Another important role of the mouth in food digestion is the mechanical action of teeth. In contrast to bone, neither the tooth enamel nor dentin can be repaired or replaced by any natural process other than simple remineralization of small areas and deposition of secondary dentin around the pulp chamber. Mineral deposition and resorption influence the supporting bone structure. Alveolar bone is primarily trabecular bone (bony spikes forming a meshwork of spaces in cancellous bone) and cancellous bone (internal bone that appears spongy with little hollows that contain bone marrow). When negative calcium balance occurs, the alveolar process (crest of the maxilla and mandible serving as the bony investment for the teeth) is more susceptible to resorption than other cortical bones (compact external part of the skeleton that surrounds the bone marrow). The maxilla and mandible to some extent depend on the presence of teeth and occlusal forces associated with chewing to prevent calcium resorption. Chewing firm foods helps maintain proper balance between alveolar bone resorption and new bone formation. Teeth and supporting bone structures are affected by intake of adequate nutrients, adequate digestive function, and hormonal balance.

Diagram of a tooth.

 
   Chewing reduces food particle size. Inability to masticate food adequately may result in larger chunks of food being swallowed. Larger pieces of food increase the potential for food obstruction in the airway. Food asphyxiation, which may result in sudden death, occurs in many individuals with defective, incomplete, or poorly fitting dentures. The loss of even one permanent molar may decreasemasticatory efficiency, or how well the patient prepares the food for swallowing. Even after patient become fully adjusted to well-fitted dentures, masticatory efficiency is reduced compared with patients with their natural teeth.
   Digestion of food is facilitated by increasing its surface area. Whether or not particle size affects its digestibility is uncertain. However, when elderly patients have digestive problems, masticatory efficiency is usually a factor. Frequently, when masticatory efficiency declines, people choose foods that require less chewing or use techniques to soften foods, such as stewing meats, steaming vegetables, or dunking cookies or toast in fluids. In many circumstances, hypersensitive, poorly restored, decayed, abscessed, or periodontally involved teeth affect food choices and limit the variety of foods consumed.

Nutritional Directions

• Natural teeth are more efficient for chewing and biting than any prosthesis.
• Tooth losses are not inevitable; most people can maintain their natural dentition throughout life if preventive dental measures are practiced routinely.
• If salivary flow is diminished, increase fluid intake with meals to assist in oral clearance. Nutrient-dense foods in a liquid or semi liquid form are beneficial.
• No proven intervention either enhances taste acuity or ameliorates dysgeusia. Encourage experimentation with texture, spiciness, temperature, and enhanced visual presentation of food in a calm, relaxing environment.
• To improve nutrient intake when mastication is less efficient, special cooking techniques (e.g., stewing meats), chewing longer, and choosing soft foods are preferable to pureeing foods. For example, cream-style corn can replace corn on the cob, and applesauce can replace raw apples.
• Particularly for new denture wearers, herbs and spices and contrasting food taste combinations (e.g., sweet and sour) can be used to enhance taste perception.
• New denture wearers may slow the rate of alveolar resorption by taking calcium and vitamin D supplements.

Adequate saliva flow is essential for oral health and maintenance of soft tissues in oral cavity, including the taste buds. Saliva, secreted by the salivary glands, is essential in taste sensations, functioning to:

1. lubricate oral tissues to assist in chewing, swallowing, and digestion
2. remove debris from teeth
3. provide antibacterial action
4. neutralize, dilute, and buffer bacterial acids
5. aid in remineralization (the restoration or return of calcium, phosphates, and other minerals into areas that have been damaged, as by incipient caries, abrasion, or erosion)
6. affect the rate of plaque accumulation
7. influence taste
8. allow for ease in talking

   This complex fluid helps maintain the integrity of the teeth against physical, chemical, and microbial insults. Saliva is supersaturated with calcium phosphates that allow demineralized areas of the hydroxyapatite in enamel to be remineralized. Demineralization occurs as a result of the removal or loss of calcium, phosphate, and other minerals from tooth enamel, causing tooth enamel to dissolve.
   Acidic, sour, or bitter tastes stimulate saliva flow. Saliva production is also increased with consumption of tasty foods and gum chewing. An increase in oral clearance rate decreases risk of caries formation. Saliva blended with food particles moistens foods so that they are more easily manipulated and prepared for swallowing. 
Some chemical action or hydrolysis of nutrients begins in the mouth.

