Tea & Caffeine – What’s the Story?

What is Caffeine?

Caffeine is a naturally occurring substance found in the leaves, seeds or fruits of at least 100 different species worldwide and is part of a group of compounds known as methylxanthines. The most commonly known sources of caffeine are coffee, cocoa beans, cola nuts and tea leaves. People have enjoyed caffeinated beverages for many years. Caffeine is also added to specifically formulated ‘energy drinks’ and pharmaceutical products such as cold and flu remedies.

Coffee and tea also contain other dimethylxanthines; theophylline which has similar properties to caffeine and theobromine whose pharmacological actions is far less potent than caffeine and theophylline.

The amount of caffeine present in products depends on the type of the product, the serving size and the preparation method. For example a 190ml cup of tea contains 50mg of caffeine, one third less than the same amount of an instant cup of coffee (75mg). Table 1 below gives an indication of the amount of caffeine found in other drinks compared to tea:

Table 1 – Type of Product Caffeine (mg/ serving)

  • Tea All types 50mg/ 190ml serving (1)
  • Coffee Brewed (filter or percolated) 100-115mg/ 190ml serving (1)
  • Instant 75mg/ 190ml serving 1 Cola drinks Standard and Sugar Free 11-70mg/ 330 ml can (2)
  • ‘Energy’ drinks All types 28-87mg/ 250ml serving (2)
  • Chocolate Bar 5.5-35.5mg/ 50g bar (2)

On average we consume 3.98mg of caffeine /kg body weight per day ie 239mg/ day for a 60kg person (3).

What is a safe intake of caffeine?

Up to 300mg/day (6 cups of tea) is considered moderate, with no evidence of harmful effects in the vast majority of the adult population. Some individuals are sensitive to caffeine and will feel effects at smaller doses than other individuals who are less sensitive. For this reason, these individuals may need to limit their caffeine intake.

Metabolism and Clearance

Caffeine does not accumulate in the body over a course of time and is normally excreted within several hours of consumption. The rate of caffeine elimination varies between individuals and this maybe as a result of genetic factors affecting the enzymes involved in the metabolism, or due to certain lifestyle factors e.g., smoking.

Children also metabolize caffeine at a quicker rate. Generally caffeine absorption is complete within about one hour after ingestion and the plasma concentration peaks (2) after about 60-90 minutes. The half-life of caffeine in the plasma is about 2.5 – 4.5 hours in healthy adults.

Caffeine Tolerance

A number of different factors affect individual tolerance to caffeine, including the amount ingested, the frequency of caffeine consumption and individual metabolism. It is widely recognized that gradual tolerance develops with prolonged caffeine use.

Physiological Effects

Caffeine is a pharmacologically active substance, and depending on the dose, has a number of actions:-

• Central Nervous System Stimulant. A moderate caffeine intake can cause mild stimulation that maybe beneficial in terms of increased alertness, concentration, improved performance and decreased fatigue. (5-10) However, higher intakes may affect sleep, cause nervousness and an irregular heartbeat.

• Weak Bronchodilator. As a result, interest has been shown in its potential role as an asthma treatment. A number of studies have explored the effects of caffeine in asthma and the conclusions from a Cochrane Review suggest that caffeine appears to improve airways function modestly in people with asthma for up to four hours after consumption. (11)

• Diuretic. The diuretic action of caffeine may be due to an increase in renal blood flow, leading to an increased glomerular filtration rate (GFR), or due to a decreased re-absorption of sodium in the renal tubules. The diuretic effect of caffeine is dependent on the amount consumed and duration of intake e.g. the caffeine in tea does not have a diuretic effect unless the amount of tea consumed at one sitting contains more than 250-300mg of caffeine, equivalent to between 5 and 6 cups of tea. (12-17).

In fact, due to the volume of fluid that is drunk whilst enjoying a cup of tea, the British Dietetic Association advises that tea can contribute towards the daily recommended fluid intake of 1.5 to 2 litres.

