Ghrelin is an important hormone when it comes to health. It’s not “good” or “bad” but is more dependent on the person. Ghrelin plays a role in cognitive function, gut function, inflammation, metabolism, weight, fertility and emotional states, to name a few. See how this hormone pertains to you.
- What is Ghrelin?
- Ghrelin: The Good
- 1) Ghrelin Reduces Inflammation
- 2) Ghrelin Protects Against Autoimmune Disease
- 3) Ghrelin Improves Learning and Memory
- 4) Ghrelin Activates the Vagus Nerve
- 5) Ghrelin Increases Stomach Acid and Gut Flow
- 6) Ghrelin Prevents and Treats Heart Disease
- 7) Ghrelin Increases Bone Formation
- 8) Ghrelin Increases Growth Hormone Release
- 9) Ghrelin Improves the Mitochondria
- 10) Ghrelin Increases Dopamine
- Ghrelin: The Bad
- Genetics of Ghrelin
- Testing Ghrelin
- Ways to Increase Ghrelin
- Ways to Reduce Ghrelin
What is Ghrelin?
The less body fat we carry, the more ghrelin we produce (R) – a mechanism by which the body tries to increase body weight.
Ghrelin tells the brain that we don’t have enough energy, that we need to eat, and that we need to conserve our energy (R).
Chronically elevated levels of ghrelin are associated with obesity, overeating, and inflammation-related diseases including Ulcerative Colitis, Crohn’s Disease, Pancreatitis, and possibly Rheumatoid Arthritis (R).
Ghrelin affects the immune system, the reproductive system, strengthens bone, and promotes muscle development (R).
Ghrelin: The Good
1) Ghrelin Reduces Inflammation
A number of reports describe ghrelin to be a potent anti-inflammatory mediator both in organisms and in cells and a promising therapeutic agent for the treatment of inflammatory diseases and injury.
Ghrelin reduces cell death and increases cell production (R).
Elderly patients aged 70 and older, who cannot produce as much ghrelin as younger patients, experience more severe disease symptoms (R).
2) Ghrelin Protects Against Autoimmune Disease
Ghrelin may help patients with autoimmune/inflammatory diseases, including Rheumatoid Arthritis, Ulcerative Colitis, Multiple Sclerosis, Parkinson’s Disease, Crohn’s Disease, Cardiovascular disease, and inflammation from brain injury (R).
Ghrelin protects the lungs, liver, kidneys, and other organs from toxic by-products of oxygen reactions and inflammation injury (R).
Ghrelin has shown potent anti-inflammatory effects in rat and mice models of arthritis, resulting in a slowed progression of the disease (R).
Ghrelin also protects the heart from inflammation injury and improves heart function in mouse models of heart disease (R).
3) Ghrelin Improves Learning and Memory
Ghrelin produced in the stomach can enter the hippocampus (an area of the brain important for long-term memory storage) through the blood.
Similarly, rats injected with ghrelin demonstrated better memory retention (R).
Restricting calorie intake, which has been shown to increase ghrelin levels, improved memory in the elderly (R).
4) Ghrelin Activates the Vagus Nerve
5) Ghrelin Increases Stomach Acid and Gut Flow
In cells, ghrelin dose-dependently enhances the contraction of stomach muscle cells when stimulated (R).
6) Ghrelin Prevents and Treats Heart Disease
Ghrelin decreases blood pressure in healthy subjects (R).
In animal models with heart failure, ghrelin improved cardiac output (R).
In patients with chronic heart failure, ghrelin improved heart function, increased heart output and increased muscle strength (R).
The mechanisms responsible for the low blood pressure effects of ghrelin include the suppression of fight or flight activity (R), inhibiting the renin-angiotensin system in humans (R) or direct vasodilatory action (R, R2).
Acute ghrelin treatment improved survival in a heart attack by preventing an increase in the frequency of heart arrhythmias (rats) (R).
7) Ghrelin Increases Bone Formation
Bone formation is induced by ghrelin.
In humans, blood ghrelin level was positively correlated with bone mineral density in peri-, post-, and pre- menopausal women (R).
In a randomized, double-blind, placebo-controlled study, ghrelin infusion had no acute effect on markers of bone turnover in healthy controls. However, people who had high ghrelin levels had less bone destruction (R).
8) Ghrelin Increases Growth Hormone Release
Ghrelin causes the release of growth hormone by activating the growth hormone secretagogue receptor (R).
Many of the benefits of ghrelin come as a result of activating this receptor.
9) Ghrelin Improves the Mitochondria
Ghrelin increases the production of mitochondria (R).
Ghrelin is a robust activator of mitochondrial function in the hypothalamus (R).
10) Ghrelin Increases Dopamine
Ghrelin: The Bad
1) Ghrelin Affects Mood and Increases Anxiety
Whether ghrelin acts as an antidepressant or as a depressant is debated.
Recent studies suggest that Ghrelin may have antidepressant properties.
Antidepressant-like behaviors in mice have been observed in response to increased ghrelin levels. These mice were more social and motivated to survive in a forced swim test (R).
However, a study on rats found that ghrelin activity in the brain caused depressive-like behaviors. These rats were less motivated to survive in a forced swim test (R).
Most studies, however, agree that ghrelin increases anxiety.
Similar results were found in rats with increased ghrelin levels. These rats were less social and avoided open areas (R).
2) Ghrelin is Linked to Weight Gain and Obesity
The more fat you have, the less ghrelin you produce, which is supposed to make you thinner and keep your weight in homeostasis (R).
