Insulin Cortisol Melatonin Leptin Connection

by Jes Williams @feelmoregooder

It’s all Connected

You may have heard “it’s all connected” before in terms of how our body functions, moves, and operates. This is actually true, and its depth and complexity likely far surpass what many of us may assume. The intricacies of how our systems communicate with each other are extensive and truly astounding. Additionally, the environmental inputs we interface with (light, nutrition, extrinsic stressors) influence these responses and also trigger a cascade of events in the body (think: dominos falling). (1)

Our highly intelligent physiological system is constantly orchestrating a symphony of events ranging from hormonal responses, to neurotransmitter responses, to musculoskeletal responses. If we understand some of the core, foundational aspects of how these systems work, we can use them to achieve better health. This is significant for feeling empowered to take care of yourself (and even lose weight)(2), considering that you have control over many of these things.

Understanding Cortisol

Cortisol, commonly referred to as the “stress-response hormone” is actually set by the circadian rhythm. As the lux of morning sunlight increases, so does cortisol. Ideally, cortisol peaks in the morning and then gradually tapers off as the day progresses. However, modern lifestyles and implications have introduced us to junk light, blood sugar dysregulation, and emotional stress – all of which contribute to chronically high cortisol levels.

The intensity and concentration of systemic cortisol ought to mimic the path of the sun, ideally. This perhaps makes it apparent why focusing on circadian rhythm (sufficient sunlight during the day and darkness at night) impacts hormones. Conversely, not honoring the light and dark cycles will lead to cortisol dysregulation in part because you are squandering melatonin production. (1, 6)

Understanding Melatonin

Melatonin, the hormone that our bodies at night to repair and recover, is also influenced similarly. Ideally, melatonin levels are low when the sun is its brightest and highest when the sun has retired. Too, we want to honor and optimize our body’s ability to use melatonin, otherwise there are negative downstream effects. (3)

Ways that humans disrupt this natural rhythm is by being exposed to artificial blue light at night (stops melatonin production & utilization), eating when the sun is not up (elevates insulin & lowers leptin), and not getting enough sunlight. On the sunlight note, know that there is actually a subcellular mitochondrial production of melatonin, different from pineal melatonin production, that is activated by sunlight exposure. (4,5)

Importantly, we can also strategically use the polyphenol plant compound berberine (found in a bioavailable, functional dose in our product, BerbElite) to help bring insulin levels down. This positively impacts sleep and health because it allows melatonin to surge. (8, 9)

Understanding Insulin

Insulin, the hormone that’s tasked with blood sugar regulation, is secreted by the pancreas in order to allow your cells to use the glucose for energy. The common understanding is that ingestion of carbohydrates elevates blood sugar. This is true, although eating carbohydrates under sunlight versus artificial light makes a difference, as sunlight lowers blood sugar.

Another connection to make here is that exposure to artificial blue light at night (when it’s not intended for our biology) raises blood sugar levels, even when we are not eating. The “wrong” light alone does this, it is how our biology is built, as our system intrinsically is entrained to respond to light. This incorrect light input can lead to insulin resistance, leptin resistance, and an inability to lose weight.

Too, a 2023 study makes it known that insulin is also impacted by the suprachiamastic nucleus in the brain, which sits right above the hypothalamus. The SCN is responsible for creating a top-down cascade of systemic effects in response to light. (1)

Understanding Leptin

Leptin, a hormone discovered in the literature only in 1994 (7), is chiefly in charge of energy regulation, appetite, food intake, body weight, and metabolism. And, it is healthfully impacted by exposure to morning sunlight. (1) This vital hormone helps round out the picture in terms of how light, stressors, and eating patterns influence our ability to stay healthy and even lose weight.

Ideally, leptin docks at night and communicates to the brain how much energy is available for use on the body. Optimizing night time production of leptin is important at night because leptin can only enter the hypothalamus in the brain at night when it is dark in your environment. Interestingly, the science shows that use of an iPad without night shift mode used at night effects leptin levels. (1)

Understanding the Interconnectedness

The absence of light, as well as the presence of sunlight during the day keep these hormones in their proper rhythms. Additionally, stressors and eating food after dark can prevent these hormones from being optimal.

When cortisol is up, so is insulin. When insulin is up, leptin is low. When cortisol and insulin are up, melatonin is down. The body is set up to downregulate certain processes when others are taking place. (10) The key things to remember are that these hormones are all interconnected, they have implications on the other hormones in the body (like the reproductive hormones), and they are negatively impacted by improper light exposure, meal timings, and extrinsic stressors.

References:

1. https://pubmed.ncbi.nlm.nih.gov/36986120/
2. https://pubmed.ncbi.nlm.nih.gov/23429094/
3. https://pubmed.ncbi.nlm.nih.gov/32700826/
4. https://pmc.ncbi.nlm.nih.gov/articles/PMC8621753/
5. https://pmc.ncbi.nlm.nih.gov/articles/PMC5187924/
6. https://pubmed.ncbi.nlm.nih.gov/23505190/
7. https://pmc.ncbi.nlm.nih.gov/articles/PMC3413641/
8. https://pmc.ncbi.nlm.nih.gov/articles/PMC6434235/
9. https://pmc.ncbi.nlm.nih.gov/articles/PMC8696197/
10. https://pmc.ncbi.nlm.nih.gov/articles/PMC6222335/