A gram of wisdom

Health-conscious consumers and eaters want to know that they’ve chosen the foods with the best nutritional profile. Our society’s quest for perfection greatly influences our eating behaviours, as it implores us to seek out foods that have the highest amounts of all known and suspected nutrients. With increasing frequency, foods that rank anywhere other than top of the list  are seen to be less-than and should be scrapped in favour of the nutritional winners.

I plan to fully address the issues with comparing foods and identifying so-called superfoods in another post at another time. What I would like to point out here is how foods are compared for a certain nutrient and how that compares to what we really eat.

I got this idea when I stumbled across an article highlighting the nutritional values of a little-known herb (at least in North America), purslane. Many other articles are using this evidence to place this plant as a superfood  – perhaps 2016’s answer to kale? The biggest claim to fame of this small sidewalk-dweller is that gram for gram, it contains more omega-3 fats than other green vegetables and most notably, it contains eicosapentanoic acid (EPA), a heart healthy omega-3 that is generally only found in marine plants and animals. The issue at hand here is not the actual nutrient claims, I have no reason to doubt these. No, the key words are the gram-for-gram comparison.

Scientifically, this makes sense as standard measures remove confounding variables and thus better data. Culinarily, standard measures are only useful for similar types of foods or ingredients e.g. comparing 100g of chicken to 100g of beef is useful while comparing 100g baking soda to 100g beef is not). Gastronomically, we tend to eat by volume, not by mass, thus foods that are filling tend to be more satiating; we tend not to care what the weight of a food is, so long as it is enough to fill us up.

Back to purslane. Per 100g portion, it ranks middle of the road for omega-3 content, and amazingly provides only 20 calories. While I couldn’t find exactly the volume of 100g of purslane, an entire bag of baby spinach leaves (the common green often disparaged by purslane proponents) weighs about 114g; I would hazard a guess that most people are not eating an entire bag’s worth of greens in one sitting on a regular basis. So consuming either of these greens in smaller portions, the relative omega-3 content ranking drops dramatically. Similarly, 100g of rapeseed or walnut oil – which top the charts for omega-3 content – is about 1/2 cup, an amount unlikely to be consumed even over a day unless pretty much every you eat is deep fried.

Portion is important. Understanding the food you eat and how you typically eat it will help sort through the fact and the hype of nutrition claims.

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