diet contain a wide range of organic and inorganic compounds. Considering these from an elemental perspective, 5 so-called macroelements, calcium, potassium, sodium, phosphorus and chlorine, are contained in comparatively large quantities in foods compared to all other elements. This chapter attempts to review the importance of these dietary macroelements on oral health, and in particular their role in tooth loss, dental caries, erosive tooth wear and periodontal disease. Calcium and phosphate make up the bulk of the mineralized human tissues. Adequate intake of both is therefore of crucial importance in maintaining the health, function and retention of teeth and bones. Supplementation of the diet with calcium has also been shown to aid in maintaining and improving oral health. Several attempts have been made to lessen the erosive potential of beverages through calcium supplementation. Adequate calcium intake is also crucial for maintaining periodontal health. In many areas, however, the evidence is still emerging or controversial. Phosphate supplementation of the diet was once thought to decrease caries incidence, although studies in children were not successful. Furthermore, little attention has been paid to the other macroelements, highlighting the need for more well-controlled and comprehensive studies.
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Introduction
As the terms “minerals” and “elements” are often used interchangeably, a few clarifying definitions will be presented first: Minerals are naturally occurring, solid, inorganic, crystalline substances which can contain a wide range of elements, although some minerals contain only one element (e.g., gold, diamond [carbon]). Elements, on the other hand, are substances that cannot be chemically interconverted or broken down into simpler substances, with each element being distinguished by its atomic number (i.e., the number of protons in the nuclei of its atoms). In biological tissues or foods, minerals are defined as the inorganic residue after ashing, a process by which water and organic matter are removed through prolonged, extensive heating in the presence of oxidizing agents, such as oxygen. Depending on the abundance of individual elements within the ash, elements can be divided into macro-, micro- or (ultra-) trace elements. Depending on their physiological importance, these elements can be also, or further, divided into essential, non-essential and toxic elements, although Paracelsus’ pearl (gemstone, not a mineral) of wisdom – “All things are poisons, for there is nothing without poisonous qualities. It is only the dose which makes a thing poison.” – must be borne in mind. These classifications are arguably somewhat arbitrary and perhaps highlight that our knowledge of the physiological importance of all naturally occurring elements is still evolving.
All macroelements (Ca, K, Na, P, Cl), the topic of this chapter, are essential as they fulfil a variety of biological functions. However, these elements have physiological importance only in their ionic state and are consumed primarily in the form of salts. Virtually all potassium and sodium salts are soluble, whereas most physiologically relevant calcium salts are sparingly, poorly soluble or insoluble. Although the solubility of salts is determined by the anion(s), of physiological importance are primarily cations. Table 1 summarizes the most common sources of macroelements in the diet.
In addition to macro- and other elements supplied to the oral cavity through topical application of oral care products [1], with calcium, fluoride and some inherently antimicrobial trace elements (see Chapter 4) being the most important in the present context, foods containing macroelements pass through the oral cavity on their way to the stomach. During mastication with simultaneous lubrication, solubilization, and enzymatic digestion by saliva [2], macroelements can be released to come into contact with the oral soft and hard tissues and intra-oral biofilms. Ingested macroelements pass through the stomach into the intestine where they can be absorbed and transported to other parts of the human body in serum. Some elements/substances also require the co-presence of other compounds to be absorbed, with the most important being calcium requiring vitamin D (see Chapter 6) [3]. As elements can interact with the oral cavity in several ways, a distinction can be made between their topical and systemic effects. Both depend on the element’s or compound’s bioavailability; that is, the proportion of a substance that has an active effect, which for topical effects is directly related to its solubility.
Despite the macroelements being present in a wide range of foods and in sufficient amounts, the consumption of (arguably questionable) dietary supplements to boost the nutritional value of one’s diet has become increasingly popular. From a nutritional perspective, dietary supplements can be differentiated from foods, although they are considered a category of food. These supplements often contain high doses of individual (macro-) elements as a bioavailable salt in tablet form, although concentrated solutions have also become commercially available recently. Matrix effects or potential incompatibilities with other ions or compounds (e.g., oxalate contained in rhubarb or other plant leaves reduces the bioavailability of calcium) have been mitigated. It goes without saying that tablets have exclusively systemic effects, whereas solutions have topical as well as systemic effects. While the diet itself has been implicated as a risk factor for a range of diseases and conditions (e.g. see Chapter 7 for sugar and dental caries and Chapter 9 for fruit juices/acidic drinks and dental erosion), the effect of dietary supplements, although somewhat unintentionally and indirectly related to their nutritional benefits (e.g., effects of calcium supplementation on tooth loss and periodontal disease – see below), has also been the subject of oral health research.
Oral Health Relevance
The role of macroelements in the following topics relating to oral health will be discussed in more detail: tooth loss, dental caries and erosive tooth wear, periodontal disease, and saliva.
Tooth Loss
Tooth loss can occur due to a variety of reasons and is not necessarily related to periodontal disease or dental caries. Therefore, care must be taken when interpreting data, especially from cross-sectional but also from longitudinal studies, and in particular those that did not investigate the aetiology of tooth loss.
Table 1. Macroelements in the diet and their physiological importance [73–79]
A longitudinal study conducted on individuals born in 1927 and, at the beginning of the study in 1998, residing in Niigata (Japan) provided valuable insight into the “relationship between general health status, including nutrient intake and anthropometry, and dental diseases” [4]. The impact of the overall diet on the number of teeth was studied in a small subset of participants for which a positive association between the intake of sodium, potassium and phosphorus, but not calcium, on the number of teeth was demonstrated. However, only sodium intake was of significance when comparing between those with 20+ versus <20 teeth [4]. Furthermore, the study participants provided evidence for the fact that nutrient intake also depends on oral health status. Those with a compromised dentition or an ill-fitting denture had less intake of potassium and calcium, but not sodium [5]. Over a period of 5 years, a greater decline in intake of sodium, potassium and calcium was shown in participants with an impaired dentition compared to those with an uncompromised
