Periodontal disease is characterized by microbial-associated, host-mediated inflammation, and it brings about the diminished density of alveolar bone as well as the destruction of bone structure [1
]. Progression of periodontal disease is a major risk factor of tooth loss in adult populations. According to the Global Burden Disease Study 2015, the prevalence of periodontal disease increased by 25.4% from 2005 to 2015 [2
] and the global cost was estimated at 442 billion USD. The data from the Korea National survey reported that the prevalence of periodontal disease was about 29.8% in Korean adults aged over 19 years and 47.2% for those aged over 50 years [3
]. Thus, the burden of periodontal disease will likely be even more increased in a rapidly aging population. Diet and nutrition are associated with the risk of periodontal disease [4
]. Recently, dairy products have been proposed to have a beneficial effect on periodontal disease due to the various nutrients and food components [7
]. A few studies have examined the association between total dairy intake and periodontal disease, but the results were conflicting. Al-Zahrani et al., showed that an increased intake of dairy foods was inversely associated with the prevalence of periodontal disease [8
]. However, Shimazaki et al. found that lactic acid foods, but not total dairy intake, was associated with periodontal disease [9
]. Additionally, only one study has examined the relationship between different types of dairy foods and periodontal disease [10
]; however, this study was conducted only in older adults aged ≥65 years, not the general population, and it had a very small sample size.
Dairy foods are good sources of various nutrients including calcium, which may have beneficial effects on health outcome, such as bone development [11
]. The content of calcium and other components (e.g., whey, casein, Bifidobacterium
) may vary in different types of dairy products [12
] and thus different types of dairy food products may have different effects on periodontal disease.
Therefore, this study was conducted to examine the associations between individual dairy consumption as well as total dairy intake and the risk of periodontal disease in the general Korean population using a large scale of nationally representative data examined recently.
We found that dairy food consumption was inversely associated with the prevalence of periodontal disease in Korean adults. Higher total dairy intake and milk intake were associated with 25% lower risks of periodontal disease, after adjusting for potential confounders, such as age, sex, education, income level, smoking status, alcohol consumption, BMI, diabetes mellitus status, calcium intake, tooth brushing frequency, and use of dental floss. These results suggest that frequent intake of dairy foods including milk may have a protective effect on periodontal disease.
Our results are in line with previous findings. Adegboye et al., reported that frequent consumption of both dairy foods and milk was associated with a 4% lower risk of periodontitis, as defined as the number of teeth with attachment loss ≥ 3 mm in older Danish adults (aged over 65 years) [10
]. The data from the National Health and Nutrition Examination Survey found that individuals in the highest quintile of dairy intake had a 20% lower prevalence of periodontal disease (defined as probing pocket depth ≥ 4 mm and clinical attachment loss ≥ 3 mm [22
]) than those in the lowest quintile in US adults over 18 years after adjusting for age, gender, ethnicity, smoking, education, diabetes, poverty index, vitamin use, body mass index, and physical activity [8
The mechanism behind the inverse association between dairy food intake and periodontal disease has not been revealed yet. Dairy foods are good sources of various nutrients needed for bone development and maintenance, such as calcium, magnesium, phosphorus, potassium, vitamin D, and proteins. For example, dairy calcium may have a favorable effect on periodontal health by enhancing alveolar bone density [23
]. High calcium intake from dairy foods may prevent bone loss by inhibiting the secretion of parathyroid hormone, which contributes to bone resorption [24
]. A clinical trial showed that calcium supplementation of 500 mg/day for 3 months significantly increased alveolar bone density and reduced gingival inflammation in Indian adults aged 35–55 years [25
]. Dairy proteins, such as whey protein and lactoferrin, may help with the prevention of periodontal disease. Whey protein may prevent alveolar bone loss by increasing hydroxyproline, which can strengthen the coherence of bone [26
]. A rat study proved that alveolar bone loss was significantly decreased in the 1.0% whey protein powder group compared to the control group [27
]. Additionally, lactoferrin, an iron-binding glycoprotein in milk, may have a favorable effect on periodontal disease. In an intervention study, Porphyromonas gingivalis
and Fusobacterium nucleatum
, the causative bacteria of periodontal disease and tooth decay, were significantly decreased in a treatment group with lactoferrin compared to the control group [28
Fermented dairy products, such as yogurt, contain lactic acid. Lactic acid may help the inhibition of bacteria growth or result in the interference of the activities of periodontal pathogens by decreasing oral pH [29
]. The probiotic bacteria from lactic acid, such as Lactobacillus
, may have a protective effect on periodontal disease by inhibiting excessive growth of periodontal pathogens and by stimulating the immune system [30
]. Shimazaki et al. reported that individuals consuming lactic acid foods including yogurt and lactic acid drinks (≥55 g/day) had lower values in both mean probing depth and severe clinical attachment loss than those not eating these foods after adjusting for potential risk factors in Japanese adults aged 40 to 79 years [9
]. These beneficial components of dairy foods may have synergistic favorable effects on periodontal disease.
In the present study, yogurt consumption tended to be associated with lower prevalence of periodontal disease, even though statistical significance was not reached. The different result may be due to lower intake of yogurt in the Korean population. In European countries, the majority of people consumed more than 1 serving (100 g) of yogurt per day and more than one-third of the population had 5 servings of yogurt [31
], whereas Koreans, on average, consumed only 13 grams of yogurt per day [32
The association between cheese consumption and periodontal disease was not examined in this study because cheese intake was not measured in KNHANES. Previously, two cross-sectional studies examined the association in Danish adults aged 65 years and older and Japanese adults aged 40 to 75 years [9
]. Neither of the studies showed a significant association between cheese intake and periodontal disease.
Several limitations exist in this study. First, the results cannot prove a causal relationship between dairy intake and periodontal disease because the study was designed cross-sectionally. Second, there is a difficulty in applying results to other age groups, since children and adolescents are not included in the analysis. Third, the prevalence of periodontal disease could be different depending on the criteria used to diagnose periodontal disease. Various criteria for diagnosis of periodontal disease, such as probing pocket depth and clinical attachment loss, can be used, but periodontal disease was diagnosed based on only probing pocket depth in this study. Lastly, oral hygiene index (e.g., Simplified Oral Hygiene Index and Plaque Index) and the number of present teeth, which might have affected periodontal disease, were not measured in this study. Despite these limitations, this study was the first study to explore the effect of individual dairy foods such as milk or yogurt as well as overall dairy foods on periodontal disease. In addition, dietary assessment was evaluated by semi-quantitative food frequency questionnaire and thus the habitual dairy intake of subjects could be compared with other studies. Also, this study included specific potential confounders for oral health behaviors such as tooth brushing frequency and the use of dental floss in the analysis.