Dieticians at Work

Caffeine
How Much Is Too Much?

	In a world where we are rewarded for working more and sleeping less it is no wonder that most South Africans start their day by reaching for a hot cup of coffee or tea. Caffeine consumption from coffee, tea, carbonated drinks and other beverages is prevalent in almost every culture and society and if you are like most adults, caffeine is part of your daily routine. Coffee alone is second only to oil as the world’s most traded commodity. But what effect is this “stimulant” having on our bodies and bodily functions, and what should our daily limit be.
What effect does Caffeine have on my Body?
Most of us know caffeine for its “Energy-Boosting” properties and the feeling of heightened alertness that it provides, we use it to stay awake and learn for our exams, or to stay awake during work after waking up feeling exhausted. Medically caffeine is useful as a cardiac stimulant and also as a mild diuretic to increase urine production. But what effect is caffeine having on our brain to enable this wonderful feeling. Caffeine has both short term and long term effects on the body. Short term it blocks your adenosine receptors in the brain which causes the blood vessels in your brain to constrict as well as preventing your brain’s nerve cells from slowing down or becoming “drowsy”. Your body reacts to these changes by secreting adrenaline which causes your pupils to dilate, your airway to open up, your heart to beat faster, your blood vessels on the surface to get smaller, your blood pressure to rise, your blood flow to the stomach to slow, your liver to release sugar into the bloodstream for extra energy and your muscles to tighten up. This explains why, after consuming a big cup of coffee, your hands get cold, your muscles tense up, you feel excited and you can feel your heart beat increasing. On a more long term basis caffeine also increases dopamine levels in your body. Dopamine is used by the body to activate pleasure centres in certain parts of the brain, similar to Heroin and Cocaine. The problem with this is once the adrenaline and pleasurable feeling wears off from your 1st cup you face fatigue and depression so you continue to consume more caffeine to get the adrenaline and happy feelings going again. As you might imagine, having your body in a state of emergency all day long isn't very healthy, and it also makes you jumpy and irritable. Another negative long term effect is caffeine’s disruptive effect on sleep. When caffeine blocks the adenosine receptors it is preventing your body from entering into its deep sleep necessary for complete rest. If you consume a big cup of coffee with 200 mg of caffeine in it at 3:00pm by 9:00pm about 100 mg of that caffeine is still in your system preventing your body from reaping the benefits of deep sleep.
What should my daily limit of Caffeine be?
We all know that excessive amounts of caffeine intake can cause many negative side effects, but how much exactly is too much? Medical experts agree that ingesting more than 250 mg of caffeine in a short period of time can cause restlessness, insomnia, muscle twitching, gastrointestinal disturbance, cardiac arrhythmia and a host of other problems. In order to answer the question of ‘how much is too much” we need to look at the individual consuming the caffeine. 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 anxiety, restlessness, irritability and sleep problems. Factors that effect your reaction to caffeine include:

	How often you drink caffeine containing drinks
	Gender (men are more susceptible to caffeine’s effects)
	Weight
	Age
	Medication use & health conditions (especially anxiety disorders)

Did you know that even your genes (DNA) can have an influence on your reaction to caffeine. Our body’s natural detoxification system is a two phase process. Caffeine is metabolised by the 1st phase of this process and when your first phase is sluggish, due to alterations in your genes, caffeine builds up in your body resulting in longer lasting effects of the caffeine.
For most healthy adults 200 to 300 milligrams (mg), about two to four cups of brewed coffee and five cups of brewed tea per day, are not harmful, in fact they may actually have health promoting benefits. Remember it is not just the caffeine we need to worry about but also the effects of drinking coffee or tea such as increasing urination. It is a good idea to aim for no more than 3 cups of coffee or tea daily. You should not take in more than 400mg of caffeine per day. Heavy daily caffeine use—more than 500 to 600 mg a day—may cause insomnia, nervousness, restlessness, irritability, stomach upset, fast heartbeat and muscle tremors.

Where do we find caffeine?
Caffeine is a naturally occurring substance in cocoa beans (chocolate), coffee beans (coffee) and tea leaves (tea), but it is also artificially added to many other beverages such as Coca-Cola and energy drinks. It’s also found in diet pills and some over-the-counter pain relievers and medicines. Below you will find a list of different beverages that contain caffeine including how much they contain
Beverage	Volume	Amount of Caffeine
Brewed Black Tea	240ml	35mg
Instant Tea	180ml (tea cup)	20mg
Green Tea	180ml (tea cup)	19mg
Brewed Herbal Tea Eg. Camomile	180ml (tea cup)	Zero
Coffee – Brewed (filter)	200ml (small mug)	78mg – 92mg
Coffee - Instant	200ml (small mug)	48mg - 52mg
Coffee - Espresso	60ml	105mg
Coffee – Brewed (Decaf)	200ml (small mug)	5mg
McDonalds Coffee	355ml	109mg
Coca-Cola, Regular	330ml can	33mg
Coca – Cola, Zero	330ml can	33mg
Tab	330ml can	44mg
Sprite	330ml can	Zero
7 - Up	330ml can	Zero
Nestea Ice Tea	330ml can	24mg
Red Bull	250ml can	80mg

Note: The values for tea & coffee are only estimates as the actual caffeine content can vary from day to day because of roasting, grinding and brewing times.

Written by :Claudia Misselhorn RD (SA) - Dieticians at work- March 2011