Functional Sports Drinks – Ian Craig

Raised a scientist, I will never ever believe the advertising claims of nutrition products without a closer look. I read scientific reports about how certain foods and drinks affect our energy, strength and performance, but more than that, I now rely strongly on gut instinct when discerning nutrition quality.

For example, it makes intuitive sense to me that an organic, freshly squeezed fruit or vegetable juice is better for our body than a translucently orange or blue fluid that, according to clever marketing, will give us unrivalled amounts of energy or even wings. Or, for that matter, a delicious smoothie made from natural kefir, fruit and an unflavoured protein powder might be inclined to nourish us more than a meal replacement that sits with authority in a large black plastic tub on the top shelf of your local pharmacy.

Over the past few years, there has been an emergence in the marketplace of some very health-focused drinks, which are now finding a position in the sporting arena. These ‘functional’ products are whole-plant extracts with very tangible health benefits to the consumer. So, after taking a peek at the science of sports drinks, in this article, I will review these particular products: beetroot, cherry and grape juices, coconut water, and rooibos tea. The list, however, could easily be extended to include blueberry, pomegranate, cranberry juices, and green tea.

So what do all of these drinks have in common? The ability to nourish the body beyond a simple calculation of how much sugar, fat and protein they contain. What interests me the most is how to incorporate their use into current scientific thinking about what makes the best sports drink.

Science of sports drinks

Endurance, high-intensity, and intermittent exercise performance have consistently been shown to improve with carbohydrate intake, believed to be due to the maintenance of a high carbohydrate (CHO) oxidation rate and CHO availability within skeletal muscles. For example, Coyle and colleagues (1) asked seven trained cyclists to ride to exhaustion at 71 per cent VO₂max on two occasions. A glucose polymer solution was given at 20-minute intervals on one occasion and a sweetened placebo drink on the other. The rate of endogenous CHO oxidation in the body was reduced in the glucose polymer trial, and cyclists averaged one hour longer before hitting exhaustion (average of 4 hrs vs. 3 hrs for the placebo trial). 

A lot of research has been done over the years to ascertain the appropriate composition of the fluids that should be consumed during endurance exercise. Of primary importance is to attain maximum carbohydrate uptake while retaining high rates of gastric emptying. Quite a few factors can slow gastric emptying, including exercise intensity, stress, dehydration, pH of the fluid, and sugar concentration (2). Ron Maughan (2) has reviewed this topic extensively and has reported that sugar solutions beyond approximately five per cent concentration slow gastric emptying, but they may supply more sugar to the body per unit time.

Sports drink companies have mostly settled on a six to eight per cent sugar solution for optimal rate of carbohydrate uptake. This thinking has led to the evolution of a plethora of sports drinks produced on a large commercial scale. Brands like Lucozade, Energade, Powerade and Gatorade have led this massive new marketplace, and with perceptions like “if it is good for an athlete, it must be good for me”, it has also infiltrated the general population sector.

If you are a label-reader like me, though, you will know that these sports drinks consist of just sugar plus water, with a bit of salt, and a whole load of other ingredients that we can’t pronounce, mostly comprised of colours, flavours, preservatives and sweeteners. Whether it is in the form of glucose, sucrose or maltodextrin, the active ingredient for endurance extension in sports people (along with fat deposition in sedentary folk) is sugar. Going beyond an hour or two in the heat, you may gain some additional benefit from the salts (electrolytes) that have been added. So the basic ingredients to improve endurance performance (compared to water alone) are in these products – there is no doubting the science on this one.

To make your own version of this product at a fraction of the price, all you need is 60g of glucose or sucrose in a litre of water, with a pinch of sea salt. It doesn’t taste particularly exciting, but you won’t emanate fluorescent shades after dark, either! And this is what worries me hugely about commercial sports drinks. Anything that is not nutritive to the body must be detoxified. So the flavours, colours, preservatives and sweeteners found in sports drinks need to be ‘cleaned’ by the liver and other detoxification organs.

The detoxification process requires a greater supply of ATP, the chemical form of energy, than any other biochemical process in the body (3). So by consuming these drinks, you’re energy-supporting and energy-depleting at the same time! The detoxification load is probably not a big concern to the weekend warriors, who have a bottle of Energade after their Saturday game, but it could be very detrimental to a top athlete consuming sports drinks daily while their body is already taking strain.

