Photo credit: Joe Taylor / BBC pictures

Dr Xand van Tulleken investigates different types of carbohydrate and how they may be impacting our health in this hour-long documentary, which aired on BBC 1 on the 6th of June 2018. The documentary will be available on BBC iPlayer for a further 30 days. If you’re outside the UK, you can currently view the documentary here.

The documentary contains a lot of useful and interesting information on carbs and their effects on the body, delivered in an easily-digestible way, using expert interviews, animations, testimonials and lab test examples to articulate points. There are some areas of the documentary that could use more elaboratio, and there are perhaps a few inaccuracies, but overall, the documentary is a big step in the right direction concerning health and nutrition on television.

Types of carbs

Early o, Xand helps us to differentiate between the different types of carbs, separating them into three groups: white carbs (sugars), beige carbs (starches) and green carbs (fibre). Xand explains that white and beige carbs, such as sugary drinks, biscuits, bread, pasta and potatoes are all broken down into glucose in the body, and this glucose has the potential to be stored as fat if it’s not used or burned off. Meanwhile, the green carbs release energy much more slowly and act as food for our gut bacteria. Thus, getting more green carbs from non-starchy vegetables and whole fruit, while limiting intake of white and beige carbs is likely a good policy for maintaining weight and gut health.

Have carbs contributed towards poor world health?

Xand explains that around 12,000 years ago, we developed large-scale agriculture, which allowed us easy access to large amounts of dietary carbohydrate. Before this, carbs were not so easy to obtain as hunter-gatherers. Now, in the modern age, we always know where our next meal is coming from, and because carbohydrates are cheap and readily available, whenever most of us grab something to eat at home or at work, it’s usually something carb-heavy like a sandwich or a pasta salad. For some people, this way of eating can eventually lead to weight gain.

Not everyone becomes unhealthy and obese just by eating carbs. We as individuals all have a different genetic makeup, and this impacts on how our bodies deal with all sorts of nutrients, including carbs. So some people have a better carb tolerance than others. To demonstrate this, Xand runs Dr. Sharon Moalem’s cracker test on some students, getting them to chew on crackers as he times how long it takes for the flavour to change from savoury to sweet in their mouths. What he finds is that the times vary significantly. This is relevant as, in an emerging field of research, lower levels of amylase, the enzyme that breaks down starch, have been associated with higher BMI.

Blood sugar bingo

To illustrate how different carbohydrate-based foods can impact our blood sugar levels, Xand, with the help of dietician Alison Barnes, lays out a spread of different foods on a table, and tasks a group of office workers to guess how much sugar (in sugar cube equivalents) the foods release into the blood when eaten. This makes for some surprising results, with servings of beige carbs such as bread, potato and rice having more power to raise blood sugars than a chocolate muffin. In contrast, a bowl of strawberries has a much smaller effect on blood sugar than any of these. Xand reiterates that unless all of this glucose is burned off, it could be converted into fat.

Smart carbs and resistant starch

Although sugar and regular starch are rapidly broken down into glucose, there exists a form of fibre called resistant starch. This makes it all the way to the large intestine before being broken down by our gut bacteria. Xand is told by professor Harry Flint that increasing the amount of resistant starch in the diet could improve gut health.

Xand explains that wholegrain bread contains the fibre and resistant starch that has been removed from white bread. He also shares a little life-hack for those who don’t want to give up bread. Keeping bread in the freezer before toasting it, Xand says, can convert some of the starch into resistant starch and reduce the glycaemic index. Likewise, cooking, cooling and reheating foods like potato, rice and porridge can form some extra resistant starch.

Whilst there is good evidence to suggest more resistant starch is good for us, it’s worth noting that its proportion even in foods like wholegrain bread is very small, and that the main bulk of the starch is still rapidly digested into glucose. For people with diabetes especially, even wholegrain and freeze-thawed foods will spike blood sugars, and this is something that is not fully appreciated in the documentary. For a helpful infographic on the blood sugar effects of different types of bread, click here.

Carbs and exercise

Some people believe that dietary carbs are vital for athletic performance and, as Xand points out, this serves the sports snacks and drinks industry very well. But interestingly, one may not have to actually swallow any carbs to receive a benefit. The work of Dr Howard Hurst, whom Xand pays a visit, has shown that simply swilling a carbohydrate solution around the mouth for ten seconds is enough to improve cycling performance. This is thought to occur through receptors in the mouth communicating with the brain to reduce perceived effort. This bizarre research suggests that it’s possible to get a performance benefit out of swilling and spitting out a sports drink, rather than taking in the sugar.

Insulin resistance and type 2 diabetes

Xand explains that the glucose produced when we consume carbs requires the hormone insulin to transport it into cells, and keep blood sugars under control. Type 2 diabetes is a disease characterised by insulin resistance, where insulin can no longer perform its role, and is strongly associated with obesity. As Xand states, many believe that the epidemic of type 2 diabetes (3.5 million people in the UK) is partly due to the type and quantity of carbs people are consuming.

