An article I came across on PrecisionNutrition.com about Cortisol

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All About Cortisol

by The Precision Nutrition Team

What is cortisol?

Cortisol is what's called a " glucocorticoid " (a hormone) and is

secreted by the adrenal cortex (located in your adrenal glands).

Glucocorticoids affect every cell in the body so needless to say,

they're pretty important.

The main glucocorticoid in humans is cortisol.

Glucocorticoids released in the body send feedback to the brain and

influence the release of CRH (corticotropin-releasing hormone) and

ACTH (adrenocorticotropic hormone).

ACTH stimulates the adrenal glands to secrete cortisol. The rise in

cortisol secretion follows ACTH release after a 15-minute to 30-minute

delay.

Cortisol:

http://www.icgeb.trieste.it/~p450srv/ligand/cortisol.gif

Cortisol feedback loop:

http://faculty.clintoncc.suny.edu/fa...m/cortisol.gif

Why is cortisol so important?

Cortisol accelerates the breakdown of proteins into amino acids

(except in liver cells). These amino acids move out of the tissues

into the blood and to liver cells. This is where they are changed to

glucose in a process called gluconeogenesis.

A prolonged high blood concentration of cortisol in the blood results

in a net loss of tissue proteins and higher levels of blood glucose.

So isn't this bad?

Well, not exactly. By raising plasma glucose levels, cortisol provides

the body with the energy it requires to combat stress from trauma,

illness, fright, infection, bleeding, etc.

So, obviously, this is bad from a muscle breakdown perspective –

however, the body is simply trying to preserve carbohydrate stores and

deliver energy when it's needed most.

Acutely, cortisol ALSO mobilizes fatty acids from fat cells and even

helps to maintain blood pressure.

High levels of cortisol in the blood can decrease white blood cells

and antibody formation which can lower immunity.

Cortisol is necessary for recovery from injury (as it's part of

inflammatory response).

This is the most important therapeutic property of glucocorticoids,

since they can reduce the inflammatory response and this, in itself,

suppresses immunity.

So, in summary, cortisol is:

· Protein-mobilizing

· Gluconeogenic

· Hyperglycemic

How cortisol responds to nutrition and exercise:

http://www.nature.com/icb/journal/v7...cb200076f1.gif

What you should know

Cortisol reference ranges:

· Cortisol, free (urine) 20-90 mcg/day

· Cortisol (serum) 4-22 mcg/dL (morning specimen)

· Cortisol (serum) 3-17 mcg/dL (afternoon specimen)

To be indicative of overtraining, cortisol increases may need to be

higher than 800 nmol/L.

Now, a lot has been said about cortisol and exercise. And yes, the

type of exercise regimen performed can dictate hormonal response.

Acute high intensity resistance exercise is associated with increased

plasma cortisol concentration. The response is similar to that seen of

growth hormone. The most dramatic increases occur when rest periods

are short and total volume is high.

Cortisol responses to increased training volume are variable. Response

depends on specific training protocols and diurnal variations

(variations over the course of the day).

When muscle glycogen concentrations are low, cortisol is released and

fuel use shifts toward protein or fat so that judicious use is made of

the little glucose that remains. However, in the long-term, excessive

cortisol will encourage fat synthesis and storage, along with

provoking appetite.

Aerobic endurance training, particularly running, is linked with

protein loss from muscle (partially induced by cortisol). Endurance

trained individuals typically have a higher cortisol response; while

resistance trained individuals have a higher testosterone response.

Secretion of cortisol is elicited at exercise intensities between 80%

and 90% of VO2max - so we're not necessarily talking recreational

exercise here - we're talking endurance training.

The degree of cortisol release during high intensity exercise is

dependent in part on the time of day and the timing of meals. When

exercise is performed during a time of already high cortisol levels

(AM hours) – it doesn't increase above already elevated levels.

Cortisol secretion displays 7 - 15 spontaneous or meal-associated

pulses throughout the day.

Cortisol circadian rhythms are closely coupled to the sleep-wake

cycle. Peak cortisol release occurs between 7 and 9 in the morning,

the time of dark-light transition.

24 hour cortisol changes:

http://www.abcbodybuilding.com/diurnal_files/chart6.jpg

Cortisol causes atrophy in muscle (mainly fast twitch type 2) and

bone. The anabolic effects of testosterone and insulin oppose

cortisol's catabolic effects.

The acute increases in cortisol following exercise also implicate

acute inflammatory response mechanisms involved with tissue

remodeling. This is a necessary response, and only the chronic

cortisol elevations seem to be responsible for adverse catabolic effects.

Stress (both psychological and physical) can result in the " alarm

reaction. " This can cause enlarged adrenal glands and atrophied

lymphatic organs. With the enlarged adrenals, excessive cortisol can

be produced. With the shrunken lymphatic organs, fewer white blood

cells may be created. The immunosuppressive effects of intense

exercise have been attributed to high plasma cortisol concentrations

that prevail after prolonged intense exercise.

For extra credit

· Excessive secretion of glucocorticoids produces a collection of

symptoms called Cushing's syndrome, one of the symptoms is a

redistribution of body fat.

· Protein and carbohydrate consumption after exercise can offset

the cortisol response.

· High blood levels of glucocorticoids can stimulate gastric acid

and pepsin production and may exacerbate ulcers.

· Cortisol levels can be up to 50% higher in animals under stress

if alone.

· Estradiol increases the binding protein for cortisol so that

circumstances associated with increased (pregnancy) or decreased

(exercise induced amenorrhea and menopause) estradiol alters the

amount of circulating free cortisol and its actions.

· Exercising in a depleted state can result in high levels of

gluconeogenesis (protein breakdown).

Summary and Recommendations

· Take regular, planned breaks from intense training

· Consume enough calories from non-processed foods to prevent

depletion

· Get 7-9 hours of sleep per night to decrease stress and cortisol

release

· Consume carbohydrates and protein after exercise sessions

· Don't isolate yourself – spend time with friends and family

· Regularly participate in a stress-relieving activity like mild

yoga or meditation

· Avoid excessive amounts of intense aerobic endurance training

(unless training for endurance event)

For more see here:

http://www.johnberardi.com/articles/...ertraining.htm

http://www.johnberardi.com/articles/...training_2.htm

http://www.johnberardi.com/articles/...training_3.htm

http://www.johnberardi.com/articles/.../immunesys.htm

See also

If you want to know more about optimal health and nutrition, we

encourage you to check out the comprehensive Precision Nutrition

program. This program is our recommendation for the top practical

nutrition resource on the market today.

References

Pawlak L. Stop Gaining Weight. 1st ed. Biomed General. Concord, CA. 2004.

Thibodeau GA & Patton KT. Eds. Anatomy & Physiology, 4th ed. Mosby,

Inc. St. Louis, MO. 1999.

Borer KT. Exercise Endocrinology. Human Kinetics. Champaign, IL. 2003.

Beers MH, Berkow R eds. Merck Manual. 17th ed. Merck Research

Laboratories. Whitehouse Station, NJ. 1999.

Harvey RA, Champe PC eds. Pharmacology 2nd ed. Lippincott &

Wilkins. 2000.

Baechle TR & Earle RW. Essentials of Strength Training and

Conditioning. National Strength Training Association, 2nd ed. Human

Kinetics. Champaign, IL. 2000.

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