As a gut-health dietitian, I often emphasize the importance of understanding how our diet choices, including the types of foods and when we eat them, influence our overall well-being. Today, we will explore the intricate world of macronutrients and specific dietary approaches—like the low-carb/Keto diet and fasting—and their impacts on thyroid and gut health.
Macronutrients and Their Effect on Thyroid Health
To start, let’s break down what macronutrients are. Essentially, they’re the nutrients our body needs in large amounts: carbohydrates, proteins, and fats. Each plays a unique role in our health.
Carbohydrates: Carbs, often vilified in today’s diet culture, are SO important, as they’re our body’s primary energy source. The thyroid gland requires glucose, a form of carbohydrate, to trigger the release of a hormone called thyrotropin-releasing hormone. This hormone tells our pituitary gland to produce thyroid-stimulating hormone (TSH), which then prompts the thyroid gland to release its hormones. These hormones govern everything from metabolism to mood. Without adequate carbohydrate intake, our body can potentially struggle to regulate these essential functions. In other words, carbs help our thyroid work correctly.
Proteins: Essential for tissue repair and production of enzymes and hormones. The thyroid gland utilizes specific amino acids, the building blocks of protein, to produce its hormones.
Fats: Fats are crucial for hormone production, including thyroid hormones. Research has indicated that omega-3 fats can reduce inflammation that might impact the thyroid. This anti-inflammatory effect of omega-3s can be especially helpful for individuals with autoimmune thyroid issues like Hashimoto’s. In such conditions, the immune response targets the thyroid, leading to inflammation. This can trigger the release of thyroid antibodies, potentially causing hypothyroidism (when the thyroid gland doesn’t produce enough thyroid hormone). Omega-3s help maintain the health of cell membranes, ensuring they remain undamaged and facilitating effective cell communication.
Low Carb/Keto Diet and Its Effects on Thyroid and Gut Health
The ketogenic or “keto” diet is a high-fat, low-carb diet that has gained immense popularity for its potential weight loss benefits. But what does it mean for our thyroid and gut?
Thyroid: While the keto diet can help some people, there are concerns about how it affects thyroid health. By drastically reducing carb intake, there may be less glucose available for thyrotropin-releasing hormone production, potentially impacting thyroid function. Some individuals on long-term, very low-carb diets have reported elevated TSH levels, a marker that the thyroid might not be functioning optimally.
Additionally, the majority of the thyroid hormone (T4) produced by the thyroid gland isn’t immediately usable by the body. It needs to be activated by organs like the liver through a process known as deiodination. The end result of this process is the active thyroid hormone, T3.
Studies indicate that:
- Carbohydrates play an important role in deiodination and influence T3 levels in the body.
- And the amount of carbohydrates in your diet directly impacts how much of T4 gets converted to T3, the functional form of thyroid hormone.
Gut: Our gut loves fiber—a carbohydrate. On a strict keto diet, there might be a reduction in fiber intake, which can affect gut bacteria. Beneficial bacteria feed on fiber, producing short-chain fatty acids that maintain a healthy gut lining. Without enough fiber, we might starve these friendly bacteria, potentially affecting our overall gut health. Some research has shown that a low-carb diet not only decreases overall bacterial levels but also diminishes bacterial variety. Furthermore, research has identified shifts in the types of probiotics present, with low-carb diets leading to a decrease in beneficial, inflammation-fighting species and an increase in less favorable probiotic types.
Fasting and Its Effects on Thyroid and Gut Health
Intermittent fasting, where individuals cycle between eating and fasting periods, has been highlighted for its potential health benefits, from weight loss to improved brain function. But how does it impact our thyroid and gut?
Thyroid: Research indicates that intermittent fasting can significantly impact thyroid function, as it can cause T3 levels to drop by more than half in the blood during fasting periods. This could be concerning for individuals with hypothyroidism, given that their thyroid already lacks this particular hormone. The good news is that these impacts are short-lived. After eating your subsequent meal, the thyroid hormone levels should return to what they were before the fasting period. In essence, while short-term fasting might not drastically impact thyroid health for most people, longer fasting periods could. Keep in mind that the stricter your diet, the higher the chances of triggering inflammation. Such inflammation can amplify autoimmune responses or disrupt your thyroid’s functioning. Therefore, it’s important to follow a dietary approach that you can sustain over time (which is exactly what I help my clients achieve! Learn more here.)
Gut: Fasting gives our digestive system a break, potentially promoting repair and reducing inflammation. Intermittent fasting may have some benefits on our gut microbiota, however, most research is based on animals or limited human studies, often during Ramadan.
Additionally, there may be some benefit for those who have an imbalance in their gut microbiota (aka dysbiosis). Other potential benefits are that possible changes can lead to genetic shifts relating to carbohydrate metabolism, which may help to improve blood glucose and body mass index. These benefits tend to occur with longer time-restricted feeding windows of 16 hours or more.
Bottom Line
Diet choices, from the types of foods we consume to when we eat them, play a crucial role in our thyroid and gut health. It’s essential to remember that every individual is unique. What works wonders for one person might not for another. As a gut-health dietitian, my advice is always to listen to your body, stay informed, and consult with health professionals before making significant dietary changes. Your body, especially your thyroid and gut, will thank you for it!
