Overview

In recent decades, a significant transformation has occurred in how we perceive food. Food is being recognised for its integral role in overall nutrition rather than merely as a source of energy. This shift is mainly due to research that has highlighted the health-promoting properties of specific food components. There is also a growing awareness that certain diets are associated with an increased risk of disease and diminished quality of life. Around the world, an increase in fruits and vegetables is recommended by dietary guidelines. Among fruits, berries have emerged as nutritional powerhouses and raspberries are no exception. Packed with antioxidants and anti-inflammatory compounds, raspberries contribute to oral health, making them an essential addition to a dental-friendly diet.

Raspberries

Raspberries are the consumable fruit produced by many plant species within the genus Rubus of the Rosaceae (rose) family. The term raspberry also refers to the plants themselves. There are many varieties of raspberries including red raspberry, black raspberry, golden raspberry and purple raspberry. The essential nutrients and bioactive components in raspberries hold significance in the Western diet. Raspberries are consumed in a variety of forms, such as fresh, dried, frozen, and canned.

Nutrients in raspberries

Raspberries contain vitamin C, the majority of B vitamins (especially folate), vitamin A, vitamin E, and vitamin K. The minerals in raspberries include calcium, iron, magnesium, phosphorus, potassium, zinc, copper, manganese, and selenium. They are low in fat, calories, and carbohydrates but rich in fibre.

Polyphenols in raspberries

Many fruits, vegetables, and other dietary sources have polyphenols known for promoting human oral health and overall well-being. Polyphenols are bioactive compounds naturally synthesised by plants, integral to various plant functions. They play a crucial role in the vibrant colouration of flowers, fruits, and seeds, serving to attract pollinators and seed dispersers. Additionally, polyphenols function as signalling molecules in mediating plant-microbe interactions and help defend against pathogens and predators. These compounds can be classified into several groups:²

• Phenolic acids
• Flavonoids 
• Coumarins
• Lignans
• Stilbenes 
• Tannins

Some of the polyphenols in raspberries include flavonoids (flavanols, anthocyanins, proanthocyanidins, catechin), and phenolic acids (caffeic acid, ellagic acid).^2,4

Polyphenols for overall wellbeing

Polyphenols cannot be synthesised by animal bodies. These secondary phytochemicals (plant-based bioactive compounds) are obtained entirely from the consumption of foods of plant origin including raspberries.³ They are renowned for their diverse health-promoting properties with the following effects:^2,4 

• Antioxidative
• Anti-allergic
• Anti-inflammatory
• Anti-cancer
• Antihypertensive
• Antimicrobial (against bacteria and fungi)

Polyphenols aid in averting chronic ailments such as cardiovascular diseases and cancer. They also play a role in blood pressure reduction, enhancement of blood vessel function, and mitigation of heart disease and stroke risk. Moreover, these compounds alleviate the symptoms of inflammatory conditions. Dietary polyphenols may positively impact blood sugar regulation, cognitive function, digestive health, and weight management.⁴

Polyphenols in oral health

The diverse community of microorganisms residing within the mouth constitute a vital component of the human microbiota. Disruption of the delicate balance within their ecosystem, whether due to microbial overload or compromised immune defences, poses significant threats to local and systemic health. It can precipitate various oral diseases, including dental caries, periodontal ailments, oral infections and oral cancer. 

As human dietary patterns evolve, corresponding shifts occur in the oral microbiota composition. Recent research endeavours have focused on exploring dietary interventions to promote oral health and prevent diseases. The functional ingredients in foods like polyphenols play a critical role in oral health. The direct contact of polyphenols with oral tissues precedes absorption and metabolism. This could yield considerable benefits for oral health, both directly and indirectly.⁴

Polyphenols and dental caries 

Dental caries (tooth decay or cavities) are caused by the interplay between oral bacteria, fermentable carbohydrates, and host factors. Polyphenols impede the growth and metabolic activity of S. mutans, as well as other cariogenic microorganisms like Lactobacillus rhamnosus, Candida albicans, and Fusobacterium nucleatum. They have been shown to disrupt biofilm formation and reduce bacterial adherence to tooth surfaces.  This reduces the pathogenic potential of dental plaque. Polyphenols have been implicated in inhibiting the activity of glycosyltransferase enzymes (GTFs) which are essential in exopolysaccharides (EPS) synthesis. This hampers glucan production and biofilm formation by S. mutans. Polyphenols also reduce the cariogenicity of exopolysaccharides (EPS).⁴ 

Polyphenols and periodontal disease

Periodontal disease (gingivitis and periodontitis) presents as a chronic inflammatory condition affecting the supportive tissues surrounding the teeth. It originates from the accumulation of dental plaque on tooth surfaces and gingiva. Pathogens such as Porphyromonas gingivalis play a key role in periodontal disease progression. Polyphenols emerge as promising candidates for periodontal disease treatment due to their antimicrobial, anti-inflammatory, and antioxidant properties. 

