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Cortisol

Episodes

Posted on October 4th 2023 (over 1 year)

In this clip, Dr. Martin Gibala delves into the nuances of sex-based differences in exercise response and their implications for individual outcomes.

Posted on September 19th 2023 (over 1 year)

Dr. Martin Gibala discusses HIIT's health benefits and describes common HIIT protocols.

Posted on April 9th 2022 (about 3 years)

In this clip, Dr. Matthew Walker explains how altering the timing and duration of daytime light exposure influences sleep.

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News & Publications

  • From the publication:

    When epidemiological and interventional studies are considered collectively, sleep loss and lower sleep duration are associated with lower morning, afternoon and 24-h testosterone; as well as higher afternoon, but not morning or 24-h cortisol. These reciprocal changes imbalances anabolic-catabolic signaling because testosterone and cortisol are respectively the main anabolic and catabolic signals in man. Fixing testosterone-cortisol balance by means of a novel dual-hormone clamp mitigates the induction of insulin resistance by sleep restriction and provided the first proof-of-concept that the metabolic harm from sleep loss can be ameliorated by approaches that do not require sleeping more. Obstructive sleep apnea is associated with lower testosterone, even after controlling for age and obesity whereas the conclusion that continuous positive airway pressure therapy has no effect on testosterone is premature because available studies are underpowered and better-quality studies suggest otherwise. High dose testosterone therapy induces OSA [obstructive sleep apnea], but more physiological dosing may not; and this effect may be transient or may dissipate with longer term therapy.

  • The human body responds to mental stress by releasing hormones called corticosteroids, triggering the body’s fight or flight response. Chronic activation of these hormones can impair immune function, increasing susceptibility to infection and disease. Findings from an early study in mice demonstrate that vitamin C mitigates the body’s stress response, thereby improving immunity.

    The authors of the study immobilized mice for an hour every day for three weeks to induce stress. They also fed the mice 200 milligrams of vitamin C daily – roughly equivalent to several grams per day in humans. A control group of mice also received vitamin C but they were not subjected to stress.

    The stressed mice that received large doses of vitamin C in their diets exhibited fewer signs of stress as evidenced by lower levels of corticosteroid hormones as well as other physical manifestations, such as weight loss. The mice also exhibited higher levels of IgG, the most abundant antibody in circulation, responsible for binding a broad selection of pathogens, including viruses, bacteria, and fungi, to prevent infection. Interestingly, the non-stressed mice that received large doses of vitamin C exhibited even greater increases in IgG, suggesting that stress cancels out some of the beneficial effects of the vitamin.

    These findings suggest that high dose vitamin C might improve immune function, especially during times of mental and physical stress.