Researchers wanted to find the best way to check if people are eating too much salt. They tested two methods: asking people questions about their urine collection and using a special chemical marker. The study involved 868 people in the UK and found that simply asking people worked just as well as the more complicated lab method. Both approaches showed that about 70% of people eat more salt than health experts recommend. This is good news because it means doctors and health officials can use the easier method to track salt intake in large groups of people.

The Quick Take

  • What they studied: Whether asking people simple questions about collecting their urine for 24 hours works as well as using a special chemical test to measure how much salt they eat
  • Who participated: 868 adults aged 19 to 64 years old living in England, part of a larger national nutrition study
  • Key finding: Both methods—asking people questions and using the chemical test—gave almost identical results. About 70% of people in both groups were eating more salt than recommended, and the actual salt amounts measured were nearly the same
  • What it means for you: If you’re asked to collect urine for a salt intake study, answering simple questions about your collection is just as accurate as using fancy lab tests. This makes it easier and cheaper for health organizations to track salt intake in communities

The Research Details

This study compared two different ways of checking whether people correctly collected their urine samples over 24 hours. The first method was simple: researchers asked participants if they collected urine for the right amount of time (23-25 hours), didn’t miss any bathroom trips, and collected enough urine (more than 0.4 liters). The second method used a chemical marker called PABA that people swallowed, which shows up in urine and helps scientists verify the collection was complete.

The researchers used information from 868 people who participated in the England Sodium Survey in 2018-2019, which is part of a larger UK nutrition study. They compared how many people each method said had complete collections and whether the salt measurements were different between the two approaches.

This type of comparison study is important because it helps researchers figure out which method is practical for large health surveys while still being accurate enough to make good decisions about public health.

Measuring salt intake accurately is important for public health because eating too much salt increases the risk of high blood pressure and heart disease. The 24-hour urine collection method is considered the gold standard for measuring salt intake, but it only works if the collection is complete. If people don’t collect all their urine, the measurements will be wrong. This study matters because it shows that health organizations don’t need expensive lab tests to verify completeness—they can just ask people simple questions and get reliable results.

This study has several strengths: it used a large, representative sample of UK adults; it compared the two methods directly on the same people; and the results were very similar between methods, which increases confidence. The study was published in a respected nutrition journal. One thing to note is that about 31% of people didn’t complete the chemical marker protocol correctly, which is typical for this type of study but means the comparison was based on those who did complete it properly.

What the Results Show

The study found that 69% of people who completed the chemical marker protocol had complete 24-hour urine collections, while 71% of people reported having complete collections based on the simple questions. This 2% difference is very small and not meaningful.

When measuring actual salt intake, both methods gave nearly identical results. Using the chemical marker method, the average salt intake was 7.40 grams per day. Using the simple question method, it was 7.38 grams per day. These numbers are so close they’re essentially the same.

Both methods also agreed on how many people were eating too much salt. According to UK health guidelines, people should eat no more than 6 grams of salt per day. Both methods found that 70% of participants were exceeding this recommendation. This consistency is important because it means health officials can rely on the simpler method to track salt intake in the population.

The study also looked at the range of salt intake amounts. Most people’s salt intake fell between 5.65 and 9.94 grams per day (using the chemical marker) or between 4.53 and 8.83 grams per day (using self-report). While there’s some variation in individual measurements, the overall patterns and conclusions were the same regardless of which method was used.

Previous research has questioned whether people can accurately report whether they’ve collected their urine completely. This study adds to that discussion by showing that, at least for measuring salt intake in population surveys, self-reported completeness works just as well as objective chemical verification. This supports the idea that simple, practical methods can be trusted for large-scale health monitoring.

The main limitation is that only about two-thirds of people who started the chemical marker protocol completed it correctly, so the comparison wasn’t made on everyone. Additionally, this study was done in the UK with a specific population, so results might be slightly different in other countries or groups. The study also doesn’t explain why the two methods worked equally well—it just shows that they do. Finally, while the methods agreed overall, there was some variation in individual measurements, so for any single person, the results might differ slightly between methods.

The Bottom Line

Health organizations can confidently use simple self-report questions to assess whether 24-hour urine collections are complete, rather than requiring expensive chemical marker tests. This recommendation has moderate to high confidence because the study showed consistent results across a large sample. For individuals participating in salt intake studies, answering the simple questions honestly about your collection is sufficient.

Public health officials and researchers conducting large nutrition surveys should care about this finding because it simplifies data collection. People participating in salt intake studies should care because it means they don’t need to worry about additional testing. Healthcare providers monitoring individual patients’ salt intake may still want more detailed verification. This doesn’t apply to people who aren’t participating in formal salt intake studies.

If you’re participating in a salt intake study, you’ll get results from your 24-hour urine collection within days to weeks, depending on the lab’s processing time. The benefits of knowing your salt intake (being able to reduce it if needed) can start as soon as you get your results and begin making dietary changes.

Want to Apply This Research?

  • If you’ve had your salt intake measured, track your daily sodium intake using food labels and a nutrition app. Set a goal of staying under 6 grams of salt (2,400 mg of sodium) per day and log your meals to monitor progress toward this target.
  • Use the app to identify which foods and meals are your biggest sources of salt. Common culprits include processed foods, restaurant meals, and condiments. Set reminders to check nutrition labels before eating packaged foods, and gradually reduce salt in home cooking by using herbs and spices instead.
  • Track your salt intake weekly and look for patterns. Note which days you go over your target and what foods contributed most. After 4-6 weeks of tracking, reassess your average intake. If you’re still above 6 grams per day, identify 2-3 specific foods to reduce or replace with lower-salt alternatives.

This research shows that simple self-report methods work well for measuring salt intake in large population studies. However, this study does not provide personalized medical advice. If you have high blood pressure, heart disease, or kidney problems, consult your doctor about your individual salt intake needs—they may recommend limits different from the general 6 grams per day guideline. This study was conducted in the UK and results may vary in other populations. Always discuss dietary changes with your healthcare provider, especially if you take medications or have existing health conditions.