Dispelling nutrition myths, ranting, and occasionally, raving


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Only the thin die young

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I’m all for looking at overweight and obesity in new ways. I absolutely believe that it’s possible to be overweight and healthy. I am, however, sick of seeing claims that being overweight is protective against death. The implication being that those of us who are “healthy” weights are actually more likely to die than those who are slightly overweight.

Yet another article came out last week touting the headline: People deemed overweight may actually have a lower risk of dying than those who are healthy, study says. The fact that we’re all going to die notwithstanding there are other significant issues with such claims.

To start, I’d like to take exception to the headline itself. Who writes these things? If they had inserted weight after “healthy” it would have made quite a difference. As it’s written it implies that “healthy” and “overweight” are two discrete mutually exclusive categories. This is not the case. It’s entirely possible to be overweight and healthy. It’s entirely possible to be “healthy” weight and unhealthy.

Now that, that’s out of the way, let’s get to the bigger problems with the study results, as covered in the news article. When people are ill, especially mortally ill, they often lose weight. As a result, when looking at death rates and weight it’s incredibly difficult to tease these issues apart. Thus, claims that being overweight protecting against death are essentially meaningless and potentially detrimental. I say detrimental, because if people are dissuaded from eating healthily and exercising regularly by the suggestion that it’s healthier for them to be overweight then it’s quite likely that their health will suffer. We also know that many chronic diseases such as type 2 diabetes and hypertension can be better managed with weight loss, following a balanced diet, and incorporating regular physical activity. While it’s possible that being overweight is actually protective, it’s more likely that the apparent association between lower weight and death is a result of weight loss during illness.

The other significant problem with the claim that overweight is protective against death is that it doesn’t take into consideration quality of life. Many people who are overweight will be prescribed various medications to keep related conditions in-check. This may result in a longer lifespan than someone who’s “healthy” weight who, because of appearing to be in good health (as a result of the conflation of overall health and healthy weight) may go without similar treatment. The “healthy” weight individuals may lead shorter but higher quality lives without the side effects of medications (i.e. they may have shorter lifespans but longer healthspans).

To sum it up: yes, you can be healthy and overweight. You can also be unhealthy. Ditto for both for “healthy” weight. Regardless of your weight the best way to ensure that you lead the longest healthiest life possible is by taking care of yourself.

 


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The spice for life

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A recent study was being touted in the media for the benefits of eating spicy foods. The study looked at the diets of 512, 891 people (yes, that’s a huge sample size) in several areas of China. Participants were asked how often they ate hot spicy foods; never or almost never, only occasionally, 1 or 2 days a week, 3 to 5 days a week, or 6 or 7 days a week. Spicy foods were defined as; fresh chilli pepper, dried chilli pepper, chilli sauce, chilli oil, and other or don’t know. They found that those who consumed spicy foods most frequently were 14% less likely to die in the next five years than those who never or almost never consumed spicy foods.

Now, I love spicy foods, but I don’t eat them to live longer and this study isn’t really convincing me that any of us should be. One big precaution is the fact that the research was only looking at people in China. The effects may not apply to people of other ethnicities. Also, “spicy” is subjective. Something that I find only slightly spicy might be unbearably spicy to another person, and vice versa. There’s a huge risk of confounding variables when looking at things like this. It’s hard to say for certain whether any reduced risk of mortality can be attributed to the spice. In addition, the study looked at a huge range of ages (30-79) and many causes of mortality making it extremely difficult to ascertain whether or not spicy foods could be held accountable for keeping people alive. In fact, we don’t know if these people actually lived for longer, just that they were less likely to die during the course of the study.

Go ahead, go for the jalapenos if you like them, but don’t suffer through fiery meals 6-7 days a week in an effort to live a little longer.


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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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Why the nut study made me nuts

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A study published last week in the New England Journal of Medicine found that the consumption of nuts was tied to lower mortality rates. I love nuts but I hate studies like this.

The research was funded by the International Tree Nut Council Nutrition Research and Education Foundation. Yep, that sounds like an impartial sponsor. I’m sure that didn’t affect the results whatsoever. Yes, they may have had no influence on the design and results but if they study hadn’t found a benefit to eating nuts would it have been published? Would it still have been promoted in the press?

Even putting aside the significant issue of bias, this study wasn’t great. It used the data from the Nurses’ Health Study. Why do I see this as an issue? Well, it relied on self-reported data. We know that self-reported food intake surveys are flawed and tend to provide inaccurate information. Even if the information provided was accurate, we don’t know how generalizable the results from a survey solely of nursing staff is to the general population. These nurses may differ in some fundamental way from the general populace. There’s huge potential for confounding factors in studies like this. Lower mortality rates may be attributed to other aspects of lifestyle, diet, or socioeconomic status. The nut eaters could have been eating the nuts with something else that was the actual health promoter or they may have been eating the nuts in place of something else that was detrimental to health.

It also bothers me that people who had previously had cancer, heart disease, or stroke were excluded from the study. This means that even if eating nuts benefits healthy people (as the study claims) we still don’t know if it benefits those who are, or who have been, ill.

The study also fails to tell us if there is a limit to how many nuts we should eat in a day for maximum benefit. They found that those who eat nuts at least daily had the lowest mortality rates. However, they didn’t say how many nuts people were eating each day. Nuts are undoubtedly delicious and nutrient dense. They are also calorie dense. Having a handful of nuts on your oatmeal or a walnut pesto on your pasta may be beneficial but eating a large bag of trail mix for a snack most likely is not. Simply telling people to eat more nuts is not helpful dietary advice.