Nutrition affects oral health and oral health affects nutrition.This interdependent relationship sees good nutritional health (including the quantity and qualityof dietary intake and nutritional status) promoting good oral health (encompassing gingival status, the well-being of teeth and jaw, salivary quantity and quality, and sensatory dimensions of taste and pain),and vice versa. On the other hand, poor nutritional health is associated with poor oral health, and vice versa.

Malnutrition, Infectious Diseases, and the Immune System

Nutrition is a major factor in infection and inflammation. Several reports emphasize the synergistic relationship between malnutrition, infectious diseases and the immune system; for example, infections promote malnutrition, the malnutrition elicits dysfunctions of the immune system, and this impaired immunity intensifies the infectious disease. In oral health, caries and periodontal disease, as well as many diseases of the mucous membranes, tongue and salivary glands, are infectious. Such oral infections can not only disrupt the integrity of the oral cavity, but can also affect general health by several possible pathways.

Nutrition and Periodontitis

Periodontal diseases,characterized by chronic inflammation and a loss of the bone and soft tissues that surround the teeth, constitute one of the most common chronic infections in humans. They are especially prevalent and severe in socio- economically deprived communities. In children with severe protein-energy malnutrition, for example,susceptibility to rare, aggressive,and often fatal infections is increased. A nutritious diet, including adequate amounts of protein, vitamins, essential fatty acids and micro-nutrients, can play an important role in the resistanceto infectious conditions, including periodontitis. For example

• Antioxidants, vitamin A, zinc,iron and dietary fish oils improve host resistance to infections;
• Zinc, copper, selenium,N-acetylcysteine, vitamin E and dietary fish oils reduce inflammation;
• Vitamins C, D, E and fish n-3 fatty acids reduce tissue destruction,enhance wound healing, and increase bone strength and rate of bone formation;
• Calcium and vitamin D have a beneficial effect on bones and on tooth retention.

Though not available to everyone, a well-balanced diet,consisting of a complex mixture of good quality macro-nutrients (i.e.,carbohydrates, lipids, and proteins) and micro-nutrients (i.e., vitamins and minerals), is required for maintenance of optimal general and oral health.

Nutrition on Saliva and Oral Health

Nutritional intake influences the oral tissues to which bacteria bind (i.e., epithelium, collagen,bone, teeth), as well as saliva. Secretory proteins (mucins) found within saliva provide an effective barrier against desiccation, penetration, physical and chemical irritants, and bacteria. The contents of saliva are likely influenced by nutrients consumed daily, with consequences to oral health.

• Synthesis of glyco proteins, such as mucin, requires vitamin A. In protein-energy malnutrition,retinol deficiency can reduce mucin production, leading to compromised salivary flow, weakened tooth integrity, and a marked increase in risk for caries.
• The presence of immunologic and non-immunologic antibacterial systems within saliva, in addition to the neutralizing and buffering components, can counter the acids formed in bacterial plaques when cariogenic bacteria ferment sugars and soluble starches.
• Saliva is saturated with calcium and phosphate salts that can remineralize submicroscopic defects in tooth minerals when plaque acids initiate the caries process.
• In the presence of fluoride in the oral environment, saliva’s function of remineralization can potentially reverse the caries process.

Nutrition on Stress Hormones and Oral Health

Malnutrition is also characterized by increased production and secretion of stress hormones (gluco corticoids) and decreased secretion of insulin (among other hormonal changes). Elevated circulating levels of cortisol in malnutrition imply a similar change in the content of this hormone in saliva and gingival fluid.

• Elevated circulating gluco corticoid levels, even at physiological concentrations, elicit macrophage dysfunction and reduce the production of cytokines in response to inflammatory stimuli.
• Cytokines play a prominent role in growth, differentiation, host defenses, and tissue damage.
• Cytokines also inhibit chemokines and other cells involved in attracting inflammatory cells at the site of inflammation, which ultimately impact the tissue healing process.

Oral Health on Nutrition and General Health

Poor oral health can affect dietary quality and nutrient intake in a manner that potentially increases the risk of several systemic diseases.

• Tooth loss can result in chewing difficulty because of inadequate occlusive surfaces or the limitations of prostheses.
• Reduced masticatory ability alters food selection and dietary quality, which can affect nutritional status.
• Oral pain resulting from caries, advanced periodontal disease, soft tissue lesions or poorly fitting prostheses may also lead to changes in diet and subsequent nutritional status.

Nutrient intake deteriorates in quality with fewer teeth.It has been observed that people with more teeth generally consumed fewer calories,more vegetables, more fiber, more carotene, and less cholesterol and saturated fat than their counterparts with fewer teeth. Edentulous individuals are particularly prone to inappropriate dietary intake, ingesting too few nutrient-dense foods and too many calorie-rich, high fat foods. Loss of natural teeth causes reduced masticatory efficiency even after replacement with dentures.

Among community- dwelling older adults, edentulousness is an important risk factor for weight loss, as chewing difficulty or oral discomfort due to poorly fitting dentures can contribute to food aversion and diminished nutrient intake. It has also been reported that denture-wearing individuals consume more refined carbohydrates and dietary cholesterol than dentate individuals. Such detrimental changes in food choices may, inturn, increase the risks of certain systemic diseases.The general health status of the individual, the use of alcohol,drugs or medications, and behaviors such as smoking, can all alter appetite, nutrient requirements and nutritional intake.

Ample evidence has been presented here to show that nutrition affects oral well-being,and oral well-being affects nutrition. Accordingly, with the assessment of patients’ nutritional status by dental care providers, appropriate counseling and recommendations will become an increasingly important part of dental practice for patients to learn the importance of nutrition for their oral health.