Tea, derived from steeping the leaves of Camellia sinensis in water, is the most widely consumed beverage in the world aside from water. It contains high concentrations of polyphenolic compounds. While hot tea has been studied for its potential health benefits, iced tea also offers unique advantages, particularly in the realm of weight management and overall well-being.
Types of Tea and Their Processing
The three major types of tea-black, oolong, and green-differ in terms of processing, chemical composition, and consumption patterns. Green tea is consumed primarily in Japan, China, and a small subset of Middle Eastern and North African countries. During the processing of green tea, fresh leaves are pan-fried to inactivate endogenous polyphenol oxidase, which preserves the characteristic monomeric flavan-3-ols known as catechins. (−)-Epigallocatechin-3-gallate (EGCG) is the most abundant and widely studied green tea catechin. By contrast, during the processing of black tea, fresh leaves are crushed and allowed to undergo oxidation, resulting in the formation of polyphenolic oligomers and polymers known as theaflavins and thearubigins. Black tea is commonly consumed primarily in Europe, India, and the United States. Oolong tea is a product that undergoes an intermediate level of oxidation and is consumed most widely in China.
The Association Between Tea Consumption and Body Weight
Tea and tea polyphenols have been extensively studied for their potential as preventive agents for cancer, heart disease, neurodegenerative disease, and other chronic conditions. A limited number of epidemiological studies have been conducted to determine the association between tea consumption and body weight. Wu and colleagues found that habitual tea consumption (primarily green and oolong) was associated with lower waist: hip ratio in Taiwanese adults; Hughes and colleagues found that black tea consumption was associated with lower BMI in the Netherlands. Most recently, a cross-sectional study between tea consumption and body weight status in US adults was reported by Bouchard and colleagues. The authors found that tea was inversely related to waist circumference, however, the method for evaluating tea intake was relatively weak; the authors used only a single cycle of NHANES, which was not adequately weighted for generalizable analysis. To our knowledge, no studies have been conducted to determine the association between tea consumption and multiple markers for MetS in US adults. Although the current literature derived from weight loss trials are useful in assessing the utility of tea supplementation for improving body weight status in individuals actively trying to lose weight, larger data-sets are needed to evaluate whether regular tea consumption is associated with lower body weight in persons regardless of intentions for weight loss. The objective of this study was to determine the relationship between tea consumption (including black, green and oolong, both hot and iced) and markers for MetS in a representative sample of 5,948 adults (54% female) from the 2003-2006 National Health and Nutrition Examination Survey (NHANES) data. The NHANES is a large, cross-sectional survey conducted by National Center for Health Statistics. NHANES is designed to monitor the health and nutritional status of non-institutionalized civilians in the US; data is collected on a continual basis and released in two-year increments. Data from the 2003-2004 and 2005-2006 NHANES survey cycles were combined for this study to maximize power. These cycles were chosen due to the use of both Food Frequency Questionnaire (FFQ) and 24-hour recall data as methods of dietary assessment.. Specific status codes were used to indicate the quality, reliability, and completeness of the dietary data. One day of dietary recall data was collected by trained interviewers from participants during their visit to the Mobile Examination Unit; a second day of dietary data was collected using an interviewer-administered phone survey. For this analysis, all adults 18 years of age or older were initially included (n=11,183). Adults who did not have 2 had 2 days of reliable 24-hour recall data in addition to FFQ data (n=3,505) were excluded, as well as pregnant and lactating women (n=364) were excluded from this analysis since WC and weight status were primary outcome measures. Participants with abnormal or implausible dietary recall (>7500 kcal/d or <300 kcal/day; n=149), or who reported currently following a weight-loss diet (n=557) were dropped from the analysis in order to maximize accuracy. Participants with missing outcome measures (n=140, i.e.: BMI, WC) were also eliminated, resulting in a final analytical sample of 6,472 (due to overlap of missing components) adults (53% female) for analysis regarding tea consumption and anthropometric measures. Of these adults, a small subset also underwent additional procedures to