Fall and winter seasons bring colder temperatures, cloudy skies, and a lower angle of the sun in the sky. We spend more time indoors and have less skin exposed when outdoors. These factors significantly impact your ability to make vitamin D from the sun and make it even more important to ensure dietary and supplemental intake.

Vitamin D

Vitamin D does many things. It is immensely important for your bones and dental health, growth and development, immune system defense, mitochondria and energy production, genetics, colon health, blood sugar metabolism, thyroid hormone function, cholesterol management, and so much more. Every cell in your body uses vitamin D and it is involved with countless gene signals. Here are some recent findings on how vastly important vitamin D is for your whole body.

Highlights for Vitamin D and Brain Health

Brain health research provides a fascinating glimpse into the delicate workings of vitamin D throughout the brain and nervous system. High amounts of vitamin D receptors are found deep within the limbic system, including the hippocampus (memory center), hypothalamus and thalamus, substantia nigra, etc. along with nerves and glial cells where vitamin D is used for neurological function.

The hippocampus is the memory center of your brain and affects short-term, long-term, and spatial memory. The hypothalamus helps to regulate body temperature, emotions, sleep cycle, growth, hunger/appetite, weight, sex drive, autonomic nervous system function and is the commander for hormone release elsewhere in the body.

The thalamus is a relay system, connecting other parts of the brain and body to the hypothalamus. It is involved with sensory pathways, including smell, and interpreting sensory information. Substantia nigra is closely involved with movement, motivation, and dopamine storage. Your vitamin D status affects these life-essential processes and functions, genes, and genetic regulations within your brain.

In addition to high levels of vitamin D receptors in these life-vital brain regions, vitamin D also regulates and manages nerve growth and repair mechanisms and is directly involve with the synthesis of the neurotransmitters acetylcholine (autonomic nervous system, memory, coordination), dopamine (focus, mood, movement), and GABA (relaxation, sleep).

Vitamin D also helps the insulation layer, or the myelin sheath, around your nerves. It is used by nerves to repair and regenerate throughout your body. It provides a neuroprotective effect, as it helps regulate neurotrophin, which regulates growth and survival of nerves and modulates calcium levels within nerve tissues.

Vitamin D Supports Cardiac Nerves and Rhythm

Vitamin D is required for your heart’s neurological function and rhythm. It safely supports function and conductivity of nerves, including resting heart rate variability. Vitamin D supports parasympathetic (rest/relax/repair) activity while it buffers against oxidative stress, increased blood sugar stress, and excitatory neurochemicals that provoke autonomic nervous system irritation.

Vitamin D Essential for Circadian Rhythm and Autonomic Nervous System

Vitamin D also impacts your circadian rhythm and blood pressure. Given the vast impact that vitamin D has on the hippocampus, hypothalamus, and global brain function, this makes complete sense.

Two interesting studies evaluated children’s vitamin D status on autonomic nervous system and cardiac nerve activity and the tendency towards fainting. Children with adequate vitamin D had more stable blood pressure management because of its impact on the autonomic nervous system and circadian rhythm. Children with adequate vitamin D had superior cardiac nervous system tone compared to those who had low vitamin D levels.

Other research in healthy adults showed that cardiac autonomic nervous system activity and heart rate correlated with vitamin D status. Individuals with adequate vitamin D status also experienced superior cardiac nervous system tone like the children’s study above.

Vitamin D: Gut Lining Integrity and Immune Regulation

Vitamin D plays an integral role with your gut microbiome and intestinal lining mucosal barrier. It helps strengthen “tight junctions”, which reduces germs and toxic by-products from going into circulation and helps maintain healthier gut flora. A healthy gut mucosal barrier puts less stress on liver and detoxification, supports healthier blood sugar management, reduces risk of immune dysregulation, and greatly protects your brain and nervous system from metabolic stress.

