EXPERTQ&A Paleo Lo-Carb

High Fiber

Glycemic Index

Mediterranean

Vegan

Which for Type 2 ?

Karen Beer, PA-C, MSPAS, RD, LD, CDE

rescribed diets can be trying for both whole , , , , Karen Beer practices at the Oregon Medical patients and providers; patients of- and products, and an emphasis on Group in Eugene. P ten struggle to adhere to them, and foods higher in fiber and lower in glycemic providers must determine which plan is load.2 suitable for which patient. The optimal diet Additionally, the ADA, the American for patients with diabetes—and whether it Association of Diabetes Educators, and the is sustainable—remains controversial. Academy of and Dietetics advise A plant-based diet high in polyunsatu- that all individuals with diabetes receive rated and monounsaturated , with lim- individualized Medical Nutrition Therapy ited saturated and avoidance of trans- (MNT), preferably with a registered di- fatty acids, is supported by the American etitian nutritionist (RDN) knowledgeable Association of Clinical Endocrinologists. and skilled in providing diabetes-specific Caloric restriction is recommended when nutrition education. MNT delivered by an is appropriate.1 The American RDN has been shown to reduce A1C levels Diabetes Association (ADA) recommends by up to 2% in people with a Mediterranean-style diet rich in mono- (T2DM).3 unsaturated fats with carbohydrates from This flexibility in recommendations cre-

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ates uncertainty about the correct dietary drates) demonstrated beneficial effects on choice. Several diet plans are endorsed glucose, A1C, and triglyceride levels. for the management of diabetes, includ- Nine of the studies evaluated glycemic con- ing Mediterranean, low carbohydrate, Pa- trol and found A1C reduction with lower leolithic, vegan, high fiber, and glycemic carbohydrate diets; the greatest reductions index (GI). Which should your patients in A1C and triglycerides were correlated adhere to? Several randomized controlled with the lowest carbohydrate intakes. No trials (RCTs), meta-analyses, and literature significant effects were seen for total, HDL, reviews have examined and compared the or LDL cholesterol.6 benefits of these eating habits for manage- In the literature review by Ajala et al, ment of diabetes. low-carbohydrate, low-GI, and Mediterra- nean diets all improved lipid profiles. HDL MEDITERRANEAN cholesterol increased the most with a low- The incorporates plant carbohydrate diet.5 foods such as greens, tomatoes, onions, A two-week study of 10 adults with T2DM garlic, herbs, whole grains, legumes, nuts, found that just one week on a low-carbo- and as the primary source of fat. A hydrate diet decreased the average 24-h crossover trial of adults with T2DM demon- plasma glucose from 135 mg/dL to 113 mg/ strated a statistically significant A1C reduc- dL. Over the two-week study period, triglyc- tion (from 7.1% to 6.8%) after 12 weeks on erides decreased by 35%, cholesterol by 10%, the Mediterranean diet.4 and A1C by 0.5%. Patients were allowed to In a of 20 RCTs, Ajala consume as much protein and fat as desired. Food sources included beef and ground tur- With low-carb diets, the majority of key patties, chicken breasts, turkey, ham, † steamed vegetables, , diet gelatin, weight loss was explained by a decrease in and a limited amount of . Mean cal- body fat, not loss of water weight. orie intake decreased from 3,111 to 2,164 calories/d. Carbohydrate intake decreased et al analyzed data for nearly 3,500 patients from 300 to 20 g/d. Weight loss was entirely with T2DM who adhered to either a low- explained by the mean energy deficit.6 Pa- carbohydrate, vegetarian, vegan, low-GI, tients experienced no difference in , high-fiber, Mediterranean, or high-protein satisfaction, or energy level with a low-carb diet for at least six months. The research- diet compared to their usual diet.7 ers found that Mediterranean, low-carbo- A literature review of six studies examined hydrate, low-GI, and high-protein diets all the effects of low-carb diets (between 20- led to A1C reductions—but the largest re- 95 g/d) on body weight and A1C in patients duction was observed with patients on the with T2DM. Three of the studies restricted Mediterranean diet. Low-carbohydrate and carbohydrate intake to less than 50 g/d. All Mediterranean diets resulted in the most reported reductions in body weight and A1C. weight loss.5 In two studies, the majority of the weight loss was explained by a decrease in body fat, not LOW-CARBOHYDRATE loss of water weight. No deleterious effects Low-carbohydrate diets have decreased on risk, renal func- in popularity due to concerns about their tion, or nutritional intake were seen. The effects on renal function, possible lack of researchers concluded that low-carb diets nutrients, and speculation that their mac- are safe and effective over the short term for ronutrient composition may have effects people with T2DM.8 on weight beyond those explained by ca- loric deficit. A meta-analysis of 13 studies of adults with T2DM following a low-carbohy- The (also referred to as the drate diet (≤ 45% of calories from carbohy- caveman diet, diet, and hunter-

