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The Journal of Nutrition. First published ahead of print June 16, 2010 as doi:10.3945/jn.109.118901.

The Journal of Nutrition
Nutrition and Disease

Oral Sea Buckthorn Oil Attenuates Tear Film Osmolarity and Symptoms in Individuals with Dry Eye


Petra S. Larmo,5 Riikka L. Ja¨ rvinen,5* Niko L. Seta¨ la¨ ,6 Baoru Yang,5 Matti H. Viitanen,7
Janne R. K. Engblom,8 Raija L. Tahvonen,9 and Heikki P. Kallio5

5Department of Biochemistry and Food Chemistry and 6Department of Ophthalmology, University of Turku, Turku 20014, Finland 7Turku City Hospital, Turku 20700, Finland 8Turku School of Economics, University of Turku, Turku 20014, Finland; and 9MTT Agrifood Research Finland/BEL, Jokioinen 31600, Finland

Abstract

Dry eye is a common condition that can severely impair the quality of life. We aimed to find out whether oral sea buckthorn (SB) oil, containing (n-3) and (n-6) fatty acids and antioxidants, affects dry eye. In this double-blind, randomized, parallel trial,20- to 75-y-old women and men experiencing dry eye symptoms consumed 2 g of SB or placebo oil daily for 3 mo from fall to winter. One hundred participants were recruited and 86 completed the study. Clinical dry eye tests and symptom follow-ups were performed. Tear film hyperosmolarity is a focal factor in dry eye. There was a general increase in the osmolarity from baseline to the end of the intervention. Compared with the placebo group, the increase was significantly less in the SB group when all participants were included [intention to treat (ITT), P = 0.04] and when only participants consuming the study products for at least 80% of the intervention days were included [per protocol (PP), P = 0.02]. The maximum intensities of redness and burning tended to be lower in the SB group. In the ITT participants, the group difference was significant for redness (P = 0.04) but not for burning (P = 0.05). In the PP participants, the group difference was significant for burning (P = 0.04) but not for redness (P = 0.11). In conclusion, SB oil attenuated the increase in tear film osmolarity during the cold season and positively affected the dry eye symptoms. J. Nutr. doi: 10.3945/jn.109.118901.


Introduction

Dry eye can cause severe discomfort and greatly compromise the quality of life (1). Depending on the population and definition, prevalence from ,1% to over 30% in people aged 50 y and older has been reported (1,2). Dry eye can be caused by several interlinked factors, which makes defining, diagnosing, and treating the condition challenging. The dry eye definition by the 2007 Dry Eye Workshop emphasizes the aspects of inflammation and increased osmolarity of the tear film as features common to different forms of dry eye (3).
The 2 main types of dry eye, although sometimes difficult to clearly separate, are aqueous-deficient and evaporative dry eye. In the aqueous-deficient form, the lacrimal secretion is reduced, leading to tear hyperosmolarity and activation of inflammatory pathways. In evaporative dry eye, the lacrimal secretion is normal, but water evaporation from the ocular surface is in- creased. The most common cause of evaporative dry eye is meibomian gland dysfunction associated with a deficient tear film lipid layer that is not stable enough to prevent water loss (3). Hyperosmolarity resulting from either of the 2 mechanisms can damage the ocular surface epithelium by activating inflammation via the mitogen-activated protein kinase and nuclear factor-kB signaling pathways (3,4). Epithelial damage and cell death further interrupt normal functions of the eye, leading to a vicious cycle (3). Dry eye risk factors include, among others, older age, female gender, and contact lens wear (2). Artificial tears are the common treatment for dry eye. Although they relieve symptoms, they likely do not affect the causative factors or the inflammation accompanying dry eye. Antiinflammatory drugs relieve the inflammation, but not all of them are suitable for long-term use and side effects may occur (5). Earlier studies suggest positive effects of (n-3) fatty acids, a combination of (n-6) linoleic [18:2(n-6)] and g-linolenic [18:3 (n-6)] acids, and antioxidants on dry eye (6–11). Mechanisms suggested for these effects include inflammation attenuation, effects on tear secretion, and prevention of oxidative damage. Dietary supplementation with (n-6) fatty acids may increase the level of dihomo g-linolenic acid, which is a precursor for antiinflammatory eicosanoids (8).


Sea buckthorn (Hippophae¨ rhamnoides) (SB)10 has been used in Asian traditional medicine for centuries, and SB berries are
included in the Chinese Pharmacopeia (12,13). SB oil is rich in lipophilic antioxidants and SB seed oil especially contains high proportions of (n-3) and (n-6) fatty acids (14). Positive effects of SB oil on skin and mucous membrane have been re- ported (13,15,16), as well as antiatherogenic (17) and platelet aggregation-inhibiting effects (18). Our objective was to inves tigate whether consuming SB oil can affect dry eye. Effects on both objective clinical responses and subjective symptoms experienced by the participants were studied.

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