Exactly Why You Need Vitamin D + Sunlight For Optimal Health

The Science-Backed Health Benefits Of Sunlight + Vitamin D Dr. Will Cole

After a long dreary winter, few things feel better than warm sunshine, longer days, and the cheerful, kick-back attitude that comes with summertime. As a functional medicine practitioner who often consults via webcam, I see this summer-loving attitude no matter where my patients live. But is it just a mood change, or are there actual, physiological benefits to the sunnier season? Let’s take a look:

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The Health Benefits of Sunshine

1. Sunlight cheers you up

Shorter, darker fall and winter days can lead to SAD or seasonal affective disorder, (1) a condition that affects about 6 percent of people severely, causing depression, and about 20 percent more mildly. SAD is four times more common in women, but fortunately it is alleviated by spring and summer seasons. One mechanism for this is the brain’s ability to produce (2) more serotonin, that feel-good neurotransmitter, with increased exposure to sunlight. Full-spectrum lights can treat SAD during wintertime – ask your doctor about getting a prescription for these lights.

One study found that people were no happier in southern California than in the cold, cloudy, snowy, rainy Midwest, and that suicide rates are actually even higher in warmer South Korea than in icy Scandinavian countries. Infact, Scandinavians are listed as some of the happiest people in the world. Must be all the hygge

Another factor may be the genetics of different populations, which could impact such biochemical functions as vitamin D metabolism. We must also consider the diet of very happy people who live in colder, cloudier parts of the world, as traditional diets consist of wild-caught fatty fish – rich in vitamin D. Sun benefits are just as present in your diet as they are in your actual sunlight exposure.

2. Seasonal food boosts your mood

All the best fruits and vegetables are fresh, ripe, and ready to eat during the warmer months and are much more likely to be available locally, through farmers markets or your very own garden. That means people tend to eat more produce in the summer, and therefore get more vitamins, minerals, and other phytonutrients that boost immune function and mood.

3. The sunshine vitamin feeds your brain

When your skin is exposed to the sun it starts synthesizing good ol’ vitamin D, the sunshine vitamin., What is vitamin D from the sun good for? It is responsible for the proper workings of hundreds of different pathways that control your mood, immune system, and brain function. Every single cell of your body needs vitamin D to do its best work. Which time of sunlight is good for vitamin D absorption? There is no better time to bask in that vitamin producing sunshine than in the summer or clear afternoons (assuming you are practicing safe skin care simultaneously). When it comes to vitamin d, sun benefits are abundant. 

4. Nature calls

Nature heals, and that’s a fact. When it’s cold, people spend more time inside – another fact. One study published in the Proceedings of the National Academy of Sciences, demonstrated that when a group of people walked for 90 minutes in nature they reported fewer negative thoughts compared to the group who walked in the city. Functional MRI brain scans also revealed that the nature walkers had less activity in the subgenual prefrontal cortex, an area of the brain that plays a role in mood disorders and negative thoughts than the city walkers. So city folk, look for a park!

5. Fresh air fights viruses

Poorly ventilated rooms are more likely to foster (3) the cold virus, which also tends to spread more (4) during colder months. Other studies from the NIH found that the flu virus actually became tougher (5) during winter.

6. More sun means better sleep

The presence and absence of sunlight talks to your brain’s pineal gland, telling it to slow down the production of that sleepy-time hormone melatonin when it’s light, and increase production when it’s dark. When the dark hours are longer, and you are outside in the sunlight less often, it can be harder to wake up in the morning, and you may feel sleepier during the day. This can also leave you with less melatonin production at night, reducing sleep quality because your pineal gland isn’t getting those natural signals.

7. Genes adjust to the seasons

About 25% of your DNA actually changes with the seasons, according to one fascinating study (6) published in the scientific journal Nature. The study found that during the winter months, DNA changes seemed to be geared toward preparing for increased exposure to viruses. In the summer, different sets of genes were turned on that were more geared toward blood sugar balance, perhaps in anticipation of all that delicious summer produce. This summer change helps calm cravings and burn off winter fat, too.

8. Sun calms over-reactive immune responses

Sunlight is sometimes used to treat autoimmune diseases of the skin, like psoriasis, because sun exposure can actually help suppress an overactive immune system. This may be because sun exposure increases white blood cells, which help fight disease and defend the body against infection.

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Benefits of vitamin D

You have 60,000 miles of blood vessels running through your body, and you produce 25 million new cells each second!

And while your trillions of cells all have their own purpose, they also have one thing in common….They all need vitamin D.

Your body absorbs sunlight using cholesterol, which helps convert sunlight into a form of vitamin D that your body can use. And you might not guess it from its name, but vitamin D is actually more like a hormone than a vitamin. It helps to regulate hundreds of different pathways in your body. Here are some benefits of vitamin D from the sun:

1. Fights depression

The vitamin D activated by sun exposure acts as an antidepressant in your system, which makes sense when you consider how many people get the “winter blues” coinciding with decreasing amounts of sunshine during the colder months. Low levels of vitamin D are linked to a 14 percent increase in depression and a 50 percent increase (7) in suicide rates. So do the seasons affect your mood, energy, and health? Absolutely, but they are far from the only factor. Dietary choices, activity level, family and social bonds, and attitude play a large role in mood status as well.