In the immune system, vitamin D stimulates production of antimicrobial peptides. It promotes T-regs, a type of T-cell, impairs B cells, and modulates levels of pro-inflammatory compounds Th17 and Th1. This helps protect the gut mucosal lining and other mucosal barriers like the respiratory tract from irritation while keeping the immune system activities in balance.

Bone Quality and Implants

Vitamin D plus calcium is equated with bone density and strength in young and old alike. Vitamin D status also affects bone management and strength with joint replacements and dental implants. Animal studies suggest that vitamin D enhances and strengthens bone formation and interaction around implants, or supports “osseointegration”. Animals lacking vitamin D had poorer integration of implants and diminished healing response.

Muscles and Joints

Muscles strength, mobility, and joint comfort are also affected by vitamin D status. Studies show elderly who improved their vitamin D levels with supplementation experienced improvements in physical function, decrease risk for falls, and increased muscle strength. In addition, seniors had improved knee joint comfort, grip strength, quality of life, and physical stability after six months of vitamin D intake.

Lab measurements showed less production of free radicals like reactive oxygen species (ROS) and lower levels of pro-inflammatory substances of IL-6, TNF-a, and NF-kappaB. Other findings described modest increase in muscle fiber size and higher vitamin D content in muscles with supplementation in the elderly who were lacking adequate vitamin D.

Hair

The health of your hair also depends upon your vitamin D status. Studies that evaluated significant hair loss showed that individuals with higher levels of vitamin D had less hair loss compared to those with inadequate levels. Low vitamin D status was associated with increased oxidative stress to hair follicles and activated immune mechanisms that contributed to hair loss, while higher vitamin D levels protected hair follicles.

Don’t Assume. Get Tested.

Every cell in your body has receptor sites for vitamin D making it incredibly vital for all of your physiology. As we enter winter season, make sure your vitamin D levels are optimal. Don’t assume your vitamin D status is adequate because of time spent outdoors this summer or just by guessing. Get your vitamin D levels tested via a blood test at least once a year.

Optimal vitamin D levels are considered 50-80 nmol/L. Levels lower than 30 nmol/L are inadequate and put your body at much higher risk for immune challenges, loss of bone and dental quality, mood, memory, and neurological changes, compromised gut health and more.

Dietary Sources

Fatty fish, beef liver, egg yolks, dairy and fortified foods contain vitamin D and are the best food sources. Mushrooms provide variable amounts of vitamin D for those on a strict plant-based diet, but these amounts are inconsistent compared to animal foods. One egg provides 44 IU, one cup of fortified 2% milk provides 120 IU, sockeye salmon, cooked 3 ounces provides 645 IU, and cod liver oil, 1 tablespoon provides 1360 IU of vitamin D. Fruits, vegetables, legumes, and grains do not naturally contain vitamin D.

The best source for vitamin D production is sunshine. Mid-day summer sun with significant skin exposure for 20 minutes provides about 20,000 IU of vitamin D. Think about how good you felt when you were out in the sun compared to a cloudy, winter day.

The FDA’s Daily Value for adults and children 4 years and older is 20 mcg or 800 IU per day. Sunshine exposure provides 10,000 - 20,000 IU during the summer. Vitamin D becomes activated by the liver and kidneys, which requires adequate levels of the antioxidant glutathione to accomplish this. Nutritional supplements provide vitamin D3.

Statin drugs, steroids like prednisone, and some weight loss drugs deplete or interfere with the production of vitamin D. If you don’t have a gallbladder or have poor digestion, this too can impair absorption of vitamin D from foods.

Your health depends upon adequate vitamin D! Are You Getting Enough?

Additional Resources

Vitamin D and Your Immune System – Are You Getting Enough?

Glutathione and Vitamin D: A Powerful Essential Connection

Vitamin D and Magnesium: Essential Partnership for Health

Vitamin D Reduces Muscle Fatigue

Nutrient Status and Immune Vitality

Low Vitamin D Associated with Falls and Loss of Mobility in Elderly

Vitamin D is Lacking in Americans