Merry Christmas and best wishes for 2019: Are you concerned about Christmas creep? That extra weight that you put on over the festive season. If you are keen to start 2019 with a better understanding of weight control then we would love to help you. Read more »



Diet therapy

Can caffeine fix performance?

You only have to view the pile of bikes outside a coffee bar on a Saturday morning to realize that many cyclists are coffee addicts who need their caffeine fix each day.  So does caffeine hydrate, dope up or enhance performance?

What is caffeine?

Caffeine is a substance from the methylxanthine family that occurs naturally in the leaves, nuts and seeds of a number of plants.

Major dietary sources of caffeine, such as tea, coffee, chocolate and cola drinks typically provide 30-100 mg of caffeine per serve, while some non-prescriptive medications contain 100 -200 mg of caffeine per tablet.

The recent introduction of caffeine (or guarana) to ‘energy drinks’, confectionery and sports foods/supplements has increased the opportunities for athletes to consume caffeine, either as part of their everyday diet or for specific use as an ergogenic (performance enhancing)aid. ref Table 1.


Table 1. The Caffeine content of products

Serving Size Caffeine (mg)
Instant Coffee 250ml 60-80
Percolated Coffee 250ml 60-120
Red Bull® 250ml 80
V Energy Drink® 250ml 78
Tea 250ml 10-50
Coca-Cola® 355ml 36
NoDoz® (regular) 1 tablet 100
NoDoz® (max strength) 1 tablet 200

IOC/ WADA position

In 1 January 2004, caffeine was removed from the 2004 World Anti-Doping Agency Prohibited List, allowing athletes who compete in sports that are compliant with the WADA code to consume caffeine, within their usual diets or for specific purposes of performance, without fear of sanctions.

It was recognised that caffeine is metabolised at very different rates in individuals with associated wide-ranging effects. Currently caffeine is only on WADA’s monitoring program in order to detect patterns of misuse in sport and it is worth noting that the 2010-11 program recorded a significant increase in the amount of caffeine consumed by athletes.

Caffeine effects

Glycogen sparing

Originally it was thought that caffeine enhanced endurance performance because it promoted an increase in the utilisation of fat as an exercise fuel thereby ‘sparing’ the use of the limited muscle stores of glucose (glycogen) for later in the race.

In fact, studies now show that the effect of caffeine on ‘glycogen sparing’ during sub-maximal exercise is short-lived and inconsistent – not all athletes respond in this way. Therefore, it is unlikely to explain the enhancement of exercise capacity and performance seen in prolonged continuous events and exercise regimes.


It was also believed that caffeine-containing drinks have a diuretic effect and cause an athlete to become dehydrated. However it is now thought that caffeine-containing drinks such as tea, coffee and cola drinks provide a significant source of fluid in the everyday diets of many people and any effect of caffeine on urine losses is minor – particularly in people who are habitual caffeine users.

Altered perception of fatigue

It is now thought that the main benefit is caffeine’s ability to bind to adenosine receptors that help regulate many physiological, neurological and immunological processes which may lead to a reduced perception of effort or fatigue. Caffeine may have a direct effect on the circulatory system and also skeletal muscle before and after fatigue as demonstrated by electrical stimulation.

Circulatory system

At a peripheral level caffeine causes relaxation of muscle cells in the blood vessels (except those in the brain). The blood vessels relax and expand, an effect called vasodilation. Vasodilation coupled with caffeine’s tendency to increase heart rate may cause a temporary increase in blood pressure. The American Heart Association states that daily consumption of 1 to 2 cups of coffee per day does not cause harm in people with high blood pressure

Method of use

In the past caffeine was taken one hour before an event in doses equivalent to 6mg/kg of body weight (around 300-500mg per athlete). Evidence from recent studies involving prolonged exercise lasting 60 minutes or longer have found benefit at lower levels 1-3mg/kg (approx. 70-200mg per athlete) when caffeine is taken at a variety of times ( before, during or towards the end of the event) particularly when the athlete is noticing fatigue.


There is no dose-response relationship to caffeine, as everybody responds to it differently and taking more does not lead to increased performance.

