Docosahexaenoic Acid

Figure 1. The chemical structure of Docosahexaenoic acid.

Docosahexaenoic acid (DHA) is an Omega-3 fatty acid and the primary structural component of the human brain, cerebral cortex, skin, and retina. DHA is the most abundant Omega-3 fatty acid in the brain and retina. 40% of the polyunsaturated fatty acids (PUFAs) in the brain and 60% of the PUFAs in the retina are comprised of DHA. Additionally, 50% of neuronal plasma membrane is composed of DHA.

DHA is mainly located in cell membranes, where it makes the membranes and gaps between cells more fluid. This makes it easier for nerve cells to send and receive electrical signals. Having low levels of DHA may slow the signalling between cells, resulting in poor signalling in the brain or the eye.

DHA can be synthesised from alpha-linolenic acid in the human body, obtained from breast milk, or consumed via one's diet. Although DHA can be converted from alpha-linolenic acid, it is not efficient and only 0.5%-5% is typically converted. DHA may also be converted in small amounts from Eicosapentaenoic acid (EPA).

Food Sources

DHA is mainly found in seafood, such as fish, shellfish, and fish oils. It also occurs in some types of algae. Some good sources include:

• Mackerel
• Salmon
• Herring
• Sardines
  
• Anchovies
• Eel

Cod Liver Oil is an excellent source of DHA.

Taken as a Dietary Supplement

DHA is extremely important for brain tissue growth and function, especially during development and infancy. It needs to accumulate in the central nervous system for your eyes and brain to develop normally.

DHA is also critical for healthy brain aging. Studies have shown that DHA may help improve memory, learning, and verbal fluency in the brain as the brain ages, characterized by increased oxidative stress, altered energy metabolism, and DNA damage. DHA may help reduce the risk of Alzheimer's disease.

DHA helps activate rhodopsin, a membrane protein in the rods found in the eye which determines how the brain receives images by changing the membrane's permeability, fluidity, and thickness. DHA is typically found in baby formulas to reduce the risk of vision impairment in babies.

Like other Omega-3 fatty acids, DHA is commonly used to help with the management of high cholesterol or other fats in the blood. DHA may reduce blood triglycerides, blood pressure, increase HDL (good cholesterol), and protect against endothelial dysfunction. This leads to improved overall heart health and decreased risk of heart disease.