Seed Oils and Thyroid: How PUFAs Influence Energy
Seed Oils and Thyroid: How PUFAs Influence Energy
TL;DR
Your thyroid produces T3 hormone that tells cells to make energy. PUFAs from seed oils block T3 from entering cells. The hormone circulates in your blood but can't reach mitochondria. Your temperature drops below 97.8°F. Energy crashes. Swap seed oils for butter. Track morning temperature. It rises within 2-3 weeks for most people.
You wake up exhausted.
Coffee makes you functional. More coffee keeps you there. By 3 PM you crash.
Your hands are cold even in summer. You gain weight eating the same calories.
Your doctor tests your thyroid. TSH normal. T3 normal. T4 normal.
"Everything's fine," she says.
But you feel hypothyroid.
Your thyroid is a thermostat sending signals. PUFAs jam the wiring. The signal gets sent but never arrives. Your house stays cold.
How Your Thyroid Works
Your thyroid makes T3 and T4. T4 is storage. T3 is active.
T3 enters your cells. Binds to receptors. Tells mitochondria to make energy. More T3 in cells means more ATP production. More heat. Higher body temperature. Faster pulse.
Healthy waking temperature: 97.8°F to 98.6°F. Measured under your tongue before you get up.
Below 97.8°F? Suppressed thyroid function at the cellular level.
Your blood tests measure hormone levels in your blood. They don't measure what's happening inside your cells. You can have normal T3 in blood and low T3 in cells.
This is where PUFAs interfere.
What PUFAs Do
PUFAs oxidize easily. They incorporate into cell membranes. Your cell membranes are supposed to be fluid. Flexible. Allow hormones to pass through.
PUFA-rich membranes are rigid. Less permeable. T3 has trouble passing through. Learn the fundamental difference between PUFAs and saturated fats.
The hormone is in your blood. Your thyroid is making it. But it can't reach the mitochondria where energy production happens.
PUFAs also suppress conversion of T4 to T3. Less active hormone gets made. And what does get made can't enter cells efficiently.
Double block.
Ray Peat spent decades documenting this. He found that polyunsaturated fats suppress metabolic rate independent of thyroid gland function. The gland works. The membranes don't.
Your temperature drops. Your energy drops. You feel cold and sluggish even though your labs look fine.
Where You're Getting PUFAs
Every restaurant cooks with seed oils. Canola. Soybean. Vegetable oil. Cheap. High smoke point. No flavor.
Your salad dressing is soybean oil with vinegar.
Your bread has vegetable oil to stay soft.
Your granola has sunflower oil to get crispy.
Your protein bar has canola oil as a binder.
You're eating oxidized fats three times a day. They accumulate in your membranes. Your thyroid hormone can't get through.
In Germany and Austria, labels say "Rapsöl" (rapeseed/canola) or "Sonnenblumenöl" (sunflower). More transparent than US labels. But restaurants still use cheap oils. Ask before ordering.
What You Do
Stop eating seed oils. Two weeks minimum.
Cook with butter, coconut oil, or ghee. These saturated fats don't oxidize. They create fluid membranes that respond to thyroid hormone properly.
Eat enough carbohydrates. Your body needs glucose to convert T4 to T3. Fruit. Potatoes. Rice. Honey. Orange juice.
Low-carb diets suppress T3 conversion in many people. If you're cold and tired on low-carb, add carbs back. Watch your temperature rise.
Track your waking temperature daily. Same thermometer. Same time. Under your tongue before you move. Full temperature tracking protocol here.
Week 1: Might feel worse. You're clearing stored PUFAs. Headaches. Fatigue. Irritability. Push through.
Week 2: Wake up easier. Hands warmer. Energy more stable.
Week 3: Temperature climbs toward 97.8°F or higher. Pulse strengthens. Brain fog clears. Better temperature rhythm means better sleep too.
This is your thyroid function recovering. Not because you fixed your gland. Because you stopped blocking the hormone.
FAQ
Q: Can seed oils cause thyroid disease like Hashimoto's? A: No. Autoimmune thyroid disease has different causes. But PUFAs suppress thyroid function at the cellular level. Different mechanism. Similar symptoms. Worth addressing either way.
Q: What if I'm already on thyroid medication? A: Keep taking it. Don't stop without your doctor. But eliminating seed oils might help it work better. Better cellular uptake. Track your temperature. Your doctor can adjust your dose if needed.
Q: How long until my temperature rises? A: Most people see changes within 2-4 weeks. Some faster. Some slower. Depends how PUFA-loaded you are and how strict you are about elimination. Track it daily. Look for trends.
Q: What about omega-3 fish oil? A: Also polyunsaturated. Also oxidizes. Fresh fatty fish is different—comes with antioxidants. Fish oil capsules oxidize quickly. Watch your temperature response. If it drops, stop taking it.
This isn't medical advice. I'm not your doctor. If you have diagnosed thyroid disease, work with a professional.
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