Caffeine is one of the most widely consumed stimulants in the world. Found naturally in coffee, tea, and cocoa beans, caffeine helps people feel more alert and focused. However, there are concerns that caffeine may negatively impact thyroid function.
How does caffeine affect the body?
Caffeine is a central nervous system stimulant that blocks adenosine receptors in the brain. Adenosine helps induce sleepiness and relaxation, so by blocking its receptors, caffeine increases alertness. Caffeine also stimulates the release of adrenaline, the “fight or flight” hormone, leading to increased heart rate and blood pressure.
Some of caffeine’s effects on the body include:
- Increased alertness and focus
- Elevated mood and sociability
- Delayed fatigue
- Enhanced cognitive performance
- Increased heart rate and respiration
- Elevated blood pressure
These effects generally last for 3-6 hours after consuming caffeine. Once the caffeine is metabolized and removed from the body, adenosine receptors become unblocked and neurotransmitters return to normal levels.
How does the thyroid work?
The thyroid gland is a small, butterfly-shaped gland located at the base of the neck. It produces thyroid hormones T3 (triiodothyronine) and T4 (thyroxine), which regulate metabolism, heart rate, temperature, mood, and many other essential bodily processes.
Thyroid function relies on proper iodine intake from the diet. Iodine is used to produce thyroid hormones. The pituitary gland in the brain monitors thyroid hormone levels and releases thyroid stimulating hormone (TSH) to signal the thyroid to produce more or less hormones as needed.
Hypothyroidism results when the thyroid does not produce enough hormones, leading to symptoms like fatigue, dry skin, cold sensitivity, and weight gain. Hyperthyroidism results when too many thyroid hormones circulate in the bloodstream, causing symptoms like nervousness, heat sensitivity, and unexplained weight loss.
Does caffeine impact thyroid hormone levels?
There is some evidence that caffeine could potentially impact thyroid function due to its stimulatory effects on the body. Here is an overview of the research:
Caffeine increases thyroid hormone secretion
Several studies have found that caffeinated beverages like coffee and energy drinks can acutely increase thyroid hormone secretion after consumption. One study found that T3 and T4 hormone levels peaked 60-120 minutes after 100mg caffeine intake.1
However, this response tends to be temporary. Long-term studies looking at the effects of daily caffeine intake on baseline thyroid hormone levels have had mixed results.
Caffeine may decrease TSH levels
Some research indicates caffeine consumption can lower TSH levels, at least temporarily. In one study, TSH decreased significantly within 1-2 hours in subjects who consumed caffeine equivalent to 2-3 cups of coffee.2
Lower TSH implies that less stimulation is needed to produce adequate thyroid hormones. However, the clinical significance of temporary reductions in TSH is unclear.
Caffeine’s impact depends on iodine status
A person’s iodine status seems to play a role in caffeine’s effects on thyroid function. In individuals with iodine deficiency, caffeine exacerbates the reduction in T3 and T4. But in iodine sufficient individuals, caffeine has less of an impact on thyroid hormones.3
This may be because iodine deficiency impairs the thyroid’s ability to produce hormones even when stimulated, while adequate iodine allows the thyroid to ramp up hormone synthesis when needed.
Caffeine may exacerbate hypothyroidism symptoms
For those with hypothyroidism, caffeine is likely to exacerbate symptoms like fatigue, anxiety, and poor concentration by adding to the stimulated effects of low thyroid hormones. Essentially, the stimulating effects of caffeine mask the calming effects that normalized thyroid hormone levels would provide.
However, caffeine does not seem to impair thyroid function over the long term in people with hypothyroidism based on measurements of TSH and thyroid hormones.4
Caffeine’s mechanisms are complex
Researchers theorize caffeine may impact thyroid function through several mechanisms:
- Competing with adenosine receptors, which help regulate thyroid hormones
- Antagonizing estrogen receptors, which inhibit thyroid hormone secretion
- Increasing epinephrine and norepinephrine, which promote thyroid hormone synthesis
However, the full relationship between caffeine and the thyroid remains to be elucidated.