DIY sports drinks

In the past, I made my own sports drinks using a few key ingredients – in this way, I avoided the additives and had the license to add what I wanted. I would start with a base of plain maltodextrin powder, a long-chain glucose-based sugar that you can buy in plain form. The quantity would be 60g per litre of water as the science says (6% solution), plus I would add a pinch of sea salt or an electrolyte product such as ‘elete electrolyte’ for longer duration training. Into the mix might also go some fructose (which is absorbed differently from glucose and can hence increase grams of sugar absorbed by the body per hour), glutamine powder (the main amino acid fuel provided during exercise), perhaps some magnesium powder (especially for longer distances if there is any history of cramping), and potentially a little vitamin C powder for antioxidant support.

Nourishing sports drinks

This approach avoided all of the additives that are in sports drinks, but didn’t taste very exciting, plus was a bit complicated to do. One day, after demonstrating a DIY drink in class, a lady handed me the Thrive Diet by Brendon Brazier. A key part of his approach is to increase the alkalinity of a person’s diet: some foods are acid-forming (lower pH) in the body, and others are alkaline-forming (raised pH).

Many experts agree that for good health, we should keep the pH of our bodies fairly neutral, but much of the food that we eat and the stressful lifestyles that we follow are pulling us into an acidic state, which may be related to the occurrence of chronic health problems. Athletes may have a hard time maintaining the alkalinity of their body if they have an otherwise stressful lifestyle and don’t eat well: heavy training produces a lot of metabolic acidity from lactate production. As an aside, one thing I have theorised is whether an alkaline diet can improve lactate buffering – this is something that will need to be tested by science at some stage.

Anyway, back to sports drinks: plain sugar is acid-forming in the body. Fruits and vegetables, on the other hand, fruits and vegetables are actually alkaline-forming in the body, and this is one of the many reasons why certain ‘foodies’ (people passionate about health and food quality) juice the entire contents of their fridge every morning! So, what about using real food as a basis for your sports drink? With the emergence of the ‘functional sports drinks’, I’m about to discuss, this is now possible without buying an expensive juicer. I will now review a few of my favourite natural sports drinks and then wrap up the discussion with some science: 

Beetroot juice

Beetroot juice has received considerable attention within the sport over the past few years. It is high in nitrates, which are thought to increase the oxygenation of red blood cells and hence improve oxygen transportation around the body. At the University of Exeter, well-known sports scientist Andy Jones (@BeetrootAndy) and colleagues conducted tests to assess the effect of regular consumption of beetroot juice compared to blackcurrant cordial on bicycle time to exhaustion (4). On average, subjects cycled 16 per cent longer after consuming 500ml of the beetroot juice daily for six days. Additionally, further research (5) has demonstrated that beetroot juice may decrease oxygen consumption whilst walking, thereby improving metabolic efficiency. The economy of motion (e.g. running economy) has been shown to be an important variable for endurance performance, so this is another relevant finding.

Cherry juice

Cherry juice has been heavily featured since the ‘CherryActive’ company started sharing case studies demonstrating how their product has helped some athletes with some very impressive achievements. CherryActive is extremely high in antioxidants, and, in particular, a 30ml shot contains 274mg of anthocyanins (the same level of anthocyanins you’d find in over 180 blueberries). 30ml CherryActive has an antioxidant ORAC* value of over 8000 units, compared to, for example, a medium banana that contains 850.

Here is an early research study that was conducted with CherryActive (6): 10 well-trained rugby and football players, plus martial artists, took the cherry concentrate or an iso-caloric placebo for 10 days (double-blind, placebo-controlled, cross-over). On Day 8, the participants did heavy leg extension exercises with a focus on the eccentric phase (to produce maximal muscle damage). Muscle strength recovered to 91 per cent 24 hours later with the cherry extract, compared to 85 per cent with placebo, a small but significant difference. Additionally, there was less exercise-induced oxidative muscle damage in the CherryActive trial.

