In general, caffeine is considered safe if people stay within recommended limits. To avoid robbing the body of calcium and negative health effects, such as increased blood pressure, which can result from overusing caffeine, it's best to keep total intake below 400 mg a day, advises Health Canada. That's true whether you are drinking coffee, soda, other beverages that contain the drug or a combination of such drinks. Caffeine can occur naturally in plants such as coffee or be manufactured and added to foods such as soda. The amount of caffeine in soda and coffee can differ depending on the manufacturer and the variety.
Information offered to the public is often generalized when stating the amount of caffeine in soda or coffee. For example, a report in the journal "Food and Chemical Toxicology" recommends the following standards: 85 mg for a 5 oz cup of brewed coffee, 60 mg for a 5 oz cup of instant coffee, 3 mg for a 5 oz cup decaf coffee and 18 mg per 6 oz serving, or a half can of soda. However, the report also acknowledges that some products have higher caffeine contents than others.
A plain, 8 oz cup of brewed coffee typically has 95 to 150 mg caffeine, depending on the coffee variety and brand. A typical 16 oz latte has 150 mg caffeine, according to Connecticut's Sacred Heart University. However, the amount of caffeine can vary widely by brand, with a 16 oz serving of drip brew from one popular coffee producer containing 100 mg more caffeine than the same serving size of another, reports National Public Radio. The amount of caffeine in coffee purchased at drink stands can vary by day as well, even if a person buys the same size and type of coffee, according to the news agency.
Some sodas have no caffeine, including lemon-lime drinks. The amount in cola drinks differs depending on the brand. For example, Coca-Cola products generally have 35 mg in a 12 oz can, while Pepsi products have 35 to 38. Dr. Pepper has 41 mg, and sodas such as Mountain Dew and Mellow Yellow have even more caffeine, at 53 to 54 mg. Some brands of root beer have lower amounts, registering at 23 mg. It's always best to check a soda's label for caffeine. Some sodas that don't bring caffeine to mind, such as orange soda, often do contain caffeine. One orange soda brand has even more caffeine than cola, at 41 mg, according to SHU.
The leading dietary source of caffeine for U.S. adults is coffee. The leading source for children is soda. About 70 percent of sodas contain caffeine, according to Johns Hopkins University. Estimates for North America say that 80 to 90 percent of adults and children consume caffeine habitually.
The average per capita daily intake of caffeine in the United States is 280 mg. That's generally the equivalent of 17 oz brewed coffee or 84 oz soda, according to Johns Hopkins University.
Staying within recommended caffeine limits can promote a person's ability to pay attention, according to SHU. Thirty mg or less of caffeine can alter mood and affect a person's behavior, while 100 mg daily can cause physical dependence along with withdrawal symptoms upon abstinence, reports Johns Hopkins University. While there are general recommendations for caffeine intake, the drug's effect does depend on person's physical condition, weight and sensitivity to caffeine. When a person consumes more than his tolerance, his thinking abilities and concentration worsen, and concern about health risks such as increased blood pressure comes into play. Symptoms of too much caffeine include sweating, anxiety, tenseness and inability to concentrate, according SHU.