collect fasting (3,118) blood samples. Age at the time of exam, education level, smoking status (current, former, non-smoker), physical activity (measured in MET units), race and socioeconomic status were all provided in the NHANES data set. Socioeconomic status was quantified as a continuous variable using poverty-income ratio (PIR), or the ratio of family income to family-size specific poverty threshold. Participants were coded into one of four categories of tea consumption for both hot and iced tea: non-consumers (rarely or never drink tea), infrequent consumers (1c/week or fewer), weekly consumers (2-6 c/week), daily consumers (1 c/day), or multiple cups/day. Weight status was assessed using BMI (kg/m2). In both cycles of NHANES, height and weight were measured by trained examiners using standardized protocols and calibrated equipment. Adults were classified as lean (BMI ≤24.9), overweight (BMI of 25.0-29.9) or obese (BMI≥30). Body fatness was evaluated using two measures: WC and skin fold thickness. Blood samples were collected on a smaller subset of the population to asses other markers for MetS. Non-fasting samples were collected on afternoon participants, and included HDL-cholesterol (direct measure; mmol/L), total cholesterol (mmol/L) and C-reative protein (CRP). All blood samples were collected in the CLIA-certified NHAMES Mobile Examination Center (MEC) unit and sent out for analysis. Fasting blood samples were collected on participants who were examined in the morning session and included: serum insulin (pmol/L), serum glucose (mmol/L), serum triglycerides (mmol/L), and LDL-cholesterol, HDL-cholesterol (direct measure; mmol/L), and total cholesterol (mmol/L). Total cholesterol, HDL-cholesterol and triglycerides were sent to the Johns Hopkins University Lipoprotein Analytical Laboratory for analysis. Total cholesterol was measured enzymatically in serum using Roche Hitachi equipment; LDL-cholesterol was calculated according to the Friedewald calculation only in participants with triglycerides less than or equal to 400 mg/dL; specific status codes were assigned to identify these participants. Serum glucose was assessed using the hexokinase method; insulin was assessed with ELISA. In order to accurately categorize regular intake behavior, participant FFQ responses pertaining to tea consumption were analyzed against both days of 24-h recall data. The USDA Food and Nutrition Database, versions 2.0 and 3.0 were used to process NHANES dietary data intake and evaluate tea consumption. Iced tea consumption included prepared bottled iced tea as well as iced tea made from powder or tea bags. These categories were based on the combined responses to FFQ questions regarding tea intake along with 24-h dietary recall data. Chemically, herbal tea is not synonymous to C. sinensis-based tea. Therefore, for the purposes of this study, any subject that reported that they “always or almost always” consume herbal or decaffeinated tea were not considered to be tea consumers. If participants reported occasionally consuming herbal or decaffeinated tea, they were identified as an herbal tea consumer, and herbal tea consumption was used as a covariate in all regression models. All data was analyzed using SAS version 9.3 (SAS Institute, Cary, NC). Specific survey procedures were used in the analysis to account for sample weights, unequal selection probability, and clustered design. Analysis of the subset of fasting subjects required use of different survey weights in order to account for the specific characteristics of this subpopulation. Multivariate regression was used to evaluate the association of tea consumption with health outcomes related to obesity (e.g body mass index, waist circumference, skinfold thickness, serum lipid levels, fasting glucose and insulin, etc.). Sex-specific analysis was conducted to take into account the natural differences in body composition and caloric needs between men and women. Endpoints are adjusted for age, race, family income, education, smoking status, physical activity, total energy intake, total sugar intake, herbal tea consumption, and self-reported disease status. Self-reported disease status was collected during subject interview. Subjects reported if they had a history of a variety of conditions (i.e.: diabetes), and each condition that is specific to the outcome measure was included in that model. For example, self-reported diabetic (i.e.: subject reported diabetic status, but did not have a medical history of diabetes) was a covariate for models assessing fasting blood glucose; self-reported high cholesterol without a medical history of high cholesterol was included for serum lipids). Medically diagnosed conditions were excluded for corresponding variables (i.e.: an individual with a medical history of diabetes was excluded from analysis of fasting glucose and insulin, but not BMI or waist circumference). Results are presented