Cola 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. In the 1940s, Coca-Cola
Cola 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, ascorbic acid, 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