ARTICLE
Auteur(s) : René
van Hoorn, Rakesh Kapoor, Johan Kamphuis
Bioriginal Europe/Asia, Bosland 40, 3258 AC Den Bommel, The
Netherlands
Over the last decade, the publicity of food supplements in the
area of healthful fatty acids has been dominated by the omega-3
fatty acids, more specifically those found in Fish, EPA and DHA.
This publicity is based upon a large body of scientific evidence
which has established links between fish oil, or the prominent
individual fatty acid in there, to decreased incidence of a number
of diseases. The strongest and most widely accepted link is that of
fish oil intake and lowered risk of coronary heart disease (CHD)
[1].
In the same body of evidence which suggests the promising role
of n-3 fatty acids on human health, n-6 fatty acids are often
mentioned as a potential health threat. The basis for this bad
reputation are epidemiological studies showing an improper balance
between total n-3:n-6 can lead to serious health problems. The
estimated ratios between of n-3:n-6 are quite diverse and range
anywhere from 1:8 to 1:15 [2]. There is still much scientific
debate ongoing to what the optimum ratio might be, but already
there are authoritative bodies, like the ministry of health, labour
and welfare in Japan, recommending consumers a n-3:n-6 ratio of
1:4.
One reason for the unbalance in the ratio is the low intake of
fatty fish in our western diets. The second reason, which is just
as obvious as the first, is the high intake of n-6 fatty acids, in
particular of linoleic (LA) and arachidonic acid (ARA). These two
fatty acids combined account for the majority of the n-6 intake, to
which the lower n-3:n-6 ratio and consequent harmful effects seen
in the epidemiological studies, are linked to. The n-6 fatty acid
gamma-linolenic acid (GLA), however, is only taken in small amount
but is potentially just as healthful as the n-3 fatty acids.
Evidence of such positive effects will be demonstrated below.
GLA is mainly found in vegetable oils, with Borage oil (24% GLA)
being nature richest source. GLA is biosynthesized from LA, the
true essential fatty acid of the n-6 pathway, as all enzymes needed
for further conversion are present in the body (figure 1).
Historically, evening primrose oil (EPO) got most attention as
the majority of the research, that started in the late-70’s, was
done on this oil. Much of the GLA research was pioneered by the
late David Horrobin, who, through science, laid the foundation for
the commercial success of GLA-rich plants oils [3, 4]. More
recently, starting in mid-eighties, Borage oil was found to be a
GLA-rich and commercially viable oil and, together with EPO, now
makes up the majority of the GLA market. GLA nowadays is found in a
number of applications including (pet)food, food supplements,
skincare products and medical nutrition.
Proven health benefits of GLA
There are a number of different areas of use for GLA-rich oils. In
this section we will try and highlight a few of the (disease)
conditions that have been treated with GLA-rich oils.
Coronary heart disease
We already mentioned the well accepted benefits of fish oil in the
prevention CHD, but correlations between the intake of GLA and CHD
also exist. These correlations are less clear than for fish oil,
but the effects are apparent.
Mice being fed a high GLA diet showed a reduction of VLDL and
LDL cholesterol, as well as a reduction of atherosclerotic lesions
[5, 6]. Similar effects were seen in an intervention study with
seniors [7]. In that study the researchers showed effective
bioconversion of GLA dihomo-DGLA and consequent reduction of a
number of CHD risk factors.
Next to (V)LDL cholesterol and atherosclerotic lesions,
hypertension is also a common risk factors of CHD. Independent
studies showed that supplementation with GLA led to a reduction of
blood pressure, up to 6-16%, which is even better compared to some
pharmaceutical agents [8-10].
Arthritis
Symptoms of arthritis include morning stiffness, inflammation and,
generally, painful joints.
