Decreased gluconeogenesis Increased risk of neuropathy Hypoglycaemia Increased risk of obesity and malnutrition Increased insulin resistance Increased frequency of accidents, gastritis, psychiatric problems Hyperglycaemia Liver disease Increased free fatty acids, ketones, ketoacidosis Increased risk of breast and other and lactic acidosis (if treated with metformin) cancers Increased triglycerides Pancreatitis Hypertension Cardiomyopathy/heart failure Pancreatitis Source: Adapted from Bell (37).
Copyright # 1996 American Diabetes Association.
From Diabetes Care, Vol. 19, 1996; 509, 513.
Reprinted with permission from The American Diabetes Association.
metabolic profile of Type 2 diabetes, together with small dense LDL and low concentrations of HDL cholesterol.
Hypertriglyceridaemia is an independent risk factor for coronary artery disease especially for people with Type 2 diabetes; reduction of alcohol intakes; tight glycaemic control and weight loss can help to reduce this risk (29).
In subjects with alcohol-induced hypertriglyceridaemia, alcohol withdrawal has beneficial effects on the LDL profile by shifting the particle size from small to large, thus reducing susceptibility to oxidation.
With moderate alcohol consumption the increase in HDL becomes the predominant feature in the reduction of CHD risk and maximal benefit appears to be at the level of one drink per day (30).
In irregular binge drinkers the increase in HDL cholesterol is not seen, adverse changes in LDL are acquired (31) and cardiovascular risk increases (Table 13.3).
Antioxidants in alcoholic beverages, especially polyphenolic compounds in red wine, have been proposed as an important contributory factor to the protective effect of regular alcohol use against atherosclerotic cardiovascular disease, by reducing oxidative damage to LDL, reducing its potential atherogenicity.
The unique cardioprotective properties of red wine reside in the action of flavonoids which are minimal in white wine (except champagne).
These flavonoids, especially resveratrol and quercetin, confer more potent antioxidant properties than alpha- tocopherol (32).
These phenolic compounds found in wine are also thought to decrease platelet aggregation and prevent thrombus formation.
INSULIN SENSITIVITY Moderate alcohol consumption among healthy subjects may be associated with increased insulin sensitivity and a reduced risk of diabetes (28). Reaven and
DIABETES AND ALCOHOL 211
co-workers (33) found that light to moderate alcohol consumption is associated with enhanced insulin-mediated glucose uptake, lower plasma glucose and insulin concentrations in response to oral glucose in healthy men and women.
For people with diabetes, light to moderate alcohol intakes with meals do not substantially alter the blood glucose concentration (34,35).
However, heavy intakes may be associated with an increase in glucose intolerance.
So the effect on insulin sensitivity depends on the amount of alcohol consumed (36).
OBESITY Whether or not the consumption of alcohol constitutes a risk for weight gain and ‘whether alcohol calories count’ has been widely debated.
Alcohol is utilised as an energy substrate by the body, contributing 7 kcal/g to energy intakes, however, unlike other energy sources, there is no immediate storage mechanism in the body.
The net efficiency of energy utilisation is lower from alcohol than for fat and carbohydrate and its thermogenic effect has been assessed as 15% from acute doses (38).
Lieber (39), when proposing the microsomal ethanol oxidising system (MEOS) for metabolising alcohol, hypothesised that in heavy drinkers this is uncoupled and energy from alcohol is dissipated.
Another major issue for body-weight regulation is the extent to which alcohol spares other energy substrates from oxidation (40).
As alcohol cannot be stored readily it is oxidised at a steady rate in preference to other substrates, thus being carbohydrate- and fat-sparing.
There is no evidence that consuming alcohol under isoenergetic conditions, i.e. replacing carbohydrate or fat calories with alcohol calories, increases the risk of obesity.
Indeed some researchers have found an inverse relationship between alcohol intake and BMI and adiposity, despite an increase in total energy intake (41).
Further research is needed to investigate the extent to which alcohol calories taken in addition to ‘normal’ diet increase the risk of weight gain.
NEUROLOGICAL EFFECTS The acute neurological effects of alcohol include a lowering or removal of inhibition, stimulation, an antidepressant effect and increased aggressiveness. Longer-term effects include brain damage, physical dependence (on alcohol) and sleep disturbances. It is thought that these effects are mediated through the involvement of biogenic amines (dopamine, noradrenaline, 5-hydroxy- tryptamine).
NEUROPATHY Neuropathy is any disease of the peripheral nerves, usually causing weakness and numbness. Neuropathy is a complication of both diabetes and excessive
212 NUTRITIONAL MANAGEMENT OF DIABETES MELLITUS
alcohol intakes. Therefore the risk of neuropathy increases when diabetics regularly drink more than the recommended levels of alcohol (42), and there is a direct and linear relationship between increasing alcohol intakes and worsening symptoms of neuropathy.
IMPOTENCE
There is some evidence of a correlation between heavy alcohol intakes and an increased risk of impotence in men with diabetes compared to those who report moderate intakes (43). In people with diabetes and non-diabetics there is an increased risk of functional loss of peripheral sensory and motor nerves and autonomic neuropathy with chronic heavy alcohol intakes.
Evidence from many studies in the general population points to beneficial effects of small to moderate daily intakes of alcoholic drinks, but there is also strong evidence of the risks of heavier intakes.
For the person with diabetes perhaps the most concerning of these risks is the impact on blood pressure, particularly for African, Caribbean men (at lower intakes), dramatically increasing the risk of stroke.
For people with Type 2 diabetes small to moderate daily intakes can improve their metabolic profile and reduce CHD risk by raising HDL cholesterol, increasing insulin sensitivity, increasing fibrinolytic activity, reducing platelet aggregation, improving antioxidant status and improving blood pressure.
For people with Type 1 diabetes the benefits of small to moderate intakes are similar to those for the general population, but the risks from heavier intakes are severe hypoglycaemia (which can be mistaken for intoxication) or ketoacidosis.
There is a need for further work to accurately evaluate at what level of alcohol intake the risks outweigh the benefits, as most of the studies use self- reported data, which because of underestimation could mean there is a lower apparent threshold of alcohol-related effects.
BIBLIOGRAPHY
Newsholme EA and Leech AR. 1990. Biochemistry for the Medical Sciences. John Wiley & Sons Ltd.