Protein and Fiber Tracking

What each number means

Protein is a nutrient made of amino acids that the body uses to build and repair cells. MedlinePlus says amino acids are found in animal sources such as meat, milk, fish and eggs, and in plant sources such as soy, beans, legumes and nut butters. [1] It also notes you do not need to eat animal products to get all the protein you need. [1]

Dietary fiber is a plant substance and a type of carbohydrate; good sources include whole grains, nuts and seeds, fruit and vegetables. [2] In US labeling rules, dietary fiber is defined as non-digestible soluble and insoluble carbohydrates and lignin that are intrinsic and intact in plants, plus isolated or synthetic non-digestible carbohydrates the FDA has determined to have beneficial physiological effects. [3]

What is measured and what is calculated

On a US label, protein can be calculated by multiplying the nitrogen content of the food by 6.25. [3] So even the label's protein figure is a calculation, not a direct count of amino acids. In an app, the protein or fiber figure is looked up in a database and multiplied by the portion you enter. See nutrition apps and database quality.

How accurate is tracking?

• Self-report. In pooled US validation studies, under-reporting was lower for protein than for energy. [4] A review also concluded that protein is least under-reported, though it is not known which specific foods are commonly under-reported. [5]
• Even so, errors remain. Using a single 24-hour recall, the correlation with true intake was 0.40 for protein versus 0.26 for energy, far from perfect agreement. [4]
• Apps. In an Italian comparison of five apps with a 3-day food diary reference, apps tended to underestimate lipids and, to a lesser extent, carbohydrate and fiber, while two apps overestimated protein. [6] A Belgian study of one app found strong correlations with a national food database for energy and several nutrients, with a fixed bias for fiber. [7]
• Labels. Under US rules, reasonable excesses of protein and fiber over the labeled amount are acceptable, and naturally occurring amounts must be at least 80 percent of the declared value. [3]

These studies used different methods and populations, so they do not rank apps or tell you how accurate your own log is.

Fiber: what the official sources say

The UK NHS says government guidelines advise 30g of fiber a day for adults as part of a balanced diet, and that adults in the UK average about 20g. [8] MedlinePlus says most Americans do not eat enough dietary fiber, and that increasing fiber too quickly can cause gas, bloating and cramps. [2] These are population-level statements, not a personal target. For food-first approaches see fiber, fluids and meal patterns; for supplement forms see psyllium and fiber supplements.

Protein: where tracking can mislead

MedlinePlus lists a recommended range of 10% to 35% of total calories from protein for healthy adults. [1] Protein needs differ by age, health condition and activity, and this library does not give personal targets. Tracking grams can make protein look like a score to maximize; there is no source we read showing that tracking protein improves health outcomes in people generally: Proper evidence not found (we checked PubMed and official nutrition pages). For muscle and aging see protein intake and aging and protein foundations.