Nevertheless, Bang and Dyerberg’s studies set a ball rolling that culminated in a large and lucrative omega- 3 supplement industry. According to a recent market research report
(Packaged Facts; Rockville, Maryland, USA), the market value
of EPA + DHA packaged products is projected to reach $34.7
billion in 2016, with a compound annual growth rate of
6.4% from 2011 ( http://tinyurl.com/omega3market). Fish oil,
which contains a mixture of DHA, EPA, and other fatty acids
extracted from fish, is now the most popular nonvitamin,
nonmineral supplement in the United States, taken by approximately 7.8% of adults in 2012 (up from 4.8% in 2007; http://
tinyurl.com/cdc-omega-report). Between 2005 and 2012,
fish oils sales more than doubled worldwide (O’Connor, A.,
The New York Times, http://tinyurl.com/fishoilclaims, 2015).
Enzymes in the human body can synthesize low levels of EPA
and DHA from α-linoleic acid (ALA, C18:3n- 3) consumed in the
diet from plant-derived foods, such as canola and soybean oils
and walnuts. However, the process is very inefficient because
ALA competes with linoleic acid (an omega- 6 fatty acid) for
the same enzymes. Because the human body cannot make
ALA or linoleic acid, they are both essential fatty acids that
must be obtained through the diet or supplements.
Other enzymes convert EPA and DHA into eicosanoids
such as prostaglandins, thromboxanes, and leukotrienes—
signaling molecules that have potent anti-inflammatory, anti-thrombotic, antiarrhythmic, and vasodilatory effects (Jain,
A. P., et al., Eur. Rev. Med. Pharmacol. Sci., 2015). In contrast,
omega- 6 fatty acids such as linoleic acid are converted into
arachidonic acid (C20:4n- 6), a precursor to different eicosanoids that are pro-inflammatory and pro-thrombotic. Vegetable oils such as corn and sunflower are high in omega- 6 fatty
acids. Increasing consumption of vegetable oils in the past
century has shifted omega-6:omega- 3 ratios from 1: 1 in 1900
Paul Clayton, fellow at the Institute of Food, Brain & Behav-
ior in Oxford, UK. “If you have a diet that is excessively loaded
with omega-6s, creating an excessive omega- 6 to omega- 3
ratio, then you start producing a much more toxic mix of
pro-inflammatory lipid mediators,” Clayton says. Many
researchers believe that this drastic dietary change underlies
the surge in diseases characterized by chronic inflammation,
such as atherosclerosis, type 2 diabetes, and cancer.
DHA and EPA consumed in the diet or through
supplements are key components of cell membranes.
Neuronal membranes are particularly enriched in DHA, leading researchers to propose that the omega- 3 fatty acid is
important for brain health. Although DHA is typically present at much higher levels in cell membranes than EPA, both
omega-3s can bind to membrane-bound proteins and block
ion channels. Omega-3s can also enter cells and interact with
enzymes and transcription factors to alter metabolism.
Three large randomized, controlled clinical trials of fish or fish
oil supplements for the treatment of cardiovascular disease
bolstered the enthusiasm for omega-3s as cardioprotective
agents. The Diet and Reinfarction Trial (DART) study followed
for two years 2,033 men who had experienced myocardial
infarction (Burr, M. L., et al., Lancet, 1989). Men who were
instructed to consume at least two meals of coldwater fatty
fish (for example, mackerel, sardine, or salmon; corresponding to 500–800 mg DHA/EPA per day) per week had a 32%
reduced incidence of reinfarction and a 29% reduction in all-cause mortality, compared with a control group that received
no instructions to eat fish.
Another major study, the Gruppo Italiano per lo Studio
della Sopravvivenza nell’Infarto Miocardico (GISSI) Preven-zione, randomized 11,323 survivors of myocardial infarction
to two groups: one that received a combined EPA/DHA dose
of 1 gram from fish oil supplements, and a control group that
received regular care (Marchioli, R., et al., Circulation, 2002).
After only four months of treatment, the fish oil group had