Vitamin D

Vitamin D belongs to the vitamins known as fat-soluble, below you will find all the information about this vitamin.

NAMES

Name in Portuguese : vitamin D ( sometimes called the sunshine vitamin ). The active form of vitamin D , which  is transformed in the body , is called calcitriol ( see below).

There are two main forms of non-active vitamin D : vitamin D3 ( cholecalciferol) from animal sources and vitamin D2 ( ergosterol) from plant sources .

Scientific name: cholecalciferol , calciferol (see explanation below)

Differences between the 2 non-active forms of vitamin D:
An English study published in July 2017 concluded that vitamin D3 (from animal sources) was 2 times more effective in increasing the concentration of vitamin D in the body than vitamin D2 (of vegetable origin). According to British researchers, this is proof that vitamin D2 is not the same as vitamin D3, as some institutions claim. In fact, current recommendations from some health organizations, such as the renowned National Institute of Health, believe that the 2 forms of vitamin D are equivalent and can be used with equal effects. English researchers believe not, and that we should give preference to foods with vitamin D3 over D2. This study was conducted by the University of Surrey in the UK and published on March 28, 2017 in the scientific journal Proceedings of the Nutrition Society .

Sun and vitamin D synthesis

Under the effect of the sun’s UVB rays , a molecule in the skin called  DHC ( derived from cholesterol ) is converted into cholecalciferol ( vitamin D3).

Transformation into the active form (vitamin D or calcitriol)

Vitamin D, such as cholecalciferol and ergosterol acquired through food , dietary supplements, as well as vitamin D synthesized in the skin by the effect of sunlight ( UVB rays), must pass through the liver to be transformed into 25OH vitamin D3 ( the dose of this hormone is determined to know the amount of vitamin D in the body , see below ) and by the kidneys or other cells of the body ( prostate, breast, colon  ) to be finally converted into its active form , calcitriol ( 1,25 vitamin D , 1,25 -dihydroxycholecalciferol or 1,25 – dihydroxyvitamin D ) or vitamin D.

WHERE CAN WE FIND VITAMIN D?

In food
In cod liver oil (1 tablespoon of cod liver contains 1,360 IU of vitamin D), oily fish, salmon, chicken liver, margarine, egg yolk, full-fat and semi-skimmed dairy products, cereals, etc.

Sunlight (UVB rays)
Vitamin D can be synthesized in the skin by the effect of the sun’s UVB rays (also UVB rays from tanning booths). In many countries it is the main source of vitamin D. For most people synthesis of vitamin D from sunlight accounts for about 80 to 100% of vitamin D intake.

It is known that the application of sunscreen with protection factor (SPF) 15 reduces by 98% the production of vitamin D through the skin under the effect of UV rays.

It is important to know that the pollution found in the air, as in Beijing (China), can massively reduce the production of vitamin D by the skin. These air pollution particles absorb a part of the UVB rays.

The production of vitamin D through the sun in a person aged 70 years and over is only 25% of the amount produced by a person aged 20 years exposed to the same amount of sun (source: Am J Clin Nutr 2004;80:1678-1688 ).

Food supplement
Vitamin D can be found in food supplements (capsules, drops), consult your pharmacist.

RECOMMENDED DAILY DOSE

Recommended Daily Allowance , also called RDA for Recommended Daily Allowance : 1 IU 0.00025mg = 0.025μg (1 millionth of a gram )

Amount Recommended by US Authorities
The US Institute of Medicine recommends:
 Adults under 70 years of age: 600 IU/day ( 15 µg /day)
 Adults over 70 years of age: 800 IU/day (20 µg / day) day )
American experts do not recommend consuming more than 4,000 IU per day.

Amount Recommended
 by Canadian Authorities
The Canadian Cancer Society recommends:
– To prevent cancer in adults: 1,000 IU/day ( 25 µg /day ) of vitamin in autumn and winter . In people who are at risk of deficiency , consume 1,000 IU/day year-round .
Some people estimate that in Canada the daily dose should be 2000 IU to 4000 IU per day.
In case of exposure to the sun in summer between 10 am and 3 pm (before and after these times the sun’s rays contain very little UVB ,only this type of UV can synthesize vitamin D) for about 10 to 20 minutes and without using sunscreens , the external dose of vitamin D by dietary supplements can be reduced . In Canada, health authorities generally recommend for adults a daily intake of vitamin D in the form of a food supplement of 400 to 600 IU, as reported in an interview with Create health in March 2017 by Dr. Earl Bogoch of University of Toronto.

In Canada, health authorities even advise people who for different reasons have enough vitamin D (eg exposure to sunlight or food) to consume vitamin D food supplements throughout the year.