Treatment of arthritis, which is a chronic disease, is usually
done with non-steroidal anti-inflammatory drugs (NSAIDs). In
different clinical trials arthritis sufferers were supplemented
with GLA and a sharp decrease was seen in all the mentioned
symptoms above. Most noticeably was the reduction in NSAIDs users,
which decreased from 100% to approximately 25% after 9 months of
supplementation [11].
Skin health
Our skin is the biggest organ we have and its’ key function is that
of a barrier. A healthy skin is rich in lipid membranes, that
combined with coernocytes, form the structural basis for the
barrier role.
Topical application, as well as oral supplementation with GLA,
has been shown to improve skin smoothness and moisture in healthy
human subjects. With the oral supplementation a 18% increase was
noticed after 12 wks of supplementation with 700 mg GLA/day
[12, 13].
Eczema (approx. 10% of the population) and Psoriasis (approx. 2%
of the population) are common skin problems affecting the quality
of life for many. In psoriasis inflamed skin lesions are formed,
with varying intensity and lesion sizes. Normally this is treated
with topically applied corticosteroids, but these are not always
effective. In two independent case studies patients were
supplemented GLA for five months or more and the results showed a
dramatic decrease of symptoms (97% and 72%) [14].
GLA has also been shown to be effective in treating eczema.
After twelve weeks of GLA supplementation, patients scored common
eczema symptoms as inflammation, oozing and vesicle formation
slightly lower, and itching significantly lower (Intensity at start
7.8; after twelve weeks 1.0) [15].
Discussion and conclusion
Only a few health benefits have been mentioned in this article, but
other researchers have pointed out that there are many more
possible beneficial roles of GLA e.g. diabetes, cancer and even
weight management [16]. We have looked at all the disease
conditions mentioned here and it seems that inflammation/reactive
oxygen species (ROS) form a commonality. Inflammation is most
obviously seen in arthritis and skin conditions, but it is also
well evidenced that ROS play a major role in the formation of
oxidation of LDL and atherosclerotic lesions in CHD [17]. Also, a
surplus of ROS on a cellular level can lead to DNA mutations,
possibly leading cancer [18].
Inflammation and ROS, the latter also being formed during
inflammation itself, are believed to be a function of genetic,
lifestyle and dietary factors. We know that activity of an
important rate limiting enzyme as delta-6-desaturase (D6D) is
heavily influenced by its location in the body. In the skin this
enzyme does not seem to be active, not allowing further downstream
conversion, as shown in figure 1. Another enzyme in
the pathway, delta-5-desaturase, is also inactive in skin [12].
The effect of lifestyle and dietary factors upon disease is
still not well understood, however, technology of the last 20 years
have allowed science to progress rapidly. It is now well known that
smoking, for instance, has a detrimental effect upon the activity
of D6D.
A deficiency in nutrients as vitamin B6 and zinc also decreases
the activity of D6D, as they are important co-factors.
From the above it is obvious that many factors can influence the
activity of crucial enzymes in the fatty acid biosynthesis pathway,
but adding to that is, of course, the actual intake of fatty acids
themselves. As mentioned in the introduction, most western diets
are unbalanced in their n-6:n-3 intake but a closer look also shows
us an imbalanced consumption within the n-6 family.
LA is the most available n-6 fatty acid in our diets and can be
found in common vegetable fats, margarines and other products. Next
to LA, ARA in our diets is found mostly in meats. GLA, on the other
hand, is hardly consumed and only found in a few specific plant
oils.
Taking into account the slow conversion of LA to GLA, as
mentioned earlier, a shortage of GLA and a surplus of ARA may exist
for those living a “western” life style. This is an unfavourable
balance as from ARA pro-inflammatory eicosanoids are formed,
contributing to the disease conditions described earlier.
Supplementation with GLA, therefore, might restore a more healthy
balance within the n-6 fatty acid family. We believe that this
restored balance between GLA and ARA will contribute to increased
production of more favourable anti-inflammatory eicosanoids and
could help improve disease conditions that have
inflammation/ROS-like causes, as evidenced in this article.
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