IGF-1 is commonly known to help build muscle or as something to avoid when dealing with cancer. However, IGF-1 is also crucial in healing and tends to be low in those with chronic inflammation. Learn all about how this growth factor works here.
What is Insulin-Like Growth Factor 1?
Insulin-Like Growth Factor 1 (IGF-1) is a hormone that is similar in structure to insulin and works with Growth Hormone to reproduce and regenerate cells.
Growth Hormone, made by the pituitary gland, stimulates the liver to produce IGF-1 and IGF-1 subsequently stimulates growth in cells throughout the body, leading to growth and development (as in the womb and through adolescence), strengthening of tissues (improving bone density, building muscle), and healing (skin, bones, gut lining, etc.), depending on what the body needs [1].
IGF-1 is so crucial to development that if it is not present in adequate amounts during the time when a child is developing, short stature may result.
IGF-1, Overall Health, and Longevity
In several organisms such as fruit flies, worms, and rats, IGF-I is involved in the control of lifespan.
In most studies in mice, inhibiting Growth Hormone/IGF-I results in an increase in lifespan (up to 55%). However, in humans, the association between IGF-I levels and life expectancy doesn’t hold up [2].
Unlike lab animals, humans are exposed to various infections, stress, and other environmental factors that IGF-1 might help.
Several population-based studies describing a relationship between IGF-I and risk of dying were published with conflicting results. Two studies showed a higher risk with higher IGF-I levels, while three showed higher risk with lower IGF-I levels. And in six studies there was no clear association at all [2].
Having either low or high IGF-1 was associated with higher cancer mortality in older men. This was one small study, and though its results were intriguing, they would need to be repeated before they can be taken as conclusive [3].
In a meta-analysis of twelve studies done in 2011 with 14,906 participants, the risk of dying from all causes was increased in subjects with low as well as high IGF-1 levels [4].
People with low IGF-1 were at a 1.27X increased risk of dying from all causes, while those with higher levels were at a 1.18X increased risk.
The activity of IGF-I is influenced by at least six binding proteins (IGFBP). The most abundant is IGFBP-3, which binds more than 90% of IGF-1 in the circulation. Although IGF-I and IGFBP-3 are typically well-correlated, there is speculative evidence that IGF-1 has an independent impact on disease risk, for example, on cancer [5].
Effects of IGF-1
1) Anti-aging
The length of telomeres in the DNA has shown to be important predictors of longevity. IGF-1 has been shown to correlate with greater telomere length in healthy subjects of all ages [6] and in elderly men, in another study [7].
In the famous Framingham Heart Study of 525 people between the ages of 72 and 92, greater levels of IGF-1 were associated with a decreased risk of dying in the next 2 years [8].
IGF-1 helped prevent age-related cognitive decline in rats, possibly by promoting new cell growth in the brain [9].
Aging [10], and its associated frailties, such as lowered muscle strength, slower walking, and less mobility are associated with lower levels of IGF-1 in older women [11].
Critically ill patients tended to have lower IGF-1 levels [12].
2) Antioxidants
IGF-1 increases glutathione peroxidase, an important antioxidant enzyme [13].
It protects cells exposed to radiation, by preventing cell death and increasing the antioxidant status [14].
3) Inflammation and Autoimmunity
When IGF-1 levels are low, inflammation tends to be high [15, 16].
In mouse models of autoimmunity and brain inflammation, administration of IGF-1 delayed disease onset; however, giving IGF-1 after the disease had developed led to an enhanced worsening of the disease [17].
Allergic contact dermatitis, Multiple Sclerosis and type 1 diabetes is reduced in mice when they’re given IGF-1 [18].
Low IGF-1 levels have been documented in patients with HIV [19] and inflammatory bowel diseases.
Patients with chronic inflammatory diseases, such as Rheumatoid Arthritis and Lupus tend to have lower levels of circulating IGF-1 [20].
IGF-1 helps combat autoimmunity by increasing T Regulatory Cells. IGF-1 also decreases MHCI gene expression [21].
In animals studies, high histamine levels in the body are associated with low IGF-1 in the blood (reduced via a histamine H1 receptor-mediated pathway) [22].
4) Brain Health
IGF-1 improves learning and memory in animal models [23].
It works as an anti-anxiety and antidepressant in mouse studies [24].
Lower levels of IGF-1 are associated with depression in aged mice [25].
It speeds up mental processing in a study of 25 older men [26].
IGF-1 prevents the accumulation of amyloid plaque in the brain, in a rat model of Alzheimer’s disease [27].
