Remember what you ate yesterday? Me neither.
Memory is a tricky thing.
Tell me, what did you eat yesterday? What about the day before? What about 3 months ago – perhaps on October 20th? (well, ok maybe that’s cheating since it was my birthday – so for me the answer is cake and a lot of it.) In nutrition, we rely on the ability of our memories to accurately recall what we ate yesterday (as in a 24 hour recall), which is problematic at best. Now imagine trying to get an accurate picture of what you’ve been eating over the last 3 to 6 months or so (as in a food frequency questionnaire)? Trusting our own recall and honesty is often problematic at best, and what can be worse is using the information we get from our own recall in an inappropriate fashion. Is there a better way?
A very well-written article in the Huffington Post by Dr. David Katz has a nice discussion on both the strengths and limitations of using things like dietary recalls, body mass index (BMI), and other measures of energy balance in nutrition research. He attempts to make sense of two recent but conflicting reports on the topic – one which says that self-reports of energy intake and expenditure are effectively useless and one that says these measures still have some use, so long as they’re used appropriately. Ultimately, he sides with the latter argument, believing that despite their imperfect nature, subjective measures of energy balance still have utility. He states “…perfect measures don’t exist, but that the right conclusions for policy and practice can be reached just the same when how we measure is appropriately contingent on what it will be used for”. Translation: nothing is perfect, we do the best we can with what we have. But is there still a better way?
The world of assessing micronutrient requirements faces a very similar dilemma – with so much driven by subjective assessments of dietary intake. It’s no secret to regular readers of Talking Nutrition that we are strong proponents of using objective measures of nutrient status over subjective measures such as dietary intake assessments when it comes to understanding micronutrients. But does that mean we feel that intake assessments are completely useless? Of course not. Much like Dr. Katz’s argument for energy balance, intake assessments for micronutrients are still valid when used appropriately and so long as we understand the limitations within. Nevertheless, utilizing markers of nutrient status (that is, measures such as blood and tissue concentrations of nutrients) offers a way to determine one’s nutrient needs (and to an extent their level of intake) of vitamins, minerals, and essential fatty acids that does not rely upon unreliable narrators like our own memory.
Dhurandhar NV, Schoeller D, Brown AW, et al. Energy balance measurement: when something is not better than nothing. Int J Obesity 2014; Nov 13 (epub ahead of print).
Satija A, Yu E, Willett WC, et al. Understanding nutritional epidemiology and its role in policy. Adv Nutr 2015; 6: 5-18.