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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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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Leo Glavine: Meet the social determinants of health

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I had another post scheduled for today but then I read this article and got all fired-up. Just to cement the fact that I’m never going to be able to get a job working in public health in this province – you know, a master’s degree is far more important than actual experience in this province – I have to say: I am appalled that our provincial minister of Health and Wellness would write such an ignorant column.

To boil it down, the minister, Leo Glavine, states that to earn healthcare Nova Scotians must first prove that they’re taking care of their own health. This seems to particularly apply to those with lower-income levels as they are the ones who would be applying for financial assistance. This is so backwards!

I find it highly disturbing that Glavine appears to be unaware that income is the number one determinant of health. A whole other raft of issues go hand-in-hand with insufficient income; lack of time (how does one find the time to exercise, grocery shop, cook healthy meals, etc. when one is working a couple of part-time minimum wage jobs in an effort to pay the bills?), lack of access to programs and services (part-time work means no benefits which means no access to dietitians – let’s not get into the fact that we are woefully under covered by the majority of health care plans anyway, fitness facilities and equipment – some might argue that no equipment is necessary, everyone can walk, walking is great but not sufficient for optimal health and besides, many people who are living in poverty may live in dangerous areas and places without sidewalks and even in the city, the state of sidewalk clearing has been abysmal this winter, other healthcare providers – with the current lack of family doctors many of us don’t have a primary healthcare practitioner regardless of income or benefits). You get the point.

Aside from the fact that the social determinants of health undermine what Glavine is saying, isn’t it the government’s job to improve population health? This is done by implementing programs and policies which are designed to improve the health of all Nova Scotians. To tell us that we should be making more of an effort to improve our own health is tantamount to victim blaming. Yes, there will always be people who are not going to exercise or eat enough vegetables. Is that reason to stop encouraging everyone to lead healthier lives. The burden of proof should not be placed on the individual. We should not be being asked to “improve our attitudes” by the minister. Our government should instead be looking inward and asking themselves why we, as a population are unhealthy, and what they can do to change that.


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Sugar: Not such a sweet heart

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A study was published in JAMA Internal Medicine last week that got everyone all worked up! In case you somehow missed it, sugar is the latest white food to be blamed for obesity. While this study didn’t look at obesity it still added a whole whack (that’s a real unit of measurement, right?) of fuel to the fire of those railing against sugar.

The study looked at the data from NHANES a huge long-term US health and nutrition study and concluded that those who are consuming diets with more than 25% of calories from added sugars are significantly more likely to perish from heart disease than are those who are consuming less than 25% of their daily calories from added sugars.

Of course, there are the usual caveats with this sort of research. They relied on food frequency questionnaires which are notoriously inaccurate and put much of the research based on them in question. A little aside: I used to work as an interviewer for a large Canadian statistical agency and I wouldn’t trust any of the nutrition information we collected. I mean, vegetable intake was determined by asking questions such as “how often do you eat carrots?”. I think we asked about consumption of three kinds of vegetables (including potatoes which were meant to exclude fried and potato chips) and “other vegetables” to determine total vegetable intake. People could answer on a daily, weekly, or monthly basis. Interviewees often seemed confused about hot to answer the questions and I often wondered to myself what people were eating when, based on their answers, they seemed to eat one carrot a month and a slice of bread everyday. Anyway… let’s put aside the fact that these studies are flawed. Let’s pretend that we do actually know how many calories people are consuming every day from sugar. Can we be sure that the increase in heart disease is attributable to sugar consumption? Perhaps it’s due to displacement of other foods. If someone is consuming 25% of their daily calories from sugar that either means that they’re consuming an excessive number of calories and obtaining adequate quantities of required nutrients, they’re consuming excess calories but not meeting nutrient requirements, or they’re consuming reasonable amounts of calories and not meeting nutrient requirements. Odds are, if they’re getting too much sugar, they’re getting too little of a number of essential vitamins and minerals.

I don’t think that we should be obtaining 25% of our daily calories from added sugar. While the “safe” amount of sugar is still up for debate, the previously suggested maximum of 10% of daily calories from the WHO seems reasonable and achievable. I don’t think that we should be rushing out and lobbying the food industry for sugar to be removed from everything. I certainly don’t think that this research lends any support to the case for sugar causing obesity. I think that we should take it as a caution and aim to be more conscious of the sugars we’re consuming on a daily basis.


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Musings on body image

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I’ve been thinking about body image lately. A few things I’ve seen on social media lately have led to me wondering if, when helping clients with weight management, we (i.e. dietitians, personal trainers, doctors) should be giving clients a bit of a disclaimer.

Someone I know posted a letter from a girl complaining about how every time she goes to a hairstylist, she’s informed that they can’t do what she wants with her hair. She brings stacks of photos and is frustrated that they continue to tell her that it won’t work with her hair. Honestly, that’s the mark of a good stylist that they’ll be honest and upfront and not tell you that you can have big bouncy blonde curls if your hair is naturally black and stick straight.

Perhaps, as weight management professionals, we should be doing something similar with our clients. There needs to be a discussion of expectations and an acceptance of the facts. How many of us are (or have worked with) people who aspire to possess the body of some celebrity or other? Sure, such aspiration can provide motivation at the gym or resolve at the grocery store. But we need to realise that we all have different body types and for many of us no matter how much we workout, no matter how many cookies we eschew for broccoli, we’re just not going to look like *insert latest uber hot celeb name here*. And that’s not a bad thing. We need to learn to accept and love ourselves (and our clients) no matter what our size or shape. So maybe you don’t have a thigh-gap or a bikini-bridge or whatever the mythical physical trait of the day is. Who cares? Embrace not just the features you like about yourself but the ones you don’t because they’re what make you, you.

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