2. Reduces asthma

Studies show (8) that pregnant moms with higher vitamin D intake give birth to babies with a 40 percent reduced risk of developing asthma. Other research suggests (9) that vitamin D has a protective effect against upper-respiratory infections in adults.

3. Balances immunity

Vitamin D is an integral part of your immune system, so it’s no surprise that low levels of vitamin D are associated with autoimmune conditions such as MS, (10) Parkinson’s, (11) type 1 diabetes, (12) inflammatory bowel disorders, (13) and autoimmune thyroid problems (like Hashimoto’s disease (14) and rheumatoid arthritis). (15) Conversely, optimal levels are linked with symptom improvement.

4. Strengthens bones

Just in case you haven’t heard, vitamin D prevents (16) the breakdown of bone and increases the strength of the skeletal system. Strong bones can prevent disease, pain, and fragility later on in life. 

5. Boosts brain power

Vitamin D is essential for a healthy brain, and low levels of D are linked (17) to decreased memory and increased rates (18) of neurological conditions like Alzheimer’s.

6. Fights cancer

People who have optimal vitamin D levels have lower levels of breast, (19) prostate, (20) colon, (21) ovarian, (22) and pancreatic (23) cancer. There is also some evidence that this vitamin can both kill cancer cells and impede their growth by up to 50 percent!

7. Improves fertility

Healthy vitamin D levels have been shown to increase the health (24) of sperm and increase (25) healthy pregnancy rates.

8. Protects the heart

Low D levels and decreased exposure to sunlight are associated (26) with more occurrences (27) of heart attacks and strokes.

9. Calms inflammation

Inflammation is the common link between most chronic health problems, and vitamin D is an essential part of the body’s capability (28) to squelch the inflammatory storm going on.

10. Revs up metabolism

In one study, (29) supplementing with D for 12 weeks decreased body fat by 7 percent. Low levels are also linked (30) to metabolic syndrome, which is a precursor to type 2 diabetes.

11. Enhances physical performance

Supplementing with this important vitamin has been shown to boost muscle strength and physical performance. Vitamin D has also been shown in some studies to increase balance, (31) decreasing falls by 20 percent.

12. Improves sleep

Sleep is so important for feeling and looking your best, and healthy levels of D are associated with (32) better sleep quality.

Ok, vitamin D is super important; so what can I do about it?

Your Guide For Boosting Vitamin D

1. Test your vitamin D levels

In functional medicine, we aim for optimally healthy levels (not just within the lab’s reference range), which we consider to be somewhere between 60 and 80, depending on the person.

2. Get some sun

Spending some time out in the sun, about 20 to 60 minutes (depending on where you live in the world and your skin tone) without sunscreen is a great way to boost your D levels.

3. Eat more vitamin D-rich food

These are some of my favorites:

  • Cod liver oil: 1 teaspoon: 440 IU (over 100 percent Daily Value)
  • Sardines: 3 ounces: 164 IU (41 percent Daily Value)
  • Salmon: 3 ounces: 400 IU (100 percent Daily Value)
  • Mackerel: 3 ounces: 400 IU (100 percent Daily Value)
  • Tuna: 3 ounces: 228 IU (57 percent Daily Value)
  • Raw grass-fed milk: 1 cup: 98 IU (24 percent Daily Value)
  • Caviar: 1 ounce: 33 IU (8 percent Daily Value)
  • Organic eggs: 1 large: 41 IU (10 percent Daily Value)
  • Mushrooms: 1 cup: 2 IU (1 percent Daily Value)

4. Supplement as needed

Since it’s difficult to get vitamin D exclusively through food, and most of us don’t spend enough time outside in the sun, supplementation may be necessary. Based on where your starting level is, I typically suggest supplementing with anywhere between 2,000 and 6,000 IU of vitamin D each day. Because vitamin D is a fat-soluble vitamin, I prefer the drops and capsules that include mct or coconut oil. Look for supplements without added fillers or colors, and retest every two or three months to ensure your levels don’t go too high, which isn’t good either.

5. Tap into vitamin synergy

When getting your vitamin D levels up to where they should be, it’s best to include the other fat-soluble vitamins: A, E, and K2. These vitamins are uber important in their own right and help balance out the vitamin D, making it more bioavailable but also preventing levels from getting too high. You can supplement with these, but I also suggest focusing on food jam-packed with these fat-soluble vitamins. Check out my article on the subject to learn more.

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Dr. Will Cole, DNM, IFMCP, DC is a leading functional medicine expert who consults people around the globe, starting one of the first functional medicine telehealth centers in the world. Named one of the top 50 functional and integrative doctors in the nation, Dr. Will Cole provides a functional medicine approach for thyroid issues, autoimmune conditions, hormonal imbalances, digestive disorders, and brain problems. He is also the host of the popular The Art of Being Well podcast and the New York Times bestselling author of Intuitive Fasting, Ketotarian, Gut Feelings, and The Inflammation Spectrum.

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