Underactive Thyroid, Diet and Alcohol

What you eat and drink has a direct impact on thyroid health. Hypothyroidism and alcohol, for instance, don't mix. Heavy drinking may affect the production of thyroid hormones and make things worse.

Approximately 20 million Americans have thyroid disease. About 60 percent of them are undiagnosed. But that's not all — more than 12 percent of the population will experience thyroid problems at some point, reports the American Thyroid Association. Most issues affecting this gland require lifelong treatment. An underactive thyroid, or hypothyroidism, is often blamed for weight gain, fatigue, depression and joint pain, among other symptoms.

This disorder can also lead to fertility problems, high cholesterol levels and heavy menstrual periods, according to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). It occurs when the thyroid gland produces too much TSH (thyroid-stimulating hormone) and too little T4 (thyroxin). These hormones influence your metabolism, heart rate and other vital functions.

​Read more:​ Could Your Thyroid Be the Culprit? Everything You Need to Know About Thyroid Disease

It's estimated that five out of 100 Americans have an underactive thyroid. People assigned female at birth (AFAB), older adults and people with autoimmune disorders, pernicious anemia or a history of thyroid disease are at greater risk. Genetics play a role too, points out the NIDDK.

This condition can affect people of all ages, and its exact cause is unknown. Medical professionals believe that hypothyroidism may be due to iodine deficiency or iodine excess, thyroiditis, thyroid surgery, radiation therapy or some medications. Sometimes, it may occur during or after pregnancy when the immune system produces antibodies that attack this gland.

According to a July 2017 cohort study published in ​Scientific Reports​, metabolic syndrome may increase the risk of subclinical hypothyroidism. The latter condition is characterized by low T4 concentrations and affects up to 4 percent of the population. Lifestyle changes, such as losing weight, cutting down on sugar and engaging in regular exercise, may protect against metabolic syndrome and hence reduce the odds of developing thyroid disease.

Clearly, lifestyle plays a role in the onset of thyroid problems. Everything from the foods you eat to your stress levels and exercise habits can affect this butterfly-shaped gland. In fact, alcohol consumption and thyroid are strongly connected, according to a review featured in the ​Indian Journal of Endocrinology and Metabolism​ in July-August 2013.

Heavy drinking has been linked to over 60 different diseases. It's also a major contributing factor in another 200 conditions, as the researchers point out. It affects every organ in your body, including the thyroid gland. Current evidence suggests that alcohol suppresses the production of T3 (triiodothyronine, another primary thyroid hormone) and T4 while reducing thyroid volume.

​Read more:​ 9 Scary Side Effects of Social Drinking

Scientists have also identified a link between alcohol use and thyroid cancer. Surprisingly, regular drinking may decrease the risk of developing this condition. In the large-scale study cited in the ​Indian​ ​Journal of Endocrinology and Metabolism​ review, thyroid cancer risk was significantly lower in subjects who consumed two or more drinks per day.

The protective effects of alcohol are associated with its ability to prevent the proliferative action of thyroid-stimulating hormone (TSH) on the thyroid follicle. Furthermore, drinking up to three units of alcohol per day may help protect against autoimmune hypothyroidism, reports a study published in the ​European Journal of Endocrinology​ in October 2012.

There are 8 grams or 10 milliliters of pure alcohol in one unit, so three units equal 24 grams or 30 milliliters. A glass of wine, for instance, contains 2.1 units of pure alcohol, meaning that you'd have to drink one and a half glasses to reap the benefits. That's pretty much in line with the Dietary Guidelines for Americans, 2015-2020, which recommends up to one drink per day for people AFAB and two for people assigned male at birth (AMAB).

Most studies on the relationship between hypothyroidism and alcohol consumption are conflicting. For example, the review published in the ​Indian Journal of Endocrinology and Metabolism​ states that alcohol use may suppress thyroid hormone production in chronic alcohol users. Yet, it may protect against autoimmune hypothyroidism.

A small study featured in the June 2018 edition of ​Frontiers in Endocrinology​ assessed the effects of moderate to severe drinking on thyroid function in pregnant people. As the researchers note, excessive alcohol use may reduce the levels of T3 and T4, the primary thyroid hormones. Furthermore, alcohol consumption during pregnancy may suppress the baby's TSH levels.

Moderate to heavy drinking can alter maternal thyroid function, according to the above study. It has been linked to increased serum-free T3 levels, which may affect the infant's social-emotional development. Children born from abstinent pregnant people with elevated serum-free T4 levels, by contrast, tend to score higher on cognitive tests. This association was not observed in mothers who consumed alcohol.

These findings indicate that alcohol intake affects expectant mothers differently than the general population. Additionally, thyroid hormone levels produce different cognitive outcomes in babies born to people who drink during pregnancy and those born to people who abstain.

As mentioned earlier, hypothyroidism is characterized by high TSH levels and low T4 levels. Most studies suggest that heavy drinking may suppress T4 production, as noted in the ​Indian Journal of Endocrinology and Metabolism​ review. Therefore, it may contribute to this disorder and alter thyroid function. At the same time alcohol may have a protective effect on the thyroid gland due to its ability to suppress TSH.

Based on the current evidence, it's hard to determine how alcohol use affects thyroid health. If you have an underactive thyroid, discuss the risks of drinking with your physician. A medical professional can check your blood tests, assess your diet and help you make an informed decision.

Beware that alcohol can interact with levothyroxine, a drug used to treat this condition. This medication contains a synthetic form of the thyroid hormone T4. Like most medications, it's processed by your liver. If you drink regularly, you may develop liver disease, which in turn, may affect levothyroxine metabolism, warns the American Association of Endocrine Surgeons.

​Read more:​ Levothyroxine and Vitamin Supplements

As with everything else, moderation is the key. Try not to exceed one to two drinks per day. Occasional drinking is unlikely to affect your thyroid. Heavy alcohol use, on the other hand, may not be safe, especially for individuals with thyroid disorders and those who are prone to hypothyroidism.