• Cardiac Muscle Stimulant. Moderate caffeine consumption does not increase cardiac arrhythmias. (18)

If regular caffeine consumption is stopped abruptly, symptoms such as headaches, irritability and fatigue may occur. These effects are usually temporary, disappearing after a day or so and can be avoided if caffeine cessation is gradual.

Caffeine and Health

The role of caffeine in the development of certain diseases and conditions has been the subject of extensive research in recent years.


A number of studies investigating the impact of caffeine in the development of cancer have failed to establish a relationship. (19-22) In fact, tea is one of the richest sources of flavonoids, a powerful group of antioxidants. The role of antioxidants in the prevention of free radical damage has led to suggestions that tea maybe anti-carcinogenic. (23). Despite interesting preliminary research, further work is required to prove its beneficial effect in this area.

Heart Disease.

The relationship between caffeine and heart disease has been the subject of a number of studies, and results from these and epidemiological studies have led to the conclusion that the ingestion of moderate amounts of caffeine is not associated with any increased risk of heart disease. (24-28) The Committee on Medical Aspects of Food Policy concluded that ‘there is little evidence that caffeine itself has any relation with CHD risk’ in the 1994 Nutritional Aspects of Cardiovascular Disease report. (29)

Parkinson’s Disease.

Observational studies have suggested that caffeine may play a role in protecting against Parkinson’s disease, (30-31). Further research to try to determine the exact mechanism is required.

Relief of headaches.

In a study of 301 regular headache sufferers, researchers found that a combination of ibuprofen and caffeine was better than either drug alone in relieving pain. (32)

Although a caffeine ‘pill’ was used in this trial, the researchers believed that caffeinated beverages would work just as well. However, they did warn that chronic headache sufferers should avoid caffeine because it might exacerbate symptoms. More work is required in this field before firm conclusions about caffeine and pain relief can be drawn.


Caffeine crosses the placenta and achieves blood and tissue concentrations in the foetus that are similar to maternal concentrations. For this reason recent advice published by the Food Standards Agency (33) recommends that pregnant women should limit their intake of caffeine consumption to less than 300mg/ day (equivalent to 6 cups of tea/ day). At this level there is little evidence to suggest that the health of the unborn child or mother is affected.

In Summary…

Despite recent publicity about caffeine, the fact remains that the consumption of caffeine at intakes of 300mg/ day has no adverse effects in the vast majority of the adult population. For this reason an average intake of three to four cups of tea (34) a day is well within the level considered safe.

Caffeine and Breastfeeding.

Caffeine enters breast-milk in small amounts (about 1% of the mother’s plasma level) but it does accumulate in smaller babies. Six to eight cups of coffee a day can result in infant wakefulness and hyperactivity. Smoking augments this effect. Of course the dose of caffeine from one cup of tea a day is nothing like the dose from several cups of coffee a day, but it makes sense to keep the dose the baby gets as low as possible.


1. Gray J (1998). Caffeine, coffee and health. Nutrition and Food Science 6:314- 319

2. Ministry of Agriculture, Fisheries and Food (MAFF) (1998). Survey of caffeine and other methylxanthines in energy drinks and other caffeine containing products (updated). Food Surveillance Information Sheet No. 144 (No. 103 revised). London

3. Barone JJ, et al. (1996) Caffeine consumption. Food and Chemical Toxicology 34:119-129

4. Graham TE (1997) The possible actions of methylxanthines on various tissues. In Reily T., Orme M (eds). The clinical pharmacology of sports and exercise. Elsevier Science, Amsterdam. 257-270

5. Lieberman HR, et al (1987). The effects of low doses of caffeine on human performance and mood. Psychopharmacology 93:308-312

6. Jarvis M. (1993). Does caffeine intake enhance absolute levels of cognitive performance? Psychopharmacology 110:45-52

7. Hindmarch I, et al. (1998). The effects of black tea and other beverages on aspects of cognition and psychomotor performance. Psychopharmacology 139(3) :230-238