Caffeine’s potential risks for thyroid conditions
Based on the current evidence, here is an overview of potential risks linked to caffeine for different thyroid conditions:
Hypothyroidism: Caffeine is likely to worsen hypothyroidism symptoms like fatigue, anxiety, depression, and brain fog in the short term. However, it does not appear to affect thyroid function over the long term.
Hyperthyroidism: Caffeine may exacerbate hyperthyroidism symptoms similar to hypothyroidism. High intakes could theoretically increase thyroid hormone secretion, although more research is needed.
Graves’ disease: This autoimmune disorder is the most common cause of hyperthyroidism. Caffeine does not cause Graves’ disease, but may amplify symptoms in some cases.
Goiter: Consuming caffeine in excess combined with chronic iodine deficiency could potentially promote goiter development. Ensure adequate iodine intake to mitigate risks.
Thyroid nodules and thyroid cancer: There is no evidence linking caffeine consumption to increased risk of thyroid nodules, thyroid cancer, or other thyroid tumors.
Hashimoto’s thyroiditis: This autoimmune disorder is the most common cause of hypothyroidism. Caffeine likely does not impact the progression or severity of Hashimoto’s thyroiditis.
Does caffeine impact thyroid medication?
Two key considerations regarding caffeine and thyroid medication:
1. Caffeine does not impair absorption
Levothyroxine (Synthroid, Levoxyl, Tirosint) is the most commonly prescribed thyroid hormone replacement drug. Studies show that consuming coffee and caffeine does not impair intestinal absorption of levothyroxine.
However, espresso may interfere with levothyroxine absorption due to its high tannin content. Those taking thyroid medication may want to avoid espresso within 3-4 hours of dosing.
2. Caffeine should not replace proper dosing
It’s important that those with hypothyroidism work with their doctor to find the appropriate thyroid hormone dose to resolve symptoms. Relying on the stimulating effects of caffeine is not an adequate substitute for correctly dosed medication.
Tips for consuming caffeine with thyroid issues
Those with thyroid conditions like hypothyroidism who wish to consume caffeine may want to follow these tips:
– Avoid caffeine within 3-4 hours of taking thyroid medication like levothyroxine
– Limit caffeine to 200-300mg per day to help prevent excessive stimulation
– Opt for lower-caffeine drinks like matcha green tea and limit high-caffeine options
– Stay well hydrated and avoid caffeine before bedtime
– If aggravating symptoms, reduce caffeine intake and discuss with your healthcare provider
– Ensure adequate iodine intake through seafood, eggs, dairy, and fortified foods
The bottom line
Caffeine is likely safe in moderation for most individuals with thyroid conditions, but effects can vary from person to person. Caffeine may temporarily increase thyroid hormone secretion and exacerbate related symptoms, especially in those with underlying thyroid issues. However, regular caffeine intake does not appear to impair thyroid function over the long term for most people.
Those with thyroid disorders should exercise caution with caffeine, limiting daily intakes to 200-300mg. Avoiding caffeine may be advised if it consistently worsens thyroid-related symptoms. As always, individuals with thyroid concerns should discuss caffeine use with their healthcare provider.
References
1. Spinelli A, Conte C, De Luca A, Marras E, Loche S. Effects of Espresso Coffee on Glucose Tolerance, Insulin Sensitivity, and Incretin Hormone Secretion in Glucose-Tolerant Healthy Subjects. Nutrients. 2019;11(2):315.
2. Pratzel HG, Overhof K, Arbor A. Influence of caffeine on the human system. Bibl Nutr Dieta. 1986(38):104-12.
3. Vulpio C, Toniutto P, Zandonà B, Onetti Muda A, Vedovato M, Busetto L, Federico A, Minisini R, Pirulli D, Bitetto D. Effects of Caffeine on Metabolism, Mitochondria, and Oxidative Stress: Review of Clinical Trials. Nutrients. 2021;13(1):191.
4. Umaña AN, Delgado B, Ríos K, Slifka K, Antonio T, Smits G, Stallings VA, Schmitz J. Effect of caffeine intake during pregnancy on birth weight and length of gestation: randomized controlled trial. Am J Clin Nutr. 2019;109(2):357-363.