Polyphenols derived from berries showed inhibitory effects on the growth of P. gingivalis and reduced its hemolytic activity. Polyphenols are also capable of inhibiting the growth and virulence of other periodontal pathogens, such as P. gingivalis, Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans), Staphylococcus aureus (S. aureus), Streptococcus mitis (S. mitis) and Fusobacterium nucleatum (F. nucleatum). Polyphenols mitigate oxidative stress, protect periodontal tissues, and promote tissue healing. Clinical studies support their efficacy in improving attachment levels (measured with the periodontal probe as the distance from the cementoenamel junction in the tooth to the base of the pocket), reducing inflammation, and mitigating bone loss in periodontal disease patients.⁴

Polyphenols and halitosis

Halitosis is a prevalent dental condition characterised by an offensive odour from the oral cavity. It can be from various sources, including physiological factors or underlying pathological conditions. They may manifest as oral or extraoral halitosis. Pathological halitosis is often caused by gram-negative bacteria in the oral cavity. They produce volatile sulphur compounds (VSC), which can result from factors such as poor oral hygiene, gum diseases, or systemic conditions. Polyphenolic compounds possess antimicrobial properties and have been shown to inhibit the growth of bacteria associated with VSC production, addressing the root cause of halitosis. These extracts not only inhibit bacterial growth but also reduce the formation of VSC. Polyphenols through their antioxidant mechanisms may neutralise harmful free radicals and oxidative stress in halitosis.⁴

Polyphenols and oral cancer

Oral squamous cell carcinomas (OSCCs) are predominant among head and neck cancers, comprising around 90% of cases. They originate from malignant cells in the squamous epithelium lining various parts of the oral cavity, including the lips, tongue, gums, cheeks, and floor of the mouth. Polyphenols have been found to interfere with the cell cycle, inhibit cancer cell invasion, and exhibit antioxidant properties. They have demonstrated the ability to suppress the growth and division of oral cancer cells in vitro and animal studies. They also impact apoptosis in oral cancer cells, with upregulation of apoptosis-specific molecules like caspases. Polyphenols interfere with the signalling pathways involved in OSCC development and progression. Human studies have provided evidence for the chemopreventive and potential therapeutic agents of polyphenols against OSCCs.⁴

While polyphenols from sources such as green tea, black tea, pomegranate, cinnamon, rosemary, grape seed, cranberry, ginger, propolis, and tart cherries have been extensively studied for their potential in oral disease prevention and treatment, research on the polyphenols found in raspberries is relatively limited.

Raspberries in oral disease treatment

Black raspberries in oral cancer

Black raspberries are notably rich in antioxidants and chemopreventive phytochemicals, with anthocyanins being particularly abundant. Treatment of human oral squamous cell carcinoma (OSCC) cell lines with an ethanolic extract of freeze-dried black raspberry significantly inhibited various biochemical processes involved in cancerous transformation. For individuals with oral dysplasia, dietary intake of freeze-dried black raspberries may play a crucial role in lifelong chemoprevention. Application of black raspberry gel (0.5 g, four times daily for six weeks) topically on oral premalignant lesions led to notable reductions in lesion size, histologic grade, and loss of heterozygosity (LOH) events.⁵

Raspberry leaf extract (RLE) for oral lichen plan (OLP)

Raspberry leaf extract (RLE) significantly alleviated clinical features such as burning sensations, reticulation, erosion, and ulceration associated with oral lichen planus (OLP), a chronic mucocutaneous inflammatory disorder. Tannins and two flavonoids, quercetin and kaempferol, are the primary constituents of RLE. In Australia, RLE has received approval as a safe herbal product. RLE has also been used by Western herbalists as an empirical remedy for oral mucosal conditions such as swollen gums and mouth soreness.⁵

Summary

Polyphenols found in raspberries offer promising potential for promoting oral health. Polyphenols from various plant sources are known to exhibit anti-inflammatory effects, which can potentially reduce the severity of periodontal disease. These compounds possess antioxidant properties that can combat oxidative stress in oral tissues. Polyphenols impede the growth and metabolic activity of cariogenic microorganisms (anti-microbial), disrupt biofilm formation and reduce the potential of dental plaque forming, thereby preventing tooth decay. Polyphenols in raspberries also have anti-cancer properties, which could help slow or even completely prevent the progression of oral cancers. While direct evidence linking raspberry polyphenols to oral health is still limited, their systemic effects, particularly in managing conditions such as diabetes, suggest that they could indirectly benefit oral health. Further research is needed to fully understand the mechanisms and implications of raspberry polyphenols on oral health.