bite my words

Dispelling nutrition myths, ranting, and occasionally, raving


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Will canned fruit really kill me? Lessons from epi research

 

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One of my twitter friends retweeted the above tweet yesterday (identifying info removed to protect the guilty). I asked if they had a link to research to support this claim and received a link to this article in Science Daily in response. Dutifully, I followed-up with reading the full journal article. I just couldn’t fathom how eating canned or frozen fruit and vegetables could increase your risk of cancer.

For one thing, right off the bat, the authors are make no mention of frozen vegetables, they refer only to frozen fruit. Just to be clear, that was not a claim they were making.

It’s important to note that the study is observational epidemiological research. It’s impossible to infer causation from such research. At best we can say that there is a correlation between fruit and veg consumption and cancer diagnoses. We can’t say that fruit and veg consumption, or lack thereof, is causing the cancer.

The researchers questioned the participants regarding their fruit and vegetable consumption on the previous day, once a year, for seven years. This data was then linked to all-cause mortality up until 2013.  A few points to make here: 1. fruit and vegetable consumption included fruit juice and dried fruit, as well as pulses (e.g. lentils, beans, legumes) which many would categorize as meat alternatives; 2. dietary recall is notoriously inaccurate… can you remember everything you ate yesterday, including the quantities? 3. we are operating under the assumption that one day is truly representative of most days for the study participants, rather a large assumption.

Some potential confounding variables were controlled for; such as, physical activity, education, socioeconomic status, and BMI. However, it is not outside the realm of possibility that some variables were overlooked. As the researchers themselves point out, they didn’t look at total calorie consumption or other specific aspects of diet (e.g. sodium intake, macronutrient composition, consumption of fast food, timing of food intake, changes in diet, sedentary time, etc). Any of these things could have affected the apparent relationship between fruit and vegetable consumption and mortality from cardiovascular disease (CVD) or cancer.

As someone else on twitter pointed out, it’s also worth noting that the relative risk of dying was quite small. Out of 85, 347 participants, 1, 336 died from cancer and 1, 482 died from CVD. That’s a whooping 3.3% of all participants. Although the researchers found an inverse relationship between fruit and vegetable consumption (except for canned and frozen fruit for which they found a positive relationship) and all-cause mortality I question how meaningful this is. After all, suicide was the leading cause of death in both men and women between the ages of 20-34 years, accidental poisoning was second, and car accidents were third in England and Wales in 2012 (1). Is diet that much of a factor in such deaths? Why look at all-cause mortality? Why not focus solely on lifestyle related deaths?

Yes, it would appear that consuming more fruit and veg is correlated with reduced risk of dying, particularly from CVD. It’s certainly not going to harm you to eat more fruit and veg, unless you’re eating more canned and frozen fruit. So, why would that be? Well, remember the researchers didn’t examine the entire diet, nor did they distinguish between fruit packed in syrup and canned fruit packed in water, or frozen fruit without additives. It’s quite possible that other aspects of the overall diet (or the type of canned/frozen fruit) is responsible for the apparent increase in all-cause mortality in canned/frozen fruit eaters.

That brings me back to the tweet that started all of this. It came from someone who promotes health and fitness and who has a number of followers. Personally, I think that it’s irresponsible to tweet something like that. The tweet misinterpreted the findings by lumping frozen and canned fruit and vegetables together. It also sent a terrible message: if you can’t/don’t eat fresh fruit and veg you may as well not bother; you’re probably going to get cancer if you eat canned/frozen so you’re likely better off polishing off that box of Oreos. Sigh. Many people can’t afford, or don’t have easy access to fresh fruit and vegetables. Frozen and canned are preferable to none, especially if you make good choices. Frozen fruit and vegetables (without added sauces or syrups) are often more nutritious than their fresh counterparts as they are picked and frozen at peak-ripeness rather than under-ripe and spending time in transit, warehouses, on grocery store and fridge shelves. I would also argue that canned are preferable to that box of Oreos. If possible, choose fruit packed in water or juice, not syrup. Choose veg that are packed without added salt. If you can’t find vegetables without added salt, drain and rinse them well before using; you can get rid of up to 40% of the added sodium by doing this.

Don’t be discouraged if you feel that 7+ servings of fruit and veg are beyond your reach. Remember that every little bit helps; fresh, frozen, or canned.

 


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Another salt study

This headline made me cringe: Bread and cereal highest contributors to children’s salt intake: Study.
One, because we’ve known this for years, and it doesn’t just apply to children. In Western nations most people obtain the majority of their sodium from bread products.

Two, as the director of the Federation of Bakers points out toward the end of the article, it’s not because bread contains high amounts of salt, per se, it’s because people consume large quantities of bread products. Despite the focus of the article (and apparently the researchers) on pushing the food industry to lower amounts of salt in bread, it’s unlikely that this is the best response. For one thing, the industry is likely to replace the salt with something else that will turn out to be worse for us. For another, we should be focusing on encouraging people to consume a variety of foods, particularly those that are minimally processed, rather than emphasizing reformulating current packaged foods. Different bread is not the answer, less bread is.


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Forget sugar. Protein is the new smoking.

