Aim The aim of this study was to investigate the most commonly used approaches to measure individual genome-wide heterozygosity (IGWH) and to investigate whether IGWH can be considered as a health risk factor or a protective factor in humans. Methods This study was based on two samples from isolated communities of Croatian Adriatic islands, with a total of 1,930 adult examinees from Islands of Vis (N=986) and Korcula (N=944). Examinees were genotyped with a total of 302,662 single nucleotide polymorphisms. Heterozygosity was estimated using five commonly calculated methods. Results Correlation coefficients between different heterozygosity methods were generally in the range of 0.7-0.8. A worsening in some phenotypic traits, including cholesterol and triglycerides as well as increased odds for osteoporosis and metabolic syndrome was recorded in cases of IGWH reduction. Nevertheless, in these cases heterozygosity explained a relatively low amount of variance, generally in range of 0.4-0.6% of total trait variance. Conclusion However, these results were significant in Vis Island sample, while in the replication sample, Korcula Island, most of the associations were not significant, possibly due to the overall lower amount of inbreeding and higher heterozygosity in Korcula Island sample. The results warrant further research in order to provide more information on the extent and importance of individual genome-wide heterozygosity, which might have an important role in communities which experience consanguinity on a greater scale. Two main shortcomings of the study include possible lack of power to detect inbreeding depression and the need to replicate the results in other populations.