Journals Watch - Dieting, diabetes and insomnia

Too busy to catch up on the latest research? Let Dr Simon Hunter update you on recent papers.

Calorie restriction and bone health Arch Intern Med 2008; 168: 1,859-66
As the Western population becomes increasingly obese, we are storing up not just fat, but trouble for the future with associated morbidity.

To lose weight there has to be a certain degree of calorie restriction, but previous studies have suggested that this may lead to bone loss and associated fractures.

This small study used four groups to look at calorie restriction and bone health in young, overweight patients: controls who carried on with a normal diet, a calorie restriction group who had a 25 per cent reduction in calories, a group who achieved a 25 per cent energy deficit by a combination of calorie restriction and aerobic exercise, and the fourth group who had a low calorie diet of 890 kcal a day.

The first two intervention groups lost 10 per cent of body weight after six months and the low calorie group did better at 13 per cent weight loss. None of the intervention groups lost any bone mineral density for total body or hip.

This was just for six months so the long-term effects are unknown but it is an encouraging start.

Treating gestational diabetes with glibenclamide Diabetes Obes Metab 2008; 10: 906-11
Gestational diabetes mellitus (GDM) has traditionally been treated with diet or insulin because early sulphonylureas crossed the placenta to cause fetal hyperinsulinaemia with macrosomia, an increase in caesarean sections and profound neonatal hyperinsulinaemic hypoglycaemia.

It has since been shown that glibenclamide does not cross the placenta. This study looked at how effective glibenclamide was in treating GDM and found that 77 per cent of the women gained acceptable glycaemic control.

Maternal and fetal outcomes were assessed in women treated with insulin (45) or glibenclamide (44), and compared with women treated by diet alone (55). There was no significant difference in birth weight, mode of birth or neonatal hypoglycaemia between women treated with insulin or glibenclamide.

Although the trial was relatively small, the results are very encouraging.

Melatonin for insomnia Clin Med 2008; 8: 381-3
Insomnia affects up to a third of the population and none of the conventional medical treatments are particularly successful or without problems.

The hormone melatonin is increasingly being used for certain types of insomnia, for example in the blind where a daylight cue cannot be used. This is despite a lack of good clinical trials and a lack of conformity in preparations.

This review paper looked at the indications and set about proposing a dosage in terms of strength and timing for various conditions, for example, in the elderly with dementia, with jet lag, or children with neurodisabilities.

The authors conclude that there is limited clinical evidence and guidelines are needed.

Treating heart failure with polyunsaturated fats Lancet 2008; 372: 1,223-30
Polyunsaturated fats, the 'good fats' found in fish and wholewheat, have been shown to have possible antiarrhythmic activity and play a role in primary and secondary prevention of cardiovascular disease.

This large randomised placebo-controlled trial set out to test the efficacy of polyunsaturated fatty acids (eicosapentaeoic acid and docosahexaenoic acid) in what is considered the poor relation in heart disease treatment - heart failure.

Polyunsaturated fatty acids are thought to be of benefit due to their known anti-inflammatory processes and beneficial effects on platelet aggregation, BP, heart rate and ventricular function, and because they are well and widely tolerated.

A population of patients with symptomatic heart failure already treated with existing therapies were followed up for four years, with primary end points of time to death or admission to hospital for cardiovascular reasons. The addition of 1g daily of n-3 polyunsaturated fatty acids gave a modest but significant improvement in all-cause mortality and in cardiovascular admissions.

In real terms, the NNT for four years to prevent one death was 56 and to prevent one admission was 44.

Preventing hypertension in type-1 diabetes Arch Intern Med 2008; 168: 1,867-73
Diabetes and hypertension are both associated with cardiovascular disease. Ironically, it is feared that the hyperinsulinaemia, often needed for good control of diabetes, can itself cause hypertension.

This study examined the data from the Diabetes Control and Complications Trial (DCCT), in which two cohorts of type-1 diabetics were treated, one conventionally and the other intensively, and its follow-up study Epidemiology of Diabetes Intervention and Complications (EDIC).

They found that during DCCT the incidence of hypertension was similar in both groups, but in the EDIC follow-up study the incidence of hypertension was 24 per cent lower in the previously intensively treated cohort compared with the conventionally treated group. This shows that intensive insulin therapy, far from causing hypertension, actually prevents it.

Dr Hunter is a GP in Bishop's Waltham, Hampshire and a member of our team who regularly review the journals.

The quick study

  • Calorie restriction did not lead to a significant loss in bone mineral density in overweight patients.
  • Gestational diabetes mellitus may be successfully treated with glibenclamide.
  • Melatonin may be a useful option for treating insomina.
  • Polyunsaturated fatty acids reduced cardiovascular admissions in patients with heart failure.
  • Intensive insulin therapy can prevent hypertension in diabetics.

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