Low carb diets – results from one general practice

Xand pays a visit to the home of Drs David and Jen Unwin, who use a low carb approach with their type 2 diabetes patients to great effect, saving the NHS thousands of pounds on medication. Dr Unwin agrees that many people are eating more carbs than they need, and states that this can be avoided by swapping dense sources of carbs (white and beige) for low carb greens. He explains that people can restrict their carbohydrate intake depending on what goals they have in mind, for example, an obese type 2 diabetic may wish to go lower than someone of normal weight who is just looking to give up sugary foods. The Unwins stress that this way of eating should be seen as a lifestyle, rather than a diet, and that people should focus on eating healthy foods that don’t contain refined carbohydrates, rather than focusing on calories.

To demonstrate the power of the low carb approach on controlling type 2 diabetes, Xand meets one of Dr Unwin’s patients, who managed to come off all three of his diabetes medications within 6 months of starting a low carb lifestyle.

Setting up the low carb trial

To get further insight on the benefits of a low carb lifestyle, Xand follows Dr Faisal Maassarani and a group of his patients, who are a mix of obese non-diabetics, prediabetics and type 2 diabetics, as they’re placed on a low carb program for 2 weeks. During these 2 weeks, the patients use the FreeStyle Libre to continuously approximate their blood glucose levels (Xand incorrectly says this is a blood glucose monitor – it actually monitors glucose levels in the interstitial fluid under the skin).

At the start of Dr Maassarani’s experiment, the participants eat a typical breakfast high in refined (white and beige) carbs: a bowl of cereal with milk, a slice of toast, a banana and a glass of apple juice. This unsurprisingly spikes the type 2 diabetic participants’ blood sugars well into the diabetic range. At this point, Xand offers whole-oat porridge as a healthier breakfast alternative, however it’s worth noting that despite a higher fibre content, this is still high in (beige) carbs and can easily spike the blood sugars of someone with diabetes. Interestingly, they did not measure the paticipants’ blood sugar response to porridge here. Xand’s second suggestio, having eggs for breakfast, is much more sensible for someone with diabetes. For those who have their own blood glucose monitor, testing can be helpful for working out which foods spike blood sugars and which don’t.

With the help of chef David Critchley and dietician Alison Barnes, Xand shows how a range of carb-laden foods can be substituted or tweaked to create lower carb alternatives that are tasty and fulfilling. For example, roasted potatoes can be replaced with roasted celeriac and a low carb key lime pie can be made using almond flour. Again, it’s worth noting that replacing white rice with wholegrain rice may not make enough of a difference for those with poor blood sugar control, and decreasing carbs further (for example, replacement with cauliflower rice) may be more beneficial.

Other conditions affected by diet

In this section, Xand first visits surgeon Ken Park for a colonoscopy. This is to highlight the link between a healthy diet and bowel cancer, which is the second most common cause of cancer death in the UK. Research shows that eating the recommended 30 grams of fibre per day can reduce risk of bowel cancer by 30%.

Next, Xand explores the role of carbs in fertility and pregnancy. He visits reproductive biologist Grace Dugdale who explains that metabolic health is responsible for the efficiency of both egg and sperm, and that this can be impacted by the quality and quantity of carbohydrates in the diet. She goes on to say that too many refined carbs like white bread and sugars can damage the “battery of the cell” (the mitochondrion) which is responsible for providing energy to cells. She recommends getting more fibre and not overdoing carbs in general, for those trying to conceive. It’s also worth noting that metabolic health is a large factor in polycystic ovarian syndrome (PCOS), a cause of infertility. Grace then explains how, interestingly, the diet of both mother and father can alter genetic information and lead to life-long effects in the next generation.

Results of the low carb trial

Xand returns to Dr Maassarani’s low carb participants to see how they’re doing after two weeks on the program. The group felt that they didn’t struggle to adhere to the low carb lifestyle and that it didn’t feel like anything too different from what they’re used to eating.

Xand mentions the importance of social media and online support groups in staying enthused and motivated when following a healthy way of eating. Those who would like structured low carb lifestyle education could try joining the Low Carb Program.

Each of the group lost half a stone (7 lbs or 3.2 kg) in these two weeks, and saw a range of improvements including reduced waist measurements, improvements in HbA1c (a measure of average blood sugar levels) and reduced fatty liver. Perhaps the most impressive result comes from Dave, who has had type 2 diabetes for 17 years, but is now in part-remissio, meaning he has a very good chance of full remission if he continues to follow his new-found way of eating. For context, remission of type 2 diabetes is sometimes thought of as an impossibility, even by healthcare professionals, but studies utilising dietary approaches are now proving it to be an attainable goal.

Hope for the future

If upscaled, the work of healthcare professionals like Drs Unwin and Maassarani could save each NHS practice thousands of pounds on diabetes medications, all while improving people’s lives. The low carb plan is currently being adopted by the Royal College of General Practitioners (RCGP) as an online education program for GPs across the UK.

The results of the low carb trial performed in this documentary, along with the growing scientific evidence base show that it is indeed possible to reverse the epidemic of obesity and type 2 diabetes that has occurred not just in the UK, but all over the world.

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