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Sunday, 26 January 2020

Why you need more Vitamin D in the winter

By: Margherita T. Cantorna, Distinguished Professor of Molecular Immunology
Pennsylvania State University

"Winter is upon us and so is the risk of vitamin D deficiency and infections. Vitamin D, which is made in our skin following sunlight exposure and also found in oily fish (mackerel, tuna, and sardines), mushrooms and fortified dairy and non dairy substitutes, is essential for good health. 

Humans need vitamin D to keep healthy and to fight infections. The irony is that in winter when people need vitamin D the most, most of us are not getting enough. So how much should we take? Should we take supplements? How do we get more? And, who needs it most? 

I am a medical microbiologist and immunologist who studies the functions of vitamin D in immune cells. My laboratory has been interested in figuring out why the immune system has vitamin D receptors that determine which cells can use vitamin D. In the immune system, vitamin D acts to improve your ability to fight infections and to reduce inflammation. 

Where to get your vitamin D 
Vitamin D is called the sunshine vitamin since it is made in the skin after exposure to the sun. The same UVB rays that cause a sunburn also make vitamin D. Sunscreen, darker skin pigmentation, clothing and reduced daylight in winter diminish the skin’s ability to make vitamin D. The people who experience the biggest seasonal swings in vitamin D levels are fair-skinned individuals living in the northern regions of the U.S. and at higher latitudes around the globe where there is very little daylight in winter. 

But those most at risk for low vitamin D levels are people of colour and people living at higher latitudes. Dark-skinned individuals are more likely than fair-skinned individuals to below for vitamin D year-round because the darker skin blocks the UVB rays from producing vitamin D. However, even in dark-skinned individuals, vitamin D is lowest in the winter. 

In the winter, in addition to high vitamin D food, adults should take additional vitamin D from foods and/or supplements to get at least 600 IU per day of vitamin D. People who have dark skin or avoid sunshine should eat more vitamin D year-round.


Vitamin D is important for bones and your microbes 
Originally, doctors thought that vitamin D was only important for bone health. This was because vitamin D deficiency caused bone diseases like rickets in children and osteoporosis in adults. However, in the 1980s scientists discovered that immune cells had receptors for vitamin D. 

My group’s research has shown that vitamin D plays an important role in maintaining health in the gastrointestinal tract. Higher levels of vitamin D reduce susceptibility to inflammatory bowel disease and Crohn’s disease, gut and lung infections in animals and people. 

My colleagues and I have discovered that one of the ways vitamin D functions is by keeping the microbes in the gut healthy and happy. Vitamin D increases the number and diversity of microbes living in the gut, which together reduce inflammation throughout the body. 

Low vitamin D levels are associated with inflammatory bowel disease in humans. Researchers have found that inflammatory bowel disease patients in Japan have more symptoms in winter than during other seasons.

Why is vitamin D more important in winter? 
In the winter, humans are exposed to more infections and spend less time outside. Exactly how much vitamin D healthy adults should have is debated. Some authorities recommend 200 IU per day to 2,000 IU per day. 

In the U.S., the Institutes of Medicine recommends 600-800 IU per day for adults, while the Endocrine Society states that optimal vitamin D status may require 1500-2,000 IU per day. 

In the winter, people have a reduced ability to make vitamin D when they go outside, so amounts of at least 600 IU per day of vitamin D from food or supplements would help maintain vitamin D status at summer levels. 

But, just like many things, too much vitamin D can be harmful. Vitamin D toxicity does not result in too much sun or food. 

Because of the risk of skin cancer, dermatologists and other health professionals do not recommend unprotected sun exposure to boost your vitamin D. Instead they suggest supplements. But vitamin D toxicity can occur if an individual takes too many. 

The experts that set the national intakes of vitamin D for the U.S. recommend that adult individuals take no more than 4,000 IU per day of vitamin D to avoid toxic side effects. 

Vitamin D helps you absorb calcium from your diet, but when vitamin D is too high, calcium levels in the blood go up and that can lead to kidney disease. 

By consuming more vitamin D during the winter your gut microbes will be healthier and you’ll be more resistant to infection and inflammation year-round."
The above from article here and read the original article here 

Related Reads
NHS Guidelines on Vitamin D - see here
Public Health England Vitamin D advice - see here

Recipe Suggestions

Roast Vegetable Frittata with Mackerel - more details here 

Tuna Fish Casserole - more details here
Sardine Stuffed Avocado -more details here

As regular readers know, this blog is presented in a magazine style - we hope something for everyone. You will find a variety of articles, studies, thoughts, photographs, music and recipes!

However, not all the recipes ideas featured in this blog may be suitable for you. If you may have any food allergies, or underlying health issues these must always be taken into account. If you are a diabetic and not sure how certain foods may affect your blood sugars, test is best, i.e. use your meter.

All the best Jan

39 comments:

Tom said...

...for some reason getting enough vitamin D has never been a problem.

Chatty Crone said...

Do you recommend it from food or vitamin?

Lowcarb team member said...

Chatty Crone said...
Do you recommend it from food or vitamin?

Hello there, and many thanks for your comment and question.

