IGF-1, also known as insulin-like growth factor 1, is a complex and interesting hormone due to its potential to have both beneficial and harmful effects on your health, depending on how much your body produces. IGF-1’s most important job is to promote cell growth (hence the name). IGF is known as a growth factor and is part of a group of tissue and cell-building hormones that also includes epidermal growth factor, platelet-derived growth factor and nerve growth factor.
On one hand, IGF-1 possesses certain anti-aging and performance-boosting effects — including helping to build and retain muscle mass and bone mass. But on the other hand, high levels of IGF-1 have been associated with an increased risk for developing some types of cancer and even decreased lifespan. (1)
Below we’ll look at both the good and bad effects of IGF-1, plus discuss lifestyle factors that both increase and inhibit IGF-1.
What Is IGF-1?
What does IGF-1 mean? IGF-1 stands for “insulin like growth factor 1.” What is the role of IGF-1? IGF-1 is an anabolic peptide hormone that has the role of stimulating growth, and to a lesser degree supporting maintenance of normal blood sugar levels. It was formerly called somatomedin (or somatomedin C) because it’s a peptide in the somatomedin family. (2) It’s been determined that IGF1 is a “single chain 70-amino acid polypeptide cross-linked by 3 disulfide bridges.”
IGF-1 got its current name because it has certain insulin-like actions in the body (including lowering blood sugar), but it isn’t nearly as powerful as insulin when it comes to controlling blood glucose levels. (3) Because it mediates many of the effects of human growth hormone, many people discuss these two hormones interchangeably.
Another peptide hormone that is similar to IGF-1 is called IGF-2. Both of these growth factors have a similar structure to insulin. They’re both produced primarily in the liver, and also in other tissues, in response to the release of growth hormone by the pituitary gland. Both are considered extensions of human growth hormone because they have many of the same effects.
How do IGF-1 and IGF-2 differ from another? They bind to and activate different receptors, causing the growth of different cells and tissues. IGF-1 primarily stimulates hypertrophy (increase in cell size) and hyperplasia (increase in cell number) in both children and adults. It does this in tissues including muscles and bones. IGF-2 is highly active during fetal development, helping with cell growth (proliferation) and tissue formation, but becomes much less active after birth. (4)
IGF-1: The Good vs. the Bad
What are the benefits of IGF-1, and do these outweigh the risks involved with having higher IGF-1 levels?
Here are some of the positive things that IGF-1 does for us (more on these below):
- Helps build muscle mass and increase strength (5)
- Helps prevent muscle wasting
- May enhance physical performance, support muscle recovery and help with healing from injuries
- Can help regulate levels of body fat (adipose tissue) (6)
- Builds strength in response to strength-training.
- Helps build bones and protect against bone loss
- Can help regulate blood sugar levels and decrease diabetes risk factors
- Supports growth and development in children
- May help protect cognitive health and fight against neurological diseases or loss of brain cells by acting as a neurotrophic factor
- Supports vascular endothelial growth
- May help prevent skin thinning (7)
- May help prevent hypoglycemia (low sugar levels)
- Can help support kidney function and blood filtration
On the other hand, here are some of the negative effects that IGF-1 can have on our health:
- May promote cancer development
- May lead to decreased lifespan (according to animal studies)
For some people, when they hear the word IGF-1, the first thing that comes to mind is performance-enhancing drugs. It’s important to point out that supplementing IGF-1 for boosting performance is not recommended and not necessarily safe. This has been associated with side effects including:
- Impaired glucose metabolism and hypoglycemia
- Retinal edema
- Changes in sexual function
- Severe muscle pain
5 Benefits of IGF-1
1. Helps to Build Muscle & Fights Muscle Wasting
Many studies show that IGF-1 stimulates skeletal muscle hypertrophy and a switch to glycolytic metabolism, allowing you to build strength. IGF-1 activates several channels that help with the expression of other growth factors. And IGF-1 can also help to decrease age-related muscle wasting (also called sarcopenia or muscle atrophy) by preserving lean muscle mass.
