bullshit.

I went to their website to look for the science to back-up their claims; i.e. an increase in productivity. Naturally, the truBrain research team conducted the study. Surely no bias there. The study itself? Seven. Yep, seven, participants were examined for changes in EEG results following one week of truBrain consumption. The EEG was used to measure brain activity. There was no control group and no blinding (read: high likelihood of bias). Even with the deck so well stacked in their favour, the “researchers” found no significant results at a group level. This pilot study is the only research cited on their website.

Okay, so there’s no real science to support the claim that truBrain can increase productivity. Perhaps a look at the ingredients can provide more illumination:

375 mg of CDP-Choline – The lovely folks at examine.com indicate that there is some minor evidence to support the use of CDP-Choline to support memory and attention, and decreased cognitive decline in older adults. If there is a benefit conferred by CDP-Choline, this might be an effective dose.

200 mg of DHA – This is an omega-3 fatty acid. There may be benefits seen at this dose, although there is no scientific consensus. Also, benefits are most likely seen in individuals who do not regularly consume fatty fish.

375 mg of L-carnitine – This is quite a low dose. While there is some limited research to support the use of L-carnitine to increase cognition in the elderly, there is no research to support its use in the young.

300 mg of L-theanine – This is an amino acid that may promote relaxation. There is no research supporting its use to improve cognition.

375 mg of L-tyrosine – Another amino acid. As a supplement, it may reduce stress and memory in the presence of an acute stressor.

120 mg of magnesium- Many of us don’t consume enough magnesium in our diets so it’s hard for me to knock the inclusion of this mineral in their beverage. However, this is a rather low dose. Some forms of magnesium can cause gastrointestinal distress and diarrhea. It’s also important to note that magnesium supplementation is unlikely to have any effect on cognitive performance.

800 mg of oxiracetam – This is a mild stimulant that may improve memory but there aren’t currently human studies to support this.

In addition to the “medicinal” ingredients, truBrain drinks also contain the following “natural” sweeteners: pomegranate, stevia, blue agave, cranberry, sugar cane, and monk fruit. Six sweeteners. Sweet enough for ya? Not mentioned in any of the ingredient lists is caffeine. The website shows an option for purchasing “non-caffeine drinks” but at the moment they have not yet developed any.

At the low end of the scale you can purchase 15 drinks for a one time fee of $60 or $50 per month. That’s $4 per packet. Unfortunately, the website doesn’t clearly state the size of each drink packet nor the full ingredient list or nutrition information. Without complete information, I can’t completely rip these truBrain supplements to shreds.

Apparently these supplements were developed by neuroscientists. While this might seem to lend an air of believability to their claims, it truly only shows that no profession is exempt from quackery and the desire to turn a profit.

 


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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.