Amount recommended by UK authorities
In England, the institution Public Health England  recommends consuming 400 IU per day (10 μg / d) of vitamin D throughout the year for all people aged 4 years and over (data from July of 2017).

Other recommendations for the use of vitamin D Some media and doctors recommend : – Up to 1 year : 400 to 1000 IU/day of vitamin D.  D and 1 to 18 years: 600 to 1000 IU/day of vitamin D. – From 19 years : 1,500 to 2,000 IU/day of vitamin D.

In a letter published in March 2015 in the scientific journal Nutrients, researchers from the University of California, San Diego (UC San Diego) and Creighton University (Nebraska) stated that the recommended daily amount of vitamin D in the United States in adults does not it should be 600-800 IU/day, but 7,000 IU/day, or about 10 times more than today.

According to the IOM (Institute of Medicine, USA), the maximum daily dose of vitamin D considered safe, that is, without the risk of side effects, is 10,000 IU/day. (Source: Creighton University press release, March 17, 2015)

INDICATIONS

– Prevention of osteoporosis , maintenance of calcium balance, which contributes to the formation of bones and teeth (especially in children), helps with clotting, reduces fractures due to falls (according to a study published in 2009 in the British Medical Journal, preparations of vitamin D reduce the overall risk of fracture by 14%, for hip fractures the decrease is 9%).

Critical Study on the Use of Vitamin D or Calcium in Fractures in People Over
50 according to a Chinese study published December 26, 2017 in the scientific journal JAMA (DOI: 10.1001 / jama.2017.19344).
This study, a meta-analysis (review of studies), took 51,145 adults over 50 who did not live in an institution or community such as a nursing home, but lived at home. These adults participated in 33 randomized clinical trials comparing the use of dietary supplements (calcium, vitamin D, or both) with a placebo or no treatment and the risk of new fractures. The results of this research work go against other studies published in the past. Therefore, Chinese scientists who released a statement about the study in December 2017 discouraged the regular use of dietary supplements containing calcium, vitamin D or both in adults over 50 years of age for the prevention of fractures.

– Cancer prevention, as in the book “Cancer” by David Servan-Schreiber, particularly colorectal cancer. Also in the prevention of skin cancer (possible effect against cancer, studies are contradictory).

In the United States, the renowned National Institutes of Health (NIH) medical institute does not recommend the use of vitamin D in cancer prevention, due to lack of evidence, it is estimated that there is no cause-effect relationship between low levels of vitamin D, often observed in the tumor, and the development of a cancer.

However, in April 2016, a study carried out by Professor Garland at the University of California, San Diego ( UCSD ), showed that the incidence of cancer decreased with the increase in blood levels of 25(OH)D, a metabolized form of vitamin D. Women with a 25(OH)D concentration of 40 ng/ml or greater had a 67% lower risk of having cancer than women with a concentration equal to or less than 20 ng/ml.
According to Professor Garland: “This research suggests that increasing the concentration of vitamin D in the blood is an important tool in the prevention of cancer.”

– A study published in November 2016 in the journal JAMA Oncology showed that women with the highest levels of vitamin D had, on average, a 30% higher breast cancer survival rate compared to women with the lowest levels of vitamin D. vitamin D. Over 1600 people were enrolled in this study between 2006 and 2013. The study was conducted by Kaiser Permanente in Oakland, California and the Roswell Park Cancer Institute in New York.

– Prevention of cardiovascular disease (possible effect, studies are contradictory). Note: One study showed that vitamin D was useless against hypertension .

– Lupus and other autoimmune diseases (possible effect, studies are contradictory).

–  Multiple sclerosis (possible effect). Read multiple sclerosis therapy tips and prevention tips for more information.

– Possible prevention of Alzheimer’s disease . Indeed, a correlation has been observed between vitamin D deficiency and Alzheimer’s, as shown by several studies, including a British study published in August 2014. According to the British study, the risk of suffering from Alzheimer’s increased by 69% in participants with moderate vitamin D deficiency and up to 122% in participants with severe deficiency. Note that this is an observation and not necessarily a sign of cause and effect.

– Possible prevention of diabetes . Vitamin D is known to increase insulin secretion and sensitivity by causing a decrease in the number of insulin receptors. Vitamin D would thus have an effect against diabetes.

– Possible prevention of allergic rhinitis in children if the mother consumes foods rich in vitamin D during pregnancy. According to research published in February 2016 in the journal  The Journal of Allergy and Clinical Immunology,  considerable consumption of foods rich in vitamin D during pregnancy – but without dietary supplements containing vitamin D – was associated with a  20% risk of allergic rhinitis lower than those born. This study was performed by the Icahn School of Medicine at Mount Sinai in New York.

