Raviteja Nekkalapu

Posted on Dec 14

Why Your Nutrition App's Data Might Be Wrong (And How to Fix It)

#nutrition #showdev #api #serverless

Have you ever seen this in a nutrition app?

Total Fat: 8g

Saturated: 2.1g

Monounsaturated: 3.2g

Polyunsaturated: 1.8g

2.1 + 3.2 + 1.8 = 7.1g ... but total is 8g?

Where's the missing 0.9g?

This isn't a bug. It's a fundamental misunderstanding of how fat data works.

The Problem

Most nutrition APIs return fat data like this:

{
  "totalFat": 8.0,
  "saturatedFat": 2.1,
  "monounsaturatedFat": 3.2,
  "polyunsaturatedFat": 1.8
}

Developers (reasonably) assume: total = saturated + mono + poly

But that's wrong.

Why Fat Doesn't Add Up

Total fat includes:

Saturated fat
Monounsaturated fat
Polyunsaturated fat
Trans fat
Plus:
- Phospholipids (cell membrane fats)
- Sterols (cholesterol-like compounds)
- Glycolipids (sugar-fat molecules)
- Minor fatty acids

These "other" fats aren't usually reported separately, but they're included in the total.

How I Solved This

In the Nutrition Tracker API, I added a hierarchical fat breakdown:

{
  "Fat": {
    "value": 8.0,
    "unit": "g",
    "breakdown": {
      "saturated": { "value": 2.1, "unit": "g" },
      "monounsaturated": { "value": 3.2, "unit": "g" },
      "polyunsaturated": { "value": 1.8, "unit": "g" },
      "trans": { "value": 0.02, "unit": "g" },
      "other": { 
        "value": 0.88, 
        "unit": "g",
        "note": "Includes phospholipids, sterols, and minor fatty acids"
      }
    }
  }
}

Now: 2.1 + 3.2 + 1.8 + 0.02 + 0.88 = 8.0 ✓

Other Common Data Issues

Issue 1: Missing Nutrients

Many APIs return only 5-10 nutrients in free tiers. For a complete picture, you need:

Macros (energy, protein, fat, carbs)
Vitamins (A, B1-B12, C, D, E, K)
Minerals (calcium, iron, magnesium, zinc, etc.)

Issue 2: Inconsistent Units

Some APIs mix units without warning:

Energy in kcal vs kJ
Vitamin A in IU vs mcg RAE
Sodium in mg vs g

Issue 3: Unknown Data Sources

Where does the data come from?

USDA (gold standard, lab-analyzed)
User-submitted (variable quality)
Third-party databases (check their sources)

What to Look for in a Nutrition API

Criterion	Good Sign	Red Flag
Data source	USDA, official government	"Proprietary database"
Nutrient count	20+	5-10
Fat breakdown	Includes "other"	Doesn't add up
Units	Clearly labeled	Inconsistent
Validation	Schema checks	No validation

The Takeaway

Before choosing a nutrition API for your app:

✅ Check if fat values add up
✅ Verify the data source (USDA preferred)
✅ Test with real foods
✅ Confirm all units are consistent
✅ Ensure you get enough nutrients for your use case

Get your data right, and your users will thank you.

Using a nutrition API in your project? I'd love to hear about your experience with data quality issues.

DEV Community