•  Mucin (glycoprotein) lubricates food for easier passage and protects lining of the gastrointestinal tract
   
•  Ptyalin – amylase (enzyme) initiates hydrolysis of complex carbohydrates to simple sugars
    
• Lysozyme – antibody (enzyme) breaks down cell walls of some ingested bacteria

Because food is normally in the mouth briefly, ptyalin, or salivary amylase, initiates starch digestion. If a carbohydrate food, such as a cracker, is chewed and held in the mouth for a few seconds, it will begin to taste sweet, denoting the fact that some starch is being hydrolyzed to dextrin and maltose.
   Dry mouth from inadequate salivary secretion, also called xerostomia, leads to diminished gustatory function. Xerostomia may result in frequent oral ulcerations, increased sensitivity of the tongue to spices and flavors, and increased risk of dental caries. Many drugs, including diuretics, cause xerostomia. Diuretics, prescribed to help the body eliminate fluids, also cause a decrease in salivary flow. Increasing fluid intake to 8 to 10 cups daily is important to compensate for these losses.

Taste and Smell

      Generally, food choices are influenced by the three sensory perceptions: sight, smell, and taste. Gustatory (taste) sensations evoke pronounced feelings of pleasure or aversion; in the United States, taste is the primary determinant of food choices. The presentation of food, its color and aroma, may be the basis for acceptance or rejection. Food flavors are prompted from characteristics of substances ingested, including taste, aroma, texture, temperature, and irritating properties. Approximately 75% of flavor is derived from odors.
   The mouth, or oral cavity, plays an important role in the digestive system. It is the “port of entry” where receptors for the sense of taste, or taste buds, are located. A taste bud consists of 30 to 100 cells embedded in the surrounding epithelium, termed papillae. Taste papillae appear on the tongue as little red dots, or raised bumps, and are most numerous on the dorsal epithelium. These cells replace themselves every 3 to 10 days; disease, drugs, nutritional status, radiation, and age can affect them. As food is chewed, gustatory receptors come into contact with chemicals dissolved in the saliva. 
   Nerve cells carry messages to the brain, which interprets the flavor as sweet, sour, salty, or bitter. These four basic tastes reflect specific constituents of food. Taste buds for all four sensations are located throughout the mouth, but specific kinds of buds are concentrated in certain (but overlapping) areas. Taste buds also are found on the soft palate, epiglottis, larynx, and posterior wall of the pharynx. Taste and smell are essential for maintaining intake to meet physiological needs.
   Food stimulates taste buds, and aromas stimulate olfactory nerves, the receptors for smell. In contrast to gustatory sensations, an almost unlimited number of unique odors can be detected. No tactile sensation indicates the origin of odor sensations. Food-related aromas may be confused with taste sensations, and taste disorders are often the result of problems in smell rather than taste. The prevalence of olfactory impairment is high in older adults, and the problem increases with age. This is most likely the reason an elderly patient will state that food “just doesn’t taste good.”

