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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Of doctors, nutritional nonsense, and tweets

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I stumbled across a tweet from a doctor in the US last week and was so surprised by it that I did a little Internetting to determine if this tweeter was a licenced MD. Yep, she was. Now I’m not going to use her name because, perhaps (although based on Rate my MD, it seems unlikely) she’s a far better physician than she is a tweeter. My aim is not to attack her. My aim to to combat the outrageous information she’s tweeting. So… What’s she been saying?

The first tweet I saw said:

… Along with flax seeds, throw some China seeds into smoothies or yogurt. No flashes!

Wow. Who knew, all you have to do to prevent hot flashes during menopause is to include chia (I assume that’s what she meant by “China” – hey, typos happen to the best of us!) seeds in our diets. Is this true? Maybe. Although I’m highly doubtful that it’s that simple and as far as I can tell there’s been no published research on the subject. There are some studies of chia and weight loss in post-menopausal women but none investigating the effect of chia seed consumption on hot flashes during menopause. There is some anecdotal “evidence” on the Internet extolling the benefits of chia seeds for reduction/elimination of menopause symptoms. And while there’s certainly nothing wrong with incorporating chia seeds into your diet at any stage of life, no sensible health care professional would be providing this unsolicited, unsubstantiated advice on social media.

Scrolling through the docs timeline I came across a few other gems. How about?:

Those of you with hypothyroidism should be taking iodine and selenium supplements to help the conversion of T4 to T3.Helps metabolism

Um. No. The only reason for those with hypothyroidism to take iodine supplements is when the condition is caused by iodine deficiency, which is rare in North America (1). There may be benefits to selenium supplementation for those with hypothyroidism. However, there may also be risks associated with long-term supplementation and supplements should be discussed with your primary health care practitioner, not undertaken upon the advice of a tweet.

There are more horrifying tweets but I have to stop somewhere. One last one:

HIgh cholesterol? You are eating too much refined carbs ie #BREAD, white rice, potatoes and not enough fat ie #butter, fatty fish.#krilloil!

High cholesterol has many causes. Not least of which is heredity. Yes, there are lifestyle efforts we can all undertake to reduce our risk of elevated LDL (low density lipoproteins AKA “Bad cholesterol). However, these will only go so far and some people can lead extremely healthy lifestyles and still have high LDL. While it’s likely that saturated fats are not the evil, cholesterol raising nutrients we once believed them to be there is also no reason to think that increasing consumption of them will reduce blood cholesterol levels. The evidence is not there to support supplementation with krill oil either. As for the refined carbs the doctor lists, unless she’s referring to potato chips or french fries there’s no reason to diss potatoes. In fact, potatoes are one of the most under-rated foods.

Guys, be cautious. You’ve all seen Doctor Oz. He’s not the only doctor spewing nutrition nonsense. Question everything you read.


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Dietitians and brand recommendations

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The above tweet really bothered me. Why? For a couple of reasons. One, where is this data coming from? I assume it’s in regards to dietitians in the US, as that’s where the tweet originated. So, can we really paint all dietitians with the same brush? Would dietitians in other countries also be recommending products to clients by brand name 90% of the time in other countries? Are we even talking about dietitians in all areas of practice? After all, we’re a pretty diverse bunch, working in many different areas. 

Two, the implied assumption that this is a bad thing. Maybe I’m the only one, but I immediately felt like we dietitians were somehow doing a disservice to our clients by recommending foods by brand name. The 90% is really quite meaningless. It could mean that a dietitian recommends every food by brand, or it could mean that the dietitian recommends but one of all of the recommended foods by brand. 

Personally, I tend not to recommend foods by brand name. However, I can see times when it might be useful. For example, when telling a client with celiac disease about gluten-free products. Or when someone asks which coconut milk doesn’t contain preservatives or stabilizers. Or when advising someone about humane meat products available at the grocery store. Or when identifying a product which is unique in the market. I don’t think that recommending a product by brand name necessarily means that a dietitian is being influenced by the company in question. I don’t think that it should be taken to mean that his or her credibility is in question. It may simply mean that they are trying to simplify the navigation of grocery store aisles for their clients. 


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Keeping the math in diabetes

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I was innocently reading twitter last night when I saw the following tweet from a Holistic Nutritionist: 

Are you Diabetic? Get away from the numbers! No carb counting, no constant testing, just REAL FOOD! That’s the answer.

I completely understand what she was getting at. I speak with many newly diagnosed diabetics who are overwhelmed and have no idea what they can eat. I also get a lot of them looking for “diabetic” cookies, granola bars, and sweets. This is during their first grocery shop after diagnosis. I loathe the vast majority of sweets marketed to people with diabetes. Most of them would not fall under the heading of “real food”. They’re full of sugar alcohols and highly processed ingredients. And despite that, they still often have a considerable amount of sugar. What so many people don’t understand is that people with diabetes can eat “real food”. They don’t need to have specially formulated bars and snacks. In fact, the diet that’s recommended for people with diabetes is the diet we should all be following: lots of vegetables along with protein, healthy starches, and dairy (or alternative) products. So, yes, “real food” is the recommended diet for all.

This is where I get ranty… This advice is dangerous. If I was newly diagnosed as diabetic I would not find this helpful. Yes, constant testing of blood sugar is no longer recommended. That doesn’t mean that people with diabetes shouldn’t check their blood sugar at all. It can be very helpful for people with diabetes (especially those who have just been diagnosed) to figure out what foods and activities may trigger highs and lows. It can also help people to become attuned to what high and low blood sugar feels like. Carb counting is also a useful tool for those with diabetes. Consistent quantities of carbohydrates are needed to ensure that appropriate doses of medicine are prescribed. Carb counting helps to make sure that appropriate serving sizes of carbohydrate are being consumed and can help reduce the need for medications. For those with insulin pumps, carb counting is necessary to determine how much insulin should be administered at meal times.

Yes, “real food” is important but taken alone it’s a simplistic solution. The numbers are useful tools to help people figure out when, what, and how much of “real foods” to consume.


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Vitamin A and Iron Absorption

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And this is a prime example of why 140 characters are not enough to provide nutrition counselling. It does appear that lower doses of vitamin A (such as the quantities you might obtain from eating the foods listed above) may increase absorption of non-heme iron (i.e. plant sources of iron). However, the increase seems to be minimal in comparison to consuming an iron supplement alone. In addition, when vitamin A supplements of 1, 800 µg were consumed with iron supplements they actually deceased iron absorption (1). Vitamin C, however, has been proven to increase iron absorption (2).

Lessons here:

1. Do your own research. It’s difficult for a 140 character tweet to convey sufficient information for you to make an informed dietary decision.

2. Try to get most of your nutrients from food, rather than supplements. While consuming foods that contain vitamin A may aid in iron absorption, consuming vitamin A supplements may actually decrease iron absorption.

 

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