Herbal "diet teas" for weight loss — Herbalicious?

Dear Tea and Bowels,

Without knowing the ingredients that are in your friend's tea, it is hard to predict the long term effects of drinking it regularly. However, we can talk in generalities: the products senna, aloe, rhubarb root, buckthorn, and castor oil have been used for centuries to help with constipation and bowel movements. These items are commonly found in many so-called "diet teas." Drinking or eating an excess of products that contain these ingredients may lead to loose, watery stools, as well as more serious side effects like vomiting, nausea, persistent diarrhea, abdominal cramps, and even fainting and dehydration.

Some dieters believe that having diarrhea (a result of the laxative) means fewer calories are being absorbed by the body, but this is not the case. Calorie absorption occurs in the small intestine, the area of the body's digestive tract that comes before the colon. Laxatives (herbal or otherwise) tend to work on the colon, and would therefore have very little to no effect reducing how many calories one is taking in. One danger of overusing laxatives is that the colon can become dependent on them in order to have a successful bowel movement, known as a lax colon. In some extreme cases, the colon shuts down completely and must be removed. Other side effects of long-term use include electrolyte disorders, chronic pain, and even constipation.

The laxative effect of these teas may be marketed as "natural bowel cleansers" on the tea's package. One may experience temporary weight loss when drinking these teas, because the teas rid the body of excess water. This weight loss will be reversed once s/he drinks something.

In addition to the products listed above, bulk-producing agents, such as methylcellulose, psyllium, and agar are often added to diet products because they are supposed to produce a sense of fullness in the gastrointestinal tract, thus suppressing appetite. These agents swell when mixed with water and are much more effective as laxatives than as appetite suppresants. Glucomannan, a bulk-producing starch derived from konjac tubers, is often touted by health food enthusiasts as a "natural" weight loss method. There is no evidence that glucomannan or any other bulk producer reduces appetite or produces weight loss.

Some herbal diet teas claim to work by suppressing the appetite while simultaneously increasing metabolism. These teas are most commonly marked as the naturally caffeinated black or green teas, as well as Guarana, Kola Nut, and Ma Huang. There is still very little evidence to prove that caffeine can boost one's metabolism, although it may increase energy levels in some people. These teas have been shown to increase anxiety, restlessness, insomnia, and headaches.  

Your friend may be able to lose weight by drinking tea if she is substituting regular tea in place of high-calorie beverages such as sodas or juices. In this scenario she could be losing weight because of a reduction in her daily caloric intake, rather than a laxative or appetite suppressing effect from the tea. If she is looking for other ways to lose weight, you may want to suggest that she visit a registered dietitian or other health care professional for advice on how to do so safely.

Good luck giving your friend the skinny on dieter's tea!