In people, Alzheimer’s Disease and Dementia are associated with lower IGF-1 levels [28], and IGF-1 resistance accompanies insulin resistance in the brain in Alzheimer’s Disease [29].
It increases BDNF in the brain, mimicking the effects of exercise [30].
It helps motor neuron diseases like ALS (Amyotrophic Lateral Sclerosis) [31, 32]. ALS is associated with lower IGF-1.
5) Muscle Growth & Wasting
IGF-1 is important for building muscle [33], and for reducing muscle loss in aging and disease.
6) Blood Sugar
Lower IGF-1 is associated with Metabolic syndrome [34].
IGF-1 infusions helped lower blood sugar, improve insulin sensitivity, and lower triglycerides in a study of Diabetes Type 2 patients [35].
People who are obese are more likely to have lower free IGF-1 [36].
In hepatitis C, people have lower IGF-1 and they are more likely to be insulin resistant, and it’s thought that these might be connected [37].
7) Heart Disease
IGF-1 has shown to have anti-inflammatory and anti-oxidant effects on blood vessels, stabilizing existing plaque and reducing additional plaque accumulation [38].
Cardiovascular disease (coronary artery disease, fatal ischemic heart disease, ischemic stroke, congestive heart failure, as well as slower recovery after a heart attack) is associated with reduced IGF-1.
Lower IGF-1 levels were associated with a higher risk of stroke in a study of a Chinese population [39].
8) Growth/Height
Growth Hormone’s (GH) activity in the body is dependent on IGF-1. So, IGF-1 deficiency causes insensitivity to GH and its effects on growth and repair.
IGF-1 helps restore height in children with IGF-deficiency [40].
Poor growth of an infant in the womb can be due to lowered IGF-1 [41].
Laron Syndrome (a type of dwarfism) is associated with lower IGF-1 in children [42].
9) Bone Density
Higher IGF-1 levels are associated with greater bone mineral density in older women.
We know that IGF-1 is a direct promoter of bone growth [43].
However, IGF-1’s muscle-building (anabolic) effect may also promote bone density, since increasing muscle mass, in turn, requires greater bone strength [44].
10) Gut Health
In animal models of colitis, burns and jaundice, treatment with IGF-1 improved gut health. It stimulated mucosal DNA and protein content and drastically reduced the incidence of bacterial translocation [45, 46, 47].
In animal models of small bowel transplantation, IGF-I improved the mucosal structure and absorptive function and reduced bacterial translocation [48].
Infants with gut permeability showed faster healing times when given IGF-1 [49].
12) Bacterial Infections
In animal models, IGF-1 helps clear bacterial infections and improves survival in sepsis [50].
In animal models of cystic fibrosis, IGF-1 was able to help clear bacteria from the lungs [51].
13) The Immune System
IGF-1 can help increase natural killer cell activity [52].
IGF-I drives B-cells to multiply [53].
14) Electrolyte Balance
IGF-1 has been shown to help restore fluid balance in the rats [54, 55] and in humans [56].
15) Is Good For Skin
Reviving stagnant collagen synthesis can help protect skin against aging [57].
Insulin-like growth factor-I (IGF-I) is the most potent stimulator of collagen biosynthesis and may help prevent skin aging [57].
Other
IGF-1 and growth hormone inhibit urea synthesis [58], which may cause lower blood urea nitrogen. Growth Hormone-deficient children given human growth hormone results in lower urea nitrogen and this is due to decreased urea synthesis [59].
Advanced liver cirrhosis correlates with low IGF-1, in adults [10].
Other Effects of IGF-1
1) May Contribute to Cancer Development
Because IGF-1 stimulates growth, cancer cells can hijack it to support their own development.
IGF-1 creates an environment conducive to breast cancer and resists anti-cancer drugs [60].
IGF-1 was shown to increase the invasiveness of breast cancer [61].
A review of 17 studies found that IGF-1 is positively associated with breast cancer risk, taking levels of IGF binding protein (IGFBP3) into account, due to its effects on estrogen-sensitive tumors [62].
High IGF-1 is associated with an increased risk for prostate cancer [63].
Blood IGF-1 levels are higher in those with lung cancer than controls [64] (or maybe not [65]).
Higher IGF-1 levels in the blood are associated with colorectal cancer [66].
However, another study found that both low and high IGF-1 increased the chance of dying from cancer [3].
NOTE: Studies are unclear. Some take into account IGF-binding protein 3, and some do not. IGF-binding protein 3 (IGFBP3) is supposed to keep IGF-1 levels in the body in balance. When IGF binding protein (IGFBP) levels are low, free IGF-1 is unchecked and can cause growth that is out of control [65].
