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Conjugated Linoleic Acid and Thyroid


Conjugated Linoleic Acid and Thyroid


DISCLAIMER: This article has been written for informational and educational purposes only and is not intended to be a substitute for professional medical advice, diagnosis, or treatment.

People suffering from thyroid diseases are often prescribed dietary and herbal supplements. These supplements are either used for underactive thyroid (hypothyroidism) or overactive thyroid (hyperthyroidism). Conjugated linoleic acid is one of those dietary supplements people use for thyroid diseases.

This article details conjugated linoleic acid, its potential benefits for the thyroid, and possible risks or side effects associated with overconsumption.

What is Conjugated Linoleic Acid?

Conjugated linoleic acid is a dietary supplement with polyunsaturated fatty acid. CLA is often prescribed as a weight loss supplement due to its ability to burn fats. Beef and dairy products are good sources of this essential fatty acid. It is a potent antioxidant and anti-inflammatory compound and offers a variety of benefits to the body. It helps prevent cancer, restrict the hardening and narrowing of arteries, manage weight loss, help bodybuilding, and decrease allergic reactions.

Dietary fats including omega-6 fatty acids affect thyroid hormone and keep a balance between T3, T4, and thyroxine which play an essential role in metabolism. It is, therefore, necessary to take these healthy fats in adequate quantities to avoid any health problems.

Is CLA Effective for Thyroid?

For optimal thyroid functions, various dietary supplements are prescribed that help people with hypothyroidism and hyperthyroidism. Several studies revealed that dietary fats are an essential component of our diet and provide various benefits to the body.

It is also observed that excessive consumption of linoleic acid may affect the functions of the endocrine system. High fat consumption may lead to thyroid dysfunction leading to hypothyroidism. However, the exact mechanism of the development of thyroid diseases is still unclear.

The thyroid gland is a crucial gland that secretes thyroid hormone and involves in differentiation, growth and development, and metabolism. Studies revealed that the consumption of healthy fats helps improve thyroid function.

How Does It Work?

Maintenance of thyroid health is essential for normal growth and development and healthy fats like linoleic acid seem to be beneficial in maintaining thyroid health. The hypothalamus-pituitary thyroid axis regulates the production and secretion of thyroid hormones. The pituitary gland regulates thyrotropin levels (TSH) in response to feedback from free thyroxin and triiodothyronine and serves as an advanced biosensor of thyroid hormone levels. As the amount of thyroid hormone in the blood decreases, TSH is released by the pituitary gland. TSH stimulates the production of thyroid hormone and releases through particular receptors on the thyroid follicular cell membrane. Several molecules like sodium iodide symporter, thyroglobulin, and thyroperoxidase are involved in hormone synthesis.

What Does Research Say?

Several studies were conducted to evaluate the effects of fat consumption on thyroid hormones. Only a few studies have shown that animals fed a high-fat diet experienced changes in thyroid hormone levels. In a study, a high-fat meal in mice caused raised blood TSH levels but TT3 and TT4 levels were in the normal range. In another study, there was a drop in serum T3 and T4 levels after the consumption of a high-fat diet.

In another study in mice, the effect of dietary fat on thyroid hormone was observed. Hyperthyroidism was induced by adding thyroid hormones T3 and T4 to drinking water. Mice with hyperthyroidism and normal thyroid function were given a diet that included 18% w/w total lipids containing different fatty acid compositions. Diets contained low saturated fats and high polyunsaturated fats, like linoleic acid or low saturated fats with low linoleic acid. The diet was given for 21-22 days and changes were observed.  Results revealed that GPDH levels were high in mice with normal thyroid function. However, mice with low saturated and high linoleic diets showed a remarkable increase in GPDH activity.

However, some of the studies revealed conflicting results showing that a diet rich in fats does not affect the levels of thyroid hormone. In a study, a saturated or unsaturated fat up to 13.6% of weight or 30% of the calorie content of an iodine-deficient diet was given and results showed no hyperplasia of the thyroid.

Other Benefits of Conjugated Linoleic Acid

Besides affecting thyroid health, conjugated linoleic acid offers a variety of benefits to the body.

Helps Burn Fat and Lose Weight

CLA supplements are often prescribed as weight loss supplements due to their ability to burn fats and increase feelings of fullness. According to a study, consumption of conjugated linoleic acid restrict calorie consumption, boost fat burning, increase fat breakdown and prevent fat production ultimately leading to weight loss.

Help in Bodybuilding

There is limited research on the effects of conjugated linoleic acid on bodybuilding. However, it is believed that the consumption of CLA supplements leads to decreased body fat and improved lean body mass.

According to a study, individuals were instructed to consume 1.8 mg of CLA for 12 weeks and they did work out for 90 minutes 3 days a week. Results revealed that CLA supplements helped reduce body fat and restrict fat deposition.

May Improve Heart Health

Atherosclerosis is a condition resulting from the deposition of fat in the arteries and is the main risk factor for heart disease. A study revealed that CLA supplements may reduce the risk of atherosclerosis and improve heart health.


There is no standard dosage of CLA supplements, however, most studies have used 3.2-6.4 g per day. Some studies suggest that a dosage of up to 3g is effective for weight loss.

It is observed that a dosage of 6g per day is safe and well tolerated without causing any side effects.

Potential Risks or Side Effects

Studies revealed that small amounts of CLA from food provides various benefits. However, CLA prepared from vegetable oils may cause possible risks in some people.

Excessive consumption of CLA supplements may increase the deposition of fat in the liver leading to the metabolic syndrome called diabetes.

Some studies suggest that increased consumption of CLA supplements may cause inflammation, increase insulin resistance and decrease HDL levels which is good cholesterol.

It is noted that animal studies used higher doses of these supplements compared to those prescribed to humans.

Some people may experience moderate side effects like diarrhea, constipation, indigestion, upset stomach, and insulin resistance.

Some studies suggest that CLA supplements also worsen the symptoms of fatty liver disease.

Bottom Line

Conjugated linoleic acid is a dietary supplement prescribed for various health conditions. They help improve thyroid health, promote weight loss, increase fat burning, help build lean body mass, and reduce the risk of atherosclerosis and heart attack. They may interact with some medications and should be used with extensive care.

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Williams Textbook of Endocrinology