Coffee drinking is mired in controversy with antagonists and protagonists swearing regarding the danger and virtues of this beverage. There are many reports supporting both the views though no conclusion can be drawn as to whether it should be shunned or can be taken as a refreshing beverage. There are many people for whom a good day is supposed to start with a cup of hot coffee. Connoisseurs of coffee make their own roasted coffee seeds, grind them, prepare the brew in their own way using percolators and create a superb blend of milk and coffee brew with typical aroma and taste. For them there is no compromise on quality of coffee drink with respect to seed ( Robusta or Arabica), roasting (mild, medium or dark roast), grinding, particle size of the powder, extent of chicory used, percolator design, the way the powder bed is prepared, the quality and 'temperature' of water used for the brew, freshness of boiled milk, proportion of milk used, mixing of milk and coffee brew, extent of foaming of the final product and the way it is sipped. Instant coffee products whether made by spray drying or freeze drying are not acceptable to many because of the flavor differences perceptible in coffee drink when it is made with instant powder. The ready to use milk-coffee powder combo products have not made their appearance in India due to their grossly inferior beverage quality, though they are accepted in other countries.
It is interesting to note that coffee brew home percolators contains more caffeine than that in instant coffee. Generally a half cup brewed coffee is equivalent to 1 cup of instant coffee. This is probably due to the pressure extraction used for extraction during the manufacturing process of instant coffee where carbohydrates are hydrolyzed and solubilized increasing the extraction yield. While almost 55% solids are extracted under pressure, the home brew rarely contains more than 20% coffee solids. This accounts for the difference in caffeine levels in the two versions of coffee drink. Caffeine is a Central Nervous System stimulant that temporarily wards off drowsiness and restores alertness. Caffeine is absorbed within an hour of its ingestion through the stomach and the small intestine. Coffee if moderately consumed can increase significantly one's capacity for mental and physical work.
The half life of caffeine in normal adults is 3-4 hours while in pregnant women it can be as long as 10-12 hours. The liver cytochrome P-450 Oxidase system converts caffeine first into three break down products, Paraxanthene (increased lipolysis), Theobromine (dilating blood vessels and increasing urine volume) and Theophylline ( relaxing smooth muscles of bronchi). These are further metabolized into smaller molecular entities and eventually excreted through the kidneys.
If consumed excessively caffeine can bring about undesirable consequences causing intoxication, nervousness, irritability, anxiety, muscle twitching, insomnia, headache and heart palpitation. 3 cups of brewed coffee or 7 cups of instant coffee or 9 servings of cola drink or 6 cups of strong tea will contain more than 300 mg of caffeine sufficient to bring about some undesirable effect.Most of those, consuming 7 cups of coffee, tend to have a higher tendency to experience hallucinations by seeing things or hearing voices that were not there, though this is not a serious manifestation of any psychotic problem.
Excess caffeine is claimed to exacerbate the physiological effects of stress. Under stress body is known to release a stress hormone called cortisol and people under stress, after drinking excess coffee, produce more of cortisol. As cortisol level has some effect on hallucinations, excess coffee consumption tends to induce temporary hallucination through increased secretion of this critical hormone into the blood stream. As a way out to avoid the undesirable effect of high coffee intake, one can have smaller doses of home brewed coffee at a time, spreading the consumption over a longer period. Many restaurants in India have reduced the serving size to hardly 75-100 ml (more for economic reasons) and consuming it even 5 or 6 times during a span of 10 hours in a day should not be a cause for worry.