A Low-Fat Vegan Diet and a Conventional Diabetes Diet in the Treatment of Type 2 Diabetes

Type 2 diabetes is a chronic medical impairment that affects how the body processes blood sugar, known as glucose. (1) Previous studies indicate that improved glycemic control can be attained for people with type II diabetes by consuming a semi-vegetarian diet, therefore facilitating the need for insulin and oral medication. Besides, other studies explain that low-fat vegan diets are correlated with reducing body mass index, increasing insulin sensitivity, and overall boosting cardiovascular health. In the article “A low-fat vegan diet and a conventional diabetes diet in the treatment of type 2 diabetes: a randomized, controlled, 74-wk clinical trial1–4,” Barnard et al. aimed to investigate the impact of a low-fat vegan diet and conventional diabetes diet in the treatment of type 2 diabetes. (2) While the study demonstrated convincing results, it had limitations related to sample size and validation of results.

Barnard et al. conducted a 74-week randomized controlled trial in Washington, D.C. The subjects in this study included free-living individuals with type II diabetes, categorized into two study groups. The first group comprised 49 subjects following a low-fat vegan diet, while the second group had 50 subjects following the American Diabetes Association (ADA) guidelines. At the beginning of the trial, the vegan group was assigned to a dosage of vitamin b-12 supplement to meet the same intervention as the conventional group. Besides, both groups had to limit their alcohol intake and were obligated not to change their activity level for the first 22 weeks. Furthermore, this study used quantitative data from the pedometer, laboratory measurements, and statistical methods to assess HbA1c, body weight, time, dietary adherence, and their interaction. HbA1c, plasma glucose, and plasma lipids were examined at weeks 0, 11, 22, 35, 48, 61, and 74, and physical activities were analyzed at weeks 0, 22, and 73 using a pedometer. Bodyweight, waist-hip ratio, and blood pressure were assessed at weeks 1, 11, 22, and 74. The researchers obtained an increase in carbohydrate, fiber, fruit, and vegetable consumption in the vegan group. On one hand, the subjects following the vegan diet noted a large increase in vitamin C, folate, magnesium, and iron, while on the other hand, a decrease in vitamin D, calcium, and zinc intake was reported. Nonetheless, no substantial difference was observed between the two groups regarding weight loss and energy consumption. Further statistical tests reflected that changes in HbA1c were greater in the vegan group as well as the reduction of LDL and non-HDL cholesterol. One unexpected finding was the extent to which different mechanisms appear to have affected energy intake in the two diets.

Nevertheless, this survey had notable shortcomings, such as a small sample and failure to validate the results. To start with, the researchers used a small sample size. In this article, of 1049 participants, only 99 completed the study. Considering the general nature of the study, this is a small sample size to base the overall findings. Instead, the researchers could consider larger samples that can provide more accurate results. Schönbrodt and Perugini portray this clearly by suggesting that sample correlations converge to the population value with larger sample size, while a small sample size often leads to inaccurate estimates. (3) The small sample size undermined the authors’ ability to detect the error-causing effects and a significant difference in (HbA1c) between the groups. Secondly, there was no evidence of research validation in the article. Barnard et al. did not demonstrate how they validated the results. According to Willis et al., examiners need to validate the results before presenting them to the general public for general application. (4) In this article, the authors did not present any significant difference in losing weight for both conventional diet and vegan groups. While making references, Barnard et al. (2019) found a substantial difference in these two groups, which vary with their work. The researchers have recorded a 0.5-1.9% difference in HbA1c for the vegan and conventional diet groups, respectively. While this difference may be brought about by the small sample size used, as earlier mentioned, the authors failed to validate the accuracy of their research as compared to others. Hence, it cannot be concluded on the accuracy of their results. Contrastingly, some scholars may argue that the sample size and data collection tools were adequate for accurate and reliable results. Nonetheless, the findings had several gaps, closely tied to the undermining effects of a small sample and failure to validate findings. For instance, Although Barnard et al. demonstrated a significant weight loss in both diet groups, the author could not differentiate the extent of the weight loss between the groups.

In conclusion, the authors evaluated an essential subject regarding the effectiveness of a low-fat vegan diet and conventional diabetes diet treatment. However, the study findings were limited by a small sample and the invalidation of results. The researchers inferred that the vegan diet has a greater impact on controlling the concentration of glycemic and plasma lipid. Still, the small sample hindered the establishment of comprehensive details on the effects of a vegan diet on the glycemic and plasma lipid concentration. Besides, there was no evidence of validation of the study outcomes, limiting the outcomes’ reliability. A further experimental investigation is needed to validate whether the clinical advantage concerning the macro- or micro-vascular difficulties of diabetes would be expected.

References

1. Papamichou D, Panagiotakos DB, Itsiopoulos C. Dietary patterns and management of type 2 diabetes: A systematic review of randomized clinical trials. Nutrition, Metabolism and Cardiovascular Diseases. 2019 Jun 1; 29(6):531-43. Available at: https://www.sciencedirect.com/science/article/pii/S0939475319300547
2. Barnard ND, Cohen J, Jenkins DJ, Turner-McGreevy G, Gloede L, Green A, Ferdowsian H. A low-fat vegan diet and a conventional diabetes diet in treating type 2 diabetes: a randomized, controlled, 74-wk clinical trial. The American journal of clinical nutrition. 2009 May 1; 89(5):1588S-96S. Available at: https://academic.oup.com/ajcn/article-abstract/89/5/1588S/4596944
3. Schönbrodt FD, Perugini M. At what sample size do correlations stabilize? Journal of Research in Personality. 2013 Oct 1; 47(5):609-12. Available at https://www.sciencedirect.com/science/article/pii/S0092656613000858
4. Willis M, Asseburg C, He J. Validation of economic and health outcomes simulation model of type 2 diabetes mellitus (ECHO-T2DM). Journal of medical economics. 2013 Aug 1; 16(8):1007-21. Available at: https://www.tandfonline.com/doi/abs/10.3111/13696998.2013.809352