Friday, 20 November 2015

Study Day

Round, ivy-clad decorative brick tower
Part of Rugby School, May 2015. I really like the slanty windows
I have mentioned carbohydrates on here so many times - they are the mainstay of the British diet in the form of cereal, bread, potatoes, pasta, rice, pastry and flour as well as all the sweet and sugary food and drink, fruit, milk and yogurt. Carbohydrate is also the dietary component that raises blood glucose in people who have diabetes, which can cause poor health in the long term. For this reason, we are coming round to the idea that it makes no sense to encourage people with diabetes to eat lots of carbohydrates.

A reduction in consumption of sugary food and drink has always been advocated, and not just for people with diabetes. This is why the 'traffic light' labelling system on the front of some food packets includes the amount of sugar. But starchy carbohydrate and natural sugars in fruit and dairy products were not restricted in the past, despite the fact that they are also converted to blood glucose when they are digested. Glucose from starchy food, fruit, milk and yogurt enters the bloodstream a bit more slowly than glucose from sweet things, that's all. But if you don't have diabetes, you only really need to care about sugar.

So when people with diabetes come to see me, they always know that they're not supposed to have sugary foods, and they commonly mention that they have been told that brown, wholemeal or granary bread is good for you, as well as lots of fruit. Sometimes they say they can't have bananas or grapes. They have usually picked up this information from non-specialist Dietitians or nurses in their GP practice, or from friends and relations with diabetes.

It now seems to be accepted among Dietitians that limiting all types of dietary carbohydrate (not just sugars) is a valid and beneficial approach for people with diabetes, and very recently Diabetes UK seems to have accepted this idea and at last - at last! - the dietary advice on its website has changed. It used to recommend that carbohydrate foods should make up a third of your diet, or up to 14 portions of starchy carbohydrate a day. Now the same web page suggests you should 'try' to have some wholegrain carbohydrate every day, but acknowledges that you may be advised to reduce the amount of carbs that you eat.

Carbohydrate intake is only half the story; the other factor that leads to raised blood glucose in Type 2 diabetes is insulin resistance, which is often caused by excess weight around the waistline. Most people with Type 2 diabetes are overweight or obese, so I try to recommend that my patients replace the carbs with vegetables that are lower in calories than carbs, which should result in a calorie deficit and very welcome weight loss. Reducing carbohydrate intake reduces blood glucose levels on a day-to-day basis, and losing weight lowers blood glucose in the long term by reducing insulin resistance,

There are some who are not particularly overweight, and therefore cutting the calories from carbohydrates needs to be balanced by an increase in calories beyond what vegetables can provide. For these people we have up to now suggested protein and healthy unsaturated fats: monounsaturated (from olive and rapeseed), polyunsaturated (from sunflowers and corn) and omega 3 (from oily fish, nuts and seeds).

Diabetes Specialist Dietitians are generally a mild-mannered lot (as are most Dietitians). However, there is a militant faction of Dietitians who declare that not only is there no evidence of harm from saturated fats (derived from animal sources), but that these fats are positively beneficial. They promote a low carb high fat (LCHF) diet, and not just any fat, but saturated fats.

The difficulty is that these LCHF people are either deluded or they are visionaries, and we have no certain evidence to tell us which. On Friday I attended a study day where one of the highlights was a debate between a leading proponent of LCHF and a respected academic research Dietitian. Both argued their case admirably, although unfortunately the advocate of the LCHF diet was a little less articulate and let herself down with a couple of poor examples that weakened her case for me. In the end, the consensus is still that we believe saturated fat promotes cardiovascular disease, but there's a chance that it doesn't. Unfortunately it is impossible to conduct human trials that are sufficiently long-term, randomised or blinded to give us the evidence we need, especially as people eat food not nutrients.

The study day also included discussions about the pros and cons of weight reduction through surgery or extreme calorie restriction, the 5:2 fasting diet, a protocol for adjusting diabetes medication in a weight loss programme, and the AGM of the Diabetes Dietitians' Specialist Group.

The session about the 5:2 diet was presented by the Dietitian who invented it within the setting of breast cancer management, and she made the point that there are now three times as many books about the diet than there were participants in the trials that supported it. The diet she invented involved two consecutive days of very low calorie intake separated by five days of 'normal' eating, whereas the common version now in the public domain has separated these two fasting days. Evidence is scanty, trial participants were all women (breast cancer, remember), and the end message was that we have no long term evidence about either benefit or harm. It's pretty unlikely to do any damage (unless there is blood glucose lowering medication or insulin in the mix) so if it works and people lose weight then we're fine with that.

The other diet discussed was the 'Diabetes Reversal' diet pioneered in Newcastle, which involves restriction to 800 calories a day. The rationale for this was because people who have bariatric surgery for weight loss and who have Type 2 diabetes often experience sudden remission in their diabetes and normal blood glucose levels immediately post-surgery. The researchers wanted to investigate whether this outcome was due to extreme caloric restriction alone, or something else to do with the surgery.

Their original study put people on the diet for 8 weeks and required a portion of vegetables every day alongside meal replacement products, and it showed impressive results. They have followed this up with a bigger study - the biggest research grant ever awarded by Diabetes UK - which is for 12 weeks' restriction with meal replacements only. All the information about the original diet is in the public domain on their website, so anyone can try it, and a number of our patients have done so. We are now considering how to support our patients if they were to choose this option for weight loss.

The other sessions I attended at the study were interesting but not remarkable. Back at work, this blog comprises the main reflection I have carried out on the day's experiences. My colleagues are working on a way to offer people a choice of weight loss pathways and I'm planning to use their approach in my service, once they have ironed out the wrinkles.

No comments:

Post a Comment

Related Posts Plugin for WordPress, Blogger...