as least-squared means and standard errors, with significance determined at P <0.05. Demographic characteristics are presented in Table 1. The majority of this sample of US adults were white (76%), and racial breakdown was similar to the US population. Approximately two-thirds of the population was overweight or obese. In this sample of US adults, 57% (n=3,506) reported some sort of hot tea consumption; 9% (n=603) consumed hot tea daily (Table 1). In contrast, 70% (n=4,244) reported consumption of iced tea. In order to evaluate the relationship of tea and body weight independently of other dietary factors, macronutrient intake, energy intake, caffeine intake and percentage of dietary fat were also examined. No significant differences in caffeine intake or macronutrient intake were observed between any of the categories of hot tea or iced tea consumption. Women who consumed multiple cups of hot tea daily had significantly higher total energy intake than non-consumers; men who consumed hot tea daily had significantly lower total energy intake, and lower sugar intake than non-consumers; as such, total energy and total sugar intake were included as covariates in all regression models. When examining the association between hot tea and various anthropometric measures, tea consumption was inversely associated with BMI in both men and women after controlling for age, race, income, education, smoking status, total energy intake, sugar intake, alcohol intake, herbal tea consumption and physical activity (Table 2). A linear decrease in BMI was observed in both sexes: women in the highest category of tea consumption had the lowest BMI (26.2 vs. 28.5 for non-consumers); the same relationship was observed in men (25.4 vs. 27.9).
Iced Tea and Weight Management
Iced tea can be a valuable addition to your weight management journey. Compared to sugary beverages like soda or fruit juices, unsweetened iced tea is low in calories and natural sugars, making it a healthier alternative. It can also help control food cravings and manage hunger. Plus, when it comes to weight loss, the number of calories you consume plays a crucial role, and by choosing unsweetened iced tea youcan enjoy a refreshing beverage without extra calorie intake. Unsweetened iced tea can also help keep you feeling full, thanks to its liquid volume. Staying properly hydrated is important for weight loss as it can help reduce hunger and prevent overeating.
The Role of Catechins
Teas contain catechins, which can increase metabolism by stimulating the body to break fats down more quickly and burn more calories. Catechins are a type of plant compound with powerful antioxidant properties. Tea is especially rich in four catechins: epicatechin (EC), epigallocatechin (EGC), epicatechin gallate (ECG), and epigallocatechin gallate (EGCG). Of these four, EGCG is the most abundant, and it is thought to contribute most to the many health benefits of tea, according to a review.
Read also: Make Your Own Iced Green Tea
The Impact of Added Sugar
It's important to note that the benefits of iced tea for weight loss are contingent on it being unsweetened. Adding sugar or artificial sweeteners can negate these benefits and potentially lead to weight gain.
Health Benefits of Unsweetened Iced Tea
Unsweetened iced tea offers a range of health benefits beyond weight management:
Heart Health
Unsweetened iced tea can be a refreshing and beneficial beverage for lowering the risk of heart disease and stroke. The polyphenols (compounds naturally found in plant foods) and flavonoids in unsweetened tea help relax and dilate blood vessels, helping to maintain healthy blood pressure levels. High blood pressure is a risk factor for heart disease and stroke, so regularly consuming unsweetened iced tea can help reduce this risk. Research suggests that the flavonoids found in tea, particularly black and green tea, possess cardioprotective properties. These antioxidants help reduce the risk of heart disease by improving blood vessel function, lowering blood pressure, and reducing LDL cholesterol levels.
Diabetes Prevention
Drinking unsweetened iced tea can offer several benefits when it comes to reducing the risk of diabetes. Not only does it help regulate blood sugar levels, the antioxidants present in iced tea can contribute to better overall health and help reduce the risk of diabetes. These antioxidants, such as flavonoids and polyphenols, have been found to decrease cellular damage and inflammation in the body. By protecting cells from damage, these antioxidants can support healthy insulin sensitivity and glucose metabolism. According to the National Institute of Health, research also indicates that one of the polyphenols in black tea called epigallocatechin gallate (EGCG) can inhibit enzymes that break down carbohydrates, slowing down their absorption and stabilizing blood sugar levels, haveing "antiobesity and antidiabetic effects".
