**5. Conclusions**

In conclusion, formula fed infants with FADS minor alleles, especially those with AA and DHA supplementation, were associated with decreased desaturase activity and lower AA and DHA levels. Breastfed infants were not affected, possibly due to the high LCPUFA content in breast milk. The AA and DHA supplementation of the infant formula provided the infants carrying major allele homozygotes with closer levels to those obtained with breastfeeding. This exposes minor alleles as a potential factor of vulnerability since the same supplementation might not be enough for them. Considering infant FADS genotype to meet the individual needs could contribute to narrow the gap of AA and DHA concentrations between breastfed and formula fed infants. A new LCPUFA supplementation dose should be explored to determine if an increased supplementation of AA and DHA might prevent the reduction of these FAs observed in the presence of FADS minor alleles. However, when breastfeeding is not possible, supplemented formulas should be considered as the second choice since they provide better AA and DHA concentrations compared to infants without supplementation.

**Supplementary Materials:** The following are available online at http://www.mdpi.com/2072-6643/11/3/602/s1, Table S1: The genetic variants studied within the FADS genes, Table S2: Fatty acid content in infant formulas, Table S3: Associations between FADS genes and fatty acid levels in infants, Table S4: Fatty acids and enzymatic indexes according to infant SNPs and study group.

**Author Contributions:** Cristina Campoy designed and coordinated the project; A.N., F.H. and E.D. performed the follow-up of the children, collected data and prepared the samples for later analysis; I.S.L. and A.d.l.G.P. performed the experimental procedures; M.C.L.-S., A.I.C., M.R.-P., I.S.L., A.M.C.T. and A.d.l.G.P. analyzed the data and designed the manuscript; A.M.C.T., I.S.L. and A.d.l.G.P. conducted the statistical analysis, interpretation of results and drafting of the manuscript. All authors read and approved the final manuscript.

**Funding:** This research was funded by ORDESA Laboratories, S.L., Spanish Ministry of Economy, Industry and Competitiveness, NEOBEFOOD Project (2010–2013) and SMARTFOODS Project (2014–2018)—CIEN Strategy (Ministry of Innovation and Science-CDTI) through 2 different contracts established between Ordesa Laboratories and the University of Granada General Foundation (ref. n◦ 3349 and n◦ 4003, respectively) and between Ordesa Laboratories and the Bosch Gimpera Foundation/University of Barcelona (ref. n◦ 306811 and 308516). The project was partially funded by EU Project DynaHEALTH (HORIZON 2020-GA No.633595).

**Acknowledgments:** The authors want to acknowledge the parents and children who participated in the study and also Ordesa laboratories, S.L. Barcelona, Spain. We are also grateful to personnel, scientists, staff and all people involved in the COGNIS team who have made this research possible.

**Conflicts of Interest:** Maria Rodríguez-Palmero is an employee of Ordesa Laboratories, S.L. She contributed to the manuscript design, analyzed the results and reviewed the final draft. The funders had no other role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.
