Published in Terveyspalvelut 2/2011

Dry eye syndrome, or dry eye, is a common condition that can occur along with ageing and certain external factors, such as low humidity and the use of contact lenses. Women suffer from dry eye more frequently than men do. In studies, even more Ophtamin Dry Eye_boxi_tyrnithan 30% of people over 50 years of age have stated that they suffer from dry eye symptoms, such as soreness, burning, redness, and itching of the eyes.

Dry eye can be caused by two, different mechanisms: there can be disturbances in lacrimal secretion (aqueous deficient dry eye), or the composition of the tear film protecting the ocular surface can be abnormal, leading to excessive evaporation of the aqueous tear film (evaporative dry eye). In both cases, the osmolarity (solute concentration) of the tear film, is increased. Inflammation reactions are also activated. Symptoms of dry eye are usually treated with humidifying eye drops that do not, however, eliminate the underlying inflammation.

A clinical study at the University of Turku: sea buckthorn oil has an effect on osmolarity and symptoms

The effects of sea buckthorn oil on dry eye were investigated in a placebo-controlled, randomized, double-blind study at the Department of Biochemistry and Food Chemistry at the University of Turku.

A hundred men and women between the ages of 20 and 75 experiencing symptoms of dry eye participated in the study. Half of the subjects were contact-lens users. For three months, half of the participants took a daily oral dose of 2 grams of SBA24®, a carbondioxide-extracted sea buckthorn oil manufactured by Aromtech Ltd, and half took a placebo oil. The placebo oil contained triacylglycerols of medium-chain fatty acids that were fractioned from coconut and palm oils. The test oils were ingested via capsules in the morning and evening.

During the study, the dry eye of the participants was evaluated with the aid of clinical dry eye tests, symptom queries, and a symptom logbook kept by the participants. In addition, samples were gathered from the participants, for determination of the fatty acid composition of the tear film.

During the observation period, the osmolarity of the tear film increased in both the sea buckthorn group and the placebo group. The increase from the beginning of the observation period to the end, however, was significantly milder in the sea buckthorn group than in the control group (sea buckthorn: +8 mOsm/L, placebo: +12 mOsm/L; P = 0.04). The observation period in the study started in the autumn and ended in the winter. Over this time, the average temperature in Turku decreased by more than 10 °C. During the cold season, the humidity of the air is low both outside and indoors, which increases the evaporation of tears and dry eye symptoms. It also explains the general increase observed in osmolarity.

Review of the symptom logbooks revealed that the redness and burning sensations of the eyes experienced were milder in the sea buckthorn group when compared to the control group. Studies have reported differences especially in the fatty acid composition of the tear film in individuals suffering from evaporative dry eye as compared to the tears of healthy individuals. In this study, wherein the test subjects had different dry eye types, there was no difference observed in the tear-film fatty acid profiles between the sea buckthorn and placebo group.

The combined effect of the oils in the soft portion of the berry and in the seeds

The sea buckthorn oil used in the study, SBA24®, contained both sea buckthorn berry oil and seed oil, which were extracted by means of supercritical car bon dioxide extraction. The oil in the soft portions of the sea buckthorn berry is rich in carotenoids, and its primary fatty acids are palmitoleic, palmitic and oleic acids. The seed oil in particular contains plenty of linoleic (n-6) and alpha-linolenic (n-3) acids. Both oils contain vitamin E and plant sterols.

The positive effects of sea buckthorn oil are most likely related to the alleviation of inflammation, which tends to maintain and increase the dryness of the eyes. In humans, linoleic and alphalinolenic fatty acids can be converted to longer-chain n-6 and n-3-fatty acids that are precursors of eicosanoids exerting control over inflammation. Previous studies have shown that n-3 fatty acids have beneficial effects on dry eye. Also the combination of linoleic acid and gamma-linolenic acid (n-6) has been found to alleviate dryness of the eyes and to increase the amount of prostaglandin E1 eicosanoid in the tears. This eicosanoid increases tear secretion and alleviates inflammation. Vitamin E and carotenoids have also been reported as having anti-inflammatory effects.

The lipids in tear film are produced mainly in the meibomian glands, located at the margins of the eyelids. They secrete lipid-containing meibum in tears. In addition to differences reported between the fatty acid composition of tears in dry-eyed and healthy persons, some studies suggest that the phosph-olipid composition of the tear film is abnormal in dry eyes, and individuals suffering from dry eyes have a thinner tear lipid layer than healthy persons do. Also, in a Raman spectroscopy study, the amount of carotenoids in the meibum of dry-eye sufferers has been noted to be smaller than that for others. It has been presented that the n-3 and n-6 fatty acids may have an effect on the differentiation of the meibomian gland cells, and hence possibly also affect the quantity of lipids being formed.

Conclusions

According to the study, the intake of sea buckthorn oil can positively affect the tear film osmolarity and dry eye symptoms. The mechanism of action is most likely related to alleviation of the inflammation that maintains and fortifies dry eye. The inflammation is affected by the bio active compounds contained in oils from both the sea buckthorn seeds and the soft portions of the berry.

Article written by Ms. Petra Larmo, Ph.D.
Research and Product Development Manager, Aromtech Oy
petra.larmo (at) aromtech.com

References:
Larmo P, Järvinen R, Setälä N, Yang B, Viitanen M, Engblom J, Tahvonen R, Kallio H. Oral sea buckthorn oil attenuates tear film osmolarity and symptoms in individuals with dry eye. Journal of Nutrition. 140: 1462-1468, 2010.
Järvinen R, Larmo P, Setälä N, Yang B, Engblom J,Viitanen M, Kallio H. Effects of oral sea buckthorn oil on tear film fatty acids in individuals with dry eye. Cornea. In press.
Larmo P. The Health Effects of Sea buckthorn Berries and Oil. Doctoral dissertation. University of Turku, Department of Biochemistry and Food Chemistry. 2011.