A few studies suggest that persons with type 2 diabetes have an increased need for protein during moderate hyperglycemia,  and an altered adaptive mechanism for protein-sparing during weight-loss,  resulting in an increased protein requirement.  However,  in many countries the protein intake for persons with diabetes is relatively high and exceeds by far the recommended dietary allowance (RDA) of 0.8 g kg ^{- 1} desirable body weight for adults. On average, protein intake was 21% of daily energy in the UKPDS. In general, there seems to be little concern that persons with diabetes may develop a deficiency in protein intake (59). The current recommendation for people with diabetes is that protein may provide 10% to 20% of total energy intake. In individuals with controlled type 2 diabetes, ingested protein does not increase glucose concentrations (14).

An association between dietary protein intake and renal disease has been shown in a large-scale cross-sectional study of people with type 1 diabetes. Those with a protein intake above 20% of total energy intake had abnormal albumin excretion rates (AER > 20 mg min ^{- 1}), particularly when hypertension was present (59). This suggests that a very high-protein intake may have undesirable effects on renal function, and it may be prudent to avoid a very high protein intake.

Several studies have focused on reversing or retarding the progression of proteinuria, and preventing nephropathy. Only a few studies have evaluated nutritional modifications, particularly a reduction of protein intake in patients with type 2 diabetes. With reductions in protein intake, to 0.8 g kg ^{- 1} body weight, AER were reduced in patients with microalbuminuria (60,61),  however,  the studies were of short duration and do not allow a general recommendation for this kind of protein restriction in microalbuminuric persons with type 2 diabetes. Whether substituting vegetable protein for protein from animal sources might result in beneficial effects has also been explored; however, there is still insufficient evidence to make firm recommendations regarding the nature of dietary protein in individuals with diabetes.

Alcohol
Precautions regarding alcohol intake that apply to the general population also apply to people with type 2 diabetes. If persons with diabetes choose to drink alcohol, intake should be no more than 10 g/day for adult women and 20 g/day for adult men.  This corresponds to approximately one or two small drinks of wine or beer per day (8,9). The cardioprotective effect of alcohol appears not to be determined by the type of the alcoholic beverages consumed. However, alcohol is an important energy source in overweight persons with type 2 diabetes,  and alcohol consumption can be associated with raised blood pressure and hypertriglyceridemia.  In individuals with diabetes,  chronic intake of moderate amounts (5 - 15 g/day)  of alcohol was associated with a decreased risk of coronary heart disease.

However, conversely, a strong association between excessive habitual intake (> 30 - 60 g/day) of alcohol and raised blood pressure was found in both men and women (62).

Alcohol can have both hypoglycemic and hyperglycemic effects in people with diabetes, depending on the amount of alcohol acutely ingested. In studies where alcoholic beverages were consumed with carbohydrate-containing food by people with diabetes, no acute effects were seen on blood glucose or insulin levels. Alcohol should therefore be consumed with food to reduce the risk of hypoglycemia and persons with diabetes are advised not to omit food when choosing to drink a moderate amount of alcoholic beverages (8,9).

Monika Toeller
German Diabetes Research Center, Heinrich-Heine University, Düsseldorf, Germany
Jim I. Mann
Department of Human Nutrition, University of Otago, Dunedin, New Zealand

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