Diet and dental health

Tooth decay

Tooth decay is one of the most common diseases in the world. Despite rates of dental caries falling in the last 30 years, it affects almost half of children and adolescents and more than 55 per cent of adults in the UK. Dental caries is a disease caused by acids - fermented sugars and starches - breaking down the tooth. It can be very painful and unsightly, and may lead to tooth loss if not managed. Thankfully it's preventable and manageable if detected early.

The white visible section of the teeth is called the tooth enamel. It's made up of minerals, especially calcium and phosphate. It's constantly being dissolved (demineralised) and reformed (remineralised) depending on its environment. The bacteria in our mouths produce acids when they break down carbohydrates. In the presence of these acids, some of the calcium within the enamel dissolves and is lost from the tooth surface. This process is known as demineralisation.

At this stage, surface damage to the tooth can be repaired. Saliva is one of the mouth's natural defences against this process and protects against dental caries in several ways:

• It helps to remove food from the teeth
• It contains bicarbonate that helps neutralise the acid production
• It delivers minerals such as calcium, phosphate and fluoride to the surface of the tooth, enabling remineralisation to take place.

Tooth decay occurs when there's more demineralisation than remineralisation.

The teeth of children under six years old, and the elderly are particularly vulnerable to demineralisation. In children the tooth enamel is still being developed and is relatively soft and in the elderly, the tooth enamel is worn.

Dental erosion is the irreversible loss of tooth enamel and the dentine layer below which are dissolved away by acid in the diet or other outside factors (eg gastric acid from vomiting). In severe cases erosion can lead to total destruction of the tooth. Sugary or carbonated soft drinks, sweetened yoghurts, pickles and acidic fruits and fruit juices all put the enamel at risk. Erosion can also be a sign of someone with an eating disorder including self-induced vomiting.

Diet and dental health

Diet plays a significant role in both dental caries (cavities or tooth decay) and dental erosion. Good nutrition prevents many dental problems and is important from the outset. From good nutrition during pregnancy to breastfeeding in infancy, a balanced diet throughout childhood and adulthood is as good for the teeth as it is for general health.

The modern UK diet contains a mix of sugars and other carbohydrates that can be fermented in the mouth by oral bacteria to produce acid. Research has shown that people in countries that eat more sugar have significantly higher levels of caries. Studies also show that when people ate less sugar, for example during World War II, there was also a reduction in dental caries.

Both total sugar intake and the frequency with which it's eaten are factors. Small amounts of sugar consumed frequently over a period of time will cause more damage than the same quantity consumed on a single occasion. Constant sugar nibbling encourages continuous demineralisation and the saliva doesn't have time to neutralise the acids. Sticky or chewy foods that remain in the mouth longer also cause more damage as the bacteria have more time to produce the acid.

Milk and cheese and dental health

Cows' milk contains the sugar lactose - the least cariogenic (decay-causing) sugar. Milk on its own doesn't promote caries and this has been attributed to the presence of protective factors: calcium, phosphate, and the milk protein casein.

Cheese protects against dental caries, partly because eating cheese causes more saliva to flow and neutralise acids, and partly because the cheese increases calcium concentration in the plaque stopping demineralisation. The fat in cheese also reduces the amount of bacteria on the surface of the teeth. So a small lump of cheese eaten after a meal or a sugary/acidic drink will help protect tooth enamel.

Tea and dental health

There has been some research that shows that tea may fight tooth decay. Tea contains polyphenols, which suppress the growth of bacteria in teeth. However, tea also contains fluoride so it's unclear whether the protective effect is due to the fluoride or the polyphenols, or both and whether it's the milk added to tea that adds to the protective effect.

Fluoride and dental health

Fluoride undoubtedly protects against dental caries and in the UK, regular use of fluoride toothpaste has contributed to improved dental health. Fluoride makes tooth enamel harder and more resistant to acid attack. It also affects plaque by reducing acid production. Fluoride occurs naturally in water in some parts of the UK and is sometimes added in fluoridation schemes. High fluoride intake however can result in fluorosis (white flecks in the surface of the tooth enamel).

Chocolate and dental health

Milk chocolate contains calcium and casein that help protect teeth as milk would. There's a protective factor in cocoa itself, but these protective factors are unlikely to override the detrimental effect on teeth of the high sugar content.

Top tips for teeth

As well as correct brushing and flossing and regular dental checks, the following dietary measures can help minimise tooth decay and erosion:

• Eat sugary foods less often, particularly those of a sticky or chewable nature. Remember that dried fruits can provide sugar and a sticky surface on teeth that encourage bacterial growth and acid production
• Limit snacking of any foods, and therefore the amount of time your teeth are exposed to a bacteria-friendly environment
• Choose raw vegetables, wholemeal bread, unsweetened yoghurt or cheese as snacks
• Avoid sugary or acidic drinks between meals. Water or milk are the best options
• If you do have sweets, eat them all at once. Avoid 'grazing' over extended periods. For example have a whole chocolate bar in one go rather than constantly dipping in to a bag of sweets
• End a meal with milk or cheese to help neutralise the acid
• Leave a gap of one to two hours each time you eat or drink to allow remineralisation to occur
• Don't have anything except water after you've brushed your teeth at night – less saliva is produced at night
• Don't brush your teeth immediately after eating acidic foods or drinks. If teeth are brushed when in a demineralised state, a layer of tooth enamel or dentine may also be removed
• Drink through a straw. Liquids sucked through a straw have less contact with teeth and are less damaging than those consumed from a glass
• Chew sugar-free gum after a meal to help produce more saliva to neutralise the acid