The power of nutrition for depression: The thyroid link

Addressing mental health holistically has never been so important. Rather than manipulating neurotransmitter levels in the brain, identifying and eliminating the psychological factors responsible for producing the imbalances in serotonin, dopamine, GABA (gamma-aminobutyric acid), and other neurotransmitters would be a preferred pathway of improving mental health.  

Depression can often be due to an underlying organic or physiologic cause. The clinical approach to treating a client with depression is to initially investigate which nutritional, environmental, social and psychological factors are involved in the disease process.

When a diagnosis of depression is received, it is essential to rule out the simple organic factors that are known to contribute to depression. 

These include:

• nutrient deficiency or excess
• drugs (e.g, prescription, recreational, alcohol, nicotine and caffeine)
• hypoglycaemia
• stress and feelings of being overwhelmed
• hormonal imbalance
• allergies
• microbial factors
• environmental factors

Many hormones are known to influence mood, including thyroid, stress and adrenal function.

Recent studies have shown one of the root cause of depression is the stress hormones. Adrenocorticotrophic Release Hormone (ACTRH) is produced in response to stress by the hypothalamus. Passing down the pituitary stalk it activates the pituitary gland to produce the Adrenocorticotrophic hormone (ACTH). This stimulates adrenal cortex activity, which produces cortisone.

It has been found that the ACTRH can be made elsewhere other than in the hypothalamus, in several sites within the brain. Persistent and undue secretion of ACTRH in unrelenting stress situations is thought to affect the seat of emotion, the hippocampus directly, and degrade its function, promoting depression.

The recognised causes of neurotransmitter failure are increased a2 adrenergic receptors which bind to noradrenaline, which acts in the brain as a neurotransmitter, being secreted by specialist brain cells. The noradrenaline passes to the hippocampus which maintains mood and promotes mood elevation.

If any mechanism inhibits the production of noradrenaline, it can result in depression. Loss of adequate levels of thyroid hormone causes extra levels or increased activity of these adrenergic receptors which can lead to depression. The brain appears to be quite sensitive to low levels of thyroid hormone. 

Hormonal factors can influence mood, depression alongside weakness and fatigue can often be the first sign of thyroid issues, as even subtle decreases in available thyroid hormone, T3 may cause symptoms of depression. The link between hypothyroidism and depression is well documented, however, whether the thyroid hypo-function is a result of depression-induced hypothalamic-pituitary dysfunction or of thyroid hypo-function, is currently undergoing research by me, as part of the ongoing PhD in Nutritional management of thyroid disorders. 

Nutritional considerations and recommendations include thyroid hormones which are made from Tyrosine and Iodine. The RDA of Iodine is small, 150mg and no more than 600mg daily. The only role of Iodine in the body is to provide Iodine synthesis, it is recommended that dietary or supplementary levels of iodine do not exceed 600mg daily for any length of time.

Zinc, Vitamin E and Vitamin A function together in the manufacture of thyroid hormone. A deficiency of any of these nutrients would result in the production of low level of active thyroid hormone. Selenium copper and zinc are required cofactors for iodothyronine iodinase, the enzyme that converts T4 to the far more active T3.

The diet should be low in raw goitrogens. They include foods of the genus Brassica (turnips, cabbage, rutabagas, mustard greens, radishes, horseradishes) as well as cassava root, soyabeans, peanuts, pine nuts and millet. Foods rich in vitamins and minerals needed for thyroid production should be consumed daily. Best sources of Selenium include unshelled brazil nuts, Zinc-rich foods include oysters, cashew nuts, pumpkin seeds and almonds. 

Exercise is important in the treatment protocol for hypothyroidism, exercise stimulates thyroid gland secretion and increases tissue sensitivity to thyroid hormones. The health benefits of exercise improve overall thyroid function, thus improving mental health.