Understanding Carbohydrates
C A R B O H Y D R A T E S \ N U T R I T I O N
Dr Linia Patel looks at carbs, what they are and their health benefits, and helps you to decide how much of them you need to eat.
The amount of carbs we should consume is a highly debated topic. The dietary guidelines suggest that we should get about half of our calories from carbohydrates. On the other hand, some claim that we should limit them in our diets as they lead to obesity and diseases like type 2 diabetes.
What are carbs?1,2
Carbohydrates are essentially sugar molecules bonded together to varying degrees. Structurally speaking, there are two types of carbohydrates: simple and complex. Simple carbohydrates are smaller, more easily digested molecules known as mono- and disaccharides. These simple sugars are also called free sugars or added sugar. When you think of simple sugars, think of refined carbs or foods that have added sugar such as:
white bread and items made with white flour like pastries and cakes
chocolate and confectionary
sugar-sweetened drinks
breakfast cereals
flavoured yogurt.
Sugars in honey, syrups (such as maple and golden) and unsweetened fruit juices, vegetable juices and smoothies (see ‘Juices and smoothies’) occur naturally, but still count as free sugars.
Complex carbohydrates are called polysaccharides since they have more than two sugar groups linked together and therefore need more digestion. Complex carbohydrates include starchy carbs and fibrous carbs. The sugar molecules in starch are bound together to a lesser degree than in fibre, hence the body can completely digest starch while it is not able to fully digest fibre.
Starch is found in:
root vegetables, such as potatoes, beetroot and parsnips
wholegrains, such as oats, wild rice, barley and quinoa
products made from grains like breads, crackers or breakfast cereals.
Good sources of fibre include:
wholegrains and products made from wholegrains
lentils and beans
vegetables and fruit.
Juices and smoothies¹,2,3,4
In whole fruit, the sugar is bound within the structure of fruit (intrinsic sugar); therefore, when you eat fruit whole, it hits your blood stream at a slower rate. Interestingly, juice counts as one of your five-a-day no matter how much you drink. The process of juicing fruit releases the sugar from the cell walls (extrinsic sugars). In addition, juicing loses most of the valuable fibre found in the whole fruit. Recommendations are that we limit the intake of fruit juice and shop-bought smoothies to 150ml per day. As a point of reference, one glass (150ml) of 100% pressed apple juice contains 15g sugar, which clocks up half of your daily free sugar intake for the day. Homemade smoothies/blended juices are different depending on the amount of pulp (fibre) they contain. Blending is when the whole fruit or vegetable is used. What you put into a blender is what you consume.
The Glycemic Index (GI)5,6
The GI and glycemic load are popular alternative classification methods, which rank carbohydrate-rich foods based on their effect on blood glucose levels. Glucose is given a glycemic index of 100. Foods with a high glycemic index, like white bread and sugary foods, are rapidly digested and cause substantial fluctuations in blood sugar. On the contrary, foods with a low glycemic index, like whole oats, are digested more slowly, prompting a more gradual rise in blood sugar.
Practically, foods with a high GI are likely to be processed. The more machines the food has been through, the higher the GI, as much of the ‘digestion’ has been done before consumption. High GI foods are also likely to taste sweet in your mouth – although there are a few exceptions to the rule. As a rule, nutrition experts recommend that you base your main meals on lower glycemic index carbohydrates.
While glycaemic index is a good guide when it comes to choosing carbohydrates, it shouldn’t be used in isolation. A chocolate bar, for example, appears to be ‘healthier’ than a slice of watermelon, as the chocolate bar has a lower glycaemic index value. Yet you know that watermelon comes with more vitamins and minerals than a chocolate bar. Nutrient density of the food being eaten needs to be considered. Whether you eat a food on its own or as part of a meal also matters. Mixing food groups on your plate will reduce the speed of absorption of the glucose in a food containing carbohydrates. For example, if you put some roast chicken (protein) and salad (low GI) on a white baguette (high GI), this brings down the overall GI of the meal. Portion sizes matter too. That is what glycemic load tells you. Glycemic load accounts for both the quantity and quality of your carbohydrates at the same time.
The more machines the food has been through, the higher the GI, as much of the ‘digestion’ has been done before consumption.
Are carbs essential?
All cells must burn fuel to function. One of the main roles of carbohydrates in the body is as a source of energy1,2. Therefore, it’s no surprise that eating too few carbs can cause tiredness. However, overindulging in carbohydrates – especially refined carbohydrates in the short term – can also cause fatigue and, over time, increases your risk of becoming overweight and developing obesity5.
