Differences in conversion of ALA in different human populations

N-3 long chain polyunsaturated fatty acids (n-3 LCPUFA) mainly refers to EPA and DHA, which are of great significance in preventing cardiovascular diseases, inhibiting the occurrence and development of allergic diseases, and promoting the development of fetal/neonatal nervous systems and cognitive functions.

 

Aquatic products, especially fish with high fat content (such as tuna), are rich in n-3 LCPUFA. Therefore, the general population should be encouraged to obtain more n-3 LCPUFA from consuming aquatic products. The dietary guidelines for Chinese residents issued in 2022 recommend that adults eat fish twice a week or 300-500g a week.

 

However, there are significant differences in dietary patterns among residents in different regions of China, and the types and quantities of aquatic products consumed by residents in inland areas are very limited. It is not realistic to encourage these populations to increase their consumption of aquatic products, especially seafood, which means that these residents have a low intake of n-3 LCPUFA.

 

The consumption of cooking oil in the diet of Chinese residents is high. According to data from monitoring in 2015, the daily intake of cooking oil per standard person has reached 43.2g. Rapeseed oil and soybean oil are the main types of cooking oil used by urban and rural residents in China, and these two types of vegetable oil contain more than or close to 10 percent α- Linolenic acid (ALA).

 

ALA is a precursor of EPA and DHA. Through endogenous synthesis, the n-3 LCPUFA can be produced. However, recent studies have shown that there are differences in the efficiency of endogenous synthesis of n-3 LCPUFA through ALA among different populations.

 

 

The studies found that there was no obvious difference in dietary intake of ALA, EPA and DHA between male and female subjects. However, the levels of EPA and DHA in the plasma of female subjects were significantly higher than those of male subjects, indicating that the ability of young women to synthesize n-3 LCPUFA, such as DHA, using ALA as a precursor was higher than that of young men.

 

 

The EPA in the plasma of male meat eaters was 28 percent and 53 percent higher than that of vegetarians and vegans respectively, and their DHA levels in plasma were 31 percent and 59 percent higher than those of vegetarians and vegans respectively. There was no correlation between EPA, DHA and ALA in the plasma, and the levels of various n-3LCPUFA in the plasma of vegetarians and vegans were not related to their length of time as vegetarians/vegans, suggesting that the endogenous synthesis efficiency of EPA and DHA in adult males is low, but stable.

 

 

The experiment has shown that the efficiency of converting dietary ALA into EPA in the plasma of that group of newborns is relatively low, at about 0.04 percent, and their efficiency of converting into DHA in the plasma is even lower.

 

However, the efficiency of converting EPA in the plasma into DHA is higher, indicating that for newborns, it is more significant to directly give n-3 LCPUFA such as DHA through diet (such as breast milk) than to give ALA to help them synthesize n-3 LCPUFA.

 

For healthy young women, they should be encouraged to consume foods rich in n-3 LCPUFA (such as aquatic products) or foods rich in ALA (such as egg yolk and rapeseed oil). Some specific populations with low conversion capacity (such as male vegetarian populations), should be encouraged to directly consume sufficient n-3 LCPUFA.