Coconut water

Sports people increasingly use the water inside young coconuts as their preferred sports beverage. Now you don’t even have to go to the beaches of India or Brazil for warm weather training – a few companies are bottling coconut water and bringing the tropics to you! The marketing highlight of coconut water, such as the nitrates in beetroot and antioxidants in cherries, is the electrolyte composition, which is apparently so well balanced for human health that it can be safely injected intravenously into the human bloodstream, sometimes saving lives. It has an alkaline pH of 5, and as a sports drink, is slightly lower in sugar than commercial drinks (~4.8 per cent sugar), but it can be comfortably drunk whilst exercising.

One warning, though… Compared to the electrolyte composition of sweat, coconut water is much higher in potassium and lower in sodium. Therefore, if athletes try and use this drink solely for long-duration events, there are chances of hyperkalaemia (high potassium levels) and/or hyponatremia (low sodium levels). Simone do Carmo has written more on this topic.

Grape juice

Not exactly a newbie to the food marketplace – we have been able to buy it in supermarkets for years, but for use during exercise, it is potentially the fruit juice that is least likely to cause gastrointestinal irritation. Grapes are very high in flavonoid antioxidants, which is one reason red wine has such purported health benefits: a glass a day keeps the doctor away ….. a bottle a day, well, that’s another matter!

Picking out one research study (7), grape extract has been shown by research to improve the antioxidant status and performance of top athletes in the sports of handball, basketball, sprinting, and volleyball. In a randomised, double-blind, placebo-controlled crossover study, they were all given a daily dose of 400mg of a product called Powergrape for one month. Scientists found improvements in the antioxidant status of the athletes’ bodies, plus reduced oxidative stress and a reduction in cell damage during exercise when consuming the grape extract.

I lived in the Stellenbosch wine region near Cape Town several years ago. Here, I first recommended using grape juice as a DIY sports drink base to my clients. By simply mixing grape juice ½ and ½ with water, you will attain the 6-8 per cent sugar concentration, and then you can add the various ingredients that I noted in my previous DIY example. This one will be significantly more alkaline to your body than a maltodextrin base, although according to the sports drink science, it is too high in fructose for optimal absorption. This might be a problem at the high-performance end, but most of my clients have found it perfectly acceptable for training and recreational-level racing.

Iced rooibos tea

Another well-known South African product, Rooibos tea (often called Red Bush), is also rich in antioxidants and has become a popular black tea substitute because it is free from caffeine. A number of years ago, when I was competing in a 200km bike race in temperatures up to 40 degrees centigrade (no, I wasn’t in Britain), at the final fuel stop, I was lucky enough to get my hands on some freezing-cold ice tea. It was the tastiest thing I’d drunk all day, and it gave me the idea for a sports drink based on rooibos or green tea (also high in antioxidants). All you need to do is brew a litre of rooibos tea, let it cool, and add the sugars (which could be honey, maple syrup, agave nectar, coconut sugar etc), salts, and other ingredients that I described in my earlier DIY sports drink. It tastes better too!

Scientific conclusions

So, what does science understand about sports drinks so far? A six to eight per cent sugar solution seems to be best for optimal absorption rates; electrolytes that in some way reflect the make-up of our own plasma are important, especially for longer durations, and there might be some merits in having added antioxidants in our drink.

I have reviewed a number of products that I would definitely describe as ‘functional’ sports drinks. All of them have been shown to have potential health and performance benefits to sports people. Some can be directly used as sports drinks during exercise: coconut water, grape juice and rooibos tea can be readily used during training or racing, as I have described. Beetroot and cherry juice have received some great verification of their worthiness for use by sports people. The research shown is based on their daily consumption, like a supplement, and maybe this is the best technique – consume them daily a few hours prior to exercise.

I am curious whether beetroot or cherry juices could be taken during training like a sports drink. If we examine the nutritional labels, ‘Beet-It’ beetroot juice (not the ‘shot’ product) contains 8.8 grams of carbohydrates per 100g, meaning that it is just over the 8 per cent sugar concentration suggested by science, so may need a little dilution. CherryActive is much more concentrated, with 81.7g carbs (59.7g as sugars) per 100 ml, which would require a 10:1 dilution with water to achieve the 6-8 per cent sugar strength. Would they be palatable during exercise? There is only one way to find out – go and check them out and enjoy your new taste experiences.

*ORAC = Oxygen Radical Absorption Capacity

• Original article written for Functional Sports Nutrition magazine in March-April 2011