Dispelling nutrition myths, ranting, and occasionally, raving


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Comparing apples to oranges

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Image by Timothy Neesam on Flickr used under a Creative Commons Licence

A couple of weeks ago I saw someone with “an interest in nutrition” (this according to their bio) attempting to argue with a dietitian on twitter about nutrition. She had posted something about whole grains (I can’t remember exactly what) and he had asserted that vegetables are a better source of fibre than grains and are therefore nutritionally superior. I bit my tongue and restrained my texting fingers as I didn’t want to get into a circular 140 character argument on twitter when I should have been going to bed. Instead I saved my ranting for you. You’re welcome.

I see the argument that vegetables are superior to grains as disingenuous. You remember the saying about comparing apples to oranges, right? Well, there’s a reason for that saying. It makes no sense to compare two things that are very different. Just like comparing apples to oranges is nonsensical, so is comparing vegetables to grains. Sure, some vegetables might have more fibre than some grains. But other vegetables have very little, and other grains have lots. We also don’t eat foods for single nutrients. There are different nutritional benefits to both grains and vegetables.

People often ask me if X vegetable is better than Y. The answer is pretty much always that they’re both good for different reasons. It’s like asking a parent which child they love more. I love all vegetables equally, but differently. Just because one vegetable has more vitamin C in it doesn’t make it better than another vegetable that may have more potassium.

We also don’t eat foods solely for their nutritional composition. Sometimes we actually eat them because they taste good! Eating doesn’t have to only be about what nutrients we can obtain from the food.

Eating isn’t a competition (unless you’re in an eating competition). It’s not an either or proposition. Foods work together to provide us with all of the nutrients we need. That can include both grains and vegetables.


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Prebiotic vs probiotic

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I came across this short but confused and confusing article a few weeks ago. The article is referencing a study on the effect of prebiotics on maternal weight gain (in rats) during pregnancy. Fairly straightforward until I read the statement: “Dr. Raylene Reimer gave prebiotics – found in food like yogurt or sauerkraut – helped to reduce fat in pregnant rats who were on a high fat and sugar diet.” See my confusion? Either the study involved prebiotics, which are fibre, or the study involved probiotics, which are bacteria (found in cultured and fermented foods such as the ones given in the example).

I found the actual journal article on the study to find out if the research had involved prebiotics or probiotics. It was prebiotics. So, the author of the news article was correct in stating “prebiotics” but confused about what prebiotics actually are. No wonder so many people confuse the two when talking about prebiotics and probiotics. And, to be fair, the terms are incredibly similar.

My trick for remembering the difference between the two? “Pre” means before, and I always think of prebiotics as being what probiotics need before they can grow. Before you can have a healthy gut microbiome, you need food for that bacteria to flourish. That food is the fibre (like that found in grains, vegetables, fruits, nuts, and seeds).


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Greens vs Grains

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Yes, I can get behind the statement that “we can all benefit from more veggies in our diet”. After that, I diverge from this weekly nutrition challenge. I don’t think that replacing grains with greens makes nutritional sense. Maybe if all of your grains are refined baked goods. Otherwise, there are nutrients in both grains and greens and replacing all of your grains with vegetables isn’t necessarily a nutritional win.

Grains tend to provide more fibre than vegetables. They’re also a good source of B vitamins and minerals such as iron and magnesium. The fibre in grains can help promote digestive health, lower LDL, and feeds the probiotics in our intestines. The gut microbiota is a fascinating emerging area of research. There seems to be many relationships between the bacteria living in our digestive tracts and other aspects of our health. Fibre also contributes to satiety. Sure, greens have lower caloric density than grains but they also don’t keep you feeling full.

Greens provide you with plenty of other nutrients. It doesn’t have to be an either or situation. I don’t understand why so many people want to attach guilt to specific foods or food groups. Grains and greens can both co-exist in a healthy balanced diet. Yes, even some refined grains.

In my mind, challenging people to eliminate food groups is not a sensible or sustainable challenge. But what do I know, I’m just a dietitian; not a “strength coach, nutritional expert and practitioner of Chinese medicine”. And greens for grains is pretty catchy. I guess catchy is more important than realistic, sound nutrition advice.


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A bit more about food combining

PB&B sandwich photo by Kevin Reese. Used under a Creative Commons Licence.

PB&B sandwich photo by Kevin Reese. Used under a Creative Commons Licence.

After I wrote about the utter nonsense of food combining last week I had a reader contact me to suggest that perhaps I could elaborate on the positive side of food combining. To be clear, this is not what is traditionally meant by “food combining” which is a complicated way of eating which erroneously is believed to aid digestion and is more based on not eating certain foods in conjunction with others than with eating a variety of foods together.

I mentioned in my previous post that combining some foods can be beneficial in terms of absorption. Fat soluble vitamins (ADEK) need to be consumed with fat in order to be absorbed. This is one of the many reasons that a low-fat diet has been decried by dietitians. Skimmed milk with added vitamin D? No sense to it unless you’re washing down a croissant (or an avocado, nuts, or other fat-containing food of your choice).

In addition to aiding absorption of fat-soluble vitamins, certain foods can help with the absorption of other nutrients. Foods containing vitamin C can help with the absorption of iron, particularly from plant foods in which the iron is less bioavailable than in meats. For example, eating peppers with your spinach salad can help you to absorb more iron. Or having an orange with your oatmeal, tomatoes and beans, etc. Of course, there are also instances where nutrients can hinder the absorption of other nutrients. Tannins and fibre may decrease the absorption of some minerals and medications. Oxalate (found in spinach and some other fruits and vegetables) can impede the absorption of calcium.

As my astute reader pointed out, there’s also the benefit of glycemic control imparted by eating certain foods together. As any reader of Wheat Belly can (and likely will) point out to you, whole wheat bread has a higher glycemic index than white sugar. The thing that’s not taken into consideration when latching onto that fact is that we rarely eat whole wheat bread in isolation. Turn your bread into a peanut butter and banana sandwich or chicken salad sandwich and you’ve altered the glycemic load of the meal because you’ve added other macronutrients. Consuming fat, protein, or fibre can all help to mitigate the effect of carbohydrates on blood sugar. This is why, if someone with diabetes is experiencing low blood sugar it’s much better to give them candy or juice than a chocolate bar. On the flip-side, this is why most dietitians will recommend that you consume two food groups at snacks. Having a piece of fruit and a few nuts or cheese and crackers, berries and yoghurt, veggies and hummus… will help to prevent a spike in your blood sugar and keep you feeling full for longer that if you were to just have a piece of fruit. It also helps you to meet your nutrient needs if you include a vegetable or fruit as part of your snack.


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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.