Are you a hardcore coffee addict who gets stabby if you haven't had five shots by midday? Or perhaps you're at the opposite end of the spectrum – your body is a temple and not a whiff of caffeine shalt cross thine threshold? Either way, you may be surprised at how much caffeine you actually consume.

We expect to find caffeine in coffee, but you may be surprised by the presence – and quantity – of caffeine in products such as corn chips, ice cream, Panadol, weight loss tablets and sports supplements. It comes from the leaves, beans and nuts of various plants including coffee, tea, cocoa, kola and guarana – all of which can end up in the food, drinks, medications and supplements we regularly consume.

Highs and lows of caffeine

Caffeine is a paradox. On the one hand it offers a number of benefits: caffeine has been linked to a lower risk of developing Parkinson's disease and gallstones. It can boost metabolism, making it a popular ingredient in weight loss supplements, and has been shown to enhance exercise capacity and improve endurance exercise performance. The stimulant can also improve alertness and cognitive performance.  

But too much caffeine can increase anxiety, make you restless, give you headaches and impair your sleep. Caffeine consumption can cause temporary increases in blood pressure and as a result has been linked to heart disease. Heavy consumption has been implicated in pregnancy and birthing complications. And excessive caffeine can affect the amount of calcium that our body absorbs, so it's sometimes cited as a risk factor for osteoporosis.

The hidden drug

The problem with caffeine is that it's hard to know how much you're getting. The presence of caffeine in some foods and drinks is regulated to an extent. But aside from the following exceptions, food and drink manufacturers don't have to disclose the amount in a product, or in many cases even its presence.

  • Australian food standards limit the caffeine in formulated caffeinated beverages (otherwise known as energy drinks) to 320mg/L, and the caffeine content must be stated on the label.
  • Cola beverages must declare the presence of caffeine, and although the total caffeine content mustn't exceed ut/L, the concentration doesn't have to be specified on the label.
  • Foods and beverages that contain guarana or its extract must be labelled as containing caffeine, although the exact source of the caffeine doesn't have to be specified or quantified.
  • Where caffeine is added to a food it must be declared on the ingredients list, but it doesn't have to be quantified.

Natural sources of caffeine (such as coffee) or products containing these natural sources aren't required to label the presence or quantity of caffeine.

We looked at the packaging of a range of energy drinks, cola drinks, over-the-counter medications and weight loss and sports supplements, and found all were labelled appropriately. Where the caffeine content information wasn't on the label the manufacturers were generally happy to supply it when we asked, but for the most part this information wasn't available on company websites.

At the very least, we want makers of products that contain caffeine – from soft drink manufacturers to coffee chains – to provide caffeine content information on their websites. And, where it's not mandatory, we think producers should consider voluntarily labelling the presence of caffeine on their product packaging.

Caffeine sources compared

The following chart shows the relative amounts of caffeine in generic foods and beverages, plus a number of leading brands of caffeine-containing products.

For branded drinks, we've provided the caffeine content for the individual pack size closest to 500mL, as this size (or similar) was most consistently available across all mentioned products and in most cases is intended for individual consumption. Many of these products are also available in smaller pack sizes. * Caffeine for this generic item was derived from a composite of retail samples meeting this product description (source: NUTTAB 2010). The caffeine content of hot tea and coffee beverages can vary widely, depending on the brand, how it's prepared, and the size of the mug or cup.

Coffee culture

Coffee is the first food or beverage we think of when talking about caffeine. And you can see by the above chart comparing caffeine sources, a long black is the indisputable leader when it comes to caffeine content. 

Australians love coffee. More than one billion cups of the stuff are consumed in cafes, restaurants and other outlets each year – an increase of 65% over the past 10 years. If you're buying your preferred brew from coffee chains and cafes and trying to monitor your daily intake, it's worth noting that a study conducted by the University of Glasgow found caffeine levels in a single espresso ranged from 51mg to a whopping 322mg across 20 different coffee chains and cafes. 

Keeping an eye on your intake

It's a good idea to keep track of how much caffeine you're consuming, especially if you need to limit your intake, but reading labels won't always give the full picture. For most healthy adults, a moderate intake of caffeine (the definition of which varies from source to source, but 300-400mg is commonly cited) won't pose a problem. But limiting or ending your caffeine intake may be warranted in the following scenarios.
  • You're pregnant. Studies showing a relationship between caffeine intake in pregnant women and its effects on the foetus including reduced birth weight, pre-term birth or stillbirth have resulted in the recommendation that pregnant women limit their daily consumption to 200mg per day.
  • You're young. Caffeine increases anxiety levels in children at doses of 95mg and can disrupt sleep patterns, and what is a moderate to high dose of caffeine for children and adolescents (100-400mg) can see them become increasingly nervous, jittery and fidgety. Energy drinks have been a particular source of public concern because of their high caffeine content combined with their edgy marketing that has obvious teen appeal. Some products, including V Double Hit, Wicked, Monster Energy and Mother, contain as much caffeine in a single 500mL can as two cups of instant coffee – a level that can cause unwelcome side effects in this age group.
  • You're taking certain medications or supplements. Some medications and herbal supplements may interact with caffeine. For example, the antibiotic Ciprofloxacin may increase the stimulatory effects of caffeine. And the combination of caffeine and fellow stimulant bitter orange, found in a number of weight loss and sports supplements, can increase your blood pressure.
  • You're a heavy caffeine consumer. Heavy daily caffeine intake – more than 600mg a day – can lead to some unpleasant effects including insomnia, nervousness, restlessness, irritability, stomach upset, fast heartbeat and muscle tremors. People with a 10-cup a day coffee habit undoubtedly fall into this category. But you may be unwittingly consuming this amount of caffeine from as little as two coffees, depending on how and where the coffee is made.
  • You're sleep deprived. Caffeine can interfere with much-needed sleep by making it harder to nod off and shortening the time you do sleep. If you then drink caffeinated beverages during the day because you have trouble staying awake it can create a cycle of poor sleep.
  • Even a little makes you jittery. Some people are more sensitive to caffeine than others. If you're susceptible to the effects of caffeine, just small amounts – even one cup of coffee or tea – may prompt unwanted effects, such as restlessness and sleep problems. People who don't regularly drink caffeine tend to be more sensitive to its negative effects.

Other factors that can determine how you react to caffeine include body mass, age, medication use and health conditions such as anxiety disorders.