While caffeine withdrawal symptoms can be unpleasant reducing caffeine intake itself does not lead to a reduction in the performance enhancing effects of caffeine on endurance exercise. So athelete’s are advised to use the lowest levels possible. Withdrawal symptoms can be minimized by slowly reducing caffeine consumption over several days.

Which sports benefit the most?

  • Short duration-high intensity events (1-5mins) e.g. sprinting
  • Prolonged high intensity events (20-60min) e.g. athletics or rowing
  • Endurance events (90min plus continuous exercise) e.g cycling or water polo
  • Ultra-endurance (4hours+) triathlon, duathlon
  • Prolonged intermittent, high intensity e.g. team and racquet sports.

Possible side effects

Fluid balance

In the short-term, urine production at rest may increase as a result of initial caffeine introduction.
However for habitual drinkers, caffeine is unlikely to alter fluid balance or lead to dehydration. Also for many people who consume tea, coffee and caffeine drink’s regularly these drinks may contribute significant levels of fluid to their daily fluid intake.


If taken in excess, caffeine can increase heart rate, impair or alter fine motor control and technique which may interfere with recovery (from training and competition) and sleep patterns which could upset concentration and precision.

Interactions with supplements

Caffeine can interfere with the actions of other supplements an athlete may be taking. For instance caffeine can inhibit the ability of creatine monohydrate to store calcium in the muscle thereby reducing its effectiveness to help the athlete to build strength and power.


Although research is yet to establish a safe level for caffeine it is not recommended for use by children and adolescents taking part in sport, particularly on hot days. Also for adults the long-term intake of large amounts of caffeine (>500mg per day) is generally discouraged by health authorities.

Long-term health benefits of tea and coffee use

Cancer prevention

Coffee consumption may protect against colorectal cancer. Green tea may protect against cancer of the stomach, colon and rectum, breast and ovary and black tea against prostate cancer

Cardio vascular

No clear evidence has been able to prove that coffee increases the risk of hypertension, myocardial infarction or other cardiovascular disease. However research both green and black tea is hopeful. The flavonol content of tea has been associated with lower coronary risk. Tea appears to improve the vascular epithelium and affect homocysteine, cholesterol, LDL oxidation and atherogenesis.


Type 2 diabetes is now being investigated with coffee rather than tea offering evidence of some protection.

Guidelines for use

It is recommended that for general consumption a caffeine intake of 400mg per day is not associated with any adverse effects. This is equivalent to approximately 4-5 cups of coffee or 13 cups of tea

If you would like to discuss your caffeine consumption with us then contact us today.


  • Sports Dietitians Australia Fact sheet on Caffeine
  • Binns C Should nutritionists recommend tea or coffee? Perspectives nutrition news and views. Issue 26, May 2009 ISSN1446-6112

About the author View all

Lea Stening

Lea is one of New Zealand’s leading paediatric dietitians and also specialises in Sports Nutrition. She has specialised in Paediatric Nutrition for 31 years and in 1985 was the first paediatric dietitian to enter private practice in New Zealand. Lea helps families through her private consultations, public lectures, newspaper and magazine articles as well as television and radio interviews. Read more »

View all posts by Lea Stening »


Leave a Reply

Also in Diet Therapy View all »

  • Are you afraid of the scales?

    Everyday we measure things such as the time, money, distance, our cholesterol, petrol etc yet many people fear measuring themselves Read more »

  • Stay in ‘the loop’ for a brighter...

    Loneliness and social isolation are being increasingly seen as risk factors to good physical and mental health. Learn how to stay connected with others and improve your sense of well being in 5 easy steps. Read more »

  • Unlock your potential with food

    The power of food can change your life and Dietitians can help you unlock your potential through food. Read more »

  • 10 Tips for better food choices this Christmas

    Weight control is the key to better health but this can be hard when Christmas often leads to overconsumption. Find out where to start. Read more »

  • Dietitians and Nutritionists what’s the...

    Dietitians are the most credible source of nutrition and food knowledge when you need to apply it to health and disease in NZ. Read more »

  • Wise up to Discretionary Foods for better health

    If you are struggling to lose weight or lower your cholesterol then taking a closer look at your intake of discretionary foods can improve your results. Read more »

  • How to put ‘real’ flavour into...