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gatherer diet) involves eating foods believed higher HDL but no significant change in to have been available to humans before ag- weight, according to Ajala et al.5 riculture—this period began about 2.5 million years ago and ended about 100,000 years ago. HIGH-FIBER Food sources include wild animal (lean A survey of 15 studies examined the rela- meat and ) and uncultivated plant foods tionship between fiber intake and glycemic (vegetables, fruits, , eggs, and nuts). It control. Interventions ranged from an addi- excludes grains, legumes, dairy products, , tional 4 to 40 g of fiber per day, with a mean refined , and processed oils. increase of 18.3 g/d. Additional fiber low- In a randomized crossover study of 13 participants with T2DM, the Paleolithic † A low-fat vegan diet has diet improved glucose control and several acceptability similar to that of a more cardiovascular disease markers, compared to a standard diabetes diet. The Paleolithic conventional diabetes diet. diet resulted in significantly lower A1C, tri- glycerides, diastolic blood pressure, body ered A1C by 0.26% in 3 to 12 weeks, com- weight, BMI, and waist circumference, as pared to placebo. The overall mean fasting well as increased HDL. Despite receiving no blood glucose reduction was 15.32 mg/dL. instruction to restrict calories, patients on No study lasted more than 12 weeks, but it the Paleolithic diet consumed fewer calo- is inferred that a longer study could result ries and carbohydrates, and more protein in a greater A1C reduction. Current dietary and fat, than those on the standard diabetes guidelines for patients with diabetes exceed diet. The caloric deficit accounted almost the amount of fiber included in most of exactly for the observed difference in weight these studies.11 loss between the two groups.9 VEGAN GLYCEMIC INDEX Ajala et al observed that patients on a vegan The GI measures the blood glucose level in- diet had lower total cholesterol, LDL, and crease in the two hours after eating a partic- A1C levels, compared to those on a low-fat ular food, with 100 representing the effect of diet. At 18 months, the vegetarian diet dem- glucose consumption. Low-GI food sources onstrated improvement in glucose control include beans, peas, lentils, , pumper- and lipids, but not weight loss.5 , bulgur, parboiled rice, barley, In one RCT, a low-fat vegan diet was and oats, while high-GI foods include pota- shown to improve glycemic control and toes, wheat flour, white bread, most break- lipid levels more than a conventional dia- fast , and rice. betes diet did. A1C decreased by 1.23% over A meta-analysis compared the effects of 22 weeks, compared to 0.38% in the conven- high- and low-GI diets on glycemic control tional diet group. Body weight decreased by in 356 patients with diabetes. Ten of 14 stud- 6.5 kg and LDL cholesterol decreased by ies documented improvements in A1C and 21.2% with the vegan diet, compared with a postprandial plasma glucose with lower GI weight loss of 3.1 kg and a 10.7% LDL reduc- diets. Low-GI diets reduced A1C by 0.43% tion in the conventional diet group.12 after an average duration of 10 weeks. The Patients on the vegan diet derived en- average GI was 83 for high-GI diets and 65 ergy primarily from carbohydrates (75%), for low-GI diets. The researchers concluded protein (15%), and fat (10%) by eating fruits, that selecting low-GI foods has a small but vegetables, grains, and legumes. Portion clinically relevant effect on medium-term size and caloric and carbohydrate intake glycemic control, similar to that offered by were not restricted. The conventional diet medications that target postprandial blood involved a caloric intake mainly from a glucose excursions.10 combination of carbohydrates and mono- Low-GI diets resulted in lower A1C and unsaturated fats (60% to 70%), protein (15%