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A recent study in Cell Metabolism prompted numerous headlines proclaiming that protein (specifically animal protein) may be just as bad as smoking for your health. Before we jump on the anti-protein bandwagon let’s take a look at the actual study.

The researchers used the results from the NHANES (National Health and Nutrition Examination Survey) in combination with mouse and cellular studies. There were over 6, 000 participants in the NHANES which is quite a robust sample. Right off the bat it makes me suspicious that the researchers would also need to incorporate mouse studies. We also know that using nutrition data from self-reported surveys is far from ideal: people tend to under-report food intake. In this case the researchers used 24-hour recall. The pro to this is that it’s one of the more accurate methods for collecting dietary data. The major con to this is that the researchers are assuming that food/nutrient intake from one day is representative of intake every day. That’s a huge assumption. I know that I might eat animal protein at a couple of meals on one day while eating none on another. That would mean I could fall into either the low or high protein intake group depending on the day data collection was undertaken. We also know that mice are not humans (duh) and that research conducted using mice may not be translatable to a human population. Okay, not enthusiastic about the methods, but let’s take a look at the results.

The researchers found no association between all cause, cardiovascular disease, nor cancer mortality and protein intake in all participants over the age of 50. They did find an increase in mortality in participants in the high protein (20% or more of total daily calories from protein) group who had diabetes. Naturally, they could not say with certainty if the high protein intake was the cause of diabetes mortality. However, when they broke the results down further (splitting the group into those aged 50-65 and 66 and up), they found a relationship between high protein intake and all-cause and cancer mortality in the 50-65 age group. They reached the conclusion that animal-based proteins were the cause of this increased mortality because when they controlled for animal protein the “association between total protein and all-cause or cancer mortality was eliminated or significantly reduced”. This was not seen when plant-based protein was controlled for. Interestingly, the opposite was found in the over 66 years age group (i.e. higher protein intakes reduced risk of mortality from cancer or cardiovascular disease).

It appears that the researchers didn’t control for all confounding variables when they were examining mortality and protein intake. There is no mention of controlling for physical fitness, economic status, or employment status. These are important factors to consider when investigating the effect of diet on mortality.

So, what can we conclude from this study? High animal protein intake may increase your risk of mortality if you’re between the ages of 50-65. After that, it may have a protective effect. This suggests that protein plays different roles at different ages and also means that we cannot extrapolate the results to those under the age of 50. We also can’t be certain that the results are accurate due to the limits when using dietary recall data as well as the lack of control for certain potential confounding variables. There may be some benefits to including more plant-based sources of protein in our diets; however, it may be premature for us all to go vegan.

After writing this post, I read the review of this study on Examine.com in which they address the mouse study. They also make some really good points about the protein-human study, including the fact that there’s no differentiation between protein sources beyond separating animal and plant proteins (can we really assume roast chicken is the same as beef jerky?). I highly recommend taking a look at their review.


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Grocery store lessons: Probiotic tea

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Catching up on my magazine reading recently I came across this probiotic tea. While more and more research is coming out to support the use of probiotics to promote healthy gut flora, which is important to overall health, I was still pretty skeptical seeing this. After all, most probiotics prefer a cool temperature and how much would you actually get by drinking a cup of tea?

I checked out the GanedenBC30 (the brand name for the bacillus coagulans used in the tea) website. Apparently their probiotics are much hardier than most strains of probiotic. They’re able to survive extreme heat, extreme cold, and the acidic environment of the stomach.

Here’s the thing: I don’t have the resources to conduct research to determine if this claim is true. The only research I can find (shout out to Vanessa for her assistance!) was financially supported by Ganden. Also, the research didn’t demonstrate the ability of the bacteria to survive extreme conditions. One study looked at the benefit of bacillus coagulans in mice with c. difficile infection. It found that there was improvement in stool consistency. However, we know that mice are not humans and results found in them may not be translatable to us. In addition, two of the authors of the paper were employees of Ganden. Another study looked at the effect of GanedenBC30 on inflammation in human blood samples. Once again, the results were positive. And, once again, the study was funded by Ganden. The  third study actually looked at the effect of GanedenBC30 on gas-related symptoms in humans. Despite stating that there was a benefit to consuming the probiotic, there was no statistically significant difference demonstrated between the placebo group and the probiotic group on many variables. Once again, this study was funded by Ganden.

What to take from all this? Ganden owns the right to this particular strain of probiotic. Thus, any research conducted using it must be approved by them. Considering this, how likely do you think it is that we’ll see any research disputing the benefits of GanedenBC30? Especially, considering that negative findings are rarely reported anyhow. Despite this,  Medline Plus states that there is “insufficient evidence” to support any of the claims attributed to bacillus coagulans. Even if we take Ganden’s word for it and accept that bacillus coagulans is beneficial to our health there are still a lot of additional assumptions we have to make regarding its consumption in tea.  We have to assume that the bacteria can indeed survive on in the tea on the store shelf for a prolonged period. We have to assume that the bacteria can indeed survive steeping in boiling water and passing through stomach acid. We also have to assume that enough bacteria will survive this process to actually be of benefit when they reach the intestines. 

I don’t know about you, but that’s too many assumptions for me. Personally, I’ll stick to my regular tea and get my probiotics from fermented foods and the occasional capsule.

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