    It can be so easy to snip the top off a packet of flavouring when cooking. But if we really want to reduce the salt, fat and sugar in our diet natural flavours are best. Find out how. Read more »

  • Dietary help for women with PCOS

    Polycystic ovarian syndrome (PCOS) is a common cause of infertility in 6-20% of women of reproductive age causing a range of hormonal and metabolic effects that can impact on a women's physical and mental health. Read more »

  • Garnishes galore and all those “little...

    Is garnishing getting out of hand? Find out how much energy those "add ons" really do add. Read more »

  • 7 Myths about weight loss

    Lea Stening shares 7 common myths about weight loss and concludes that "you actually need to eat quite a lot of food in order to lose weight". Read more »

  • Time your eating for better performance?

    If playing sport or exercising, understanding the GI can help you to select foods that will provide optimal energy at key stages of activity for better performance. Read more »

  • Tips to help you ‘shake off’ the...

    In a bid to reduce the intake of processed foods many food manufacturers are modifying their products to meet new food guidelines particularly regarding salt. Find out if you are still getting too much? Read more »

  • Is going “Gluten Free” a healthy...

    As the popularity of gluten- free diets grow we need to question whether in fact it is a healthy option for any of us and if not how can we make it so? Read more »

  • Does your diet tick all the boxes?

    Is dieting still fun if it ages you? Find out if your diet ticks all the boxes for your better health and performance. Read more »

  • 10 tips to prevent weight gain in marriage

    When couples move in together they set in motion changes to their long-term health. While there are many health benefits of living together managing weight may need extra care and attention Read more »

  • Don’t let energy deficiency ruin your health

    Energy deficiency is not just a problem of third world countries. It can be found in our hospitals, schools and kindergartens, rest homes and on our sports fields. It can affect over and underweight people. Read more »

  • Sports supplements should be taken with care

    While some supplements are well recognised as being useful to performance others can lead to positive drug testing and disqualification as well as endanger long-term health. Read more »

  • Changing our “weight talk” may...

    A child can build their confidence and self esteem if monitoring their growth rate is accompanied by positive health messages about weight, fitness and energy to achieve in life. Read more »

  • Don’t let stress fractures slow your...

    Stress fractures are not just a problem for athletes who overtrain. They can affect anybody as they also relate to lifestyle and nutrition choices. Find out if you at risk. Read more »

  • Nutrition for distance runners and “fun runs”

    Distance running and “fun runs” (and walks) of varying length and degree of difficulty are becoming popular, attracting family and community groups; recreational and elite participants. Paying attention to sports nutrition can improve an athletes performance and enjoyment of these events Read more »

  • Juice diets – are they as healthy as...

    For busy people, who might rather drink than chew their fruits and vegetables, the juicing trend sounds like a "gods send". What possible disadvantages could there be to health? Find out the pros and cons of this new diet craze. Read more »

  • Driving for a living? 10 tips to help your...

    Spending hours behind the wheel is a huge recipe for weight gain and increased risks to our health. Driving is something that affects us all. Read more »

  • Feeling full is the secret to weight loss

    Gaining an understanding of the many factors contributing to a sense of fullness can provide some very powerful tools for those seeking to lose or control body weight and find more energy for life! Read more »

  • Can coconut improve our health?

    Coconut oil was once associated with tanning. Something young people coated themselves with before lying out in the sun “to bake”. Today coconut products are being heralded by many as the new “wonder food" that can cure many ailments. We take a look at some of these claims. Read more »

  • Dietary help for depressed athletes

    Although athletes may benefit from an exhilarating endorphin rush on exertion that elevates their mood and suppresses feelings of pain it will not stop them from experiencing, at times, anxiety and bouts of depression just like the rest of us. Nutrition is one treatment option that can speed recovery. Read more »

  • Sugar control is essential for better health

    After years of encouraging a low fat diet with some success (a decline in heart disease and some forms of cancer) attention is now focusing on sugar as a possible reason for our weight and diabetic problems. Read more »

  • Boosting fibre intake offers health benefits

    Research shows that a diet high in fibre can reduce the risk of developing diseases such as type 2 diabetes, coronary heart disease, bowel and breast cancer, gallstones, diverticular disease and weight gain. It also seems that some fibres are better than others. Read more »

  • Diet can offer protection when cold conditions...