2. Helps Prevent Cognitive Decline in Older Adults
Here’s another interesting finding when it comes to slowing the effects of aging: Higher circulating concentrations of IGF-1 in older adults may help prevent neuronal loss and age-related decline in cognitive functions. (8)
Researchers from one study said:
“We found IGF-I levels to be significantly associated with the performances (controlled for education) on the Digit Symbol Substitution test and the Concept Shifting Task, which measure perceptual-motor and mental processing speed. Subjects with higher IGF-I levels performed better on these tests, performance on which is known to decline with aging.”
Experts now think that IGF-1 may help boost executive function (a set of mental skills that help you complete everyday tasks) and verbal memory. And in certain animal studies, it’s been found that IGF-1 may help protect against Parkinson’s disease and induce clearance of brain amyloid-betas, which at high levels are associated with Alzheimer’s disease. (9, 10)
3. Supports Metabolic Health & Fights Type-2 Diabetes
IGF-1 and insulin work together to keep blood sugar levels stable. Depending on what types of foods you’re eating, they determine what your body will use for energy (fat or glucose) and where excess energy will be stored. Certain studies have found that when type 2 diabetic patients are treated with IGF-1, their blood sugar levels decrease, insulin sensitivity improves, and blood lipids also improve. (11)
4. Helps Build Bones & Preserve Bone Health
IGF-1 has been shown to play a role in bone formation and can help prevent bone loss in older age (especially in post-menopausal women who are at the highest risk of bone-related disorders like osteoporosis). Researchers believe that IGF1 stimulates bone formation by having a direct effect on osteoblasts.
Growth hormone and IGF-1 are also fundamental in skeletal growth during puberty. One study that focused on bone mineral density and bone mineral content (BMC) in 59 African American and 59 white girls, aged 7-10 years, found that higher plasma IGF-1 concentrations were correlated with better BMD/BMC in younger age too. (12)
5. Facilitates Growth & Development
Studies have found that higher concentrations of IGF-1 in fetuses results in lager fetal size. In animal studies, IGF1 deficiency had been associated with impaired neurologic development, suggesting that IGF-1 has specific roles in axonal growth and myelination. Deficiency in IGF-1 has also been linked to neonatal mortality. (13)
Because IGF-1 is a growth promoter, it makes sense that blood levels of IGF-1 progressively increase during childhood and peak at the time of puberty. After puberty, when rapid growth is completed, levels of IGF-1 decrease. Defects in the gene that helps stimulate production of IGF-1 causes insulin-like growth factor I deficiency, which is associated with stunted growth and development.
Dangers of IFG-1
1. May Contribute to Cancer Development
IGF-1 is what some call “a growth-promoter”, because it has been shown to promote the growth of cancer cells. (14) This is one reason why research suggests that older adults who have lower IGF-1 levels also have a lower risk of developing certain types of cancer, including breast, ovarian, prostate, colorectal and lunge cancers.(15) Some studies have found an especially strong association between circulating IGF-1 concentrations and the risk of breast cancer in premenopausal, but not postmenopausal women.
It’s still not entirely clear how IGF-1 may contribute to cancer. Some believe that IGF-1 might cause increased cell transformation, cell migration, metastasis and growth of tumors. It seems that IGF-1 doesn’t cause cancer, but can allow it to progress and spread more quickly.
Overall there’s still more to learn about how IGF-1 can affect cancer risk, but for now it’s not considered safe to supplement with IGF-1 without being told to so by a doctor. It’s considered an illegal supplement and is banned in professional sports, which should be enough to make you think twice before taking it!
2. May Decrease Lifespan
In certain animal studies conducted on mice, worms and flies, decreased IGF-1 levels actually lead to longer lifespan. Increasing growth hormone by significant amounts has been shown in some animal studies to reduce lifespan by up to 50%, while reducing levels has been shown to boost lifespan by up to 33%. (16, 17 )
It’s still not entirely clear why this happens, and the topic remains controversial. Lower IGF-1 may promote a longer life in animals, but on the other hand, some experts believe that IGF-1 may increase expression of genes associated with stress-resistence and help fight oxidative stress. IGF-1 may help decrease inflammatory responses, suppresses oxidative stress, and decreases atherosclerosis progression. Based on these findings, there’s still unknowns about how growth hormones impact longevity, inflammatory responses and chronic disease development.
How to Increase IGF-1 vs. Inhibit
In general, in order to maintain optimal health you want to have a normal/moderate level of IGF-1, but not too much or too little. Some studies suggest that having what’s considered a very low level or very high level of IGF-1 may increase your risk for death (aka your mortality risk).