Chronically high levels of ghrelin have been shown to increase food intake and promote fat storage in white and brown fat cells (R).
Chronically high levels of ghrelin promote fat storage and weight gain in mouse models (R).
In healthy individuals, ghrelin is secreted when the stomach is empty, letting you know when it’s time to eat (R).
In healthy individuals, ghrelin levels fall after eating to reduce appetite and food intake (R).
However, in obese subjects, ghrelin levels do not significantly decrease after a meal (R).
This suggests that for obese and overweight people, ghrelin causes a biased pattern of increased food consumption, decreased energy expenditure, and increased fat storage and weight gain.
Obese and overweight individuals have lower ghrelin levels than healthy individuals, suggesting that ghrelin does not directly contribute to obesity except in patients with Prader-Willi Syndrome whose exceptionally high levels of ghrelin are correlated with obesity and over-eating (R, R2).
4) Ghrelin is Linked to Anorexia Nervosa
High ghrelin levels are associated with conditions characterized by a lack of energy, resulting in weakness and wasting of the body. Such conditions include anorexia, cancer, chronic disease, and chronic failure of the heart, kidneys, and lungs (R).
When individuals with anorexia nervosa fast, they have higher fasting levels of ghrelin than in healthy individuals. These increased ghrelin levels may be an adaptive response to stimulate eating (R).
Increased ghrelin levels may indicate the development of ghrelin resistance. In mice suffering from cancer-related wasting, ghrelin’s ability to stimulate appetite was reduced (R).
Ghrelin has been found to counteract muscle and tissue wasting syndromes associated with cancer, heart disease, and chronic disease (R).
5) Ghrelin Can Reduce Fertility
Ghrelin has been found to inhibit the function and reproduction of sex cells in males and females.
In male animals, high ghrelin levels inhibit sperm production (R).
In the female reproductive system, high ghrelin levels prevent changes in the uterus that are necessary for fertilization (R).
This is one mechanism by which calorie restriction inhibits fertility.
6) Ghrelin May Contribute to Cancer
Whether ghrelin contributes to or inhibits the growth and proliferation of cancers are debated. However, most studies have found that ghrelin contributes to cancerous growths by promoting cell production and preventing cell death (R).
Ghrelin may promote the ability of cancer cells to migrate to and invade other parts of the body (R).
This spread and growth make cancers difficult to treat, resulting in lower life-expectancy (R).
In a laboratory study of cancer, blocking ghrelin production in cells reduced the spread of cancer (R).
7) Ghrelin Can Influence Decisions
In theory, individuals are willing to take risks when they have little to lose (R). This behavior has been seen in hungry animals that take more risks searching for food when they are running low on energy (R).
Similarly, in humans, fasting-induced ghrelin levels caused people to make riskier economic choices. Normal risk avoidance was restored immediately after eating (R). This shows that higher ghrelin levels may cause us to make bad decisions.
8) Ghrelin Activates the Stress Response
Genetics of Ghrelin
SelfDecode, the best website for analyzing and decoding genetics from 23andme, has SNPs for ghrelin.
GHRL Gene (Produces Ghrelin):
GHSR Gene (Ghrelin Receptor):
- RS2232165 (GHSR) GG
- RS2922126 (GHSR) AA
- RS2948694 (GHSR) GG
- RS490683 (GHSR) GG
- RS572169 (GHSR) CC
- RS9819506 (GHSR) TT
Ghrelin levels change throughout the day. They are higher at night, and lower during the day (R).
During the day, ghrelin is highest during a fasting period when the stomach is empty, and lowest right after a meal (R).
In 31 healthy controls, the average baseline was 329±32 pmol/l after an overnight fast (R).
In 25 obese subjects, the average baseline was 165±14 pmol/l after an overnight fast (R).
Ways to Increase Ghrelin
If you have low levels of ghrelin and are genetically predisposed to autoimmunity, you might want to increase ghrelin production.
- Hydrogen water from Molecular Hydrogen Machine (R, R2).
- Fasting – Ghrelin is secreted when the stomach is empty (R).
- Fiber – Under fasting conditions, the more fiber consumed, the higher ghrelin levels (R).
- Adenosine has many of the effects of ghrelin by activating the growth hormone secretagogue receptor (R).
- Curcumin (R) -in diabetic animal models with gastroparesis.
- Fish Oil (R)
- Hi-maize Resistant Starch (R)
- Zinc (pigs) (R).
Lifestyle Factors That Increase Ghrelin
- Weight Loss – Ghrelin is lower in overweight people (R, R2).
- Sleep deprivation – Even one night of sleep deprivation led to increased ghrelin levels in healthy volunteers (R).
- Chronic stress increases ghrelin and appetite (R).
Ways to Reduce Ghrelin
If you have high levels of ghrelin, are genetically predisposed to cancer or eating disorders, or are trying to lose weight, you might want to decrease ghrelin production. Here are some habitual ways to decrease ghrelin:
- Protein (Red meat) – (R, R2) Ghrelin levels after eating a high protein meal was much lower compared to ghrelin levels after a high a calorie meal.
- Adequate sleep – (R).
- Fructose Restriction – (R) Ghrelin does not decrease as much after eating fructose. Lingering ghrelin may lead to overeating and contribute to weight gain and obesity.
- Ketogenic Diet (R)
- Acute stress has been shown to decrease ghrelin levels and reduce appetite (R).
- Acupuncture (R)
- Vitamin D3 (maybe) – Ghrelin was higher in people who were deficient in vitamin D3 (R).
- Using Honey instead of sugar (maybe) (R).
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