8. Smith AP, et al (1990-91). Effects of caffeine given before and after lunch on sustained attention. Neuropsychobiology 23(3): 160-163

9. Durlach PJ, et al (1998). The effects of a low dose of caffeine on cognitive performance. Psychopharmacology 140(1):116-119

10. Battig K. (1986) Effect of coffee on the speed of subject-paced information processing. Neuropsychobiology;16(2-3):126-30

11. Bara AI, Barley EA. (2001) Caffeine for asthma (Cochrane Review). In: The Cochrane Library, 2, Oxford

12. Nussberger, J. et al. (1990) Caffeine-induced diuresis and atrial natriuretic peptides. Journal of cardiovascular Pharmacology, 15, 685-691

13. Neuhäuser-Berthold, M. et al. (1997) Coffee consumption and total body water homeostasis as measured by fluid balance and bioelectrical impedance analysis. Annals of Nutrition & Metabolism, 41, 29-36

14. Martof, M.T. and Knox, D.K. (1997) The effect of xanthines on fluid balance. Clinical Nursing Research, 6:186-196

15. Stookey, J.D. (1999) The diuretic effects of alcohol and caffeine and total water intake misclassification. European Journal of Epidemiology, 15, 181-188 16. Passmore AP et al (1987) Renal and cardiovascular effects of caffeine: a dose response study. Clin. Sci. 72(6), 749-56

17. Grandjean AC et al (2000) The effect of caffeinated, non-caffeinated, caloric and non-caloric beverages on hydration. J. Am. Coll. Nutr. 19(5), 591-600

18. Myers MG. (1991) Caffeine and cardiac arrhythmias. Annals of Int Med,114:147-150

19. Rosenberg L. (1990). Coffee and tea consumption in relation to the risk of large bowel cancer. A Review of Epidemiological Studies. Cancer Letters 52:163-171

20. Jacobsen BK, et al (1986). Coffee drinking, Mortality and Cancer Incidence: Results from a Norwegian prospective study. Journal of the National Cancer Institute, 76:823-831

21. Gordis, L (1990). Consumption of methylxanthine-containing beverages and risk of pancreatic cancer. Cancer Letters, 52:1-12

22. Lubin F, et al. (1990) Consumption of methylxanthine-containing beverages and the risk of breast cancer. Cancer Letters, 53:81-90

23. Huang MT, et al (1992). Phenolic compounds in food and cancer prevention. Phenoloc Compounds in Food and Their Effects on Health II Washington: American Chemical Society Symposium Series.

24. Grobbee, DE, et al (1990). Coffee, caffeine and cardiovascular disease in men. The New England Journal of Medicine 323:1026-1032

25. Bak AAA, et al (1991). Caffeine, blood pressure, and serum lipids. Am J Clin Nut, 53:971-975

26. Stamler J, et al (1997). Relation of body mass and alcohol, nutrient, fiber and caffeine intakes to blood pressure in the special intervention and usual care 5 groups in the Multiple Risk Factor Intervention Trial. Am J Clin Nut, 65(Supp.): 338-365

27. Willett WC, et al (1996). Coffee consumption and coronary heart disease in women. A ten-year follow up. JAMA 275: 458-462

28. Woodward M, et al (1999). Coffee and tea consumption in the Scottish Heart Health Study follow-up: conflicting relations with coronary risk factors, coronary disease and all-cause mortality. J. Epidemiology and Community Health, 53: 481-487

29. Nutritional Aspects of Cardiovascular Disease (1994). Report of the Cardiovascular Review Group Committee on Medical Aspects of Food Policy. Department of Health 30. Ross G et al (2000). Association of coffee and caffeine intake with the risk of Parkinson Disease. JAMA, 283:2674-2679

31. Ascherio A, et al (2001). Prospective study of caffeine consumption and risk of Parkinson’s disease in men and women. Ann Neurol, 50(1):56-63

32. Diamond S, et al (2000). The Use of Ibuprofen Plus Caffeine to Treat Tensiontype Headache. Clinical Pharmacology and Therapeutics;68:312-319

33. Food Standards Agency (2001). Committee on Toxicity of Chemicals in Food, Consumer Products and the Environment. Statement on the Reproductive Effects of Caffeine

34. National Drinks Survey, April 2001

Nutrition – Starting From Zero

We are constantly bombarded with messages from the media telling us that foods we have consumed for years are suddenly bad for us. One day eggs are good for you, the next day they are bad for your heart – what is the actual situation now?