 
   Loss of smell, or anosmia, results in limited capacity to detect the flavor of food and beverages. Ability to smell food being prepared and eaten influences food selection. Foods are sometimes judged to be harmful or spoiled because of their odors, so the sense of smell is also a protective mechanism.Upper respiratory infections, nasal or sinus problems, neurological disorders, endocrine abnormalities, aging, or head trauma may cause anosmia. Individuals with a cold usually lose their appetite because of a decreased sense of smell, which affects the ability to “taste” and enjoy food. The rate of the continuous renewal process undergone by olfactory receptor cells is depressed in malnutrition and by some antibiotics. Some of these disorders are self-limited; however, chemosensory losses from chemotherapy, infection, and aging may be irreversible.
   Dysgeusia is the persistent, abnormal distortion of taste, including sweet, sour, bitter, salty, or metallic tastes. Dysgeusia without identifiable taste stimuli is called phantom taste. Dysgeusia may be caused by a previous viral upper respiratory infection, head trauma, a neurological or psychiatric disorder, a systemic condition (a disease or disorder that affects the whole body), xerostomia (dry mouth for inadequate salivary secretion), severe nutritional deficiencies, invasive dental procedures resulting in nerve damage, oral bacterial and fungal infections, and burning mouth syndrome, or it may have an iatrogenic causation. Iatrogenic refers to an adverse condition resulting from medical treatment (medications, irradiation, surgery). These conditions may also cause hypogeusia, or loss of taste, and hypergeusia, or heightened taste acuity. Dysgeusia may also result from breathing through the mouth. The dental hygienist is frequently the first healthcare provider to detect a patient’s taste disorder. Hyperkeratinization of the epithelium may be observed during an oral examination causing blockage of taste buds, which may affect dietary intake.
   Gustatory and olfactory disorders, whether caused by disease states or drugs, are not mere inconveniences or neurotic symptoms. They affect food choices and dietary habits. A poor appetite, also called anorexia, may occur when medications cause loss of taste acuity. Taste stimulants affect salivary and pancreatic secretions, gastric contractions, and intestinal motility; gustatory disorders also can affect digestion.
   Because gustatory and olfactory disorders can result in deterioration of a patient’s general condition or nutritional status, these abnormalities must always be considered in dental and nutritional care. Potentially adverse compensatory habits may develop (e.g., decreased sweetness or saltiness perceptions may result in excessive usage of sweets or salts, which may be potentially harmful, especially for patients with diabetes or hypertension). Also, the addition of sugar can lead to higher incidence of caries. Persistent taste distortions can lead to inadequate caloric intake, resulting in unintentional weight loss or malnutrition.

