A group of UK researchers evaluated five of the most popular nutrition apps based on how accurately they estimated calories.

Their study found a clear winner and loser, but there are pros and cons to each app.

Databases that allow users to input recipes and those that rely on scanned nutrition labels showed some inaccuracies.

Downloading a nutrition app is easy, but finding one that accurately reports calories is a tougher task.

For those interested in weight loss or healthy eating, choosing from among the hundreds of thousands of health and fitness apps can seem daunting — particularly when there's little scientific evidence to suggest that certain apps are more trustworthy than others.

A group of researchers has made the selection process a lot easier. Their new study evaluates the accuracy of five of the most popular nutrition apps: Samsung Health, MyFitnessPal, FatSecret, Noom Coach, and Lose It!.

The study, published in the Journal of Medical Internet Research (JMIR), compared all five nutritional databases against professional standards used by dietitians and nutritionists in the UK. Apps with nutritional data that closely matched the UK standards were deemed the most accurate.

Read more: 8 free fitness apps that can help you get in shape — and what they're best for

For the most part, all five apps provided satisfactory estimates of calories and saturated fat, but a few failed to accurately represent sodium, protein, and micronutrients like calcium and Vitamin C.

The study found a clear winner and a clear loser, but each app had its pros and cons. Take a look at the findings.