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You need to eat more leafy green vegetables, reduce your consumption of bad fats (saturated animal fats), increase your consumption of good fats (like olive oil and avocado), eat quality lean protein, eat more fish (but beware of the mercury!), reduce your intake of sugar. Eat fewer processed foods. So what is the bottom line? What are nutritionists trying to tell you? It all boils down to the fact that what you don’t eat is more important than what you do eat.

Start From Zero
The best way to figure out what you should be eating to live up to your highest health potential is to start from recording what you are eating. It’s so easy to forget that extra bit of something. So, use your digital camera or phone camera. Every time you eat, stop, think, take a picture. Remember that the camera doesn’t lie. At the end of each day, write a list of the foods shown in those pictures. This may take a while, but you will be able to see that most foods can be broken down into a few simple categories at their basic ingredients:

  • Meat (beef, pork,chicken, fish, other seafood, etc)
  • Dairy products (milk, cheese, yogurt, cream, desserts, etc)
  • Corn products (bread, chips, popcorn, etc)
  • Wheat (pastas, breads, desserts, etc)
  • Soy (bread, desserts, drinks, anything processed, etc)
  • Fruit
  • Vegetables
  • Water
  • Energy drinks
  • Alcoholic drinks

Now take out a fresh piece of paper and add only the items that fall under the category of fruits and vegetables. This is what is called starting from zero. Remove everything that does not contribute to your health and only add back those items that you know are good for you. Mark whether the food is natural or processed. Aim for unprocessed, preferably organic, fruit and vegetables.

Why Fruits and Vegetables?

The governments of the world recommend that you eat between 5 to 10 fruits and vegetables every day. This recommendation is a great one and it has helped dozens of people lose weight and become healthier. It’s easy eat 5 to 10 fruits and vegetables a day by eliminating other snacks like muffins, cakes or cookies. Apples, bananas, mandarin’s, oranges are easy to take with you almost anywhere, just wash them at home to make life a bit easier.  Find out more about the colors of fruit & vegetables HERE

It is only by eliminating the unhealthy, extraneous or over-processed foods that you will be able to incorporate the recommended quantity of healthy ones.

The Building Blocks of Health
Think of this exercise as a way to build up your health, starting from the base. By eliminating meat, dairy and aggravating grains from your diet you prepare your body for proper nutrition. You allow yourself to cleanse and you provide your body with all the enzymes, the minerals and the vitamins that your body requires for proper functioning.

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Looking at the new list of healthy foods, you might see that it needs to be improved upon a bit. Why not add some new and exotic fruits and vegetables that you never tried before? Add more healthful grains in the form of brown rice, quinoa, barley and buckwheat if you find you need something denser. Old fashioned foods like rolled oats are great for you as well as tasting good.

Give Yourself a New Start
By starting fresh you give your body a break and a chance to rejuvenate itself. If you decide that you would like to add some of the things from the original list back into your diet, do so only 30 days after this exercise. Then watch to see how your body reacts to this newly added food. If you don’t experience any side effects then you can continue to eat it, once again. Otherwise you have proof that it was never that good for you in the first place.

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Some Shortcuts to Better Health

Eliminate fat and oil already consumed by using Corn Fiber Plus – the ingredients bind with the fat so it’s eliminated naturally.

Add Spirulina, Chlorella and Stabilized Rice Bran into your diet – for the benefit of concentrated nutrition.

Make sure you’re properly hydrated – with the right purified water – Hexagon Energized Living Water

Improve your Nutrition Intelligence HERE

To your health!