DHA, or docosahexaenoic acid, and DHEA---or dehydroepiandrosterone---are two different substances that support vital functions in your body. DHA is found in fatty fish and fish oil supplements, while your body produces DHEA naturally. You may also receive synthetic DHEA created in a laboratory from a substance called wild yam extract.
DHA belongs to a class of substances called omega-3 fatty acids, according to the University of Maryland Medical Center, or UMMC. You need DHA to maintain proper brain function, and newborns and infants require DHA for proper development of their vision and nervous systems. Fatty fish species that contain significant amounts of DHA include mackerel, tuna, herring, sardines, salmon and shellfish. Vegetarian versions of DHA can also be extracted from algae and seaweed, UMMC says.
Your body produces DHEA in your adrenal glands and uses it to create both male and female sexual hormones, according to the National Library of Medicine's Medline Plus. Under normal circumstances, your stores of DHEA will begin to decline once you reach the age of 30. You may also have abnormally low levels of DHEA if you have medical conditions such as type 2 diabetes, anorexia, end-stage kidney disease, adrenal insufficiency or AIDS. Additionally, use of certain medications may deplete your DHEA stores. Examples here include opiates, insulin, danazol and corticosteroids.
In addition to DHA, fish oil contains another omega-3 fatty acid called eicosapentaenoic acid, or EPA, the UMMC reports. You can get adequate amounts of DHA and EPA by eating two or three servings of fatty fish each week. This level of intake will provide you with a DHA and EPA intake equivalent to 1,250 mg per day. You can also take daily doses of a fish oil supplement that contains between 3,000 and 4,000 mg of oil. However, you will need to check supplement labels to determine their exact DHA and EPA content. If you are pregnant, you need about 200 mg of DHA each day, according to the UMMC.
DHEA is available in tablets, capsules, topical creams and injections, Medline Plus reports. Depending on your circumstances, appropriate daily dosages range from 25 to 200 mg. If you have AIDS, you may receive a daily dose of 200 to 500 mg as a treatment for depression. Be aware that the effectiveness and safety of DHEA creams and injections are not well-established. Additionally, doctors have not thoroughly studied the safety and effectiveness of DHEA in children.
Use of DHA-containing fish oil may improve current heart disease symptoms and lower the risks of heart disease development, the UMMC notes. You may also receive DHA as a treatment for menstrual cramps, lupus and the circulation disorder called Raynaud syndrome. Use of fish oil may also help diminish the symptoms of rheumatoid arthritis.
Use of DHEA may help to improve the condition of individuals who have insufficient adrenal gland function, Medline Plus notes. You may also receive DHEA as a treatment for obesity, lupus and depression. Doctors are also studying DHEA as a potential treatment for disorders such as infertility, Alzheimer's disease and Crohn's disease.