The goals of the U.S. Public Health Services’ Healthy People 2010 nutritional objectives include increasing the proportion of adults who are at a healthy weight to 60% compared with the current level of 42% in 1988-1994, and reducing the proportion of adults who are obese to 15% compared with 32.7% adults who are overweight, 34.4% obese, and 5.9% extremely obese in 2005-2006. The goal is about half the current level of obesity. In 2007, 26% of the U.S. population was obese, increased nearly 2% from 2005. Not one state had reached the obesity prevalence goal of 15% established by Healthy People 2010. More men (26.4%) than women (24.8%) were found to be obese. During the past 20 years, the heaviest body mass index (BMI) groups have been increasing at the fastest rates. More depressing is a study that found that if the trend of the past 3 decades continues, possibly every American adult will be overweight 40 years from now. The 2010 goals related to the objectives to attain a healthy weight include increasing the proportion of adults who (1) engage in moderate physical activity for at least 30 minutes per day and (2) perform physical activities that enhance and maintain muscular strength and endurance.
   Maintaining a healthy weight is a major goal to reduce the burden of illness and its consequent reduction in quality of life and life expectancy. Obesity and overweight in adulthood go hand-in-hand with chronic diseases, notably hypertension, osteoarthritis, elevated blood cholesterol or triglyceride levels, heart disease, diabetes, gallbladder disease, sleep apnea and respiratory problems, and many cancers. These conditions are associated with significant decreases in life expectancy. Overweight and obesity are the leading cause of cancer, second only to tobacco as a risk facto r for cancer in Americans. The risk for cancer increases even with modest weight gains. Because overweight and obesity seem to contribute to other health problems, their economic impact on the healthcare system is immense. Direct medical costs, which include prevalence, diagnosis, and treatment services, constitute $93 billion, or 9% of the total national medical bill.
   The terms overweight and obesity are used interchangeably, but have different meanings. If an individual is very muscular with little fat, a BMI greater than 25 may be acceptable. However, some individuals who are normal or below normal in weight have excess amounts of fat stores. Athletes are usually overweight because of their increased muscle mass, not excess fat. Being overweight is not the same as being fat or obese. Additional muscle tissue aids body functions, but excessive fat interferes with normal body metabolism. A desirable weight depends on the amount and location of body fat and other weight-related medical problems.
   Weight distribution is also a factor in predicting health risk. Excess fat in the abdominal area (the “apple-shaped” body), known as android obesity, is characteristic of men, but some women also tend to accumulate more fat around the waist, especially after menopause. Accumulation of fat in the hips or thighs (the “pear-shaped body”), called gynecoid obesity, is typical of women. Any amount of upper body obesity or increased abdominal fat increases health risks. In contrast, lower body or gynecoid obesity is relatively benign and may even be protective. However, patients with this pattern of obesity have more difficulty losing weight and maintaining a healthy weight. 
   Larger waist measurements indicate accumulating fat stores and are associated with increased health risks. Even normal-weight women face significantly elevated risk of premature death from heart disease, stroke, or cancer with abdominal obesity. Having a proportionately large waist is associated with and accumulation of fat around the heart, liver, and other internal organs. Women greater than 5 feet in height whose waist measurement is more than 35 inches have more health risks, and for men, risk increases at 37 inches with serious concerns with more than 40 inches. If the BMI is greater than 35, waist circumference standards may not apply. Waist-to-height ratio seems to be a good indicator of overall health risks. The waist measurement should be less than half of the person’s height.
   Obesity is the result of consistent caloric overconsumption in excess of energy expenditure. The CDC estimates that average daily energy intake increased almost 7% for men and about 22% for women between 1971-2000. American men consume and average of 2600 kcal, and women consume approximately 1850 kcal. This increased intake reflects a consumption level that is conducive for weight gain in inactive individuals. Genetic influence is a significant factor contributing to obesity. Body weight is affected by genes, metabolism, hormones, food choices, behavior, environment, culture, and socioeconomic status. Although genetics and the environment may increase the risk of weight gain, the foods an individual chooses significantly affect body weight. Many factors in American culture have made food more accessible-fast food restaurants, prepackaged food, and soft drinks. Portion sizes also have increased, and more people are eating less often at home. When eating in a restaurant, people tend to consume slightly more than 100 kcal per meal. The problem results in different characteristics and warrants differing treatments.
   In some cases, understanding physiological benefits of weight loss can be motivating for some patients. Weight loss is highly desirable in individuals with certain risk factors and advisable for others. A 10% weight loss is associated with a decrease in serum glucose, cholesterol, systolic blood pressure, and uric acid. Other physical symptoms that can be expected to improve with weight loss includeshortness of breath, easy fatigability, fluid retention, gastric disorders, headaches, decreased energy level, decreased sexual interest, joint pains, muscle cramps, elevated pulse rate, sleeping disorders, urinary infection, and varicose veins.
   Treatment of obesity has a high level of noncompliance and failure. Weight management is very difficult for most individuals. It is a lifelong commitment to change one’s lifestyle-exercise regularly, make wise food choices, and modify behaviors. Weight loss should be motivated by internal rather than external reasons (“I am doing this for myself,” rather than “I will lose weight for my son’s wedding”). Any treatment for weight loss should always be a serious undertaking with a high level of motivation and long-term commitment. This approach increases chances that the plan will be followed until weight is lost, and that weight loss will be maintained.
   One pound of fat equals 3500 kcal. Losing weight can be accomplished by eating fewer kilocalories, increasing activity, or a combination of both. A ½ – to 2-lb per week weight loss is recommended to lose body fat while minimizing muscle loss. To accomplish this goal, food intake must be 500 kcal less than needed per day, which results in loss of 1lb per week. An additional energy expenditure of 500 kcal per day is recommended for the other 1 lb of weight loss. When weight loss is achieved slowly, it is usually more effective and is maintained for a longer period.
   Numerous strategies have been implemented to treat overweight and obesity. No one treatment is best for everyone; each modality varies in effectiveness, risk, and cost. Millions of obese individuals have chosen bariatric surgery (surgical procedure on the stomach or small intestine or both for weight reduction), which is very effective for weight loss, but affects the absorption of many nutrients. Drugs and surgical procedures currently being used for weight loss are beyond the scope of this text. A realistic goal regarding the rate and amount of weight loss must be established for each individual trying to reduce weight.
   Popular weight reduction diets devised for weight loss are abundant. Although many different plans “guarantee” weight loss, no guaranteed easy cure exists for maintaining a healthy weight. A weight reduction diet needs to be followed for an extended time; it must be appealing and flexible as well as affordable for the individual trying to lose weight. It can be balanced in terms of nutrients, yet hypocaloric. Reducing caloric intake to less than 1200 kcal for women and less than 1400 kcal for men is not recommended because adequate amounts of nutrients are not provided.
   Some registered dietitians and scientists believe the low-fat era created an obesity epidemic. The lack of flavor in low-fat foods may have resulted in eating more food and increased caloric intake. This simplistic message to minimize fat intake has some problems. Some types of fat have healthy physiological effects. A certain amount of fat helps individuals feel satisfied longer because fat digestion is slower than carbohydrate or protein. Healthy fats need to be included in a regimen to improve the taste of food and to help increase satiety in addition to their physiological benefits.
   Popular diets vary in their nutritional adequacy and consistency with guidelines for risk reduction. Renewed popularity of the low-carbohydrate, high-protein diet resulted in numerous controlled studies to determine effects of various types of diets. The results of several of these studies indicating that low-carbohydrate, high-protein diets are more effective in promoting weight loss and reducing blood lipid levels perplexed the scientific community. However, the long-term effects of this type of diet on health and weight control are unknown. More long-term studies indicate weight is regained when the individual stops following the diet. Some high-fat regimens seem to be unhealthy because of the emphasis on high animal fats and minimal carbohydrates, which include whole-grain products, fruits, and many healthy vegetables. A dietary regimen that stresses meat and high-fat foods but eliminates sugar and most carbohydrates is more successful at helping people lose weight because high-protein foods provide grater satiety.
   Evidence is emerging that higher protein diets, even without weight loss, may be beneficial for health. Proteins seem to suppress ghrelin (and appetite-stimulating hormone) better than carbohydrates and lipids. Diets that are considered high fat may cause undesirable cholesterol levels to increase, but weight loss itself usually improves blood lipid levels regardless of the dietary regimen. Another negative side effect of high-protein diets is dehydration.
   Different diets work for different people. A reduction diet should include foods from all food groups to provide necessary nutrients. A diet that totally eliminates one category (fat or carbohydrate) or a specific group of foods (fruits or meats) is inadvisable. Indispensable to any weight loss program is a preplanned food allotment with specified times for eating throughout the day to lessen feelings of deprivation and to eliminate excessive food intake. The total amount of food should be divided into at least three feedings. Eating only once or twice a day has been associated with consuming more kilocalories, impulsive snacking, and increased adipose tissue and serum cholesterol. Some “FREE” foods or beverages (foods containing less than 20kcal per serving) may be available for snack periods, but regular mealtimes are important. A diet that requires the least amount of change in usual dietary patterns has better long-term success. A 1200- to 1500-kcal diet is relatively safe; when accompanied by an exercise program, the rate of weight loss is augmented, and muscle mass is maintained.

