Though DHA can be synthesized from alpha-linolenic acid (ALA) by the body, the capacity for conversion has been found to be very low.
Hence it becomes necessary for us to consume DHA food sources like fatty fish or take DHA supplements to protect ourselves from fatty acid deficiency diseases.
Graham C. Burdge et all in their study on ALA metabolism have concluded that the capacity of adult males to convert ALA to DHA was either very low or absent. Hence the uptake of pre-formed DHA in diet as fatty fish or as supplements is critical for maintaining adequate membrane DHA concentrations.
Pregnant women, nursing women, infants and children are the highly vulnerable group for developing DHA deficiency as their DHA requirements are high. People taking vegetarian food and vegans also are vulnerable group for developing the deficiency. Some of the supplements are discussed here.
Fish oil fatty acid supplementsFish lipids include up to 40 percent of polyunsaturated long-chain fatty acids. Fish oil from cold water oceanic fatty fish is rich in omega-3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Fatty fish from cold waters have more omega-3 fatty acids in their body.
Bigger fish higher on the food chain accumulate toxins and heavy metals. The smaller plankton feeding fish are less contaminated. The FDA released an advisory about eating fish. Woman planning a pregnancy, Pregnant women and breastfeeding women are advised against eating shark, swordfish, king mackerel, or tilefish as they contain high levels of mercury. The FDA recommended eating two meals, or up to 12 ounces a week, canned light tuna, catfish, pollock, salmon and shrimp.
The amount of DHA fatty acids vary among the brands of fish oil supplements (10% - 20%). The amount of EPA is greater than DHA in many of the brands. The main disadvantages of fish oil supplements is the level of purity. The fatty acids in the supplements tend to become rancid and the quality of the fish oil degrades fast.
Krill oil supplementsKrill are small crustaceans found in the oceans. Krill oil is extracted from the krill species (Euphausia superba). Krill are plankton feeders and are lower on the food chain. Usually krill oil does not contain any toxic contaminant.
Moreover, 50% the DHA in krill oil is attached to phospholipids. In phospholipid form the bioavailability of supplements is greatly increased. The astaxanthin present in krill oil is a potent antioxidant and it also protects the fatty acid supplement from turning rancid.
Krill is the largest biomass in the world. Most of the marine animals are dependent directly or indirectly on krill for their survival. Hence overexploitation of krill will be disastrous. Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) is seized of this issue.
Algal supplementsProduction of DHA from algae is a spin off from NASA research. Algal DHA is produced from microalgae grown in ponds. As such in this culture method there is no depletion of natural resources. Food contaminants can be totally avoided in the farm culture.
As algal DHA is plant based it is preferred by vegetarians and vegans. The fatty algal extract is rich in DHA and very little EPA is present. As the product is plant based it can be an ideal source of omega-3 fatty acids for vegetarians and vegans.
Green-lipped mussel oil and powderDietary shellfish supplements have been the traditional remedy for inflammatory diseases like arthritis in humans. Green-lipped mussel (Perna canaliculus) is cultured in coastal farms located in sheltered or semi-sheltered areas of New Zealand. Natural mussel spat (seed mussels) encrusted on drift kelp is collected and introduced into the modified Japanese longline system. The sufficient availability of natural seed will reflect on the production trends.
Apart from DHA and EPA, green-lipped mussel oil or powder supplement contains a unique omega-3 fatty acid, eicosatetraenoic acid (ETA). It is well known that arachidonic acid oxygenation related metabolites play a major role in the inflammatory processes. ETA is found to selectively block cyclooxygenase (COX) and lipoxygenase pathways of inflammatory processes. Fatty acids DHA and ETA enhance the anti-inflammatory function of the fatty mussel extract.
Being a filter feeding animal, green-lipped mussel passes large amounts of seawater through its filters to collect its food. Filter feeding can accumulate toxins and mercury in its fatty flesh.
ConcernsAll these supplements have excellent health benefits. The issues concerned with the selection of the most beneficial supplement are:
- the toxins and heavy metal presence,
- the action taken to remove contaminants,
- the concentration of DHA,
- the display or non-display of content in the labels,
- the use of additives and preservatives,
- the oxidative process in the product,
- the environment from where they are caught and
- the process involved in the production of the DHA supplement.
Related topics in nutritional deficiency diseases:
Deficiency diseases of proteins.
Krill oil omega-3.
Protein energy malnutrition in children.
Definition of trans fatty acids.
Deficiency diseases of minerals.
DHA and health.
Deficiency diseases of vitamins.
DHA from algae.
Deficiency diseases of carbohydrates.
Fish oil DHA and EPA.
Current topic in nutritional deficiency diseases:
Supplements of DHA (docosahexaenoic acid)