News · Nutrition & Diet
Salt tracked with diabetes risk, measured in urine
A Diabetes Care study measured sodium in repeat 24-hour urine samples from 3,173 adults and found the highest intakes carried 2.66 times the risk of developing type 2 diabetes.
Based on a peer-reviewed cohort study in Diabetes Care
- Researchers pooled 3,173 adults from three prospective cohorts, publishing in Diabetes Care.
- Sodium and potassium were measured from two to four 24-hour urine collections per person, not from food questionnaires.
- 161 people developed type 2 diabetes over a median 13.6 years of follow-up.
- The highest quartile of sodium excretion carried 2.66 times the diabetes risk of the lowest (95% CI, 1.57-4.51).
- Each extra 1,000 mg a day of sodium tracked with 32% higher risk.
- Potassium on its own showed no association with diabetes risk.
- Each unit increase in the sodium-to-potassium ratio tracked with 26% higher risk.
- Observational. The authors themselves note the associations may partly reflect residual confounding.
Salt has been a blood pressure story for fifty years. A study in Diabetes Care measured it properly, in urine rather than questionnaires, and found it tracking with something else entirely.
Risk of diabetes was 2.66 times higher in participants in the highest versus the lowest group for sodium excretion.
Why this question stayed open so long
The link has been proposed before and never settled. High sodium and low potassium intake, well-established dietary risk factors for hypertension, may induce insulin resistance and increase the risk of type 2 diabetes.
The obstacle was measurement. Until now, as the authors put it, previous research based on self-reported intakes is inconclusive. People genuinely do not know how much salt they eat, because most of it arrives inside bread, sauces and processed meat rather than from a shaker.
Measuring what actually went in
Nearly all the sodium a person eats leaves in their urine within a day, which makes a full-day collection a direct measurement rather than an estimate.
The study included 3,173 adults without major chronic diseases from three prospective cohorts. Sodium and potassium excretions were assessed using two to four 24-h urine collections per participant, so each person is measured repeatedly rather than once.
That is unglamorous, expensive work, and it is the entire reason this result carries more weight than the questionnaire studies before it.
What happened over thirteen years
Among 3,173 participants with a mean age of 62.2 years, diabetes developed in 161 over a median of 13.6 years.
The gradient is steep. Each 1,000 mg/day increase in sodium excretion was associated with a 32% higher risk of diabetes, and the top fifth carried more than two and a half times the risk of the bottom.
The potassium result, which is not what you would guess
Potassium is usually cast as sodium’s counterweight, so its absence here is notable. Potassium excretion was not associated with diabetes risk.
The balance still mattered. Each unit increase in the sodium-to-potassium ratio was associated with a 26% higher risk of diabetes.
So the useful framing is not “eat more potassium” but the ratio between the two, which is roughly how the same pair behaves in blood pressure research.
What the urine data cannot show
Nobody was assigned a diet. People eating the most sodium eat differently in many other ways, and adjustment reaches only as far as the factors that were measured.
The authors are unusually direct about this, concluding that although these findings suggest that adopting a low-sodium diet may reduce diabetes risk, the associations may partly reflect residual confounding despite the adjustments they made.
That is the honest version. The measurement here is far better than the field is used to; the design is still observational, and a better ruler does not turn a cohort into a trial.
People also ask
Why does the urine measurement matter so much here?
Because self-reported salt intake is close to useless. People cannot see the salt in processed food, cannot recall it, and systematically under-report it, which is why previous research on salt and diabetes has been inconclusive. Almost all sodium eaten is excreted in urine within a day, so a 24-hour collection measures what actually went in. Doing it two to four times per person also averages out day-to-day swings.
Salt is a blood pressure problem. Why would it affect blood sugar?
The proposed route is insulin resistance. The authors note that high sodium and low potassium intake may induce insulin resistance, which is the step before type 2 diabetes. This study measured the association, not the mechanism, so that pathway remains a hypothesis rather than something demonstrated here.
Does this mean potassium does not matter?
On its own it showed nothing here. But the sodium-to-potassium ratio did track with risk, at 26% higher per unit. That pattern points at the balance between the two rather than at potassium as a protective nutrient in isolation, which is roughly how it behaves in blood pressure research too.
How much salt is 1,000 mg?
Roughly half a teaspoon of table salt, though most sodium in a typical diet does not come from the salt shaker. Bread, processed meat, sauces, cheese and ready meals carry the bulk of it, which is why intake is so hard to estimate by recall.
Should I cut salt to avoid diabetes?
This is general information rather than advice, and one cohort study does not change dietary guidance on its own. That said, existing recommendations already suggest most people eat more sodium than they need, for blood pressure reasons that are far better established. If this finding holds up, it adds a second reason rather than creating a new one.