What’s the link to thyroid function and carbs?

A massive one apparently!  Many of us seem to know little about this, until we undertake a low carb, Keto or Carnivore diet and our thyroid tanks, our metabolic rate declines, weight gain increases along with other issues and we’re left wondering why.

Delving into a pro metabolic diet for the last 8 or so years has enlightened me as to why thyroid function and carbs are so important and I’ve found an article that explains it perfectly – so our pro metabolic crew can learn as well.

It’s from a website called Chews Food Wisely…

“If you’ve been told to cut carbs to “fix” your thyroid, I want you to lean in for a second—because the truth is, the exact opposite might be what your body actually needs.

I work with women every day who are exhausted, bloated, constipated, foggy and stuck—despite following “clean eating” plans and cutting carbs in the name of health. Their thyroid labs might even come back looking “normal.” But they still feel anything but normal.

Here’s the thing no one is talking about: Your thyroid doesn’t just need nutrients to function. It needs fuel. And that fuel is glucose—the simplest form of carbohydrates.

The Carb + Thyroid Connection

Your thyroid is responsible for producing hormones that regulate energy, metabolism, body temperature, digestion, and even your menstrual cycle. But in order for it to work properly, the entire Thyroid Hormone Journey has to be supported:

1. The brain’s ability to trigger the thyroid (signaling)
2. The ability to make hormone (production)
3. The ability of the body to carry thyroid hormones (transport)
4. The ability to convert T4 to T3 (conversion)
5. The cells’ ability to absorb thyroid hormones (absorption)
6. The ability for cells to use those hormones (utilization)

Carbohydrates—especially from whole-food, nutrient-rich sources—support all three.

Let’s break this down.

1. Carbs Support Thyroid Hormone Production

Let’s start at the source: thyroglobulin—a protein that your thyroid uses to make hormones. What most people don’t realize is that thyroglobulin is a glycoprotein, meaning it actually contains carbohydrate. Without enough carbs, your thyroid can struggle to make adequate hormone in the first place.

And that’s not all…

The Na+/I- symporter—the transport system that brings iodine into the thyroid gland—is also glucose dependent. Iodine is one of the key raw materials for thyroid hormone production, but it can’t even get inside the gland without enough glucose in circulation.

Low carb = low glucose
Low glucose = poor iodine uptake + reduced hormone production

2. Carbs Are Essential for T4 ➞ T3 Conversion

Your thyroid mainly produces T4, but your cells need T3—the active form. That conversion happens in the liver, kidneys, and peripheral tissues. And guess what? It’s highly sensitive to stress.

Here’s what happens when carbs are too low:

•  Blood sugar drops
•  Cortisol and adrenaline spike to compensate
•  Cortisol blocks T4-to-T3 conversion
•  More T4 gets converted into Reverse T3 (inactive)

This is your body’s way of saying: “We don’t feel safe. Slow everything down.”

Symptoms of poor conversion + high Reverse T3:

•  Crushing fatigue
•  Brain fog
•  Slowed metabolism
•  Cold hands + feet
•  Constipation
•  Weight gain despite a “clean” diet

Carbs help buffer the stress response, stabilize blood sugar, and send a safety signal to your metabolism that it’s okay to use energy again.

3. Carbs Help Cells Use Thyroid Hormones

This part gets overlooked—even in functional medicine circles.

It’s not enough to have T3 available. Your cells have to:

• Recognize it
• Transport it into the cell
• Use it to make ATP (your body’s energy currency)

That last part happens in the mitochondria, and it’s glucose-dependent. Without enough glucose, your mitochondria struggle to respond to T3 and produce energy.

So even if your labs show “perfect” T3, you can still feel hypothyroid if your cells don’t have the fuel to act on it.

Wait… So Carbs Aren’t the Enemy?

Exactly. The quality, quantity, and distribution of carbs matter far more than the outdated idea of “cutting carbs to lose weight.”

Quality Matters

Note: The type of carbohydrates this article recommends – I disagree with some of them because of the issues Dr Ray Peat outlined. Please see below… they say:-

Choose whole-food, nutrient-dense carbs that come with fiber, minerals, and color. Think:

• Fruits: berries, apples, pears, citrus, kiwi, mango, melons
• Root veggies: sweet potatoes, carrots, beets, parsnips, turnips, rutabaga, yuca
• Starches: winter squash, peas, corn, plantains
• Whole grains (gluten-free): quinoa, certified gluten-free oats, brown rice, buckwheat
• Legumes: lentils, black beans, chickpeas
• Dairy (if tolerated): plain yogurt, kefir, whole milk

Note: from this list the following are NOT recommended in a Ray Peat inspired Pro Metabolic Diet

Starches – 100% glucose, raise blood sugar & stress hormones too high, cause gut endotoxins

Grains – are starches, issues as above plus gluten issues

Legumes – are starches, also have anti thyroid properties

 

What carbs are recommended in a Ray Peat inspired Pro Metabolic Diet

Fruits – citrus & tropical mostly, any others depending on personal tolerance

Fruit-like vegetables – tomatoes, cucumbers, zucchini, capsicum, pumpkin, squash,

Root veges – as in first list with potatoes only sparingly and definitely not at the start of a pro metabolic journey or if insulin resistant

Fruit juices – especially Orange Juice,

Sugar – plain white, so long as rest of diet is highly nutritious

 

Quantity Matters

Most women with thyroid issues are eating too few carbs to support hormone function, especially earlier in the day. Under-fueling = over-reliance on cortisol = slowed conversion and metabolism.

Distribution is KEY

Eating most of your carbs at night or being wildly inconsistent sends mixed messages to your blood sugar and thyroid.

Better strategy:

•  Include balanced carbs earlier in the day
• Pair carbs with protein and fat
• Keep them steady throughout meals and snacks

What Happens When You Don’t Get Enough Carbs?

Low or inconsistent carb intake leads to:

•  Poor thyroid hormone production
•  Blocked T4-to-T3 conversion
•  Increased Reverse T3
•  Reduced carrier proteins (like albumin + TBG)
•  Poor hormone transport
•  Low cellular utilization of T3

Translation?

Your labs might look normal, but you feel anything but.

The Big Picture

If you’re still:

• Tired no matter how clean you eat
• Bloated or constipated
• Brain foggy with slow thinking
• Cold all the time
• Holding onto weight despite restriction

… it’s time to stop fearing carbs and start using them strategically.

When you give your body the fuel it needs to produce, convert, and use thyroid hormone, everything changes.”

 

Brilliant article on thyroid function and carbs, apart from some of  the carb sources, and explains EXACTLY why carbohydrates are essential to optimise thyroid function all through out the process.

ZEN Beach Diet

This is why the ZEN Beach Diet has over 250g of carbohydrates in it’s daily meal plan along with the balanced amount of protein and fats to optimise thyroid, hormones and health without unnecessary weight gain.

Read more about the ZEN Beach Diet HERE.

Join our Ray Peat Pro Metabolic Diet Facebook group HERE.

To our health,

 

Kristy

slimbirdy.com