Considerations for Micronutrient Tracking: Precision and Difficulty

With MacroFactor radically expanding its micronutrient analytics, we thought this would be an opportune time to discuss micronutrients: what they are, what micronutrient targets represent, and considerations for tracking micronutrient intake.

This is part three of a five-part series:
1) Understanding Micronutrient and Essential Nutrient Categories
2) Understanding Nutrient Targets
3) Considerations for Micronutrient Tracking: Precision and Difficulty
4) Which Micronutrients Are Worth Monitoring?
5) Micronutrients are Important, But They Aren’t Everything

Our Knowledge Base also has an archive of additional information about each nutrient you can track in MacroFactor, including what the nutrient actually does, the likelihood of insufficient or excessive intake, and good food sources for each nutrient.

With that out of the way, let’s dive in!

The (im)precision of micronutrient tracking

If you want to track your micronutrient intake, you should be aware that estimates of micronutrient intake based on food tracking data are far more imprecise than estimates of macronutrient or energy intake based on food tracking data.

By law, the calories and macronutrients listed on a food label (typically) must be within 20% of the actual values. That’s a feasible regulation to enforce, and food-level errors of that magnitude produce considerably smaller errors in daily, weekly, and monthly calorie and macronutrient counts.

Micronutrient labeling and reporting, on the other hand, is typically based on the micronutrient content of standard reference foods. It’s simply not feasible to expect food manufacturers to do a full vitamin and mineral assay on all of the foods they produce. So, if a food contains 60g of spinach per serving, and a standard reference database says that spinach has 16.8mg of vitamin C per 60g, the food is assumed to have 16.8mg of vitamin C per serving.

However, actual micronutrient content can vary considerably within a single food product.

For example, a 2018 study testing different batches of baby spinach at different times of the year found that baby spinach contained anywhere from 5.6-39.6mg of vitamin C per 60g serving. And, unlike calorie and macronutrient content, errors in label claims may not wash out over relatively short time scales, because vitamin C content significantly varied by season. In the winter, spinach averaged 26.16mg of vitamin C per 60g serving; in the summer, it averaged just 10.74mg of vitamin C per 60g serving. So, for multiple months at a time, your actual intake of vitamin C from spinach would be 35-40% lower than you thought it was (based on your food tracking data), and for multiple months at a time, your actual intake would be ~135% higher than you thought it was.

Now, I’ll readily admit that I cherry-picked a particularly extreme example to illustrate my point. Most foods don’t have micronutrient contents that vary to that large of an extent, and not all foods have micronutrient concentrations that exhibit significant seasonal variability. But, micronutrient tracking is inherently a bit fuzzier than calorie and macronutrient tracking. Calorie and macronutrient content may differ from label claims by up to 20%, but micronutrient content can easily differ from label claims by 50% or more, due to seasonal differences, regional differences (for instance, despite being next-door neighbors, scientists tend to report higher vitamin A and vitamin C levels in German produce than in Dutch produce), and variations in soil health and farming practices. 

Much like calorie and macronutrient tracking, daily errors in micronutrient tracking should be smaller than the errors present in individual foods. Calorie counts for individual products may be off by up to 20%, but your daily tracking error should generally be smaller than 10%. The same principle should apply to micronutrient tracking: the errors for individual foods can be very large, but the error for a full day (or full week, or full month) of tracking should generally be smaller. Unfortunately, we can’t model out the size of expected daily or weekly errors because there’s not a comprehensive reference documenting the difference between labeled and actual micronutrient contents for a representative set of food products. But, given the data presented here, I think you can reasonably expect your actual daily micronutrient intake to differ from your logged micronutrient intake by up to ~25%.

So, if you log 1000mg of calcium intake, it’s very unlikely that you actually consumed exactly 1000mg, but there’s a pretty decent chance that you actually consumed somewhere between 750 and 1250mg of calcium.

However, there’s another major complication when it comes to tracking micronutrients: most branded food items don’t report the content of most micronutrients.

How to track micronutrients

If you want to track your micronutrient intake, you should make a point of primarily logging “common foods” in MacroFactor.

Government agencies don’t require food manufacturers to list all of the nutrients contained in a food, and for good reason. The point of nutrition labels is to inform consumers about the content of nutrients that are most likely to impact consumers’ health. If every nutrient was listed on every nutrition label, the sheer size of the list would divert attention away from higher-impact nutrients.

So, in most countries, food manufacturers are required to report energy content, macronutrient content, sugar content, saturated fat content, fiber content, salt (or sodium) content, and the content of micronutrients added specifically for the purpose of food fortification (i.e. iron in many wheat-based products, or iodine in table salt). Beyond that, some countries require food manufacturers to report the content of a small handful of additional vitamins and minerals. For instance, the USDA requires US food manufacturers to report iron, calcium, vitamin D, and potassium content.

All other nutrient labeling is voluntary, and most food manufacturers don’t go beyond the bare minimum requirements.

For instance, a recent study reported on the frequency at which most nutrients were reported on food labels in the UK. See if you can guess which nutrients are required to be listed on UK nutrition labels, and which nutrients are only reported on a voluntary basis.

