Sleep: The secret to sleeping well and waking refreshed. Prof. Idzikowski Chris

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      To find out how much caffeine you are really consuming, see the main caffeine offenders, opposite.

      The absorption and metabolism of caffeine

       Varied or little effect

      Heredity Caffeine metabolism is controlled by many genes and racial differences exist

      Gender Exercise and stress have no reliable effect on the absorption or metabolism of caffeine

      Pregnancy There are no placental barriers to caffeine so the foetus is continuously exposed

       Slowers-down

      Oral contraceptives, late pregnancy and liver disease cause caffeine to be eliminated more slowly

      It has been thought that grapefruit juice, though not other citrus juices, slows down metabolism. The data for this has now proved controversial

      Some drugs like cimetidine, disulfiram, even alcohol, may slow down caffeine metabolism

       Speeders-up

      Smoking induces liver enzymes which break caffeine down

      Rifamprin

      The main caffeine offenders

Foodstuff	Plant	Plant caffeine content w/w	Caffeine dose/‘cup’
Tea	Dried leaves	1-5%	10-100mg (average 40mg)
Coffee	Beans	0.75-2.0%	30-150mg
‘Decaffeinated’ coffee	Beans	0.75-2.0%	5mg
Cocoa	Seeds	0.013-1.7%	2-50mg (average 5mg)
Chocolate	Seeds		2-63mg/50g
Cola drinks	Nuts	1.5-2.0%	25-100mg (synthetic)

       did you know?

       Coffee is an ancient commodity. In AD 575, about 500 years before it became a hot beverage, the crushed beans were mixed with fat and used by Ethiopian mountain warriors to provide an energy boost during long treks and warfare.

      must know

       Sugar

       Sugar does not give you energy. A study carried out at Loughborough University, UK evaluated the energy-giving effects of sugar on ten healthy young adults. Their sleep was restricted to five hours the night before so that they would be sleepy in the afternoon, and half were given a ‘high-energy’ drink containing high levels of sugar but low levels of caffeine, and the other half a drink containing low levels of both. When submitted to vigilence and sleepiness tests the high-sugar drinkers made twice as many errors and showed higher levels of sleepiness than the control group, as well as delayed reaction times.

      Sugar

      Sugar can have a negative impact on sleep patterns because of its effect on insulin and blood sugar levels. It is released into the bloodstream to give you that instant ‘high’, but then departs from your system just as quickly, leaving you exhausted. In fact, you feel so tired that your instant impulse is to have yet another sugar fix to make you feel better. And so the cycle goes on. The continuing effect of these highs and lows can leave you feeling drained, or – depending on when you last had your sugar dose – over-excited, with pounding palpitations that stop you from sleeping. The disruptive impact on blood sugar levels can also cause sleep-disrupting hormonal imbalances in women. Sugar is found not only in biscuits and sweets, but also in fizzy drinks, refined wheat, tomato ketchup, baked beans and many processed foods. Read all food labels carefully.

      ‘Good sleep’ foods

      There is some evidence to suggest that eating slowrelease energy foods, or low glycaemic index foods, (foods that keep blood sugar levels stable), may improve general health and sleep quality (as well as helping the individual to lose fat). The idea is that the lower the glycaemic rating of a particular food, the more slowly energy, in the form of glucose, will be released into the body (see Low glycaemic index foods, opposite). Thus glucose and insulin levels are prevented from plummeting during the night, which may be beneficial for sleep. Foods such as turkey and dairy products may also be helpful, as they are high in tryptophan – the amino acid that the body uses to produce the sleep-inducing hormones serotonin and melatonin (see pages 16-17).

      Low glycaemic index foods

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Food	Carb (g)	Fibre (g)	Cal (kcal)
Granary bread, 1 slice	14	1.9	71
Rye bread, 1 slice	13.7	1.7	66
Chickpeas, small can, 200g	32.2	-	230
High-fibre bran, 40g	18.4	10.8	112
Rolled oats, 100g	62	7	368
Porridge (cooked and made with water) 100g	8.1	0.8	46
Apple, 1 medium	21	3.8	82
Avocado, half medium	8	3.4	160
Ham, honey-roast, 50g