Why Your Fitness App Can’t Tell If You Have A Vitamin Deficiency

Diet-tracking tools often include data about the vitamins and minerals you are (or aren’t) getting. While it’s fine to use that as motivation to eat a few extra veggies, you shouldn’t jump to the conclusion that you have a vitamin deficiency or need megadose supplements. Here’s why.

Pictures: Shannon Kringen, Martinak15, Melissa

Why Diet Trackers Are Flawed

You’ve probably noticed that we don’t always remember things perfectly when we track. (It’s not just you; a lot of scientific research is coming under fire because it’s based on asking people what they have eaten, and people are often wrong.) Entering foods frequently, measuring exact amounts, and improving your estimation skills can help, but the numbers in your diet tracking program are never going to be absolute truth.

You don’t have full control over the information, either. A lot of foods don’t have their full vitamin and mineral information in databases, and food labels are only required to report a handful of micronutrients: Vitamins A and C, and the minerals sodium, iron and calcium. So, even if you’re entering data directly from labels, you may be missing important components. This means that your daily intake of a vitamin — especially if it’s not one of the commonly listed ones — may appear lower than it really is, just because some of the data is missing.

Another thing we often forget: our diets change with the seasons, and over time. (How many lattes did you have this April? How much ice cream in January? How many hearty beef stews in the heat of summer?) Tracking what you eat for a few days or weeks, even if you could somehow do it perfectly, doesn’t really reflect your overall diet.

Why bother tracking vitamins at all, then? Honestly, most people probably don’t need to. If you already know (from previous discussions with a dietician or other health professional) that you have a health issue and need to watch your consumption of a certain nutrient, tracking gives you a way to keep (approximate) tabs on it. But if you’re trying to identify a problem or deficiency in the first place, your diet log by itself isn’t enough.

How Much of a Nutrient Is “Too Much”?

Everybody has their own personal requirement for each nutrient. For example, a larger person might need more than a smaller person, women might need more than men (or vice versa), and many requirements change with age. Diet tracking software may take account of these factors, but there’s also variation from person to person that software can’t possibly track: maybe you, genetically, require a little more or less than I do.

The people who calculate the recommendations understand this, which is why they don’t claim that the recommended amount of a vitamin is perfect for everyone. They study the distribution of nutrient needs in the population, and set the Reference Daily Intake (the amount you’re “supposed” to get) at a level that will meet or exceed needs for 97 per cent of people. That means that 97 per cent of people need that amount or less. If you’re getting less than the RDI but feel fine, there may not actually be anything wrong.

What if it seems you’re getting too much of something? While a few nutrients have well-publicised upper limits (like the recommendation on sodium, for example, which you’re supposed to stay under), most vitamins and minerals have a somewhat obscure upper limit. Here’s the chart you’ll need to tell if you’re really getting too much of something.

This means that you might be getting over 100 per cent of the recommended amount (the RDI) of a nutrient, but still not be getting too much. For example, there is no known upper limit for Vitamin B12, so you can have as much of that as you want. (If it’s possible to overdose, science hasn’t seen it yet.) Others have fairly high upper limits: you can get 2000 per cent of the recommended intake of Vitamin C every day and still be fine. However, you’ll hit the upper limit for zinc at only 400 per cent of the RDI. So if a high percentage is scaring you, don’t freak out until after you check whether you’re actually exceeding the upper limit on a regular basis.

Diet Is Only One Piece of the Puzzle

It’s easy to focus on the data that’s right in front of us, like the reports from your diet tracker. But sometimes that obscures the rest of the picture, where we don’t have hard numbers.

A good health professional won’t diagnose you with a deficiency based on the output from a few weeks of diet tracking. They will put that data together with other information about your health to figure out what’s really going on.

For example, they can order a test to see how much iron or Vitamin D is circulating in your bloodstream. They can ask about aspects of your life that could change your need for the nutrient or your ability to get it from other sources. (For example, if you spend a lot of time in the sun, dietary Vitamin D becomes a lot less important. And if you’re African-American, the results of your Vitamin D blood test may look low even if you’re not deficient.)

And perhaps most importantly, they can examine you. If you’re concerned about your diet because you’re experiencing symptoms that you think are related to a deficiency, don’t stay at home ordering vitamin pills; go to a doctor already where they can check whether your symptoms actually indicate a deficiency, or whether your problem might be any of the myriad other things that can go wrong with the human body.