Insulin regulates blood sugar, and insulin resistance predicts diabetes. Learn more about insulin’s function & the risk of high/low levels here.

What is Insulin?

Insulin is a hormone secreted by the pancreas [1]. Insulin is responsible for lowering glucose and storing it into bodily tissues such as fat, muscle, and liver [2].

Insulin can be fattening. It increases fat synthesis and inhibits the breakdown of fat tissue [3].

In fat tissue, insulin increases glucose uptake, which makes fat cells bigger [3].

Insulin plays a role in suppressing liver glucose excretion.

Insulin is also responsible for the stimulation of protein synthesis in muscles.

Benefits of Insulin

1) Lowers Blood Glucose

Insulin is responsible for lowering glucose and storing it in bodily tissues such as fat, muscle, and liver [2].

Lowered levels of insulin cause the liver to convert glycogen to glucose and excrete it into the blood [4].

Insulin also decreases the production of glucose from protein [4].

2) Nerves and Brain

In a literature review, insulin was shown to enter the brain through the BBB (blood brain barrier) and exert its effects via brain insulin receptors [5].

In a rat model of diabetes, insulin treatment prevented nerve conductance issues and preserved a marker for nerve health (myoinositol) [6].

Insulin is one of the many factors that can stimulate nerve growth in test tubes [7].

In test tubes, insulin and the insulin growth factors promote the growth of the sciatic nerve in test tubes [8].

Insulin growth factor 2 plays a role in motor nerve regeneration in animals [9].

The beneficial effects of exercise on the brain seem to be mediated by a hormone similar to insulin (IGF-1) [10].

In Alzheimer and healthy subjects, insulin was able to enhance memory [11].

However, insulin increased a marker of Alzheimer’s (AB42) [12].

3) Cardiovascular

In-vitro, insulin increases a growth factor known to create new blood vessels (VEGF) [13].

Insulin inhibits platelet formation via an increase of a specific compound (cGMP) [14].

In pig hearts, insulin is able to increase heart muscle contractibility [15].

Insulin forces artery wall muscles to relax, thereby increasing blood flow, especially in micro arteries. A lack of insulin reduces flow [4].

4) Builds Muscle

Insulin decreases the breakdown of protein from your muscles and also increases uptake of protein/amino acids – hence why bodybuilders like to spike insulin with glucose [4].

Muscles play a very large role in the utilization and metabolism of glucose mediated by insulin [16]. Diabetics showed much less of an ability to utilize glucose in muscle tissue due to insulin resistance [16].

Insulin causes increased blood flow (dilation) to muscles through the nitric oxide pathway [17].

A higher level of triglycerides in muscle is correlated with lower insulin sensitivity [18].

Insulin: decreases protein degradation in muscles, increases protein synthesis in muscle and increases the transport of amino acids into tissues [19].

5) Increases Stomach Acidity

Insulin increases the secretion of hydrochloric acid by parietal cells in the stomach [4].

6) Helps Retain Minerals

In healthy individuals, insulin was able to decrease the amount of sodium secreted in the urine [20].

Insulin lowers blood potassium. It does this by forcing cells to absorb blood potassium [4].

Insulin decreases water, potassium, and sodium secretion by the kidney (in-vitro) [21].

7) Bone

In isolated bone creating cells (osteoblasts), insulin increased their activity in bone creation [22].

Negatives of Insulin

1) Weight, Fat Tissue

Insulin has mixed effects with regard to weight it reduces appetite, but can increase fat mass.

Insulin is one of the big 4 hormones that determine weight [23].

Insulin puts glucose in your liver, muscle and fat cells [4].

Insulin forces fat cells to take up blood lipids and also converts those lipids to triglycerides [4]. Insulin also decreases the release of fat in your fat cells, so you store more fat [4].

In healthy men, insulin infusion decreased triglycerides by 22%, APOB by 32%, and free fatty acids by 85% [24].

Fat tissue has been shown to release hormones (adipokines) which may play a role in causing insulin resistance [25].

In-vitro, insulin stimulates the creation of fat tissue through the utilization of glucose [26].

In healthy men, elevated insulin levels were associated with greater amounts of fat around the organs (visceral fat) [27].

2) Cancer

Fasting glucose, insulin, and the presence of insulin resistance were correlated with an increased risk of pancreatic cancer [28].

Insulin increases a related hormone (IGF-1) which is elevated in people with lung cancer [29].

Hyperinsulinemia may be associated with an increased risk of colon cancer (correlation versus causation is an issue here) [30].

3) Autophagy

Insulin may in part be negative because it decreases autophagy [4].

Factors That Modify Insulin Release

In a study of men and women, higher alcohol intake was associated with lower fasting insulin levels [31].

When the fiber is taken out of fruit (fruit juice) it causes a greater insulin spike [32].

In women, increased dietary fiber intake was associated with lower levels of fasting insulin [31].

Irregular Insulin Levels?

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