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to 20%), and (< 7%). The diet REFERENCES 1. American Association of Clinical Endocrinologists; American was individualized based on caloric needs College of Endocrinology. Consensus statement by the and participants’ lipid levels. All partici- American Association of Clinical Endocrinologists and American College of Endocrinology on the comprehensive pants were given calorie intake deficits of type 2 diabetes management algorithm. Endocr Pract. 500 to 1000 kcal/d.13 Participants rated both 2016;22(1):84-113. 2. American Diabetes Association. Standards of medical care diets as satisfactory, with no significant dif- in diabetes—2016. Clin Diabetes. 2016;34(1):3-21. ferences between groups. The researchers 3. Powers MA, Bardsley J, Cypress M, et al. Diabetes self- management education and support in type 2 diabetes: a concluded that a low-fat vegan diet has ac- joint position statement of the American Diabetes Associa- ceptability similar to that of a more conven- tion, the American Association of Diabetes Educators, and 12 the Academy of Nutrition. J Acad Nutr Diet. 2015:115(8):1323- tional diabetes diet. 1334. 4. Itsiopoulos C, Brazionis L, Kaimakamis M, et al. Can the Mediterranean diet lower HbA1c in type 2 diabetes? Results CONCLUSION from a randomized cross-over study. Nutr Metab Cardio- Diabetes management strategies may in- vasc Dis. 2011;21(9):740-747. 5. Ajala O, English P, Pinkney J. Systematic review and meta- corporate a variety of dietary plans. While analysis of different dietary approaches to the management study populations are small and study du- of type 2 diabetes. Am J Clin Nutr. 2013;97(3):505-516. 6. Boden G, Sargrad K, Homko C, et al. Effect of a low-carbo- rations relatively short, the aforementioned hydrate diet on appetite, blood glucose levels, and insulin diets show improvement in biochemical resistance in obese patients with type 2 diabetes. Ann Intern Med. 2005;142(6):403-411. markers such as fasting glucose, A1C, and 7. Kirk JK, Graves DE, Craven TE, et al. Restricted-carbohy- lipid levels. The Mediterranean diet is be- drate diets in patients with type 2 diabetes: a meta-analysis. J Am Diet Assoc. 2008;108(1):91-100. lieved to be sustainable over the long term, 8. Dyson PA. A review of low and reduced carbohydrate diets given the duration of time that people in and weight loss in type 2 diabetes. J Hum Nutr Diet. 2008; 21(6):530-538. the region have survived on it. Low-carbo- 9. Jönsson T, Granfeldt Y, Ahrén B, et al. Beneficial effects of hydrate diets, including the Atkins and Pa- a Paleolithic diet on cardiovascular risk factors in type 2 leolithic diets, are very effective at lowering diabetes: a randomized cross-over pilot study. Cardiovasc Diabetol. 2009;8:35. A1C and triglycerides. Vegetarian/vegan di- 10. Brand-Miller J, Hayne S, Petocz P, et al. Low-glycemic index diets in the management of diabetes: a meta-analysis of ets may be more acceptable to patients than randomized controlled trials. Diabetes Care. 2003;26(8): previously thought. 2261-2267. 11. Post RE, Mainous AG III, King DE, Simpson KN. The long-term impact of any eating pat- for the treatment of type 2 diabetes mellitus: a meta-analy- tern will likely relate to adherence; adher- sis. J Am Board Fam Med. 2012;25(1):16-23. 12. Barnard ND, Gloede L, Cohen J, et al. A low-fat vegan diet ence is more likely when patients find a diet elicits greater macronutrient changes, but is comparable in to be acceptable, palatable, and easy to pre- adherence and acceptability, compared with a more con- ventional diabetes diet among individuals with type 2 dia- pare. Diet selection should incorporate pa- betes. J Am Diet Assoc. 2009;109(2):263-272. tient preferences and lifestyle choices, and 13. Barnard ND, Cohen J, Jenkins DJA, et al. A low-fat vegan diet and a conventional diabetes diet in the treatment of when possible, should involve an RDN with type 2 diabetes: a randomized, controlled, 74-week clinical expertise in diabetes. CR trial. Am J Clin Nutr. 2009;89(5):1588S-1596S.

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