Lycium barbarum fruits (Goji berries)
Lycium barbarum is a deciduous shrub that grows 1-3 meters high and is widespread in warm climate regions, from Southeast Europe to China . It is cultivated mostly for its edible berries, orange-to-red in color and 1-2 cm in length, known as wolfberries or Goji berries. Majority of Goji berries on the world market come from North China.
Lycium barbarum has been used in the traditional Chinese medicine for thousands of years . Its berries (fruits) have been claimed to nourish liver, kidneys and lungs, to promote sexual health and fertility, cure vision problems, reduce fatigue and headache, and increase longevity [1, 2]. History of the traditional use has been taken as evidence of its extraordinary health benefits by various alternative medicine practitioners and commercial distributors, who have promoted Goji as a quasi-miraculous cure for medical conditions and an anti-aging product . Goji berries have been heavily advertised recently and became a popular item on the health food market . They are mostly sold as raw dried fruits, but also as juice, or in the form of powder or tablets. Some scientific studies have indeed found interesting and potentially useful pharmacological properties in the Lycium barbarum fruits, however, the conclusive evidence for their benefits to humans is still lacking.
Goji fruits are abundant in several classes of compounds. The most important are polysaccharides, carotenoids and flavonoids. They also contain essential fatty acids, free amino acids and vitamins B1, B2 and C . The polysaccharide fraction is relatively characteristic for L. barbarum and has been investigated for potentially beneficial health effects.
ANTIDEPRESSANT AND NEUROPROTECTIVE EFFECTS
One study has shown that Lycium barbarum polysaccharides possess significant antidepressant properties . Depressive-like behaviour was induced in rats by repeated injections of corticosterone (the main glucocorticoid hormone in rodents, equivalent to human cortisol). Increased glucocorticoid signaling has been identified in both animal and human studies as one of the most common physiological changes in depression and anxiety disorders, accompanying characteristic brain abnormalities and behavioral symptoms. As would be expected, corticosterone treatment resulted with dendritic atrophy of pyramidal cells and decreased levels of neurogenesis in subgranular zone of the hippocampus. Oral administration of Lycium barbarum polysaccharides (LBP) in doses from 1 mg/kg to 10 mg/kg for 14 consecutive days reversed this effects, increasing both neurogenesis and dendritic spine density. Important synaptic proteins (PSD-95 and synaptophysin) were also found to be upregulated. Moreover, LBP produced a significant antidepressant response in the forced swim test. However, further experiments showed that the increased synaptic plasticity alone, not the altered rate of neurogenesis, was responsible for the antidepressant effects of LBP. It was pointed out in the study that LBP treatment exerted a more potent effect than volontary physical exercise (wheel running) in the corticosterone model of depression, which was evaluated in the previous study by the same authors .
Neurogenesis enhancing properties of LBP were also found in another study that examined its effects on sexual behaviour in male rats . Corticosterone administration was used to induce defects in sexual motivation and performance, and was shown to decrease neurogenesis in the hippocampus and the subventricular zone of the olfactory system (SVZ), as well as suppress testosterone levels. LPB treatment was found to reverse this, rescuing neurogenesis in both regions, increasing testosterone and restoring normal sexual behaviour. LBP was also capable of enhancing sexual performance in healthy male rats not treated with corticosterone. Neurogenesis was shown to be essential for both normal sexual functioning and the beneficial, pro-sexual effect of LBP.
Several other studies confirmed LBP’s pro-neurogenic effects. Treatment of rats with LBP before and after subjecting them to severe trauma reduced cognitive and behavioral defects attributed to hippocampal cell death (apoptosis) and impaired neurogenesis. LBP alleviated those cellular changes and restored the hippocampal volume . Similar observations were made in the study of hypoxia-induced injury to the hippocampus; LBP showed neuroprotective effects against oxidative damage, suppressed inflammation and apoptotic signaling, improved neurogenesis and reduced deficits in spatial memory . Its protective effects in ischemia and reperfusion injury were also reported in several studies [7, 8].
Possible beneficial effects of wolfberry on subjective states and neurological functioning have also been investigated in clinical studies. Daily consumption of Goji fruit extract was reported to increase the quality of sleep, decrease fatigue, dizziness, chest distress and anorexia in elderly subjects . In another study, a commercial Goji juice was found to improve the subjective well-being, neurological performance and gastrointestinal functioning in young healthy adults .
