A high salt intake is associated with high blood sugar levels and elevated A1C levels (a measure of long-term blood sugar control) in people with type 2 diabetes (T2D), a new study from China reports.
The researchers, who were led by Yi Lin, MD, of the University of Nottingham Ningbo China, explained that economic growth and the adoption of Westernized dietary habits and lifestyles have fueled a rapid growth in rates of type 2 diabetes in China. Between 1980 and 2017, diabetes rates have gone from less than 1% to nearly 13% in the country, and the World Health Organization recently described the rate of diabetes in China as “explosive.”
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Although people with diabetes are routinely advised to watch their salt intake because high amounts of sodium are associated with high blood pressure, as well an increased risk of stroke and cardiovascular disease, the authors pointed out that little research has been conducted on any direct link between dietary salt and type 2 diabetes.
The researchers retrieved data on 2,313 people with type 2 diabetes who had registered between March 2018 and January 2020 at the outpatient Department of Endocrinology, Ningbo First Hospital, Zhejiang Province, China with an initiative called the MMC, or Metabolic Management Center. The MMC, the authors explained, “was established as a platform for the standardized diagnosis and treatment of metabolic diseases and their long-term follow-up.”
The researchers obtained information on the subjects’ diets by having them fill out a standardized survey called the food frequency questionnaire (FFQ). The information included consumption of vegetables, fruit, soy products, red meat, poultry, fish, shrimp, and soft drinks, in addition to daily intake of salt and sugar. The researchers categorized salt intake into three groups: less than 6 grams per day, 6-8 grams per day, and more than 8 grams per day. After the subjects had fasted overnight, the researchers obtained blood samples and tested for several indicators, including plasma glucose, insulin, A1C, cholesterol, triglycerides, uric acid, and serum creatinine.
High blood sugar, A1C more common in high salt intake group
Only about one in four subjects had dietary salt intake in what the researchers considered the low range (less than or equal to 6 grams per day). Compared to them, the higher salt groups had a greater proportion of people with overweight, obesity, high blood pressure, high blood fats or lipids in the blood (hyperlipidemia), high levels of uric acid (hyperuricemia), and coronary disease. The most notable finding was that levels of blood sugar (both fasting plasma glucose and 2 hour plasma glucose) as well as A1C were “significantly higher” in the high salt intake group (more than 8 grams per day), even after adjusting for such factors as weight, BMI (body-mass index, a measure of weight that takes height into account), blood pressure, waist circumference, serum creatinine, and uric acid.
As for the possible reasons that high salt intake was found to be associated with high blood sugar, the authors commented, “The mechanism of the association between dietary salt and the glycemic response in T2D patients is unclear. Increased dietary salt intake may suppress the activity of the renin-angiotensin-aldosterone system, stimulate sympathetic activity, and cause insulin resistance. Therefore, it may contribute to the development and progression of [Type 2 diabetes] complications.” They also speculated that high dietary salt might increase appetite and therefore promote weight gain. Also, they said, “Dietary salt is a key factor in increasing the feeling of thirst, resulting in greater intake of fluid drinks,” which, of course, can also put on pounds. But whatever the reasons for the salt-blood sugar connection, the researchers stated, “Hospital-based lifestyle education with the promotion of salt reduction should be provided to [type 2 diabetes] patients.”
Want to learn more about managing blood glucose? See our “Blood Sugar Chart,” then read “What Is a Normal Blood Sugar Level?” and “Strike the Spike II: How to Manage High Blood Glucose After Meals.”