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Vitamin D is a multifunctional hormone that plays a vital role in our overall health. Synthesized from cholesterol, it's activated in our skin when exposed to UVB light from the sun. This essential hormone impacts everything from bone health and immunity to brain function and inflammation control. However, modern lifestyles and environmental factors often disrupt its balance, leaving many people deficient. In this post, we’ll explore the fascinating pathways of vitamin D metabolism, its critical functions, the signs of deficiency and toxicity, and how to optimize your levels naturally and safely.
Vitamin D Metabolism
There are two main pathways for vitamin D metabolism:
Endocrine Metabolism
Intracellular Metabolism
Endocrine Metabolism
Endocrine glands are glands that produce and secrete hormones directly into the bloodstream.
Vitamin D3 (cholecalciferol) forms in the skin when exposed to sunlight, with the help of cholesterol and fatty acids
The liver converts vitamin D3 into 25-hydroxycholecalciferol
The kidneys then convert 25-hydroxycalciferol into 1,25 dihydroxycholecalciferol, the active form of vitamin D (aka calcitriol).
Endocrine metabolism of Vitamin D
Active vitamin D has several important functions:
Increases calcium and phosphorus absorption in the small intestine
Increases calcium reabsorption in the kidneys
Stimulates calcium release from bones (this is how too much vitamin D can lead to bone loss)
Intracellular Metabolism
"Intracellular" means something is occurring within the cells themselves. Some cells can produce their own active vitamin D3 (calcitriol), independent of the body's internal hormone reserves. These cells include those in the breast, prostate, lung, skin, lymph nodes, colon, pancreas, adrenal medulla, and brain.
The cells take the inactive form of vitamin D from circulation and convert it to the active form within the cell
From there, the vitamin D binds to specific DNA sequences on target genes and activates gene transcription, influencing various bodily processes including immunity, inflammation, and cell growth
Benefits of Vitamin D
Helps control the production of new cells and the type of cells they become (cell proliferation and differentiation)
Supports healthy brain function including cognitive function, neuron protection and regeneration, and may help with depression
Increases immune function and reduces inflammation
Helps the body use insulin more effectively, lowering glucose levels
May support normal cholesterol levels
Low Vitamin D: Causes and Effects
Reduced vitamin D levels can result from:
Obesity
Aging
Prescription drug use including statins, anti-convulsants, and gluco-corticoids
Excessive sunscreen use, lack of sunlight exposure or darker skin color
Potential effects of low vitamin D include:
Increased oxidative stress
Fat-soluble vitamin imbalances (vitamins A, D, E, and K)
Development of autoimmune disease
Decreased immunity and increased infections
Imbalances in calcium and phosphorus
Essential fatty acid (EFA) deficiency
Reduced mental function and neurodegenerative diseases
Symptoms of Low Vitamin D
Bone pain, especially in the lower back
Muscle weakness, particularly in upper arms, thighs, or hips
Muscle aches, twitches, tremors, or spasms
Fatigue and poor sleep
Hair loss and pale skin
Depression
Increased susceptibility to illness
Symptoms of Vitamin D Toxicity (Hypervitaminosis D)
Excessive vitamin D intake can lead to serious health complications, including:
Kidney stones and potential kidney damage
Abnormal heart rhythm and high blood pressure
Bone pain and increased bone loss
Nausea, vomiting, and abdominal pain
Constipation and decreased appetite
Confusion and disorientation
Depression and mood changes
Muscle weakness and fatigue
Excessive thirst/dehydration
Drowsiness and potential psychosis
Always consult a healthcare professional before starting vitamin D supplements to prevent these potential health risks. Since Vitamin D is a fat-soluble vitamin, there's a risk of toxicity since they body doesn't excrete any excess. Any excess is stored in fat tissue.
Food Sources of Vitamin D
Incorporate these vitamin D-rich foods into your diet:
Cod liver oil
Wild-caught salmon
Mackerel
Tuna
Sardines
Beef liver
Egg yolks
Caviar
Supporting Vitamin D Metabolism
Before turning to supplementation, consider the various ways you can naturally optimize your body’s ability to produce and utilize vitamin D. While supplementation can be helpful in cases of true deficiency, the body has a remarkable capacity to synthesize vitamin D when given the right conditions and support.
Here's what to focus on:
Make sure you’re getting enough dietary vitamin D
Consume essential fatty acids (EFAs)
Fish oil, krill oil, green-lipped mussel, ahiflower oil, flax oil
I personally prefer green-lipped mussel over fish or krill oil (it's much more sustainable and has a wider spectrum of EFAs); ahiflower oil pairs well with green-lipped mussel for a broader spectrum of EFAs
Make sure cholesterol levels are high enough for vitamin D synthesis
Remember that vitamin D is made from cholesterol
Consider digestive enzymes with betaine HCl if you have low stomach acid (hypochlorhydria)
Symptoms of low stomach acid include digestive issues like bloating, heartburn, diarrhea or constipation, undigested food in stool, and nausea
They also include things like hair loss, brittle nails, and nutrient deficiencies
Supplement with calcium if you spend a lot of time in the sun
Don't over-supplement with calcium; take it only when you have a confirmed deficiency through blood testing or on days you spend lots of time outdoors
Calcium lactate is the best form to supplement with; it's quickly converted to the bioavailable form in the body
Support liver function (supplement with milk thistle high in silymarin, drink liver supporting teas, eliminate refined sugar from your diet)
Support kidney function (stay hydrated, supplement with spirulina, drink dandelion tea, eat more seaweed, eliminate refined sugar from your diet)
Testing and Supplementation
It's crucial to test your vitamin D levels before supplementing. The National Institutes of Health (NIH) recommends 50 ng/mL as the upper limit. You can order your own labs here, or visit your primary care provider to have your levels tested.
When supplementing, aim for levels between 45-50 ng/mL to avoid potential receptor downregulation. Receptor downregulation is like your body's volume control for cellular signals. When a hormone or molecule is constantly present at high levels, cells start to reduce the number of "antennas" (receptors) on their surface. This is the body's way of protecting itself from overstimulation, similar to how you might turn down a radio that's too loud. The end result of this downregulation for vitamin D receptors is a vitamin D deficiency.
Conventional lab testing for vitamin D lists the normal range between 30 - 100 ng/mL. This range is far too wide, with the lower limit of 30 indicating a deficiency and the upper limit of 100 being twice the number recommended by the NIH.
My favorite vitamin D supplement comes from Quicksilver Scientific. They offer nanoemulsified supplements that are well absorbed by the body. This is a higher dose of vitamin D, so if you choose to supplement, don't take it for more than 2 months consecutively. It's not meant for long-term use.
Cod liver oil is another wonderful source of vitamin D and is also an excellent source of vitamin A. I take this one a few times per week for maintenance.
The Takeaway: Support Your Health with Vitamin D
Vitamin D is more than just a nutrient—it's a prohormone essential to countless bodily functions. From supporting bone health and immunity to modulating genes and reducing inflammation, its impact is significant. However, maintaining the right balance is key. Whether through mindful sun exposure, a nutrient-rich diet, or targeted supplementation, ensuring optimal vitamin D levels requires a personalized approach. Always prioritize testing and consult a healthcare professional to customize your strategy. Supporting your vitamin D metabolism lays the foundation for improved health and overall wellness.
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This post is for educational and informational purposes only and does not constitute medical advice. The natural products and remedies mentioned here are not intended to diagnose, treat, cure, or prevent any disease. Results may vary. Always consult your healthcare provider before trying any new health regimen or natural product, especially if you have a medical condition or take medications. The information provided here does not replace professional medical advice, diagnosis, or treatment.
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