Research on green tea and thyroid disease suggests it is safe to drink in moderation. However, green tea extracts may be problematic for people with thyroid disease and should be avoided. In addition, compounds in green tea may interact with thyroid medication.
Green tea is touted as a weight-loss booster. People with hypothyroidism often struggle to keep their weight down. While green tea may help, people with thyroid disease should take a few precautions before adding green tea to their diet.
This article discusses green tea and thyroid disease. It explores how green tea may boost weight loss. It also explains what people with thyroid disease should know about green tea and how to enjoy it safely.
How Green Tea Helps With Weight Loss
When your thyroid isn’t producing enough hormones, your metabolism slows down, reducing the number of calories your body burns and often leading to weight gain. Simply put, green tea may help to increase your metabolic rate so that you burn more calories.
Research shows that green tea extract boosts your metabolic rate while also promoting fat burning. While scientists initially attributed this to caffeine, additional studies found bioactive ingredients in green tea may increase metabolism and fat oxidation.
Catechins, a type of flavonoid found in green tea, can help to break down excess body fat. Caffeine and catechins appear to work synergistically to increase the amount of energy the body uses.
While all this sounds encouraging, it is important to keep things in perspective. Even in the studies that found weight loss among those drinking green tea, the degree of weight loss was quite small.
In fact, if you put sugar in your green tea, the added calories will cancel out the extra calories you may burn.
Green Tea and Thyroid Health
Research is unclear on the impact of green tea on thyroid health. In animal studies, green tea has been linked to both improvements and worsening of thyroid conditions.
Some studies found green tea may suppress thyroid function and increase the risk of goiters. Other studies found green tea extract may promote thyroid healing. However, both of these studies were performed on rats, and it is unclear how this may translate to humans.
In vitro studies also suggest compounds in green tea may be beneficial for Hashimoto’s thyroiditis, an autoimmune disease.
Green tea extract was found to activate thyroid peroxidase in the laboratory. These findings, researchers said, suggest green tea may promote thyroid health for people with under-active thyroids.
While these studies are promising, clinical trials are needed to show how green tea may impact thyroid health in humans.
Green Tea and Thyroid Cancer
Green tea has been touted as having anti-cancer properties, and some research suggests that consuming it may cut the risk of thyroid cancer specifically.
In one meta-analysis published in the International Journal of Clinical and Experimental Medicine in 2015, scientists reviewed 14 studies involving more than 100,000 subjects, almost 3,000 of whom had thyroid cancer.
The researchers found a strong association between higher tea consumption and a reduced risk of thyroid cancer. Additional studies suggest drinking any kind of tea may reduce the risk of thyroid cancer.
However, it is unclear as to whether compounds in the tea are solely responsible for the reduction in risk or if the anti-cancer benefits are due to the fact that people who drink green tea may be more likely to adopt a healthier lifestyle in general.
Side Effects
Green tea is generally thought to be safe for thyroid patients. In this respect, it is different from some of the prescription drugs for obesity, as well as herbal products like ephedra, which can raise heart rates and blood pressure and are not recommended for those with thyroid disease.
There have been some studies, however, that suggest consuming large doses of green tea in extract form can have adverse effects on the thyroid by reducing levels of T3 and T4 in the blood while significantly raising TSH levels.
It’s important to note, though, that this research was done on rodents, so the findings are not necessarily applicable to humans.
Green Tea Extract and Thyroid Disease
While drinking a cup or two of green tea a day is very likely harmless, taking green tea extract may be another story.
Green Tea and Levothyroxine
Green tea may interfere with the thyroid medication levothyroxine. Research shows caffeine in different types of tea can inhibit the absorption of the medication.
Several studies using green tea extract (which greatly concentrates the catechins found in green tea) have reported signs of liver damage. It may not be safe for people with thyroid disease to take green tea extract.
Tea How-Tos
There are no official guidelines on how to incorporate green tea into your diet. It’s available in several forms, such as tea bags, loose tea, supplements, extracts, and in iced tea products. Except for supplements and extracts (which may be toxic if overused), any of these forms of green tea would be fine.
While green tea contains significantly less caffeine than coffee, it still supplies 30 mg to 40 mg per cup. Caffeine is known to inhibit proper absorption of the common thyroid hormone replacement drug levothyroxine. If you are taking this medication, it’s best to wait 30 minutes before consuming green tea.
A Word From Verywell
While green tea may have some metabolism-boosting effects, it is only meant to be taken in conjunction with standard weight-loss programs, and will not help you lose significant amounts of weight on its own.
Also, green tea extracts and supplements, in particular, are not regulated by the Food and Drug Administration and may provide toxic levels of catechins. It is best to avoid these forms of green tea altogether.
