Are very-low carbohydrate, low saturated fat diets the best choice for A1c control?
Adequate diet and exercise has become the cornerstone strategy for diabetes management. Different diet modalities have been investigated in order to achieve proper glycemic control in diabetes patients. A calorie-restricted diet might seem feasible based on its strong evidence of achieving adequate control. However, adherence seems to limit the use of this diet modality, as it may appear too complex for several patient populations. Other diets focus on reducing fat content due to evidence demonstrating rates of insulin resistance increasing proportionally to fat content. On the other hand, some diets focus on the carbohydrate content due to evidence suggesting that limiting the carbohydrate content can lead to improvements in glucose levels. However, food culture greatly impacts diet and exercise therapy. In the American population, it is estimated that approximately 50% of the total diet is comprised of carbohydrates, followed by fat (~34%) and protein (~16%), making it difficult to properly manage patients.
In an open-label, two-arm, randomized controlled trial conducted in the Japanese population, Juko Sato and colleagues evaluated the safety and efficacy of 130 grams/day of carbohydrates in patients with diabetes who were poorly controlled despite receiving education about their disease state. Patients were ages 20-75 with inadequate A1c control (>7.5% for more than 3 months), and BMI >23 kg/m2, and received two education sessions on calorie-restricted diets. Patients were followed up for 6 months by the same clinician and dietitian. Sixty-six patients were recruited for the study, out of which 33 patients were placed in the low carbohydrate diet (LCD) group and 32 patients were part of the calorie-restricted diet (CRD) group. Once the study concluded, significant changes were noted in BMI and A1c. The decrease in A1c was by −0.65% (−1.53 to −0.10) in the LCD group and 0.00% (−0.68 to 0.40) in the CRD group (p < 0.01). The BMI decrease in the LCD group was greater than in the CRD group (p = 0.03). These findings suggest the usefulness of a low carbohydrate diet; however, challenges will rely on defining and standardizing carbohydrate content cut-offs.
In another research study, Thomas Wycherley et al., examined the effects of very low carbohydrate, low saturated fat diet compared to a high carbohydrate-fat content diet over a 12-month period. 115 patients with type 2 diabetes mellitus were randomized in two groups, one consuming a low carbohydrate diet and the other an isocaloric high carbohydrate diet while undergoing exercise three times weekly for 60 minutes. Both groups were followed for 52 weeks. Flow mediated dilation was measured in each group in order to understand the effect of fat saturation in endothelial function. At the end of the study, both groups obtained a reduction in weight regardless of dietary approach (10.6 ± 0.7 kg; p < 0.001); similar reductions were obtained in A1c (1.05 ± 0.10%; p < 0.001). FMD did not change from baseline, highlighting the possibility that changes in FMD are not affected by weight. Nonetheless, these findings warrant further studies in order to better understand the metabolic effects associated with diet and vascular injury.
These studies highlight the benefits of diet and exercise in patients with diabetes, with positive impacts on A1c and weight. The effects of low carbohydrate diet patterns can be translated to understanding cardiovascular disease risks and the potential role of decreasing these as part of diabetes management strategies. The pathophysiological effects of diabetes on the vascular endothelium can be improved with dietary approaches, including modified fatty acid content. For example, increasing unsaturated fats, while restricting saturated fat intake, can potentially favorably impact prognostic markers of FMD. However, this warrants further evaluation to provide stronger evidence. Marked improvements can be obtained in diabetes patients by providing a proper balance of carbohydrate, protein, and fat along with an adequate exercise routine. Therefore, the key to effectively managing diabetes in patients lies in preventing end-organ complications that can negatively impact health outcomes and overall quality of life. Proper education, more frequent follow-ups, and a personalized diet can help patients achieve their target goals and prevent these complications.
- Adequate diabetes management relies on individualized nutrition therapy.
- Adjusting each patient’s carbohydrate content and incorporating exercise can help improve glycemic control and promote weight reduction in diabetes patients.
- Fat saturation can potentially affect the vascular endothelium; therefore, a modified fatty acid content can help reduce cardiovascular risks in patients with diabetes.
Sato, Junko, Akio Kanazawa, Sumiko Makita, Chie Hatae, Koji Komiya, Tomoaki Shimizu, Fuki Ikeda, Yoshifumi Tamura, Takeshi Ogihara, Tomoya Mita, Hiromasa Goto, Toyoyoshi Uchida, Takeshi Miyatsuka, Kageumi Takeno, Satoshi Shimada, Chie Ohmura, Takehito Watanabe, Kiyoe Kobayashi, Yoshiko Miura, Manami Iwaoka, Nao Hirashima, Yoshio Fujitani, and Hirotaka Watada. “A Randomized Controlled Trial of 130 g/day Low-carbohydrate Diet in Type 2 Diabetes with Poor Glycemic Control.” Clinical Nutrition (2016): n. pag. Web.
Timar, Bogdan, Romulus Timar, Adalbert Schiller, Cristian Oancea, Deiana Roman, Mihaela Vlad, Bogdan Balinisteanu, and Octavian Mazilu. “Impact of Neuropathy on the Adherence to Diabetes-related Self-care Activities: A Cross-sectional Study.” Patient Preference and Adherence PPA Volume 10 (2016): 1169-175. Web.
Wycherley, Thomas P., Campbell H. Thompson, Jonathan D. Buckley, Natalie D. Luscombe-Marsh, Manny Noakes, Gary A. Wittert, and Grant D. Brinkworth. “Long-term Effects of Weight Loss with a Very-low Carbohydrate, Low Saturated Fat Diet on Flow Mediated Dilatation in Patients with Type 2 Diabetes: A Randomised Controlled Trial.” Atherosclerosis 252 (2016): 28-31. Web.
Researched and prepared by Pablo A. Marrero-Núñez – USF College of Pharmacy Student Delegate – Doctor of Pharmacy Candidate 2017, reviewed by Dave Joffe, BSPharm, CDE