Antioxidant properties of Goji fruit extracts or purified polysaccharides have been in the focus of many studies. Protective effects of LBP against oxidative stress in animal cells and tissues have been demonstrated both in vivo and in vitro [11, 12, 13]. In the single clinical study, consumption of Goji juice increased serum antioxidant markers in healthy participants . Animal studies have shown that LBP can improve insulin sensitivity and exert hypolipidemic effects (lowering cholesterol and triglycerides) . A lot of research has focused on its immunostimulatory and antitumor properties [16, 17], including one clinical study on cancer patients where LBP in combination with immunotherapy resulted with increased remission rates .
Goji berries can be regarded as safe, even when consumed in large quantities. They have been used for a long time as food and folk medicine, with no reports of adverse effects . Recently, there have been only a few cases of allergic reactions, and adverse interactions have been documented in patients taking warfarin .
VALIDITY OF RESEARCH
It should be noted that almost all research on pharmacological properties of wolfberry was done by Chinese scientists. Clinical studies have been conducted exclusively in China, and have not been of highest quality . Typically, studies were limited by small size, lack of statistical analysis and poor controls. Some were conducted by scientists either affiliated with or directly sponsored by the company selling Goji products. Independent research is needed.
Preclinical evidence suggests that Goji products (berries, extracts or juice) might be beneficial in the treatment of depression and other neurodegenerative disorders. Clinical evidence is still insufficient, proper studies are yet to be conducted. Regular consumption of wolfberry might potentially bring some improvement in the hedonic function, in combination with other strategies and substances. Since the fruit is not toxic, one could freely experiment with different dosages to find if it could produce a mood enhancing effect, while enjoying many other health benefits.
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 Lau BW-M, Lee JC-D, Li Y, et al. Polysaccharides from Wolfberry Prevents Corticosterone-Induced Inhibition of Sexual Behavior and Increases Neurogenesis. Borlongan CV, ed. PLoS ONE. 2012;7(4):e33374. doi:10.1371/journal.pone.0033374.
 Zhang E, Yau SY, Lau BW, Ma H, Lee TM, Chang RC, et al. Synaptic plasticity, but not hippocampal neurogenesis, mediated the counteractive effect of wolfberry on depression in rats (1) Cell Transplant.2012;21:2635–49.
 Yau S. Y.; Lau B. W.; Tong J. B.; Wong R.; Ching Y. P.; Qiu G.; Tang S. W.; Lee T. M.; So K. F. Hippocampal neurogenesis and dendritic plasticity support running-improved spatial learning and depression-like behaviour in stressed rats. PLoS One 6(9):e24263; 2011.
 Gao J, Chen C, Liu Y, Li Y, Long Z, Wang H, Zhang Y, Sui J, Wu Y, Liu L, Yang C. Lycium barbarum polysaccharide improves traumatic cognition via reversing imbalance of apoptosis/regeneration in hippocampal neurons after stress. Life Sci. 2015 Jan 15;121:124-34.
 Lam C-S, Tipoe GL, So K-F, Fung M-L. Neuroprotective Mechanism of Lycium barbarum Polysaccharides against Hippocampal-Dependent Spatial Memory Deficits in a Rat Model of Obstructive Sleep Apnea. Ma D, ed. PLoS ONE. 2015;10(2):e0117990. doi:10.1371/journal.pone.0117990.
 Li S-Y, Yang D, Yeung C-M, et al. Lycium Barbarum Polysaccharides Reduce Neuronal Damage, Blood-Retinal Barrier Disruption and Oxidative Stress in Retinal Ischemia/Reperfusion Injury. Ko B, ed. PLoS ONE. 2011;6(1):e16380. doi:10.1371/journal.pone.0016380.
 He M, Pan H, Chang RC-C, So K-F, Brecha NC, Pu M. Activation of the Nrf2/HO-1 Antioxidant Pathway Contributes to the Protective Effects of Lycium Barbarum Polysaccharides in the Rodent Retina after Ischemia-Reperfusion-Induced Damage. Gallyas Jr. F, ed. PLoS ONE. 2014;9(1):e84800. doi:10.1371/journal.pone.0084800.
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 Liu L, Lao W, Ji Q-S, Yang Z-H, Yu G-C, Zhong J-X. Lycium barbarum polysaccharides protected human retinal pigment epithelial cells against oxidative stress-induced apoptosis. International Journal of Ophthalmology. 2015;8(1):11-16. doi:10.3980/j.issn.2222-3959.2015.01.02.
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