Background: The links between fatty acids (FAs) and cardiometabolic outcomes are topics of debate. There is a lack of data, from childhood to adulthood, regarding the links between dietary or serum FA composition and cardiometabolic health. The intake of omega-6 (n-6) polyunsaturated FAs (PUFAs) has been linked to both inflammation and oxidative reactions, which are potentially adverse states with regards to cardiometabolic health.

Aims: To study at a population level: 1) how FA intake (% from the total FAs) is associated with the corresponding serum FA proportions (% from the total FAs); whether serum FA proportions or FA intake in childhood are associated with 2) blood pressure or 3) carotid artery intima media thickness (cIMT) in adulthood; 4) how the adulthood FA composition affects certain cardiometabolic outcomes, such as obesity, insulin resistance (HOMA-IR), blood pressure or non-alcoholic fatty liver in adulthood; and 5) whether adulthood serum FA proportions are associated with inflammation and/or LDL oxidation.

Methods: Baseline of the Young Finns Study was conducted in 1980 (3–18 years old children, n=3596). Adulthood follow-ups for clinical data and outcomes were conducted in 2001 (n=2284), 2007 (n=2204) and/or 2011 (n=2063). Serum cholesteryl ester (CE) FA proportions were measured in 1980 and serum total FA proportions in 2001. The intake of FAs was characterized by a 48-h recall.

Results: In childhood (1980), dietary intake and serum CE proportions of FAs correlated well with each other (r=0.30 for saturated FAs (SFAs), r= -0.19 for monounsaturated FAs (MUFAs) and r=0.57 for PUFAs). Childhood CEFAs were associated with adult blood pressure in both sexes and with cIMT in females 27 years later in adulthood (1980->2007). Serum SFA, MUFA and omega-3 (n-3) PUFA proportions showed direct and omega-6s (linoleic acid, 18:2n- 6, in particular) inverse associations. Dietary data, i.e. the P/S ratio (PUFAs/SFAs) and the intake of SFAs, exhibited links which were in line with these serum-based findings. In adulthood (2001), dietary intake and serum total proportions of FAs correlated only weakly with each other, omega-3 PUFAs being an exception (r=0.40). Serum SFA and MUFA proportions showed direct, and omega-6s (+omega-3s borderline significantly) inverse links with prevalent obesity, high HOMA-IR and/or blood pressure in multivariable models. With regard to individual FAs, γ-linolenic (18:3n-6), dihomo-γ-linolenic (20:3n-6) and eicosatetraenoic acids (20:4n-3) displayed direct associations (especially with obesity), whereas the links with linoleic acid were inverse. Adulthood FA intake data did not support these outcome findings. An association profile for the corresponding incident outcomes including fatty liver (2001->2011) was weaker and in many cases statistically non-significant, but its trends were very similar as compared to the cross-sectional data. In addition, serum SFA and MUFA proportions were directly and PUFAs, including omega-6s, inversely associated with C-reactive protein levels and oxidized LDL lipids or proteins in adults (2001 data).

Conclusions: These data suggest that childhood and adulthood serum FA proportions are associated with adulthood cardiometabolic outcomes. Serum SFAs are associated with a higher outcome risk, whereas PUFAs, omega-6s and particularly linoleic acid are associated with a lower risk. The role of omega-3 PUFAs and MUFAs remains unclear. These data support dietary recommendations to replace SFAs partly with unsaturated FAs rich in omega- 6 PUFAs already in childhood to improve an individual’s cardiometabolic health.