Familial resemblance in dietary intake among singletons, twins, and spouses: a meta-analysis of family-based observations.

Background: Familial dietary intake can be influenced by both genetic and environmental factors; the current study aimed to examine the role of these two factors on dietary intake by investigating the resemblance in energy, nutrient, and food group intake among spouses and siblings in twin and family-based studies.

Methods: The online literature databases, including PubMed, Scopus, Web of Science, and Cochrane Library were systematically searched up to September 2024. The pooled correlation coefficient (r) of studies was calculated using Fisher's z and standard error (SE) of z's of all studies and our final results were reported in six groups including non-twin siblings, monozygotic (MZ) twins, dizygotic (DZ) twins, all-twins, all siblings, and spouse.

Results: Our findings on 30 observational studies indicate that siblings, especially MZ twins, tend to have similar dietary intake, with high correlations for vegetables (r: 0.59), red meat (r: 0.58), and fruits (r: 0.56). Among DZ twins, the lowest correlations were observed for eggs (r: 0.07), soft drinks (r: 0.14), and daily intake of simple carbohydrates (r: 0.17). DZ twins did not show significant differences in dietary resemblance compared to non-twin siblings. Among spouses, the highest correlations for dietary intake were found for polyunsaturated fats (r: 0.41), saturated fats (r: 0.40), and total fats (r: 0.39), while the lowest correlation was for protein intake (r: 0.24).

Conclusions: While the greatest similarity in dietary intake was observed among MZ twins, no significant difference in dietary intake similarity was noted between DZ twins and non-twin siblings. Furthermore, spouses exhibited a significant degree of similarity in their dietary consumption. Therefore, dietary intake is shaped by a complex interplay of genetic and environmental factors, warranting further investigation to validate these observations.