    Cold injuries and illness occur in a wide range of physical activities. An understanding of the importance of sports nutrition and planning appropriate meals and snacks can offer some protection and may also improve overall performance Read more »

  • Healthy diet aids menopause management

    Menopause is a natural biological process women pass through and just like puberty it is not a medical illness. A woman's experience of Menopause is very individual and so there is no one "cure" for the range of symptoms that may be experienced. Read more »

  • Could the French Diet reduce obesity in New...

    The French diet is relatively high in saturated fat and yet in 2012 the French have a low incidence of obesity (11% compared to 28% in New Zealand). Why is this? Read more »

  • How to increase the ‘Good’ fats...

    If you are thinking of cutting fat out of your diet stop right now. Fat is important for nerve and cellular function but choosing the right “type” of fat is what matters most to our long term health. Read more »

  • Sports nutrition for senior athletes

    Everyday we require sufficient energy and nutrition to meet our needs for life, activity and body repair. As we age changes occur to our body's ability to absorb and process nutrients. Senior athletes need to be aware of these factors in order to maximise their performance, long-term health and enjoyment of events. Read more »

  • Can a high fat diet improve sports performance?

    Fat carries more energy than other macro nutrients (9kcals/37kJ/g compared to 7kcal/29kJ/g for alcohol and 4kcal/17kJ/g for protein and carbohydrate respectively). So with so much energy to offer does eating more improve performance? Read more »

  • Healthy ideas for family takeaway meals

    Did you know that in 2012 around 21% of New Zealander’s weekly food expenditure was spent on eating out and takeaways? Read more »

  • Are you a “sneaky snacker”?

    Some people find it hard to control snacking and are continuously thinking about food. They may find themselves constantly picking, stock piling foods in drawers and cupboards at home and work. Read more »

  • Vegetarians face extra hurdles

    Despite the apparently healthier lifestyle vegetarian athletes (like anybody) can still become overweight, hungry, bloated and suffering from multiple nutrient deficiencies. Read more »

  • The gut-brain axis is important to sporting...

    Do you ever suffer from” runners diarrhoea”, bouts of anxiety , fatigue, abdominal pain or gas when facing competition? Read more »

  • Swim for your life

    Whether you are swimming for fun or competition this sport has many health benefits that can be enhanced with good nutrition. Knowing what to eat and when can also greatly improve your enjoyment of the sport as well as your level of performance. Read more »

  • Eat your way to healthier nails

    The quality, appearance and growth of our nails often reflect the state of our general health and the adequacy of some essential nutrients in our diet. Read more »

  • Skin care for active people

    The stress of competition, the sun and wind, sweat, chaffing and high sugar levels are just some of the things that can aggravate the skin conditions of athletes and very active people. Read more »

  • Care for “the carers” during family...

    When family members are sick or hospitalised it can be very challenging to find the time to exercise and maintain a healthy diet for yourself. Particularly if you are working, caring for children, or trying to complete a course of study. Read more »

  • Don’t let disordered eating ruin your...

    An eating disorder can affect anyone at any age, any sport, any background and any gender. The symptoms may build slowly well before the illness becomes evident. Often it is an athletes support team such as parents, friends, team mates and coaches that pick up on the symptoms and can prevent the disorder from ruining the athletes sporting career. Read more »

  • Could your weight be disabling you?

    The human body is hugely resilient, constantly strengthening muscles and remodeling bones and joints to take up new loads. However as we age and weight is gained and lost, metabolic changes can take place that alter this remodeling process and can set us on a path to failing mobility and independence. Read more »

  • Obesity problems may start in the womb

    Overweight and obese women are a greater risk of developing complications endangering their own health during pregnancy and are also more likely to bare children who are overweight themselves Read more »

  • Put Sports Nutrition to work

    Many workers use enough energy and essential nutrients each day to power a marathon. If not replaced then a lack of these key nutrients can lead to fatigue, accidents and injury that can affect their long-term health and mobility. Read more »