So what is considered a normal level of IGF 1? It depends on your age and gender. Males have higher IGF-1 levels than females. Adolescence is the time when levels should be highest, before tapering off and then decreasing during adulthood. According to the Mayo Clinic Laboratories, here is roughly the normal reference range for IGF-1 depending on your age: (18)
- 0-3 years: 18-229 ng/mL
- 4-8 years: 30-356 ng/mL
- 8-13 years: 61- 589 ng/mL
- 14-22 years: 91-442 ng/mL
- 23-35 years: 99-310 ng/mL
- 36-50 years: 48-259 ng/mL
- 51-65 years: 37-220 ng/mL
- 66-80 years: 33-192 ng/mL
- 81->91 years: 32-173 ng/mL
Is there such thing as “IGF-1 foods” that cause levels to increase? In some ways, yes. You can increase production of IGF-1 by eating a healthy diet that includes moderate amounts of protein (but not very high amounts) and is low in sugar and processed carbohydrates. It’s important to eat an unprocessed, nutrient-dense diet that helps support insulin sensitivity since IGF-1 and insulin work together in some ways and balance each other out. Insulin regulates energy metabolism and also increases the bio-activity of IGF-1.
Studies suggest that high-protein diets can increase IGF-1 levels, but that higher fat intake, in particular, saturated fat, can lead to lower levels of IGF-1. Fasting and “extreme diets” may cause IGF-1 levels to drop and stay down for a period of time. (19) IGF-1 production may decrease in response to intermittent fasting, calorie restriction or starvation because not enough fuel is temporarily available to build new tissue. However, according to some animal studies, IGF-1 levels may bounce back after 24 hours of re-feeding, although not to starting levels. (20)
Things That Increase IGF-1:
- Intense/strenuous exercise & HIIT workouts — Vigorous exercise helps release more growth hormone, especially when you just begin this type of exercise. Over time, though, as your body acclimates to intense exercise, you may start releasing less.
- Resistance/strength-training — Strength-training is one of the best ways to increase IGF-1 and retain muscle mass. (21) It helps us to adapt to the “stress” our muscles are put under when we challenge them with heavy weights. The fact that we can build strength and lean muscle mass when we strength train can partially be attributed to growth hormone and IGF-1.
- Eating high amounts of dairy and protein — There’s some evidence that high intakes of protein from dairy products can lead to higher blood levels of IGF-1.
- Eating enough calories to support your activity level and needs.
- Sleeping enough — Sleep deprivation can mess with overall hormone health in many ways. Getting quality sleep is important for the production of growth hormone, recovery from exercise, neurological health, appetite control and more.
- Sauna sessions — Certain studies suggest that 60-minute sauna sessions twice daily for one week can significantly increase production of growth hormone, which is believed to also apply to IGF-1. (22)
To reiterate my point above, it’s not safe to supplement with IGF-1 at this time. Supplementation should only be done under very specific circumstances and when you’re being monitored closely by a doctor.
Things That Inhibit IGF-1:
- Aging, since older age is associated with decreased production of growth hormones
- Calorie restriction, fasting, extreme diets and protein restriction (23)
- High insulin levels, since this may decrease the body’s need for IGF-1
- Sedentary lifestyle/lack of exercise
- Sleep deprivation
- Higher estrogen levels, such as from high intake of plant lignans and phytoestrogen foods like soy and flax (24)
- High alcohol intake
- High stress levels
Final Thoughts on IGF-1
- IGF-1 stands for “insulin-like growth factor 1.”
- IGF-1 is an anabolic peptide hormone; its role involves stimulating growth of cells and tissues, including muscles and bone.
- IGF-1 possesses both beneficial effects, including fighting the effects of aging, but also some potentially harmful ones, too.
- Benefits of IGF-1 include: building muscle mass, preventing muscle wasting, building bone mass, helping with growth, managing blood sugar levels and protecting against neurological disorders.
- Dangers of IGF-1 include: potentially increasing the risk for some cancers and reducing lifespan.
- Exercise, fasting and other “beneficial stressors” like sauna therapy may increase IGF-1 levels. Being sedentary, having high insulin levels, stress and sleep deprivation can inhibit IGF-1 levels.
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