Eyes function differently based on the level of light in the
environment. In normal daylight the eye primarily uses cones to focus the
light. In near darkness, the eye primarily uses rods to focus the light. Low
light conditions such as driving at night require both mechanisms. Lutein is an orange-red carotenoid pigment produced by
plants and is present in the diet in colorful fruits and vegetables. One of the
best sources of lutein is kale which provides more than 20 mg per cup. Cooked
spinach, collard greens and turnip greens also pack a similar punch. This
compares to romaine lettuce and raw spinach which have less than 4 mg of lutein
available for use.
In the body, lutein is one of
the predominant pigments concentrated in the macula, a specialized area of the
eye that is responsible for central vision. In addition, it is known to be
deposited in the skin. It is thought that lutein’s functional role in these vulnerable
tissues is to protect against sunlight-induced free radical production.
Ever since the Blue Mountain
Eye Study reported that higher dietary lutein and zeaxanthin intake reduced the
risk for incident of age-related macular degeneration (AMD) over 5 and 10
years, significant interest has been placed on these particular carotenoids.[1]
In an interesting study, middle-aged adults who drove for a
living (i.e. taxi drivers) were given 20 mg of lutein or a placebo for one
year. Researchers measured a variety of outcomes including something called
macular pigment optical density (MPOD) [2] MPOD has been associated with
improvements in visual function in those with age-related macular degeneration.[3]
This study showed that supplemental lutein, at this dose,
increases serum levels of lutein.
However, of key importance is the length of the study and the
measurement of vision performance. Under low light conditions, the group
receiving treatment of lutein performed better at testing of contrast
sensitivity and glare sensitivity. MPOD was also increased.
No significant side effects were reported in this study.
Carotenodermia is one concern of large doses of carotenoids and while transient
and relatively harmless, it was not seen in this study. Previous studies have considered doses of 6
and 12 mg and showed peak serum lutein levels after 3-6 months.[4],
[5],
[6],
[7]
However, in this research, peak levels were seen after just 30 days. This was
attributed to the higher dose and good compliance among participants. While
following serum levels of a specific carotenoid often does not typically have clinical
value, uptake of lutein by the macula can take several months following peak
levels. Indeed, this effect was seen in this study as well. Despite seeing a
six-fold increase in serum levels after only one month, visual performance did
not improve until three months after initiation of lutein administration. While
6 mg did not improve macular pigment optical density (MPOD) in previous
studies, this study confirmed increases in this valuable biomarker.4 Several
hypotheses remain about how macular pigment plays a role in the health of the
eye but a leading theory is that antioxidants in the pigment reduce oxidized
products produced by the interaction of light and tissues.
One of the challenges of the study was that serum levels of
lutein in the participants at baseline were found to be lower than expected. It
is thought that profession or economic status could play a role in this.
Unfortunately, it creates another question. If a person already has adequate
lutein levels in serum, will they not benefit from supplementation? This
remains to be determined.
Another question that may arise concerns other carotenoids.
The family of carotenoids (including beta carotene, alpha carotene, astaxanthin,
zeaxanthin and others) may compete for absorption and excess dosing of a single
carotenoid may hypothetically lead to insufficiencies among the other
phytonutrients. Unfortunately, serum levels of these other carotenoids were not
measured at baseline or throughout the study.
Essentially, participants taking lutein in this study could
not read a Snellen chart, the tool with the large E at the top that
optometrists and physicians use, any better than the placebo group after a year
of use. Visual acuity was not significantly different. However, seeing movement
in the periphery under low light conditions was improved. This is interesting
because visual performance is more of a real-life analysis. Especially in this
demographic studied, those whose job requires long hours of driving, even minor
improvements in vision can result in improved driving performance and safer
roads. Up to 23% of car accidents have been associated with reduced visual
performance.[8] The
challenge of the results of this study is the age-group that was studied. Young
to midlife adults are not often the ones commonly complaining of decreased
night vision. More often than not, the aging person no longer trusts their
ability to navigate in low light conditions and this may result in decreased
activity and a lower perceived quality of life. As people age, reduced
participation in activity is a concern for incidence of depression. Those who
continue to drive despite declining vision are putting themselves and others at
risk. It would be curious to see if similar results could be replicated in an older
population. Until that result is published, people may find this relatively
inexpensive and safe intervention worth a one year trial for themselves.
[1] Tan JS,Wang JJ, Flood V, Rochtchina E, SmithW, Mitchell P.
Dietary antioxidants and the long-term incidence of age-related macular
degeneration: the Blue Mountains Eye Study. Ophthalmology 2008;115(2):334–41.
[2] Lutein supplementation improves visual performance in Chinese drivers: 1-year randomized, double-blind,
placebo-controlled study. Nutrition (2013),
http://dx.doi.org/10.1016/j.nut.2012.10.017
[3]
Weigert G, Kaya S, Pemp B, Sacu S, Lasta M, Werkmeister RM, Dragostinoff N,
Simader C, Garhöfer G, Schmidt-Erfurth U, Schmetterer L.Effects of lutein
supplementation on macular pigment optical density and visual acuity in
patients with age-related macular degeneration. Invest Ophthalmol Vis Sci. 2011
Oct 17;52(11):8174-8. doi: 10.1167/iovs.11-7522.
[4] Sasamoto Y, Gomi F, Sawa M, Tsujikawa M, Nishida K. Effect of
1-year lutein supplementation on macular pigment optical density and visual
function. Graefes Arch Clin Exp Ophthalmol 2011;249:1847–54.
[5] Ma L, Lin XM, Zou ZY, Xu XR, Li Y, Xu RA. 12-week lutein
supplementation improves visual function in Chinese people with long-term
computer display light exposure. Br J Nutr 2009;102:186–90.
[6] Nolan JM, Loughman J, Akkali MC, Stack J, Scanlon G, Davison P,
et al. The impact of macular pigment augmentation on visual performance in
normal subjects: COMPASS. Vision Res 2011;51:459–69.
[7] Olmedilla B, Granado F, Blanco I, Vaquero M. Lutein, but not
alpha-tocopherol, supplementation improves visual function in patients with age-related
cataracts: a 2-y double-blind, placebo- controlled pilot study. Nutrition
2003;19:21–4.
[8] Ranny T. Psychological factors that influence car-following
and car following model development. Transportation Res 1999;Part F 2:213–9.
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