Mental Alertness and Focus
The natural caffeine content in unsweetened iced tea can provide a boost in alertness and mental focus without the jitters associated with other caffeinated beverages like coffee and soda. Caffeine acts as a natural stimulant that can enhance mental alertness, increase attention, and improve focus. In addition to caffeine, unsweet tea contains L-theanine, an amino acid that has calming and relaxing effects. L-theanine works with caffeine to promote a state of focused relaxation without causing drowsiness. Iced tea, particularly green and black teas, contains L-theanine, an amino acid known for its calming and focus-enhancing effects. The combination of L-theanine and caffeine found in iced tea promotes a state of alert relaxation, improving cognitive performance, attention, and memory.
Read also: Guilt-Free Refreshment: Lipton's Mix
Skin Protection
The antioxidant properties of unsweetened iced tea can help protect your skin from the harmful effects of UV rays. Sun exposure can lead to the production of free radicals in the skin, which can damage cells and contribute to premature aging. By consuming unsweetened tea regularly, you can increase your intake of antioxidants, which may help neutralize these free radicals and reduce the risk of sun-related skin damage. The polyphenols found in black tea can also improve skin elasticity to help promote a more youthful appearance and reduce the appearance of fine lines and wrinkles.
Digestive Health
Unsweetened iced tea not only offers numerous benefits for your skin, but it can also provide support for your digestive system and promote improved gut health. The polyphenols found in black tea have been shown to have a positive impact on the balance of bacteria in the gut. Tea's polyphenols act as prebiotics that provide nourishment for beneficial bacteria in the gut.
Source of Manganese and Fluoride
Manganese is a trace mineral that is found in your bones, liver, kidneys, and pancreas. According to the Icahn School of Medicine at Mount Sinai:“Manganese helps the body form connective tissue, bones, blood clotting factors, and sex hormones. It also plays a role in fat and carbohydrate metabolism, calcium absorption, and blood sugar regulation. Manganese is also necessary for normal brain and nerve function.” An 8-ounce serving of unsweetened iced tea provides 520 micrograms of manganese, which is 23 percent of the daily recommended intake for men and 35 percent for women. The manganese in unsweetened iced tea helps maintain the strength of your bones and promotes healthy wound healing. As you may recall from your grade-school health class, fluoride helps build strong bones and teeth. An 8-ounce glass of unsweetened tea that’s brewed with fluoridated water contains about 1 mg of fluoride. (The daily recommended amount, according to the National Institutes of Health Office of Dietary Supplements, is between 3 to 4mg for adults over the age of 19.) So drinking unsweetened tea is a great way to fight tooth decay and keep your bones strong.
Making Iced Tea for Weight Loss
To maximize the weight loss benefits of iced tea, follow these tips:
- Choose unsweetened tea: Avoid adding sugar or artificial sweeteners.
- Opt for green tea: Green tea is particularly rich in catechins, which can boost metabolism and fat burning.
- Brew your own: This allows you to control the ingredients and avoid added sugars or artificial flavors found in some bottled iced teas. Susan Powers, who used the sweet tea to lose 87 lbs and 14 inches from her waist, brewed and cooled green tea, which she read could help with metabolism. Swirling in the syrup, she took a zero-calorie sip.
- Drink it regularly: Aim for 4 to 6 cups daily, but switch to decaf after 3 pm to avoid sleep disturbances.
Iced Tea Recipes
- Basic Iced Green Tea: Steep 5 green tea bags in 24 oz of hot water for 5 minutes. Remove bags and chill.
- Flavored Iced Tea: Add slices of lemon, cucumber, or mint to your iced tea for a refreshing twist.
- "Sweet Tea" with Skinny Syrup: For hot tea, steep 1 bag green tea in 8 oz. boiling water for 5 minutes. For iced tea, steep 5 bags in 24 oz. Remove bags and transfer to a pitcher; stir in syrup (sold at discount stores and SkinnyMixes.com). Chill.