   A weight reduction diet should satisfy the following criteria:

1. meets all nutrients needs except energy
2. suits tastes and habits
3. minimizes hunger and fatigue
4. is accessible and socially acceptable
5. encourages a change in eating pattern
6. favors improvement in overall health

Individuals have indicated several reasons for discontinuing a weight loss regimen:

1. trouble controlling food choices
2. difficulty motivating oneself to eat appropriately
3. using food as a reward

    Treatment of obesity is improved when increased energy expenditure occurs along with decreased caloric intake. Exercise alone has a modest effect on weight loss; it positively affects energy metabolism. The initiation of an exercise regimen may lead to with gain in the form of muscle mass, but the health benefits are significant, including improved cardiovascular fitness, improved plasma lipoprotein profile, improved carbohydrate metabolism, increased energy expenditure, and enhanced psychological well-being.
   Behavior modification for weight control refers to getting in touch with the reality of which foods are being consumed and in what quantity, and when and why eating occurs. One of the most important components of an effective weight control program is learning new ways of dealing with old habits. Comprehensive behavior-modification programs include diet and exercise programs individually tailored for patients. A team approach including a healthcare provider, a psychologist, a registered dietitian, and the family is more effective in helping the patient make necessary long-lasting changes in food choices and lifestyle behaviors. A food diary for recording amounts and types of food eaten, emotional status, and environmental factors helps to provide new insights to devise strategies for dealing with eating habits.
   Although behavior-modification approaches to weight control are helpful, maintaining weight loss remains a major problem. Studies indicate that programs need to be approximately 20 to 24 weeks long and more comprehensive, including relapse prevention training and use of social support systems.

