196
J.G. Bell and R. Waagbø
6.4 n-3 Highly Unsaturated Fatty Acids (HUFA)
and Human Health
The efficacy of EPA and DHA in preventing or attenuating inflammatory disease in
humans was first recognized in the early 1970s when epidemiological studies
indicated a low incidence of cardiovascular disease in Inuit populations in
Greenland and that coastal populations had different disease patterns from inland
dwellers (Bang and Dyerberg 1972; Dewailly et al. 2001a,b). The reason for the
differences in disease patterns were attributed to higher fish and n-3 HUFA intake in
coastal populations. Historically, the human genome has changed little since
Paleolithic times when humans were hunter-gatherers and consumed a diet where
the ratio of n-6/n-3 PUFA was estimated to be around 1:1 (Leaf and Weber 1987;
Simopoulos 1999). Thus, over the past 10,000 years the human genome will have
changed little such that the nutritional input in the developed world in the 21st
century will be very different to that which our genetic composition is best suited.
The changes in our lipid intake from Paleolithic times to the present day are shown
in Fig. 6.1 (Leaf and Weber 1987). This demonstrates the increase in total fat intake
towards the end of the Agricultural revolution and similar increases in saturated fat
and n-6 PUFA, with decreased n-3 PUFA during the Industrial revolution. It is also
noteworthy that increased consumption of cereal grains at this time resulted in a
greatly elevated starch intake that resulted in increased lipogenesis. The n-6/n-3
PUFA ratio increased steadily from around 1:1 in the early 19th century such that
the ratio in the developed world now ranges from 5:1 to 25:1. The most dramatic
increases have been due to increased production and use of n-6-rich seed oils which
became established following the First World War and have subsequently dominated
agricultural production. They gained popularity in human nutrition due to the
improvement in serum lipid and cholesterol profile induced by n-6 PUFA compared
to saturated fat (Keys et al. 1957). Unfortunately, the dominance of n-6 PUFA in
the human food chain, due to direct consumption of vegetable oils as well as the
use of oilseeds for the production of farm animals, has seen a steady decline in n-3
PUFA and HUFA in the food chain in the 20th century (Simopoulos 1999).
Over the last 50 years the prevalence of diseases with an inflammatory pathology
has increased dramatically especially pathologies of the cardiovascular system
(Simopoulos 1991; Zheng et al. 2001). Recent evidence suggests that supplementation with EPA and DHA can reduce death from coronary heart disease (CHD) by
25% and of sudden cardiac death by 45% (Marchioli et al. 2002), and that the risk
of CHD can be predicted by a so called “Omega-3 index” based on combined blood
fatty concentrations of DHA + EPA (Harris and von Schacky 2004). Using a dose
response study, the authors studied the effectiveness of increasing DHA + EPA supplementation on red blood cell DHA + EPA content and thereby correlating
Omega-3 index with CHD risk factors identified in earlier epidemiological studies
and randomised controlled trials (Harris and von Schacky 2004). However, when
considering a healthy intake of n-3 HUFA it is also vital to consider n-6 PUFA and
HUFA intake as the n-3 and n-6 fatty acids compete during metabolic conversions
J.G. Bell and R. Waagbø
6.4 n-3 Highly Unsaturated Fatty Acids (HUFA)
and Human Health
The efficacy of EPA and DHA in preventing or attenuating inflammatory disease in
humans was first recognized in the early 1970s when epidemiological studies
indicated a low incidence of cardiovascular disease in Inuit populations in
Greenland and that coastal populations had different disease patterns from inland
dwellers (Bang and Dyerberg 1972; Dewailly et al. 2001a,b). The reason for the
differences in disease patterns were attributed to higher fish and n-3 HUFA intake in
coastal populations. Historically, the human genome has changed little since
Paleolithic times when humans were hunter-gatherers and consumed a diet where
the ratio of n-6/n-3 PUFA was estimated to be around 1:1 (Leaf and Weber 1987;
Simopoulos 1999). Thus, over the past 10,000 years the human genome will have
changed little such that the nutritional input in the developed world in the 21st
century will be very different to that which our genetic composition is best suited.
The changes in our lipid intake from Paleolithic times to the present day are shown
in Fig. 6.1 (Leaf and Weber 1987). This demonstrates the increase in total fat intake
towards the end of the Agricultural revolution and similar increases in saturated fat
and n-6 PUFA, with decreased n-3 PUFA during the Industrial revolution. It is also
noteworthy that increased consumption of cereal grains at this time resulted in a
greatly elevated starch intake that resulted in increased lipogenesis. The n-6/n-3
PUFA ratio increased steadily from around 1:1 in the early 19th century such that
the ratio in the developed world now ranges from 5:1 to 25:1. The most dramatic
increases have been due to increased production and use of n-6-rich seed oils which
became established following the First World War and have subsequently dominated
agricultural production. They gained popularity in human nutrition due to the
improvement in serum lipid and cholesterol profile induced by n-6 PUFA compared
to saturated fat (Keys et al. 1957). Unfortunately, the dominance of n-6 PUFA in
the human food chain, due to direct consumption of vegetable oils as well as the
use of oilseeds for the production of farm animals, has seen a steady decline in n-3
PUFA and HUFA in the food chain in the 20th century (Simopoulos 1999).
Over the last 50 years the prevalence of diseases with an inflammatory pathology
has increased dramatically especially pathologies of the cardiovascular system
(Simopoulos 1991; Zheng et al. 2001). Recent evidence suggests that supplementation with EPA and DHA can reduce death from coronary heart disease (CHD) by
25% and of sudden cardiac death by 45% (Marchioli et al. 2002), and that the risk
of CHD can be predicted by a so called “Omega-3 index” based on combined blood
fatty concentrations of DHA + EPA (Harris and von Schacky 2004). Using a dose
response study, the authors studied the effectiveness of increasing DHA + EPA supplementation on red blood cell DHA + EPA content and thereby correlating
Omega-3 index with CHD risk factors identified in earlier epidemiological studies
and randomised controlled trials (Harris and von Schacky 2004). However, when
considering a healthy intake of n-3 HUFA it is also vital to consider n-6 PUFA and
HUFA intake as the n-3 and n-6 fatty acids compete during metabolic conversions