Coffee and Caffeine FAQ

By means of comparison, a 7 oz cup of coffee has the following caffeine (mg) amounts, according to Bunker and McWilliams in J. Am. Diet. 74:28-32, 1979:

7oz coffee:
Drip 115-175
Brewed 80-135
Instant 65-100
Decaf, brewed 3-4
Decaf, instant 2-3

12oz tea:
Tea, iced (12 ozs.) 70
Tea, brewed, imported 60
Tea, brewed, U.S. 40
Tea, instant 30

Other:
Mate 25-150mg
Espresso 100mg of caffeine 1 serving (1.5-2oz)

Acording to The American Beverage Asscoiation the numbers are a little different:

Coffee, 8oz drip 104-192 mg
Tea, 8oz brewed 20-90
Iced Tea, 8 oz 9-50
Soft Drinks, 8 oz 20-40
Cocoa Beverage, 8oz 3-32
Milk Chocolate, 1 oz 1-15
Dark Chocolate, 1 oz 5-35

Other data on caffeine:
Generic stay-awake pill 100mg
Vivarin 200mg
Cold relief tablet with caffeine 30mg

The variability in the amount of caffeine in a cup of coffee or tea is relatively large even if prepared by the same person using the same equipment and ingredients day after day.

Reference Variability in caffeine consumption from coffee and tea: Possible significance for epidemiological studies by B. Stavric, R. Klassen, B. Watkinson, K. Karpinski, R. Stapley, and P. Fried in "Foundations of Chemical Toxicology", Volume 26, number 2, pp. 111-118, 1988 and an easy to read overview, Looking for the Perfect Brew by S. Eisenberg, "Science News", Volume 133, April 16, 1988, pp. 252-253.

Quote from the lab manual:

Caffeine is present in tea leaves and in coffee to the extent of about 4%. Tea also contains two other alkaloids, theobromine and theophylline. These last two relax the smooth muscles where caffeine stimulates the heart and respiratory systems.

The effects of theobromine are, compared to caffeine and theophylline, relatively moderate. However, cocoa contains eight times more theophylline than caffeine. As well, caffeine has been shown to combine with other substances for added potency. Thus the effects of theobromine might be enhanced by the caffeine in chocolate.

Theobromine is highly toxic to dogs and kills many canids/year via chocolate poisoning. It takes quite a dose to reach fatal levels (more than 200 mg/kg bodyweight) but some dogs have a bad habit of eating out of garbage cans and some owners have a bad habit of feeding dogs candy. A few oreos won't hurt a dog, but a pound of chocolate can do considerable damage.

Clinical signs of theobromine toxicity in canids usually manifest 8 hours after ingestion and can include: thirst, vomiting, diarrhea, urinary incontinence, nervousness, clonic muscle spasms, seizures and coma. Any dog thought to have ingested a large quantity of chocolate should be brought to an emergency clinic asap, where treatment usually includes the use of emetics and activated charcoal. The dog will thus need to be monitored to maintain proper fluid and electrolyte balance.

Pathogenesis of theobromine toxicity: evidently large quantities of theobromine have a diuretic effect, relax smooth muscles, and stimulate the heart and cns.

Reference:

Fraser, Clarence M., et al, eds. The Merck Veterinary Manual, 7th ed. Rahway, NJ: Merck & Co., Inc. 1991. pp. 1643-44.

On humans caffeine acts particularly on the brain and skeletal muscles while theophylline targets heart, bronchia, and kidneys.

The following information is from Bowes and Church's Food values of portions commonly used, by Anna De Planter Bowes. Lippincott, Phila. 1989. Pages 261-2: Caffeine.

Candy:
Chocolate               mg caffeine
baking choc, unsweetened, Bakers--1 oz(28 g) 25
german sweet, Bakers -- 1 oz (28 g)           8
semi-sweet, Bakers -- 1 oz (28 g)            13
Choc chips
Bakers -- 1/4 cup (43 g)     13
german sweet, Bakers -- 1/4 cup (43 g)       15
Chocolate bar, Cadbury  -- 1 oz (28 g)         15
1.4 oz bar of milk choc. 	  3-10
1.4 oz bar of white choc      2-4 
1.4 oz. bar of dark choc       28 
Chocolate milk  8oz             8
Chocolate milk 8 oz. glass     2-7
Desserts:
Jello Pudding Pops, Choc (47 g) 2
Choc mousse from Jell-O mix (95 g)              6
Jello choc fudge mousse (86 g) 12
Chocolate covered espresso bean3-5 
Beverages
3 heaping teaspoons of choc powder mix          8
2 tablespoons choc syrup        5
1 envelope hot cocoa mix        5
Dietary formulas
ensure, plus, choc, Ross Labs -- 8 oz (259 g)  10
Cadbury Milk Chocolate Bar
More stuff:
Guarana "Magic Power" (quite common in Germany),
15 ml alcohol with
5g Guarana Seeds        250.0 mg
Guarana capsules with
500 mg G. seeds          25.0 mg / capsule
(assuming 5% caffeine in seeds as stated in literature)

Guarana soda pop is ubiquitous in Brazil and often available at tropical groceries.

It is possible that in addition to caffeine, there is some other substance in guarana that also produces an effect, since it 'feels' different than coffee. Same goes for mate.

According to the National Soft Drink Association, the following is the caffeine content in mgs per 12 oz can of soda:

Afri-Cola 100.0 (?)
Jolt 71.2
Sugar-Free Mr. Pibb 58.8
Mountain Dew 55.0 (no caffeine in Canada)
Diet Mountain Dew 55.0
Kick citrus 54 (36mg per 8oz can, caffeine from guarana)
Mello Yellow 52.8
Surge 51.0
Tab 46.8
Battery energy drink -- 140mg/l = 46.7mg/can
Coca-Cola 45.6
Diet Cola 45.6
Shasta Cola 44.4
Shasta Cherry Cola 44.4
Shasta Diet Cola 44.4
Mr. Pibb 40.8
OK Soda 40.5
Dr. Pepper 39.6
Pepsi Cola 37.2
Aspen 36.0
Diet Pepsi 35.4
RC Cola 36.0
Diet RC 36.0
Diet Rite 36.0
Snapple Tea 31.5
Canada Dry Cola 30.0
Canada Dry Diet Cola 1.2
7 Up 0

Also check out energy fiend's Caffeine Database.