Omega-3: From Plant Sources Or Fish?
While there is a consensus that omega-3 and omega-6 fatty acids are “essential” for healthy body functions, there is a lot of confusing information surrounding their consumption from fish, fish oil supplements, and plant sources. Most people are concerned about the risk of environmental pollutants and heavy metals present in fish. However, they quite often miss the fact that the types of omega-3 fatty acids in fish versus the plant sources are not the same.
There are three main subtypes of omega-3 fatty acids: alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and the body requires all of these types in different proportions. Although plants such as walnuts, flax seeds, chia seeds, and algae contain some amounts of omega-3, their main form is alpha-linolenic acid (ALA), and it is not easily absorbed and utilized by the human body. In addition, ALA does not replace the requirement for EPA and DHA. Some studies indicate that our body can convert only 5% of ALA from plants into EPA and even less to DHA. Some attribute this low rate of conversion to the presence of high amounts of omega-6 fatty acids in the body. The ideal ratio of omega-3 to omega-6 should be between 1:1 up to 1:4, yet, in most people this ratio tends to be 1:14 on an average. This is because omega-6 fatty acids are abundantly present in our diet in soybeans, corn, meat and other food sources.
It is well known that the main dietary source of EPA and DHA is oily fish. However, environmental pollutants, toxins, and heavy metals including mercury, cadmium, lead, arsenic, and other chemicals present in water tend to accumulate in fatty fish. The levels of contamination depend on various factors such as the species of fish, its age and life span, geographical areas of fishing, tissues used for fish oil extraction (e.g., liver contains more contaminants than the muscle tissue), as well as the refining process during manufacturing. Heavy metals, DDT and other pollutants are found in higher quantities in the larger marine fish such as tuna or swordfish. These fish live longer and tend to accumulate more pollutants over time. On the other hand, smaller fish like anchovies, sardines or herring accumulate fewer contaminants, have shorter life cycles, and therefore are more sustainable and environmentally friendly. Anchovies are a rich source of EPA/DHA, and fish oil derived from anchovies contains the most natural and bioavailable form of EPA/DHA.
EPA and DHA are beneficial for cardiovascular, nervous, respiratory, and immune protection and are required in relatively higher doses to be effective. Omega-3 fatty acids have anti-inflammatory and anti-thrombotic properties that help in maintaining a healthy heart, healthy blood pressure and triglyceride levels. They are also important in brain development in infants and children and reducing the effects of aging on memory, skin, and eyes. They have been shown to be effective in certain psychological complaints, and more recently omega-3 consumption showed reduced risk of death in COVID-19 patients as well.
Daily intake of a 500-700 mg EPA/DHA combination is optimum for most healthy adults. While pregnant women and children should avoid some fish like swordfish, king mackerel, and tilefish for the fear of heavy metals contamination, they are encouraged to supplement their diet with EPA and DHA to support healthy brain development and growth in the fetus. Since omega-3 fatty acids in the form of EPA/DHA are critical for optimum health, fish oil from sustainable sources is the best choice.