Reading through the article Margherita T. Cantorna, the Distinguished Professor of Molecular Immunology who wrote the article recommends that "In the winter, in addition to high vitamin D food, adults should take additional vitamin D from foods and/or supplements to get at least 600 IU per day of vitamin D. People who have dark skin or avoid sunshine should eat more vitamin D year-round."
However, she also states that "like many things, too much vitamin D can be harmful" … and "experts that set the national intakes of vitamin D for the U.S. recommend that adult individuals take no more than 4,000 IU per day of vitamin D to avoid toxic side effects."

It is of course a personal choice whether you take supplements, and also any other health issues must always be taken into account.

Both Eddie and I eat a selection of foods that include Vitamin D.
Also different countries seem to have slightly different guidelines.

If you (or any other reader) have any queries or concerns about your level of Vitamin D it is always best to see your own Doctor / medical team.

All the best Jan

Pom Pom said...

Thank you, Jan! I love all the vitamin D foods, so yay!
I also love sunshine and I shall go out walking today and soak up a bunch!

Mary Kirkland said...

I take Vitamin D supplements because mine was so low.

Christine said...

Thanks for this good information, I do take a vitamin D supplement.

Iris Flavia said...

I sure love some of these!

CJ Kennedy said...

Good to know.

Snowbird said...

Really interesting Jan. P.s, for some reason I'm not getting email notifications of your blog, or any blogspot ones. I have no idea why, I'll just have to keep pooping by.xxx

Valerie-Jael said...

Thanks for the good information! Valerie

Elephant's Child said...

So many of us avoid being in the sun, and cover up when we are, that I think most of us would benefit from a vitamin D supplement.
I am in the garden often and thought I was getting enough. A recent blood test made a liar out of me (perhaps because I go out early?). I now start my day with a Vitamin D tablet.

Sue said...

I will definitely need to keep taking the sunny holidays! Have a very happy week, Sue xx

Fun60 said...

A really interesting article. Often wondered about supplements but I have a balanced diet and am out walking a lot so hopefully I've got this one covered.

My name is Erika. said...

This is definitely me. Thanks for the post.

aussie aNNie said...

Great information. Thinking I get enough Vit D at the moment with our extreme sunshine..trying not to get burnt in the mean time with our heat.x

dellgirl said...

This is some great information, Jan. It's good to know this. Thank you for sharing it.

Wishing you a wonderful week, dear friend!

Lady Fi said...

I take supplements all winter.

peppylady (Dora) said...

Sardine is something I take in my lunch quite often

Margaret D said...

Love the sun in our winter, it's lucky we have it.

angryparsnip said...

Since I have been very housebound lately I know I am not getting enough Vitamin D. Even though I thought I was eating well.
Doctor is giving me a supplement now
Great post Thanks.
parsnip

Crafty Green Poet said...

good article, vitamin D is so important. More so the more northerly you are

Bleubeard and Elizabeth said...

Tuna, eggs, and vitamins will possibly help me. This was a nice article, Jan.

Teresa said...

Muy buen artículo. En España también tenemos deficiencia de vitamina, mi marido toma una ampolla cada mes, yo la tengo muy bien, hasta ahora no la necesito, algunas de mis amigas también la están tomando. Besitos.

JFM said...

Thank you for another great post!
Lots of great info again 💮

Jeanie said...

I'm supposed to take vitamin D year round but I ramp it up in winter when I avoid outside!

Thickethouse.wordpress said...

A nice article. I thought I had commented yesterday, but maybe not...I work at getting enough Vitamin D. It is important.

Sandra Cox said...

Fascinating--and helpful--article, Jan. Thank you.

Lowcarb team member said...

Teresa said...
Muy buen artículo. En España también tenemos deficiencia de vitamina, mi marido toma una ampolla cada mes, yo la tengo muy bien, hasta ahora no la necesito, algunas de mis amigas también la están tomando. Besitos


Google translate:
Very good article. In Spain we also have vitamin deficiency, my husband takes a blister every month, I have it very well, so far I do not need it, some of my friends are also taking it. Kisses.

carol l mckenna said...

Wonderfully informative post about Vitamin D ~ thanks ^_^

Happy Moments to You,
A ShutterBug Explores,
aka (A Creative Harbor)

Rose said...

I need to take Vitamin D...this is just the right article to prod me to do it.

Phil Slade said...

It's no coincidence that the only time Sue and I get common colds is in January/February when the effect of dummy sun has worn off. We try to eat oily fish but it doesn't fully compensate for the lack of sun.

Bob Bushell said...

That's really news, cheers Jan.

happyone said...

Very informative. thanks

baili said...

this was needed and really important knowledge my fried
thank you for sharing i love sunshine as much as cloudy weather and i can feel the difference when we absorb sunlight ,it makes movements flexible

italiafinlandia said...

Thanks for sharing.
I am greedy of milk...

Martha said...

Good advice. I increase my vitamin D in the winter.

William Kendall said...

Good advice!

rallentanda said...

Thankyou for this interesting article. Sunblockers have been used for decades in Oz which has the highest skin cancer rate in the world. Few people realise that they are not getting enough Vitamin D and need a supplement.

baili said...

amazing and really informative article my friend

to be honest i thought hardly about this issue ,but the amount of knowledge that provides this post made me think for that negligence of mine
i am going to take step for better indeed specially for winters
blessings!