The current study examined trends in adherence to dietary recommendations and compared the levels of adherence between diagnosed and undiagnosed subjects with type 2 diabetes mellitus (T2DM) in Korea over the past 14 years.

Data were collected from the 1998-2012 Korea National Health and Nutrition Examination Surveys (KNHANES). Diagnosed diabetes was defined as giving a positive response to questions about awareness of the disease, a physician's diagnosis of diabetes, or medical treatment for diabetes, whereas undiagnosed diabetes was defined as having a fasting glucose level ≥ 126 mg/dl. Assessment of adherence level was based on 6 components of dietary guidelines, considering meal patterns and intake levels of calories, carbohydrates, vegetable/seaweed, sodium, and alcohol. The participants received 1 point if they met the criteria for each of the 6 components, and the total possible score ranged from 0 to 6 points. Multivariate generalized linear regression was performed, taking into account the complex survey design.

Among all diabetic patients aged 30 years or older, the proportion of diagnosed diabetes increased dramatically, from 40.9% in 1998 to 75.9% in 2012 ( P for trend < 0.001). The overall adherence levels to dietary recommendations were low and did not significantly differ between diagnosed and undiagnosed subjects with T2DM for all survey years. Several improvements were observed, including increased adherence to maintaining sufficient vegetable/seaweed consumption (increased from 0.12 to 0.16 points) and limiting sodium intake (increased from 0.12-0.13 points to 0.19-0.24 points; P for trend < 0.001), while adherence to maintaining moderate alcohol consumption decreased.

Analysis of data collected by the KNHANES indicates that Korean T2DM patients have poor adherence to dietary recommendations and maintenance of a healthy lifestyle, regardless of disease awareness. This finding suggests that development of practical, evidence-based guidelines is necessary and that provision and expansion of educational programs for T2DM patients is critical after diagnosis.