Using Green Tea for Weight Loss if You Have Thyroid Disease

Green tea with Mint.
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If you have hypothyroidism, it can be a struggle to lose weight, even if you're being adequately treated with medication. One of the more popular natural products you may be tempted to try for weight loss is green tea. It may indeed have some benefit to this end, but there are some special precautions those with thyroid disease need to take.

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.

In a 2008 study published in the American Journal of Clinical Nutrition, it was found that green tea extract resulted in a significant increase in energy expenditure and also had a significant effect on fat burning. While some of the effects were originally thought to be due to the caffeine content of green tea, the researchers discovered that the tea actually has properties that go beyond those that would be explained by the caffeine.

The same amount of caffeine as was in the green tea, administered alone, failed to change energy expenditure in other studies as well. This led researchers to believe that there is some interaction going on with the active ingredients of green tea that promotes increased metabolism and fat oxidation.

Additional research attributes the metabolism-boosting effect to the combination of caffeine and catechin, a type of flavonoid found in green tea. A 2010 study in the Journal of Physiological Behavior, for example, found that catechin can help break down excess fat, while both catechin and caffeine can 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 drink your green tea with sugar, the calories you are adding will overwhelm any additional calories you may burn.

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.

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.

While drinking a cup or two of green tea a day is very likely harmless, taking green tea extract may be another story. Several studies using green tea extract (which greatly concentrates the catechins found in green tea) have reported signs of liver damage. It is a bad idea 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 25 mg to 29 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.

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