Day 22 – Caffeine, how much is too much?

Day 22 of our 30-day nutrition challenge is all about the optimum amount of caffeine for you. Caffeine is in a variety of products and it affects:

  • Heart
  • Muscle
  • Mood
  • Memory
  • Alertness
  • Mental performance

It’s perfectly normal to feel sleepy as the day progresses due to the build-up of adenosine, but the adenosine receptor is blocked by caffeine which prevents sleepiness.

Caffeine also helps to release adrenaline – although helpful in short bursts, it’s not helpful if it’s too stimulating and you feel more anxious, shaky and your blood pressure also goes up, particularly if you already have high blood pressure. Other side effects of too much caffeine are headaches, insomnia, palpitations.

Half life

Caffeine is in blood for approx. 5 hours, but we dispose of it ranging from 1.5 to 9.5 hours and it’s very much dependent on the person and environmental characteristics e.g. pregnancy, obesity. Some people can tolerate caffeine, others cannot. Caffeine peaks around 15min -2 hours after consumed but it also depends on other foods/drinks consumed at the same time.

However, it’s not just about caffeine. In coffee there’s helpful substances (polyphenols) which reduce blood pressure and increase blood flow to the brain. Lighter roasted coffee beans have the higher polyphenol content.

How much?[i]

Here’s the amount of caffeine in various drinks:

  • 47-90mg black tea
  • 2mg black decaf tea
  • 20-45mg green tea
  • 6-60mg white tea
  • 95mg brewed coffee
  • 2mg brewed decaf coffee
  • 63mg espresso
  • 30-90mg instant coffee
  • 2mg instant decaf coffee

Too much?

The British Heart Foundation suggests that up to 4 cups (400mg) should be OK for most people without affecting heart rhythm or cholesterol, but it will increase blood pressure so not ideal if you already have high blood pressure – although the high blood pressure effect is only temporary.

Many articles quoting the benefits of caffeine refer to one study published in 2017 stating four cups of coffee per day was not bad for health. However as with any research it’s worth checking its credibility – duration, sample size, sponsors etc.. and in this review of 381 studies, unrestricted grants were received from the American Beverage Association[ii].

When’s the best time?

It’s suggested delaying the first caffeine drink until mid-morning. Cortisol levels are at their highest when we wake – combine this with breakfast and you shouldn’t really need caffeine until breakfast starts to wear off and energy starts to crash. Then perhaps reach for the caffeine, and the same again mid-afternoon when there is often another energy crash. However, consuming caffeine in the afternoon isn’t suggested if you suffer from insomnia.

If you’d like to cut-back beware it can be challenging. Headaches, irritability, mood swings, and fatigue are common but disappear after a few days. It may be worth reducing a cup every couple of days or substituting some for decaffeinated.

Did you know caffeine is produced by plants (kola nut, tea leaf, coco bean, coffee bean) as an insecticide!

If you’d like to find out more tips to improve your health, check out our Lockdown Nutrition webinar and our Bitesize Nutrition podcasts, especially the episode with Professor Tim Spector discussing caffeine. Listen free without registration on your phone or PC by following the podcast link in this paragraph, or also find Bitesize Nutrition on iTunes & Spotify.

Don’t forget to let us know what you think using #nutritionchallenge30

A reminder:

  • The information in this article is for educational purposes and should not replace medical advice.
  • The information is not intended to diagnose or treat any medical condition.
  • If you have a diagnosed medical condition, you should consult a doctor before making any major changes to your diet, and;
  • Some supplements may interact with medications and you should check with your GP before commencing any supplement programme.



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