Introduction
Type 1 diabetes, also known as ‘early onset’ or ‘childhood’ diabetes, affects infants/children up to late teens. This form of diabetes is insulin dependent and cannot therefore be controlled by diet alone.

Type 2 diabetes is a condition that currently affects over one million people in the UK. Type 2 diabetes used to be called `maturity onset’ diabetes because it usually appears in middle-aged or elderly people, although it does occasionally occur in younger people. The main causes are that the body no longer responds normally to its own insulin (insulin resistance) and/or that the body does not produce enough insulin (pancreatic insulin deficiency). Type 2 diabetes may be controlled by diet alone or by diet in combination with tablets. In rare cases, if these treatments are not successful, then as a last resort Doctors may prescribe insulin.

Coffee and diabetes
Coffee/caffeine have been studied in relation to both Type 1 and Type 2 diabetes and research is known to be ongoing. There is currently no evidence to suggest that individuals with diabetes need to avoid coffee.
Type 1 Diabetes
In relation to Type 1 diabetes, published research has shown that a modest amount of caffeine can increase awareness of the warning symptoms associated with the onset of a hypoglycaemic episode, and thus allow the patient to take action to avoid such an event (1). Furthermore, research has also demonstrated that the ingestion of caffeine in amounts equivalent to that found in 2 to 3 cups of filter coffee (180mg) had a beneficial effect on heart rate variability (2). Heart Rate Variability is a measure for the variation of the individual heart beats. A reduction in heart rate variability may be associated with increased risk of ventricular arrhythmias and sudden cardiac death.

Type 2 Diabetes
The evidence published to date suggests that coffee may be protective against developing Type 2 diabetes (3,4). Research published in 2004 concluded that long-term coffee consumption is associated with a statistically significantly lower risk for type 2 diabetes (5) and that coffee drinking has a graded inverse association with the risk of type 2 DM (6). These findings were further strengthened by two Swedish studies, which supported the hypothesis that coffee consumption protects from the development of diabetes (7 & 8). The mechanisms for this risk reduction are not clear, however, research conducted in the UK, found that coffee drinking had an effect on two hormones in the body that control insulin secretion, and suggest that this may be the mechanism behind the protective effect of coffee consumption and Type 2 diabetes (9). Research into the relationship between coffee drinking and the development of type 2 diabetes continues and many strong studies were published in 2006 (10-18) which add considerable weight to this area of research. A review published in 2007 titled, ‘Does Coffee Protect Against Type 2 Diabetes?’ confirmed a protective effect against type 2 diabetes and noted that the effect ‘is rather impressive and is present whatever the type of population’.

Summary

Further research is needed to confirm the mechanisms of action involved in the potentially protective effect of coffee consumption against diabetes, though findings to date are very encouraging.

In addition coffee drinkers who have diabetes can continue to enjoy their favourite drink confident in the knowledge that moderate coffee consumption, of 4-5 cups per day, is perfectly safe and may confer health benefits. Pregnant women should however moderate their intake following the guidelines issued by the Food Standards Agency, to 200mg caffeine per day from all sources.

References
1. Watson. Diabetes Care, Volume 23, 2000
2. Richardson. Diabetes Care, Volume 27, 2004
3. Zhang W, et al. Diabetes Care, February, 2009
4. Van Dieren, S. et al “Coffee and tea consumption and risk of type 2 diabetes” Diabetologia 2009
5. Salazar-Martinez. Annals of Internal Medicine, Volume 140, 2004
6. Tuomilehto. JAMA, Volume 291, 2004
7. Rosengren. Journal of Internal Medicine, Volume 255, 2004
8. Agardh. Journal of Internal Medicine, Volume 255, 2004
9. Johnston, Clifford & Morgan, American Journal of Clinical Nutrition, Volume 78, 2003
10. Van Dam. Diabetes Care, Volume 29, 2006
11. Van Dam. Nutrition, Metabolism and Cardiovascular Disease, Volume 16, 2006
12. Bidel. Horm, Metabolism, Research, Volume 38, 2006
13. Iso. Annals of Internal Medicine, Volume 144, 2006
14. Gruber. International Journal of Clinical Practice, Volume 60, 2006
15. Hu. International Journal of Obesity, 2006
16. Pereira. Archives of Internal Medicine, Volume 166, 2006
17. Paynter. American Journal o f Epidemiology, Online 2 006
18. Smith. Diabetes Care, Volume 29, 2006
19. Legrand. Rev Med Liege, Volume 62, 2007