Low-Carb Diets and Diabetes: Just What the Doctor Ordered?
Atkins, Zone, Sugar Busters, ProteinPower, South Beach—the list ofhigh-protein fad diets is seeminglyendless. All of these diets reduce theamount of carbohydrates ingested andpromise rapid weight loss. Yet, are thesediets safe for people with diabetes?
Maintaining a healthy weight isimportant for both the preventionand the treatment of diabetes. Obesityincreases the risk of developing diabetes.For people with the disease,weight loss can improve blood glucosecontrol and prevent long-term complications.Losing weight is difficult,however, and people often resort todiets that are unbalanced and potentiallyunsafe. The latest craze is lowcarbdiets, which severely restrict carbohydrates.It is claimed that thesediets reduce insulin productionthrough carbohydrate restriction,which then results in weight loss.
People do lose weight on high-protein,low-carbohydrate diets. Theweight loss, however, is largely due towater loss and reduced calories, notlower insulin levels as claimed by theauthors. Nutrition experts generallydo not recommend these diets for peoplewith diabetes: these diets are difficultto maintain over a long period oftime, and higher fat and proteinintake may increase the risk of coronaryheart disease (CHD) and kidneydamage—2 conditions for which diabeticsare already at high risk.
Diets that are high in protein tend tobe high in fat. The Atkins Diet, whichencourages high intake of meats, eggs,and dairy products, provides about 20%to 25% of calories from saturated fat.The South Beach Diet encourages amore moderate approach, limiting highfatcuts of meat and high-fat dairy products.The American Diabetes Association(ADA) recommends that no more than10% of calories come from saturated fat.
Diets high in saturated fat may raiseblood cholesterol levels, which thenincrease the risk of CHD. Two studiesof the Atkins Diet found increasedcholesterol in the participants.1,2 Theresearchers in one of the studies calculatedthat long-term use of this dietwould result in a 25% increase in cholesterol,which translates into a 50%increased risk of CHD. Another studyof a low-fat versus low-carb diet inobese patients demonstrated stablecholesterol levels in the low-carbgroup. The recommended diet in thisstudy, however, encouraged use of low-fatcuts of meat and reduced-fat dairyproducts.3 Weekly diet counseling wasprovided in the study as well.
High-protein diets also tend to be lowin fiber, which may increase the risk ofCHD. The ADA recommends 20 to 35 gof fiber per day. The Atkins and ProteinPower diets supply only 5 to 10 g per day.Research has shown that foods high insoluble fiber—such as bran, beans, andapples—can lower cholesterol levels.High-protein diets may increase therisk for renal dysfunction in people withdiabetes or exacerbate problems thatalready exist. The ADA recommends nomore than 20% of calorie intake fromprotein. Protein intake in most of thelow-carbohydrate diets is 28% to 35% ofcalories. High-protein, low-carb dietsinduce ketosis, which may lead to diabeticketoacidosis, a medical emergency.
The scientific evidence surroundingthe effects of low-carbohydrate diets isnot clear. A recent review of clinicaltrials assessing the relative effects of fatversus carbohydrate, the differencebetween fatty acids and the types ofcarbohydrate on insulin resistance,and associated risk factors for diabetesand cardiovascular disease concludedthat diets higher in monounsaturatedfatty acids, fiber, and low-glycemicindex foods showed advantages inreducing risk factors for chronic disease,especially those associated withinsulin resistance.4 The Steno-2 trial,conducted in patients with type 2 diabetes,showed fewer cardiovascularevents despite consumption of a high-carb,low-fat diet over an 8-year period.5 A recent review of studies of low-carbdiets found no advantage to thesediets, when compared with balanceddiets that contained carbohydrates.6
Currently available scientific evidencedoes not support the recommendationof low-carbohydrate dietsfor people with diabetes. All carbohydratesare not the same. The Americandiet contains large amounts ofprocessed, high-fat, calorie-densefoods, such as fast food. Our carbohydratechoices have typically favoredhigh-sugar, low-fiber carbohydratesthat have relatively little nutritionalvalue. A more sensible approach toweight management in diabeteswould include a diet with fruits, vegetables,and whole grains, as well asfoods low in saturated fat—plus a regulardose of exercise.
Dr. Garrett is a clinical pharmacist practitionerat Cornerstone Health Care, HighPoint, NC.
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