  • Athletes protect your winning smile

    Athletes protect your smile and your wallet as painful tooth erosion is not only expensive it can also rob your training time and performance. Read more »

  • 8+ Tips for managing teething troubles

    Few children escape teething without some discomfort. Rosy flushed cheeks, a runny nose, irritable behavior, disturbed sleep and bowel function are all hallmarks of tooth eruption Read more »

  • Facing the down times without weight gain

    Nothing can be more infuriating for an athlete than after months of intense training an injury sees you ‘sidelined’. Read more »

  • Nutrition and eye health

    Good vision is essential for good health and sporting performance especially when athletes are involved in precision sports that require good hand and eye co-ordination such as archery, pistol shooting, cricket, golf etc. Read more »

  • Sports nutrition for women

    Women who push the boundaries of their lives to take on new challenges and sporting events are usually also trying to juggle their work, home and training existence. With good sports nutrition advice It is possible to find renewed energy. Read more »

  • Who controls feeding – the mother or the...

    Studies of toddlers aged 20 months to 6 years, that examined baby-led weaning versus traditional spoon feeding methods have found that feeding method can influence food preferences and health related outcomes in later life. We look at the pros and cons. Read more »

  • Sports nutrition for cycling

    Cycling tests an athlete’s strength and endurance capabilities as well as their anaerobic energy systems during breakaways, hill climbs and sprints to the finish.While some athletes rely heavily on dietary supplements, these will not replace a healthy training diet that is high in carbohydrate, with moderate protein and low in fat. Read more »

  • The protein needs of young athletes

    At a time when they are also growing, young athletes may need as much as 50% more protein than their more sedentary peers. Read more »

  • Food to Fuel the Speights Coast to Coast

    Whether you are a novice or seasoned triathlete your nutrition plan could make or break your race. All those competing should read the excellent nutrition tips on the official Speight’s Coast to Coast website and seek professional help if they have any concerns. In addition here is a check list of things you should also consider. Read more »

  • Children’s bone growth and gut health...

    Every parent wants their children to grow. But the height that they finally reach is dependent on factors such as growth hormone, genetics and nutrient availability. While we can’t change genetics after their arrival or growth hormones easily, nutrient availability can make the difference and is something parents can influence and need to be more … Read more »

  • Nutrition for tendons and ligaments

    The recent Rugby World Cup has placed the spot light on sports injuries and so we thought it might be interesting to look more closely at the protective role of sports nutrition and in particularly the nutrients important to tendon and ligament health. Read more »

  • Brace yourself for the brassicas

    With Winter now upon us its time to eat more Brassica vegetables. What are they? Broccoli – 7th most popular vegetable in New Zealand Cauliflower – 13th most popular Cabbage (all types) – 12th most popular Brussel Sprouts Broccolini – consumption rocketing! Swedes Turnips Why are they so good? Brassicas contain: Antioxidants, from the following … Read more »

  • Infant nutrition influences blood pressure...

    Scientific evidence suggests that environmental factors acting early in life may affect blood pressure in adult life. A study in Britain in 2004 supported earlier studies on infant nutrition and blood pressure that show a small reduction in systolic blood pressure in children breast-fed compared to those who were bottle-fed. Other advantages of breastfeeding Breast … Read more »

  • Alcohol and type 2 diabetes

    The protective role of alcohol in protecting against heart disease has been reported throughout various media sources in previous years, however only recently has it also been shown in people with Type 2 Diabetes. Epidemiological evidence suggests that a light to moderate alcohol intake may have a protective role against the development of Diabetes in … Read more »

  • Nutrition for healthy conception

    If improving your fertility is on your mind right now then take a moment to review your current lifestyle. Read more »

Would you like to subscribe to our fantastic FREE monthly newsletter?

Each month we'll keep you up-to-date with the latest nutritional articles and healthy recipes from You are free to opt out at any time, but we think you'll enjoy what we've got in-store for you.

Plus as a bonus offer — subscribe today and receive FREE weight loss tips for two weeks! Learn how a number of foods, many one would consider 'healthy', may in fact be slowing your progress.


Yes please, it sounds great! (and it's FREE after all).



No thanks, I'm not interested (or I'm already a subscriber and really enjoying these fantastic newsletters!).