The answer is 'fermentable carbohydrates' and they are the only thing bacteria in your mouth can feed on.
So what are they? Well, carbohydrates as you are may know are our major source of energy- they come in two basic forms: starch (complex carbohydrates) and sugars (simple or fermentable carbohydrates).
Fermentable carbohydrates are those which are broken down in the mouth
by bacteria to produce acid. The others are not broken down till further along the digestive system.
Eventually all carbohydrates will be broken back down into sugars (glucose, fructose, maltose and lactose), but it is where
this happens that is the key thing.
There are two types of fermentable carbohydrates
These are naturally occurring sugars (e.g. fructose) found inside the cells of food such as fruits or vegetables. They are part of the structure of unprocessed foods and are the least damaging type. Intrinsic sugars are not considered a cause of dental caries when eaten in their natural form, but juices and dried fruits have higher concentrations of sugars (and often 'added' sugars- see 'below') making them more of a risk.
These are sugars that are either added to food to improve the taste, or those that are freely available in the food. They can be divided into:
(i) Milk sugars (lactose).
Those found in milk are considerably less harmful than:
(ii) Non-milk sugars (sucrose/maltose/glucose)
- such as syrups (maple or golden), honey, table sugar and those used in soft drinks, sweets, chocoloate and biscuits. These sugars called NME’s (non-milk extrinsic sugars) are the real bad guys and the ones that you really should cut down on; they do by far the most damage to your teeth. Sucrose is the ring leader- it is the most prominent baddy and helps to form a protective plaque layer (known as extracellular polysaccharide), this binds the plaque together; attaches it to the tooth and prevents it from being washed easily away. Fructose from fruit is considered a NME, ‘only’ if it is added to food or drinks and this, together with glucose are the other key members of the dental mafia. You should be limiting yourself or your child on average to 3 or 4 intakes of NME a day.
'Cariogenicity' is a word you may hear; it simply means 'caries- generating' or 'caries- causing'. If a sugar is cariogenic then if you eat
it enough your teeth will decay!