How A Fat Metabolism Gene Affects Nutrition and Cognition (FADS2)

The FADS2 gene plays an important role in the metabolism of certain types of fats. It does this by encoding for a protein called delta 6 desaturase (D6D) [R].

The D6D protein is responsible for converting between different types of fatty acids. This helps regulate the body’s levels of polyunsaturated fatty acids (PUFAs) [R].

PUFAs play many essential roles in the body, such as being a structural component of cells, acting as an energy source, and regulating cell signaling pathways [R].

There’s some evidence that certain genetic variants of FADS2 can impair the body’s ability to metabolize fatty acids. This may have negative effects on nutrition, especially in infants [R, R].

Learn more about fatty acids here.

The FADS2 gene is responsible for encoding a protein called delta 6 desaturase (D6D) [R].

D6D is an enzyme that works by creating double bonds in fatty acids. As discussed earlier, fatty acids become unsaturated when they contain one or more double bonds [R].

By producing double bonds, the D6D enzyme is able to produce several kinds of unsaturated fatty acids.

Some of the important end-products of D6D include EPA and DHA, which are both categorized as omega-3 fatty acids [R].

The fatty acids EPA and DHA (which are commonly found in fish oil supplements) play important roles in brain function, heart health, and infant development [R].

Human breast milk contains several kinds of polyunsaturated fatty acids (PUFAs), such as docosahexaenoic acid (DHA) and arachidonic acid (AA), which play essential roles in brain development in newborns [R].

It’s important to note that not all infant formulas contain PUFAs. This may explain why breastfed children may have higher IQs compared to non-breastfed children, according to research [R, R].

A number of studies have examined if genetics are a factor in this relationship between breastfeeding and cognition, including the FADS2 gene. We’ll discuss the research below [R, R].

Supporting Evidence

There is evidence that certain variants of rs174575 in the FADS2 gene may influence cognitive development in breastfed infants.

One study analyzed data from over 3,200 children born in New Zealand, England, and Wales [R].

According to the study, breastfed children who carry the ‘C’ allele of rs174575 had IQ scores that were 6.4 points higher on average than children who were not breastfed [R].

However, children who had the ‘GG’ genotype did not gain an advantage from being breastfed nor did they suffer a disadvantage from not being breastfed [R].

The genotype of the mother did not appear to have an effect on the IQ of the child [R].

Breastfed children carrying the ‘C’ allele may have better cognition than children who are not breastfed. However, children who have the ‘GG’ genotype do not appear to experience an advantage or disadvantage from being breastfed or not being breastfed.

Conflicting Evidence

Not all studies have found a connection between FADS2, breastfeeding, and cognition.

A meta-analysis of 10 separate studies totaling over 12,000 individuals of various ethnicities did not find an association between FADS2 and breastfeeding [R].

Likewise, another study of almost 6,000 children did not find a link between the ‘C’ allele and cognition [R]. 

A third study of 700 Australian families also does not support a connection between FADS2 and breastfeeding on cognition [R]. 

This Australian study suggests that parental education level may actually play a more important role in childhood cognition [R].

A number of studies suggest that there is no link between the FADS2 gene, breastfeeding, and cognitive development in children.

FADS2: Fatty Acid Metabolism

So far we’ve discussed the effect of FADS2 genetic variants on children. However, research suggests that adults too may be impacted.

A meta-analysis of 5 studies including a total of 2,286 participants focused on rs3834458 of the FADS2 gene [R].

The SNP rs3834458 is relatively unique in that the minor allele is a deletion allele. This means that people either carry the major allele ‘T’ or carry no allele at all [R].

Researchers of this meta-analysis found that, compared to those with the major ‘T’ allele, those carrying the deletion allele had [R]:

• Higher alpha-linolenic acid (ALA) levels
• Lower eicosapentaenoic acid (EPA) levels
• Lower docosapentaenoic acid (DPA) levels
• Lower docosahexaenoic acid (DHA) levels

These results imply that the deletion allele impairs the body’s ability to convert fatty acids into more complex PUFAs [R].

Multiple studies of the SNP rs1535 have found very similar results [R, R, R].

For example, a study including data from over 3,300 newborns and 5,200 children found that the ‘G’ allele was associated with lower ALA levels and higher EPA, DHA, and AA levels [R].

The minor alleles in rs3834458 and rs1535 may be associated with higher levels of ALA and lower levels of EPA, DPA, and DHA.

FADS2: Cholesterol, Triglycerides, & Blood Sugar

The FADS2 gene may also influence other nutritional factors, such as cholesterol, triglycerides, and blood sugar (glucose).

One study of 14,354 Korean adults looked at the SNP rs2845573 of FADS2 [R].

Researchers found that the ‘G’ allele of rs2845573 was associated with lower HDL (good cholesterol), lower blood glucose, and higher triglyceride levels, compared to the ‘A’ allele [R].

You can see your genotypes for FADS2 in the table below. However, keep in mind that these associations are based on studies from certain ethnic populations — so you should interpret your results with caution if you are not descended from one of these specific groups!

Primary SNPs: 

FADS2 rs174575

• ‘G’ = Not associated with nutrition
• ‘C’ = Associated with improved cognition in breastfed children
• Some studies do not support this link
• About 95% of all people worldwide carry at least one ‘C’ allele

FADS2 rs3834458

• ‘T’ = Not associated with nutrition
• ‘Deletion’ (no allele) = Associated with lower levels of certain PUFAs
• About 56% of people from European populations have at least one deletion allele
• About 77% of people from East Asian populations have at least one deletion allele

FADS rs1535

• ‘A’ = Not associated with nutrition
• ‘G’ = Associated with lower levels of certain PUFAs
• About 57% of people from European populations have at least one ‘G’ allele
• About 77% of people from East Asian populations have at least one ‘G’ allele

FADS2 rs2845573

• ‘A’ = Not associated with nutrition
• ‘G’ = Associated with lower HDL, lower blood glucose, and higher triglyceride levels
• About 25% of all people worldwide carry at least one ‘G’ allele