Contents lists available at ScienceDirect Trends in Food Science & Technology journal homepage: www.elsevier.com/locate/tifs Review Tea consumption and disease correlations Nevin Sanlier a,* , Buşra Basar Gokcen b , Mehmet Altuğ c a Lokman Hekim University, Faculty of Health Sciences, Nutrition and Dietetics Department, Ankara, Turkey b Gazi University, Faculty of Health Sciences, Nutrition and Dietetics Department, Ankara, Turkey c Lokman Hekim University, Faculty of Medicine, Department of Medical Biochemistry, Ankara, Turkey ARTICLE INFO Keywords: Black tea Green tea Oolong tea White tea Cancer Obesity Diabetes mellitus Cardiovascular diseases Other diseases ABSTRACT Tea is the most widely consumed beverage in the world next to water and is obtained from the leaves Camellia sinensis. In recent years, the potential health benefits and effect mechanisms of tea have attracted a lot of interest. The potential health benefits of tea have been attributed to its various phenolic compounds with unique bio- logical properties found in tea. These phenolic compounds are especially catechins and their derivatives, which constitute at most 30% of the dry weight of the tea. Tea is a new and effective strategy for reducing the severity of neurological diseases and for protecting against obesity, cardiovascular disease, type 2 diabetes and certain types of cancer (ovaryum, lung, skin, breast, endometrial, prostate, bladder, oral and colorectal cancers). Overall, the study that supports the health benefits of tea is increasing. But, the amounts of and the frequency of tea consumption that is associated with potential health benefits vary greatly from work to work and this situation creates difficulty in determining the optimal consumption amount and frequency that tea can exhibit health benefits. For this reason, we aimed to examine the health effect of the tea and how much consumption is to investigate whether it meets the claimed health benefits. Within that frame, there is a need for more studies on the possible health effects of tea. While studying on that effect, the effects of various doses, forms (in synthetic or natural product matrix), exposure in different periods (short or long term) on health should be studied. However, currently the conducted studies are promising for tea is a bioactive component like polyphenol, theaflavins, thearubigins, caffeine and mineral. In addition, although the fact intake with diet proved to be reliable at the end of the conducted acute and chronic toxicity test is another positive part, safety of bioactive component in tea should be supported through further studies. 1. Introduction The first documented sources of tea appeared in China in the third century CE (Munday, 2016), but archaeological studies indicate that the tea was first consumed in the early Palaeolithic period (Cooper, 2012). Besides its being the oldest drinks, tea has enormous medical, economic and cultural importance since ancient times (Xia et al., 2017). With the awareness that tea improves health and prevents some diseases, its consumption has been considered as a “health-promoting habit” and modern medical researchers have provided the scientific basis for this belief over time (Chen & Lin, 2015; Feng, Ng, Kua, Lee, & Preedy, 2015; Khan & Mukhtar, 2013; Venkateswara, Sirisha, & Chava, 2011). Be- cause tea has antioxidant, thermogenic, anti-inflammatory, cholesterol- lowering, antimicrobial, neuroprotective, anti-hypertensive and anti- carcinogenic properties (Li & Zhu, 2016), its presence in daily human diet is significantly high (Qi et al., 2017). Studies have shown that tea has beneficial effects on many chronic diseases such as cancer, cardi- ovascular diseases, obesity, diabetes and neurological diseases (Heber et al., 2014; Lee, Su, Pasalich, & Binns, 2013; Mao et al., 2010; Miller et al., 2016; Tomata et al., 2016; b, Wang, Yang, Zhang, & Wu, 2014). However, many topics like toxicological effects, doses, amounts, usage in the body, advantages and disadvantages, etc. of these active molecules need to be examined. For these reasons this article was re- wieved to evaluate health effects of tea. 2. Tea and its composition The tea plant has two main types, Camellia sinensis and Camellia assamica. Camellia sinensis is a long-lived and small-leaf plant that can withstand cold weather, while Camellia assamica is a short-lived, more sensitive and large-leaf plant that can grow easily in tropical and rainy regions (Üstün & Demirci, 2013). Tea is mainly produced from the leaves of plant Camellia sinensis and it is the most widely consumed beverage worldwide next to water (Tang, Li, Qiu, Zhou, & Ma, 2009b). There are four main types of tea: black tea, green tea, white tea and oolong tea (Butt et al., 2014; Vernarelli & Lambert, 2013). Worldwide, https://doi.org/10.1016/j.tifs.2018.05.026 Received 14 November 2017; Received in revised form 13 April 2018; Accepted 31 May 2018 * Corresponding author. Tel.: +90 0532 585 59 44, +90 0312 280 0808. E-mail address: nevintekgul@gmail.com (N. Sanlier). Trends in Food Science & Technology 78 (2018) 95–106 Available online 06 June 2018 0924-2244/ © 2018 Elsevier Ltd. All rights reserved. T