eng Enviro Research Publishers Current Research in Nutrition and Food Science Journal 2347-467X 2322-0007 2026-07-13 14 2 26546 article Noura Fahad Aljahdali 1 Magdi Osman 1 Nawal Abdullah Al-bader 1 Khulood Abdullah Alsiary 2 Lujain Ahmed Bahubaish 4 Department of Food Science and Nutrition, College of Food and Agriculture Sciences, King Saud University, Riyadh, Saudi Arabia. Department of Family Medicine, Ministry of the National Guard - Health Affairs, Jeddah, Saudi Arabia. King Abdullah International Medical Research Center. Jeddah, Saudi Arabia. Registered Clinical Dietitian, Ministry of National Guard for Health Affairs, PHC WR. Jeddah, Saudi Arabia. Type 2 Diabetes Mellitus (T2DM) is highly prevalent in Saudi Arabia, with a growing interest in dietary management strategies to improve outcomes. Low-carbohydrate diets (LCDs) are gaining popularity for managing glycemic control in T2DM; however, their impact on micronutrient deficiencies, particularly vitamin B, remains underexplored in this population. We aimed to evaluate the effects of a low-carbohydrate diet compared to a regular diet on vitamin B12 levels and glycemic control (HbA1c) among overweight and obese patients with T2DM. We conducted a prospective cohort study at King Abdulaziz Medical City Jeddah. Consecutive sampling was used to include participants with T2DM patients aged >30 years with a BMI >25 kg/m², receiving metformin therapy for at least three months. Forty-one eligible participants were divided into two groups: the intervention group (n=14) following an LCD, and the control group (n=27) following a regular diet. Vitamin B and HbA1c levels were measured at baseline and after 12 weeks. Statistical analyses were performed using SPSS (version 25) with a significance level of P < 0.05. The mean age of participants was 49±9.2 years, with a male-to-female ratio of 1.15. Most participants (78%) were non-smokers. No significant differences were found in baseline demographics, diabetes duration, or metformin use between groups. Both groups had similar vitamin B levels at baseline, with the majority presenting borderline levels (200-399 pg/mL). After 12 weeks, there was no statistically significant difference in vitamin B levels between the LCD and regular diet groups (P=0.543). HbA1c levels showed a non-significant downward trend in the LCD group (P=0.109), while remaining stable in the regular diet group (P=0.264). In conclusion, we did not find significant differences in vitamin B levels or HbA1c between overweight and obese T2DM patients following an LCD or regular diet over a 12-week period. The findings highlight the need for larger studies with longer follow-up to assess the long-term effects of dietary interventions on micronutrient levels and glycemic control in this population. https://www.foodandnutritionjournal.org/volume14number2/impact-of-a-low-carbohydrate-diet-versus-a-regular-diet-on-vitamin-b-levels-in-overweight-and-obese-patients-with-type-2-diabetes-mellitus-in-saudi-arabia/ Glycaemic control Low-carbohydrate diet Metformin Saudi Arabia Type 2 Diabetes Mellitus Vitamin B deficiency