Nutrition Science and Everyday Application - beta v 0.1

FATTY ACID TYPES AND FOOD SOURCES 273
acid (EPA) and docosahexaenoic acid (DHA). These long-chain polyunsaturated fatty acids have
been shown to help lower blood triglycerides and blood pressure, reduce inflammation, and
prevent blood clot formation. They also promote normal growth and development in infants,
especially in the development of the brain and eyes. Both of these important omega-3 fatty
acids can be synthesized in the body from ALA, so they are not considered essential fatty
acids. However, the rate of conversion of ALA to these omega-3s is limited, so it is beneficial
to consume them regularly in the diet. Fish, shellfish, fish oils, seaweed, and algae are
all good sources of EPA and DHA. DHA is also found in human breast milk in quantities
dependent on the mother’s own intake of DHA sources.
Figure 5.19. EPA and DHA are important but non-essential omega-3 fatty acids that can be made
in the body from ALA.
Fish oil and omega-3 supplements are among the most commonly used dietary
supplements in the United States. Researchers have hypothesized that these supplements
might decrease risk of cardiovascular disease, be helpful for those with rheumatoid arthritis,
and improve infant brain development when taken in pregnancy or in infancy. Some studies
have found such benefits of the supplements, but others haven’t. One reason for these
inconsistent results may be that studies often don’t measure participants’ baseline omega-3
levels and intake from foods, and those already consuming adequate omega-3s are less
likely to benefit from a supplement. The Dietary Guidelines for Americans recommends
consuming 8 ounces of a variety of seafood each week, and in general, people who meet this
recommendation likely consume enough omega-3 fatty acids already (along with the other
healthful nutrients found in fish) and are unlikely to see an added benefit of taking a fish
oil supplement. Some doctors may recommend that people at risk of cardiovascular disease
take a fish oil or omega-3 supplement, especially if they don’t eat fish regularly. 2