To give a real-world example, here’s a photo of a nutrition label for a can of chickpeas from my pantry:

The nutrients listed on the nutrition label are the nutrients mandated by the US government, and nothing more.

Conversely, here’s a link to the same product in the USDA food database, which reports full micronutrient content for thousands of foods. It shows that chickpeas also have non-zero amounts of magnesium, phosphorus, zinc, copper, manganese, selenium, vitamin A, all B vitamins except for B-12, vitamin C, vitamin E, vitamin K, and choline.

So, if I wanted to closely track my micronutrient intake, logging a serving of chickpeas by scanning the nutrition label of this product would result in undercounting of most micronutrients. Instead, I’d need to:

1. Calculate the energy content of my serving of chickpeas
2. Select the “common foods” entry for chickpeas
3. Adjust the serving size of the “common foods” chickpea entry to match the energy content of my serving of chickpeas
4. Log the “common foods” serving of chickpeas

The “common foods” in MacroFactor come from research-grade databases (like the USDA database and the NCCDB) with robust micronutrient reporting. So, if you want to track your micronutrient intake, you’ll need to make a point of logging common foods, instead of branded foods. If you primarily log branded foods, you’ll underestimate your intake of most micronutrients.

When you search for foods in MacroFactor, history items (items you’ve logged previously) will show up at the top of your search results, followed by custom foods you’ve created, followed by common foods, with branded foods at the bottom.

To help with common food logging, make sure to expand the list of common food results by tapping the “+15” arrow beside the “common” label. By default, your search results will show you the 5 common foods that best match your search query (based on a combination of text matching, and the frequency with which each food is logged). However, the specific item you’d like to log may not show up in the top 5 results; expanding the list to 20 foods by tapping the “+15” arrow will increase the probability of finding the common food you’d like to log. You can see an example in the video below:

For more complex foods, you might need to log individual common food ingredients that roughly match the energy and macronutrient content of the food you’d like to log. For instance, if you’re trying to log a branded egg and cheese sandwich in a way that will allow for full micronutrient reporting, you might need to log common food entries for bread, eggs, and cheese in amounts that roughly match the energy and macronutrient content of the particular branded sandwich you’re consuming.

Conversely, if you do want to primarily log branded foods due to convenience, or because you don’t care too much about closely monitoring your micronutrient intake, don’t stress out if it looks like you’re under-consuming most micronutrients. You’re probably not. You’re just logging foods that don’t have robust micronutrient reporting.

Since exclusively logging common foods is considerably more time-consuming and less convenient than tracking branded food items, you might want to consider spot-checking your micronutrient intake from time to time. For a week, make a point of exclusively (or almost exclusively) logging common foods, while consuming your normal diet. That will capture most of the upside associated with micronutrient tracking (letting you see which nutrients you might be under- or over-consuming) while minimizing most of the downside (the ongoing time cost of logging common foods instead of branded foods). As with most things in life, micronutrient tracking doesn’t need to be approached with an all-or-nothing attitude.

Of course, if monitoring your micronutrient intake matters deeply to you, and you don’t mind primarily logging common food items, there’s certainly nothing wrong with continuing to track mostly common foods so that you can monitor your micronutrient intake on an ongoing basis.

Rebecca laid out four general archetypes of micronutrient loggers in our announcement of the new micronutrient features in MacroFactor. Most people will generally conform to one of these four archetypes most of the time:

1. The Scale Shifter. This group will make no changes to their logging style because logging anything at all, even exclusively Quick Adds, is enough to take advantage of MacroFactor’s diet coaching systems, and to reach their exclusively body composition-related goals.
2. The Generalist. This group will have some additional health-related goals that involve common nutrients that are often found on nutrition labels, such as: fiber, saturated fat, sugar, or sodium. This group would be best served to avoid Quick Adds where possible, and spot check commonly consumed branded products every once in a while.
3. The Optimizer. This group will have an interest in “optimizing” their diet for micronutrient density, and will want to reference their nutrition intake versus almost every micronutrient range we have. When possible, this group will need to rely exclusively on common foods and break down multi-ingredient branded products into their common food constituent parts.
4. The Auditor. This group will oscillate between periods of rigorous micronutrient tracking to impact changes on their nutrition and periods of relaxed logging with emphasis on reaching their caloric targets. This group will be best served with using common foods exclusively during their nutrition audits and defaulting to using a combination of common foods, Quick Adds, and branded products during the majority of their app use.

Of note, it’s totally fine to be a Scale Shifter, Generalist, or Auditor. Most people don’t need to closely monitor all of their micronutrients, all of the time. But, if you do want to closely monitor your micronutrient intake, try to make a point of almost exclusively logging “common foods.”

The table below summarizes the mandatory nutrient reporting requirements in the US, Canada, Australia, and the EU. It will serve as a handy reference for which nutrients you can easily track by scanning barcodes and searching for branded foods, and which nutrients will require you to primarily log “common foods” if you’d like to monitor your intake. If a nutrient is only reported on a voluntary basis where you live, you’ll probably need to mostly log “common foods” if you’d like to accurately track your intake of that nutrient.