– A study published in October 2016 in the Cochrane Review showed that the intake of vitamin D as a food supplement in cases of people with asthma , in addition to conventional asthma treatment, significantly decreased the risk of severe asthma attacks without causing side effects . The research, which went through a sieve of 9 clinical studies, was carried out by an asthma specialist, Prof. Adrian Martineau of Queen Mary University in London.

EFFECTS

– Increases the absorption and accumulation of calcium in association with PTH ( parathyroid hormone). It is estimated that almost all cells in the body have receptors for vitamin D , which is why the hormone is often mentioned when dealing with this vitamin , also because of its role as a messenger .

NEED

Symptoms of Vitamin D Deficiency
– Bone and dental problems, osteoporosis, rickets in children, osteomalacia in adults, restlessness, bone weakness, muscle aches, etc.

Doctors may ask for levels of vitamin D, in particular, a well-known metabolite called vitamin D3 25OH, in the blood. An amount of 25OH vitamin D3 is considered normal between 30 and 100 ng/ml, a limit value of 20 to 30 ng/ml, insufficient for 10 to 20 ng/ml and severe deficiency for less than 10 ng/ml. (source: Journal of Clinic EndocrinologyMetabolism, 2005).

Possible causes of vitamin D
deficiency – Poor diet, lack of exposure to the sun, certain medications such as cortisone and anti-epileptics, people who have undergone bariatric surgery.

EXCESSES

– More than 1800 IU per day, risk of toxicity in children and adults intestinal symptoms (diarrhoea), anorexia.

However, according to Prof. Michael Holick, one of the leading experts on vitamin D at Boston University (USA), vitamin D intoxication can only occur if an adult consumes 10,000 IU of vitamin D per day for 6 months or more. Prof. Holick has written a successful book with the original title “The Vitamin D Solution” about vitamin D, he is a fan of using this vitamin in high doses to treat and prevent various diseases such as cancer and cardiovascular disease.

It is important to know that the production of vitamin D as a result of the effect of UVB rays from the sun cannot lead to intoxication, because the body is self-regulating (regulates itself). However, an intake of vitamin D in the form of food supplements can lead to intoxication (especially of calcium) in case of excessive consumption.

Regarding the concentration of 25-hydroxyvitamin D (25(OH)D) in the blood, side effects may occur at concentrations of 25(OH)D greater than 125 ng/ml. [Source: University of California, San Diego Campus, April 8, 2016]

Vitamin D Side Effects
According to a New York Times article published in April 2017, taking too much vitamin D dietary supplements (see above) can lead to side effects such as nausea and vomiting, lack of appetite, weakness, frequent urination or kidney problems.

SYNTHESIS OF VITAMIN D AT THE CHEMICAL LEVEL

Sun and vitamin D synthesis
Under the effect of UVB rays, a molecule in the skin called 7-dehydrocholesterol (a cholesterol derivative) is converted to pre-vitamin D3 and then to cholecalciferol (vitamin D3).

Transformation into its active form (vitamin D or calcitriol)
Cholecalciferol (vitamin D3), absorbed from food, a food supplement or synthesized by the skin under the effect of sunlight (UVB), passes through the liver to be transformed into 25OH vitamin D3 or 25-hydroxyvitamin D3 (this metabolite is measured, like 25OH vitamin D2, to check the amount of vitamin D in the body, see below) and then passes through the kidneys or other cells in the body (prostate, breast, colon ) to finally be converted into its active form, calcitriol (1,25 vitamin D3, 1,25-dihydroxycholecalciferol or 1,25-dihydroxyvitamin D3).

Ergosterol (vitamin D2) absorbed from food (vegetables) or a dietary supplement passes through the liver to be converted into 25OH vitamin D2 or 25-hydroxyvitamin D2 (this metabolite is also measured, as is 25OH vitamin D3, to know the amount of vitamin D in the body, read below).

GRADES

– Children little exposed to the sun can develop rickets.

– It is advisable to expose yourself to the sun every day for about 20 minutes, especially in late spring and summer, without using sunscreen (read the article on the sun exposure dilemma), as it absorbs a very large UVB. During the use of sunscreens, the synthesis of vitamin D is very low.

In summer, it is estimated that the body produces about 10,000 IU of vitamin D in 20 minutes.

Some sources estimate that exposure to the sun for 5 minutes 3 times a week would be enough to synthesize vitamin D in necessary amounts.

The duration of this exposure depends on several factors such as skin type, time of year and day, as well as latitude. People with dark skin take longer to synthesize vitamin D (about 20-30 minutes) than people with light skin (about 10 minutes).