Although it is possible to survive on a very low carb diet, it is probably not the optimal choice for the long term, as you will be missing out vital nutrients like B vitamins and fibre1,2,5,8
Focus on Fibre
While there are no miracle foods or ingredients when it comes to nutrition, a key nutrient that you will need to focus on for optimal wellbeing is fibre. Fibre is a type of carbohydrate and refers to the parts of plant-based foods that are not broken down or used by the body. Instead, these non-digestible parts make their way through the gut, contributing to our health in different ways1 , 2. Eating more fibre is a good strategy to help manage your weight. Fibre keeps your appetite in check as it keeps you fuller for longer and helps with your blood sugar control⁵,⁸. To receive the greatest health benefit, eat a wide variety of high-fibre foods. Current UK guidelines recommend we should be aiming for 30g of fibre every day, yet few of us are eating enough of it⁹.
TOP TIPS on increasing your fibre intake10:
BREAKFAST
✔ Start with whole oats. A medium bowl of porridge topped with a handful of berries gives you 8g of fibre. Boost your fibre further by adding 1 tbsp of chia or ground flaxseed (4g fibre).
✔ Make a vegetable omelette. Try to add two portions of vegetables (2 x 80g) in your omelette and this will give you about 8g of fibre. Use whatever vegetables you have – fresh, frozen or tinned.
LUNCH
✔ Lean on lentils or beans and veggies. Try having lentils instead of rice or pasta (120g of legumes gives you 10g fibre). Or, if you’re not a bean fan, why not add some veggies to the rice or pasta while it boils (add 80g veggies to get 3-4g fibre).
✔ Choose wholegrain. Where possible, opt for wholegrain varieties as they will have a higher amount of fibre per serving. Think wholegrain bread, pasta, brown or red rice, wholegrain cous-cous, quinoa or oatcakes. If you have potatoes, keep the skin on.
DINNER
✔ Base dinner on veggies. A 250g mixed vegetable stir-fry with 120g chicken will give you 10g of fibre.
✔ Have soupy dinners. Cook up a vegetable soup using the leftover vegetables you have. This includes fresh, frozen or canned. One serving (250ml) of mixed vegetable soup can give you up to 5g of fibre.
SNACKS
✔ Snack on fibre. What raw vegetables do you have in your fridge that you can snack on? 150g of sugar snap peas or raw carrots provides you with 4g of fibre. 150g of raspberries provides 10g of fibre. A medium apple and 30g unsalted nuts provide 6g of fibre.
Who needs carbs?
Who doesn’t?
Not all carbs are created equal and herein lies the challenge. The first thing to make clear is that we all need to keep our intake of simple carbs/free sugars to a minimum. Current guidance is to reduce sugar intake to less than 5% of total energy per day (30g per day or seven cubes of sugar for adults); however, the less the better for the majority4,9.
Most people
In terms of complex carbohydrates, for most people, carb reduction costs us over the long term as we require some complex carbs to function at our best7,11. In fact, research shows that a very low carbohydrate diet for too long can negatively affect our gut microbiome. Study after study is showing that the importance of maintaining a healthy gut flora (they love complex carbs) is indirectly impacting on hormone regulation and risk of diseases12.
Carb myth busted!
Carbs are the cause of obesity Though limiting your carbs can lead to weight loss7, it doesn’t mean that eating carbs will make you gain weight if you are eating the right ones in the right portions. It is true that refined carbs are linked to an increased chance of developing obesity and other negative health outcomes; however, the same is not true for fibre-rich, wholefood sources of carbohydrates5,8. However, the obesity pandemic is not caused by a single nutrient. Many healthy traditional diets are high in carbohydrates, yet what they have in common is they eat a high proportion of unprocessed carbs5,7.
Those who could benefit from a low-carb diet
Very sedentary people, as well as those who have insulin resistance (a condition in which the cells of the body become insensitive to the hormone insulin), may benefit from a lower overall carb diet for a while as part of an overall transition towards more activity and healthier metabolism5,7. Ketogenic diets (very low carbohydrate diets) are prescribed for people with epilepsy, as they seem to reduce their symptoms and cut down on seizure frequency. There is also preliminary evidence that ketogenic diets benefit other neurological disorders, such as Parkinson’s disease and Alzheimer’s disease13. There is also evidence that low carbohydrate diets could be effective in some specific instances as a short-term weight-loss solution7.
The athletes among us
Glucose is the muscles’ preferred fuel, so it is therefore not surprising that most athletes in particular do better with the inclusion of carbs; however, there are exceptions14,15. There are a few athletes who can perform on a low-carb regime as they are better fat adapted16. However, there is always individual variability16.
What works for you?
You are unique. One size doesn’t fit all. Your individual carbohydrate requirements will depend on your goals, activity level and genetics, for example. For bespoke advice about your carbohydrate intake, it is recommended that you see a registered dietitian or nutritionist.
Reference
DR LINIA PATEL - Mar/Apr - fitpro.com