Fish oil products have become increasingly popular in recent years due to the rich content of Omega-3 polyunsaturated fatty acids (PUFAs). 
More than 80% of the total Omega-3 PUFAs in fish oil are made up of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA).
Studies have shown that these fatty acids are beneficial for conditions such as diabetes, cardiovascular diseases, inflammation, dementia, depression, Alzheimer’s disease, dry eye, and neural development and health.  
What is DHA?
DHA is a long-chain of Omega-3 polyunsaturated fatty acids.  As a component of phospholipids that make up cell membrane structures, Omega-3 fatty acids, especially DHA, are particularly abundant in the retina, brain, and sperm. In particular, DHA plays an important role in transmitting light signals in retinal cells, and is therefore essential for visual function. 
DHA is also crucial for the growth and functional development of the infant brain, and is essential for maintaining adult brain function as well.
DHA is preferentially absorbed by the brain over other fatty acids, and high intake of DHA in children’s diets is proven to improve learning ability. Furthermore, research has indicated that a lack of DHA may be associated with poorer learning ability in children.
A decrease in DHA levels in the brain is associated with a decline in cognitive abilities during aging and the onset of Alzheimer’s disease. 
5 benefits of DHA
Child Health and Development
Numerous studies have confirmed that the intake of Omega 3 fatty acids by women during pregnancy has a positive effect on fetal development, including birth weight, gestational duration, visual and cognitive development, and fetal-related health.
💡A clinical trial studied pregnant women who were less than 20 weeks pregnant and gave them 469 milligrams of DHA per day. The results showed that the infants had significantly healthier weight, height, and head circumference at birth, and there was a lower rate of preterm birth. When preterm birth did occur, the length of stay in the hospital was significantly shorter, and no safety issues were found. 
💡Another clinical trial gave formula milk containing DHA to infants between 1-9 days old. The results showed that the visual evoked potential of infants who did not receive DHA was significantly lower at 12 months compared to infants who received DHA supplementation. 
💡Another clinical trial gave a daily supplement of 250 milligrams of DHA and 60 milligrams of EPA from fish oil to infants from birth to six months old. The results showed a significant improvement in language assessments, indicating that DHA supplementation was helpful for early communication development in infants. 
Many studies have shown that diets with higher levels of omega-3 fatty acids are associated with lower incidence of heart failure, coronary heart disease, and other cardiovascular diseases. 
💡Clinical research has shown that supplementation with DHA in patients with abdominal obesity can increase high-density lipoprotein cholesterol (HDL), decrease triglycerides, and improve systolic blood pressure. 
💡In a study of overweight or obese participants, providing the patients fish oil supplements with higher levels of DHA for 12 weeks resulted in significant improvements in blood pressure and arterial health as the dosage increased. 
Reduces inflammation response
Omega-3 fatty acids may help reduce inflammatory responses, and some related studies have found that omega-3 can reduce the inflammation in rheumatoid arthritis patients and help them reduce the use of non-steroidal anti-inflammatory drugs (NSAIDs).  .
💡In another clinical trial, mothers of premature babies (less than 33 weeks) were supplemented with a high-DHA diet and encouraged to breastfeed. After 18 months, the risk of infant bronchopulmonary dysplasia was significantly reduced, as was the incidence of infant allergies. 
Prevents Alzheimer’s disease, dementia, and cognitive decline
Omega-3 has been shown to help prevent Alzheimer’s disease, dementia and cognitive decline. Many studies have shown that omega-3 can improve cognitive functions such as attention, processing speed, and short-term memory in people with mild cognitive impairment. 
An analysis has found a correlation between DHA intake and the risk of Alzheimer’s disease. For every 100 mg/day increase in DHA intake, the risk of dementia decreased by 14% and the risk of Alzheimer’s disease decreased by 37%.
💡In another clinical trial, supplementation with 2 grams of DHA per day significantly helped people with mild cognitive impairment by improving their short-term memory, working memory, and verbal memory. 
Omega-3 are thought to reduce the incidence and symptoms of dry eye syndrome due to their anti-inflammatory properties. 
A retrospective study analyzed the daily diets of participants through questionnaires and found that the group with a higher average intake of omega-3 had a 17% lower risk of developing dry eye syndrome compared to the group with a lower intake of omega-3.
The study also found that DHA intake had a similar correlation, with a 12% reduction in the incidence of dry eye syndrome, while EPA intake did not show a significant correlation. 
What foods contain DHA?
Many manufacturers also add DHA and other omega-3 fatty acids to infant formulas because of their benefits in developing a baby’s brain and vision. 
Recommended intake of DHA
According to the recommendations of the Food and Agriculture Organization of the United Nations (FAO) and the World Health Organization (WHO) for the development of fetuses and young children, it is recommended to supplement 300 milligrams of EPA+DHA per day or at least 200 milligrams of DHA per day  .
What are the side effects of DHA?
According to a report from the U.S. FDA, daily intakes of up to 5 grams (DHA+EPA) is considered safe; this dosage does not cause bleeding problems, impair immune functions, or cause lipid peroxidation.