Does salt restriction increase blood sugar? Original paper

In this meta-analysis of randomized crossover studies, low-salt diets increased blood glucose levels in participants with hypertension or diabetes.

The effect of salt intake on blood glucose (sugar) levels.

485 participants (58.6% men, 41.4% women; average age of 38) with hypertension (high blood pressure; 94.4%) or diabetes (9.5%).

A meta-analysis of 6 randomized controlled crossover studies was conducted to analyze the relationship between salt intake and blood glucose levels. Because 2 of the included studies separated participants by hypertension status or used a 3-day and 7-day intervention, they were treated as independent datasets, meaning 8 “trials” were analyzed.

In the high-salt diet conditions, total sodium (as table salt, or NaCl) ranged from 4,600 to 7,866 mg/day. In the low-salt conditions, total sodium ranged from 230 to 2,070 mg/day. The durations of the majority of interventions were 3 days to 2 weeks, while one study lasted 12 weeks.

Blood glucose levels were higher after low-salt diets compared with high-salt diets, with an average difference of 3.5 mg/dL (0.19 millimoles).

While these results indicate that a low-salt diet increases blood glucose levels, most of the studies took place over 2 weeks or less, which doesn’t tell us much about the long-term impact of salt on blood glucose levels.

A major strength of this meta-analysis was the inclusion of crossover studies only, which limits variability among the participants, as they serve as their own control. Therefore, confounding factors are minimized, and internal validity is maximized.