Always avoid excessive exposure to the sun, a significant risk of skin cancer.

We also know that as we age, the production of vitamin D from the sun is less effective, in which case it is strongly recommended to take vitamin D as a food supplement.

As vitamin D is a fat-soluble molecule, it remains stored in adipose tissue and can be released after several months, especially in winter. In other words, a person well exposed to the sun in the summer can enjoy several months of vitamin A in sufficient quantity.

Regarding sun exposure, the regions of the body where we should prefer exposure are those of the arms or legs. Facial skin produces little vitamin D and is very sensitive.

– It is estimated that in France 70% to 80% of people lack vitamin D. This percentage rises to 90% among women over 45 years old. Thus, it is also important to be exposed to the sun for 20 minutes or to take food supplements that contain vitamin D. Furthermore, more than 20% of French people are in a state of significant vitamin D deficiency.

– For pregnant women, nursing mothers and those with small children, vitamin D supplementation is necessary. Talk to your doctor for the recommended dosage. Also read above
– Several studies have shown and will show (clinical studies are still lacking to confirm 100% efficiency) that vitamin D consumed in the right dose (not to exceed the daily dose) can have a curative or preventive effect against several chronic diseases, such as cancer, lupus and other autoimmune diseases. This makes vitamin D one of the most interesting and medically useful vitamins.

– However, some experts are more critical and claim that most people begin to suffer from a vitamin D deficiency from the age of 65, that is, a lack of vitamin D is relatively rare before the age of 65. These specialists criticize the idea of ​​thinking that vitamin D would be a miracle cure, in the end, few reference and large-scale scientific studies have shown the results in a clear and evident way.

– It is impossible to have vitamin D intoxication in cases of prolonged exposure to the sun.

– If vitamin D is administered through a food supplement, it can be consumed before, during or after a meal.

Interactions
Thiazide diuretics
Vitamin D may lead to interactions with thiazide diuretics (eg hydrochlorothiazide, chlorthalidone and indapamide), the possible consequence of which may be hypercalcaemia. However, according to an article published in January 2018 by the Swiss media iM@il Offizin (linked to the University of Basel), if vitamin D is consumed in normal doses (e.g., as per the guidelines of the federal public health agency of Switzerland), there is no evidence of an increased risk of hypercalcemia with the use of thiazide diuretics.

Magnesium and Vitamin D
– One study found that low levels of magnesium make vitamin D ineffective. Lake Erie College of Osteopathic Medicine scientists have observed that vitamin D cannot be metabolized without sufficient levels of magnesium. This means that vitamin D remains stored and inactive for a large part of the population. Patients with optimal magnesium levels require less vitamin D to achieve sufficient vitamin D levels. Magnesium also reduces osteoporosis by helping to reduce the risk of bone fracture, which can be attributed to low vitamin D levels, the statement said. Prof. Razzaque of the Lake Erie College of Osteopathic Medicine, who conducted this study with other researchers. As we saw in this case, in the United States, recommendations for magnesium intake are 420 mg per day for men and 320 mg per day for women, but the standard diet in the United States contains only approximately 50% of this amount. Researchers claim that consumption of magnesium from natural foods has declined in recent decades due to industrialized agriculture and changes in eating habits. This study was published in the March 2018 issue of The Journal of the American Osteopathic Association (10.7556/jaoa.2018.037).

Neurodegenerative diseases and vitamin D, critical study
Australian researchers found in a study published in July 2018 that vitamin D is unlikely to protect people from multiple sclerosis, Parkinson’s disease, Alzheimer’s disease and other brain disorders. The study was based on a systematic review of over 70 preclinical and clinical studies published in the past. Previous studies have shown that patients with neurodegenerative disease tend to have lower levels of vitamin D than the healthy population. But for the University of Adelaide scientists who conducted this study, there is no convincing evidence that vitamin D can act as a protective agent for the brain. In other words, this low level of vitamin D observed in some patients would be more a consequence than a cause of neurodegenerative diseases.Nutritional Neuroscience (DOI: 10.1080/1028415X.2018.1493807).

Sources:
University of California, San Diego ( UCSD ), JAMA (DOI: 10.1001 / jama.2017.19344),  iM@il Offizin (attached to the University of Basel), Nutritional Neuroscience (DOI: 10.1080/1028415X.2018.1493807).

Who wrote this folder?
Xavier Gruffat  (pharmacist)

 

Jeanne Kenney
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I’m a stylist trainer, a content creator, and an entrepreneur passion. Virgo sign and Pisces ascendant, I move easily between my dreams, the crazy world I want, and my feet on the ground to carry out my projects.

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