2) Contributes to Acne
Increased IGF-1 may influence acne in adult men and women. While IGF-1 appears to have a stronger effect on acne in women, testosterone/androgens may play a greater role in acne for men [67].
IGF-1 Tests
The IGF-1 blood test is currently only approved to identify growth hormone deficiency. Work with your doctor to determine whether an IGF-1 test is necessary in your case [68].
Much more research will be required before it can be used as a diagnostic tool for any of the other conditions discussed below. However, researchers have found these associations, and we think it’s interesting to look at where the research is going, so we provide them for our readers’ interest and information.
Ranges and Diseases
Breast cancer:
- Studies showed an IGF-1 range of 170 – 190 in women aged 45-60 with breast cancer [62].
- In another study, premenopausal women with IGF-1 levels over 207 were at an increased risk of breast cancer [69].
Prostate cancer:
- Studies showed an IGF-1 range of 160 – 170 for men with prostate cancer around age 60 [70].
- In another study of men with prostate cancer averaging at age 65, IGF-1 levels were around 150 – 170 [71].
- In the Physicians’ Health Study, an IGF-1 over 185 raised the risk for prostate cancer [72].
Cardiovascular Disease and Cancer:
- Higher IGF-1 (approximately 190) is associated with increased risk of cardiovascular events and deaths from cancer in elderly men (average age 75) [73].
Higher Overall Risk of Disease or Mortality:
- IGF-1 levels are about 70 – 80 or lower are associated with an overall increased risk of disease or death [74].
Factors that May Increase/Decrease IGF-1
It’s important to remember that no good evidence supports the claim that increasing or decreasing IGF-1 is good for your health. The studies we discuss below have found associations, but have not proven causation.
These lifestyle changes, supplements, and other factors may increase or decrease IGF-1 levels, but none of these strategies have been proven to affect health outcomes. Work with your doctor to treat any underlying condition causing high or low IGF-1.
Associated With Increased IGF-1
- Healthy diet and exercise [75]
- Dietary Protein [76]
- Red meat (association) [77]
- Dairy or Calcium [78]
- Increased intake of Casein (found in milk) [79]
- Vitamin C [80] – there’s a correlation between dietary vitamin C intake and IGF-1
- Increased intake of Blueberries [81]
- Growth Hormone [82]
- Estradiol [83]
- Cortisol [84]
- DHEA [85]
- Parathyroid Hormone [86]
- Prolactin [87]
- Resveratrol – increases IGF-1 in the memory center (hippocampus) of the brain [88]
- Cinnamon (skin) [57, 89]
- Leucine [90]
- HMB [91]
- Zinc [92, 93, 94] – In humans, low zinc is associated with low IGF-1, even in the presence of adequate caloric intake. Some studies suggest that zinc potentiates the action of IGF-1 [19]
- Magnesium [95] – magnesium levels were strongly and independently associated with IGF-1 levels [96]
- Selenium [97, 95]
- Astragalus [98]
- Eleuthero [98]
- Ursolic acid (muscle) [99]
- Carnitine (muscle) [100]
- Velvet Antler [101, 102]
- Soy isoflavones [103]
- Dried Plum [104]
Associated With Decreased IGF-1
- Fasting [105], especially prolonged fasting [106]
- Carbs – A Higher dietary proportion of carbohydrates is associated with lower IGF-1 [77]
- Protein restriction [107]
- Calorie restriction [108]
- Intense walking [109]
- Legumes [110]
- Royal jelly [111]
- Glucosamine [112]
- Bilberry [113]
- Luteolin [113]
- Curcumin [114]
- Resveratrol (Grapes – especially the skin, mulberries, peanuts) [115]. Inhibits IGF-1 in intestinal cells, reducing collagen formation that might otherwise lead to scarring and narrowing of the intestinal passageway. (Resveratrol increases IGF-1 in the brain – see below).
- Apigenin [116, 117] – in a study of human prostate cancer
- Lycopene (Tomatoes, guava, rosehip, watermelon, papaya, apricot, pink grapefruit) [118]
- EGCG (Green tea) [119]
- Boron (fruits & vegetables, raisins, nuts, legumes) – reduces free IGF [120]
- Genistein (Soybeans and soy products, red clover, and Sicilian pistachio) [121]
- Inflammation: Histamine [22], TNF-a [122], IL-6 [15], IL-1-alpha [15] – the negative effect of IL-6 on muscle function may be caused by lower IGF-1 [123]
- Tamoxifen [124]
Related Genes
IGF-1 is heavily influenced by your genes. If you’ve gotten your genes sequenced, SelfDecode can help you determine if your levels are high or low as a result of your genes, and then pinpoint what you can do about it.