Key Recommendations

• Individuals who choose to drink alcoholic beverages should do so sensibly and in moderation-defined as the consumption of up to one drink per day for women and up to two drinks per day for men.
• Alcoholic beverages should not be consumed by some individuals, including individuals who cannot restrict their alcohol intake, women of childbearing age who may become pregnant, pregnant and lactating women, children and adolescents, individuals taking medications that can interact with alcohol, and individuals with specific medical conditions.
• Alcoholic beverages should be avoided by individuals engaging in activities that require attention, skill, or coordination, such as driving or operating machinery.

 

Food Safety

 The food safety guideline is designed to reduce the risks from foods that are contaminated with harmful bacteria, viruses, parasites, toxins, and chemical and physical contaminants. Healthful eating requires a safe food supply provided by farmers, food producers, markets, food service establishments, and other food handlers. The guideline addresses simple food-handling principles to practice when preparing, serving, and storing food to minimize the risk of food borne illness.

 Key Recommendations  

• Do the following to avoid microbial food borne illness:

-Clean hands, food contact surfaces, and fruits and vegetables. Meat and poultry should not be washed or rinsed.

-Separate raw, cooked, and ready-to –eat foods while shopping, preparing, or storing foods.

-Cook foods to a safe temperature to kill microorganisms.

-Chill (refrigerate) perishable food promptly, and defrost foods properly.

• Avoid raw (unpasteurized) milk or any products made from unpasteurized milk, raw or partially cooked eggs or foods containing raw eggs, raw or undercooked meat and poultry, unpasteurized juices, and raw sprouts.

• All adults should avoid inactivity. Some physical activity is better than none, and adults who participate in any amount of physical activity gain some health benefits.
• For substantial health benefits, adults should do at least 150 minutes (2½ hrs) a week of moderate-intensity, or 75 minutes (1¼ hrs) weekly of vigorous-intensity aerobic physical activity, or an equivalent combination of moderate- and vigorous-intensity aerobic activity. Aerobic activity should be performed in episodes of at least 10 minutes, and preferably, it should be spread throughout the week.
• For additional and more extensive health benefits, adults should increase their aerobic physical activity to 300 minutes (5 hours) a week of moderate-intensity, or (2½ hrs) a week of vigorous-intensity aerobic physical activity, or an equivalent combination of moderate-and vigorous-intensity activity. Additional health benefits are gained by engaging in physical activity beyond this amount.
• Adults should also do muscle-strengthening activities that are moderate or high intensity and involve all major muscle groups on 2 or more days a week, as these activities provide additional health benefits.

 

Food Groups to Encourage

Protein-containing foods are important, but most Americans consume adequate amounts, so an increase is not recommended. Adding more fruits, vegetables, whole grains, and fat-free or low-fat milk and milk products may have beneficial health effects. These food groups provide good sources of the nutrients frequently lacking in American diets. When adding these beneficial foods, a decrease of less nutrient-dense foods is recommended to control kilocalorie intake.
   People who consume more fruits and vegetables gave a reduced risk of chronic diseases, including stroke and other cardiovascular diseases, type 2 diabetes, and certain cancers (oral cavity and pharynx, larynx, lung, esophagus, stomach, and colorectal). High-fiber diets from foods as fruits, vegetables, and whole grains may reduce the risk of CHD.
   Despite the initiation of the 5-A-Day campaign by the Centers for Disease Control and Prevention (CDC) in 1991 to increase fruit and vegetable consumption to five servings daily, Americans’ fruit and vegetable consumption did not increase between 1988-1994 and 1999-2002. Vegetable consumption decreased with only 11% of consumers meeting the dietary recommendations. Later, the CDC replaced its fruits and vegetables website to reflect the Fruits &Veggies-More Matters campaign.

Key Recommendations

• Consume a sufficient amount of fruits’ and vegetables while staying within energy needs. Two cups of fruit and 2½ cups of vegetables per day are recommended for a reference 2000-kcal intake, with higher or lower amounts depending on the kilocalorie level.
• Choose a variety of fruits and vegetables each day. In particular, select from all five vegetable subgroups (dark green, orange, legumes, starchy vegetables, and other vegetables) several times a week.
• Consume 3 or more ounce-equivalents of whole-grain products per day, with the rest of the recommended grains coming from enriched or whole-grain products. In general, at least half the grains should come from whole grains.
• Consume 3 cups per day of fat-free or low-fat milk or equivalent milk products.