The primary modern flavoring ingredients in a cola drink are citrusoils (from orange, lime, and lemonpeels), cinnamon, vanilla, and an acidic flavorant. Manufacturers of cola drinks add trace flavorings to create distinctively different tastes for each brand. Trace flavorings may include a wide variety of ingredients, such as spices like nutmeg or coriander, but the base flavorings that most people identify with a cola taste remain citrus, vanilla and cinnamon. Acidity is often provided by phosphoric acid, sometimes accompanied by citric or other isolated acids. Coca-Cola's recipe is maintained as a corporate trade secret.
A variety of different sweeteners may be added to cola, often partly dependent on local agricultural policy. High-fructose corn syrup (HFCS) is predominantly used in the United States and Canada due to the lower cost of government-subsidized corn. In Europe, however, HFCS is subject to production quotas designed to encourage the production of sugar; sugar is thus typically used to sweeten sodas. In addition, stevia or an artificial sweetener may be used; "sugar-free" or "diet" colas typically contain artificial sweeteners only.
Crystal Pepsi, 20 oz. bottle, as seen in the US in 2016
In Denmark, a popular clear cola was made by the CooperativeFDB in 1976. It was especially known for being the "Hippie Cola" because of the focus of the harmful effects the color additive could have on children and the boycott of multinational brands. It was inspired by a campaign on harmful additives in Denmark by the Environmental-Organisation NOAH, an independent Danish division of Friends of the Earth. This was followed up with a variety of sodas without artificial coloring. Today many organic colas are available in Denmark, but, for nostalgic reasons, clear cola has still maintained its popularity to a certain degree.
A 2007 study found that consumption of colas, both those with natural sweetening and those with artificial sweetening, was associated with increased risk of chronic kidney disease. The phosphoric acid used in colas was thought to be a possible cause.
Studies indicate "soda and sweetened drinks are the main source of calories in [the] American diet", so most nutritionists advise that Coca-Cola and other soft drinks can be harmful if consumed excessively, particularly to young children whose soft drink consumption competes with, rather than complements, a balanced diet. Studies have shown that regular soft drink users have a lower intake of calcium, magnesium, vitamin C, riboflavin, and vitamin A.
The drink has also aroused criticism for its use of caffeine, which can cause physical dependence (caffeine addiction). A link has been shown between long-term regular cola intake and osteoporosis in older women (but not men). This was thought to be due to the presence of phosphoric acid, and the risk for women was found to be greater for sugared and caffeinated colas than diet and decaffeinated variants, with a higher intake of cola correlating with lower bone density.
^Tucker KL, Morita K, Qiao N, Hannan MT, Cupples LA, Kiel DP (October 1, 2006). "Colas, but not other carbonated beverages, are associated with low bone mineral density in older women: The Framingham Osteoporosis Study". American Journal of Clinical Nutrition. 84 (4): 936-942. doi:10.1093/ajcn/84.4.936. PMID17023723.