Diet and Bone Health – The Perspective of Dietary Pattern Analysis

Traditional analyses in nutritional epidemiology typically examine diseases in relation to single or a few nutrients or foods and food groups. Therefore, the most consistently followed approach so far to examine potential relationships between dietary intake and skeletal health was based on particular (or a variety of) nutrients, e.g. calcium, phosphorus, vitamins D and K and protein and food groups such as dairy products, fruits and vegetables. Dietary pattern analysis, through consideration of nutrients and foods, their interactions, intercorrelations and cumulative effects, has been used as an alternative approach to studying overall eating. Importantly, dietary patterns reflect real-world situations where foods are consumed in combination.1 The methodology for defining dietary patterns consists of three main approaches: analysis of dietary indices, cluster analysis and factor analysis, including principal component analysis. Dietary indices, based on scientific information and dietary recommendations or guidelines, reflect diet quality and, specifically, the degree of adherence to a particular diet. On the other hand, the exploratory approach – that is, cluster or factor analysis – identifies dietary patterns representing actual eating practices based on the dietary information of the population under investigation.

The investigators from the Framingham Study were the first to examine existing overall dietary patterns within the elderly cohort of the Framingham Osteoporosis Study population (mean age 75±4 years) in terms of bone mineral density (BMD)2 using cluster analysis. Cluster analysis identified six distinct dietary patterns in this population of Framingham elderly adults, i.e. meat, dairy and bread group, meat and sweet baked products group, sweet baked products group, alcohol group, sweets group and fruit, vegetables and cereal group, and found that these dietary patterns were associated with BMD. Men with a diet high in fruit, vegetables and cereal had significantly greater BMD than men with other dietary patterns. In contrast, those consuming the most sweets had significantly lower BMD than most other groups. Results were not as clear among women, but the sweets group consistently had the lowest BMD. Although women in the fruit, vegetables and cereal group tended to have higher BMD than other groups, the alcohol group also had high BMD compared with the fruit, vegetables and cereal group at most of the examined skeletal sites. This apparent protective effect of alcohol was not seen in men. The meat, dairy and bread and the meat and sweet baked products groups tended to have intermediate BMD. These results suggested that adherence to a dietary component rich in fruit, vegetables and breakfast cereal and also high in magnesium, potassium, and vitamins C and K (nutrients recently receiving more attention in relation to bone status) may contribute to better accumulated BMD in old age, particularly in men.

A group of Japanese investigators also examined the relationship between dietary patterns and BMD in pre-menopausal Japanese farmwomen 40–55 years of age who had maintained more traditional dietary habits than typical residents of large cities. ³ In that study, factor analysis was applied in order to identify dietary patterns, and the authors focused on four patterns: the ‘healthy’ pattern, which primarily consisted of green and white vegetables, mushrooms, fish and shellfish, fruit, processed fish, seaweed and soy products; the ‘Japanese traditional’ pattern, with high amounts of rice, miso soup and soy products; the ‘western’ pattern, with high amounts of fats and oils, meat, processed meats and seasoning; and the ‘beverage and meats’ pattern, with high amounts of coffee, soft drinks, dairy products, sugary foods and meats. According to the results, women in the highest quintile of the healthy pattern (which was correlated with protein, potassium, magnesium, calcium, phosphorus and vitamins D, K and C) had significantly higher BMD compared with those in the lowest quintile after adjustment for non dietary factors and dietary supplements. Moreover, those in the highest quintile of the western pattern had significantly lower BMD than those in the lowest quintile. The authors concluded that a diet with a high intake of green vegetables, fruits, fish and shellfish and low intake of meat and processed meat may contribute to the maintenance of BMD by preventing bone loss in pre-menopausal women.

Recently, we also conducted a study in order to examine whether adherence to the Mediterranean diet – or to other dietary patterns as identified by principal component analysis – had any significant impact on bone mass maintenance in a sample of adult Greek women (mean age 48±12 years). ⁴