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How Does Caffeine Affect Us and Can We Have Too Much?

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Article by Dietitian Anthony Glanville

Over the past 20 years, coffee and caffeine has become synonymous with and intertwined within the Australian culture. From café culture, to espresso machines at home, instant, and energy drinks, caffeine is the most widely used drug (yes it’s a drug!) in Australia. So how does caffeine affect us and can we have too much?


Caffeine’s Effects in Your Body

Caffeine stimulates your nervous system via your hypothalamus, and hormones via your adrenal glands. This is called your hypothalamic-pituitary-adrenal (HPA) axis, the linked system of hypothalamus and pituitary glands in the brain, and the adrenal glands.  The adrenal glands, located on top of your kidneys, are responsible for producing your adrenal hormones such as adrenaline, aldosterone, and cortisol. These hormones are part of your stress response and make you feel more alert, increase your blood pressure, improving concentration, and raising your heart rate. Caffeine in particular places a huge demand on your adrenal glands – demanding over 3-6 hours of high level adrenal production.

These hormones influence many major physiological processors within the body including protein, fat, carbohydrate metabolism, blood sugar regulation, immune competence, inflammation control, hormone regulation and healthy cardiovascular and gastrointestinal function.

So caffeine makes us more alert, improves concentration, and if done correctly, is delicious. Sounds perfect. But with every drug, there is a catch!

One of the key hormones that the adrenal glands produce after being stimulated by caffeine is cortisol. Elevated cortisol can also affect the quality of our sleep, worsening the cycle as many people turn to processed foods and caffeine to help give them energy throughout the day. Cortisol is also associated with increased fat depositing around the waist and organs e.g. visceral fat (the one linked with heart disease, stroke, and liver disease) and may be the reason why some people struggle to lose weight. Excessive intake of caffeine over a long period of time can alter your body metabolically and increase your risk of ill health. Caffeine has an effect on your stress levels, and if you are busy at work, have a busy personal life with family and friends, your stress levels may already be high enough, let alone with caffeine being thrown into the mix.


Caffeine Threshold

Now the most important question, what is excessive? Up to 400 milligrams (mg) of caffeine a day appears to be safe for most healthy adults. The catch with getting it in coffee is that caffeine content can vary greatly depending on the roast, brewing technique, and type of bean. You can hit your caffeine threshold in 2 cups of coffee. For some that may be by 10am. Here is a list of typical caffeine rich items

Instant 80-100mg

Café 120-250mg

Energy Drink 100-150mg – 250mL can

Cola 30-40mg

Black Tea 20-50mg

Green Tea 30-50mg

Chocolate 20mg /100g bar


Smart Tips for Managing Your Caffeine Intake

#1 Timing

Caffeine is rapidly absorbed into the bloodstream, and blood levels peak after 90-100 minutes. Caffeine levels remain high for 3–5 hours, and then start to drop. This means that spacing your consumption at least 3-4 hours apart is very important.

As well as this, the time of day you have your caffeine plays a role. Your body is in ‘wake up and get going mode’ for the 2-3 hours after you wake up. This means that your adrenal glands are being stimulated already. Adding caffeine on top of this can overstimulate your adrenal glands, meaning after the caffeine wears off, your energy levels fall off a cliff. Try waiting 2-3 hours after waking before having your first hit of caffeine, this will even out your energy levels

You should avoid having caffeine from around 3pm onwards. Caffiene levels remain active in the system for up to 6-8 hours which can decrease the quality of your sleep and make it hard to settle in the evenings. (Meaning you may need more coffee the next day to get you going – starting a dangerous trend)

#2 Dose

Get to grips with how much caffeine is in what. Think about that double shot espresso or large coffee may have your daily limit of caffeine in it. Go for small milk coffee’s and single shots. Think about your non coffee based intake, as having a green tea in the evenings will affect your sleeping patterns, as will having a coke/diet coke with dinner.

#3 Alternatives

Herbal teas such as peppermint and chamomile are caffeine free and a great alternative to black or green tea. Try rooibos tea with a dash of milk in it. If you want a fizzy drink like coke, go for soda water with some flavour in it like mint or lemon. It can be tough to go to meetings or socialise without getting a coffee. There is a certain ‘vibe’ or ‘feeling’ that having a coffee with someone creates, and if you turn to tea or nothing it can alter the dynamic. In those instances, go for decaf.

Try keeping track of your caffine intake for a week – keep a diary in your phone. Not the dose and timing as well. Look to see if caffeine may be the reason your stress levels are high or that you are struggling to lose weight or having poor sleeping patters,

If you would like more tips or advice about caffeine or healthy eating and lifestyle, contact The Wellness Centre and book in to see Anthony today!