Vitamin D: A complete guide

Executive Summary

Vitamin D helps in many body functions such as calcium and phosphorus balance, blood pressure control, insulin secretion, and immunity. Its deficiency is linked to serious disorders such as high blood pressure, type 2 diabetes, cancer, memory loss, and autoimmune conditions.

Your skin produces vitamin D on exposure to sunlight. However, there are many difficulties in that process, especially for people who are not fair-skinned. Most food sources of vitamin D have too little vitamin D. Hence, vitamin D supplementation is vital.

The adequate levels of blood vitamin D are 30 ng/mL or more. But most people—especially 90% of the elderly—suffer from vitamin D deficiency. Experts recommend a daily intake of 2,000 IU of vitamin D. A mega-dose of 60,000 IU once a week can be prescribed by doctors in severely deficient people. It must be taken under their supervision and only for the advised duration. Doses of up to 10,000 IU a day are not found to cause any harm but conservatively, 4,000 IU a day is advised as a daily upper limit for vitamin D intake.

Contrary to belief, vitamin D does not cause calcium to get into bones; it helps get calcium into the blood. Therefore, with vitamin D supplementation, one is advised at least 1,200 mg of dietary calcium intake. Vitamin K₂ helps divert this calcium from the blood to the bones. Read the full article for more details.

Vitamin D is an important vitamin needed in hundreds of body functions. It has recently come into prominence because its deficiency is rampant and has been linked to many serious disorders such as cancer, type 2 diabetes, heart disease, depression, dementia, and weak immunity.

Vitamin D helps in the absorption of calcium from the intestines into the blood. So it indirectly helps to keep the bones strong. However, as you will read later in this article, vitamin D can just easily lead to fragile bones and concomitant fractures under certain conditions. Read on.

Vitamin D is produced in our body when our skin is exposed to sunlight. However, our modern lifestyle prevents most of us from getting adequate sun exposure. As a result, vitamin D food fortification and supplementation are widely considered.

All this special interest in vitamin D has developed only in the last 15 to 20 years. For example, TIME magazine nominated vitamin D as one of the top medical breakthroughs in its December 2007 issue. This is about a vitamin we studied in our schools 45 years ago.

What is Vitamin D?

In case you think you know what vitamin D is, let me confuse you a bit. Vitamin D is not really a vitamin.

The term ‘vitamin‘ was originally coined as ‘vitamine‘. Vita– means life. Vitamines were supposed to be amines that are important for life. The early scientists thought that the ‘vitamines’ contained amino acids. We now know that neither vitamin D nor any other vitamin contains amino acids.

As per modern science, a vitamin cannot be manufactured by the body. Its only source should be the food we eat. Now, vitamin D can be made by your skin using sunlight. So once again, it fails the definition of a vitamin.

Now, let me confuse you some more. The vitamin D you consume is not the real vitamin D that your body uses. The real vitamin D used by our body is called calcitriol. On the other hand, the so-called vitamin D that our body makes using sunlight is another compound called cholecalciferol. In the literature, it is referred to as vitamin D₃.

Your liver converts this vitamin D₃ to a compound called calcifediol, which circulates in your blood. That is the substance that is measured in the lab tests. So your blood test reports show you neither the real usable vitamin D (calcitriol) nor the one that your body makes (cholecalciferol).

If that is not confusing enough, enter one more guy: ergocalciferol. This is the vitamin D we get from plant sources. And your liver once again dutifully converts it to calcifediol.

Depending on your body’s actual need, your kidneys convert calcifediol to calcitriol, which gets used by the body. Think of calcifediol as the rice grains stored in the house. On a daily basis, you will take out, cook, and eat only a small portion of the stored amount.

So we have these 4 guys with similar-sounding names and functions: cholecalciferol, ergocalciferol, calcifediol, and calcitriol.

Scientists have named cholecalciferol as vitamin D₃ and ergocalciferol as vitamin D₂. Both of these are called prohormones. A prohormone is a precursor or a substance from which a hormone is formed. So the real vitamin D is actually a hormone. After all, your body makes it and it is not a vitamin. Let me summarise this chaos:

Vitamin D₃ or cholecalciferol: This is made by the skin in the presence of sunlight. You can also get it by eating animal sources such as fish oil or fatty fish.

Vitamin D₂ or ergocalciferol: This is made by plants such as wild mushrooms and algae. So eating such foods can give you vitamin D₂.

Calcifediol: Your liver converts vitamins D₂ and D₃ (neither of which are actually vitamins, as discussed) to calcifediol. This is the compound that keeps circulating in your blood in large amounts. Depending on the body’s need, the kidneys and some other organs convert it into the actual vitamin D.

Vitamin D or calcitriol: This is the real vitamin D that is used by your body.

Functions of Vitamin D

Vitamin D is useful in myriad body functions such as calcium and phosphorus balance, blood pressure control, insulin secretion, and immunity. The deficiency of vitamin D is associated with many medical conditions, such as:

• Osteopenia (weak bones) and osteoporosis (fragile bones);
• High blood pressure;
• Heart disease;
• Metabolic syndrome;
• Depression;
• Dementia;
• Childhood asthma;
• Low immunity;
• Autoimmune conditions; and
• Some types of cancers.

We don’t know if vitamin D deficiency causes any of them. However, a person with vitamin D deficiency is more likely to have those medical conditions. The management of these conditions becomes difficult unless you address the vitamin D deficiency first.

Calcium Regulation

Blood levels of calcium need to be tightly controlled. They are vital for bone growth and maintenance as well as muscle function. Vitamin D helps the intestinal calcium absorption from food as well as the calcium reabsorption that gets filtered by the kidneys. Vitamin D also pulls out calcium from the bones into the blood, if dietary calcium is insufficient.

Low levels of vitamin D can lead to bone disorders such as osteoporosis or fragile bones, osteomalacia, and rickets. If one has vitamin D deficiency, only 15% to 20% of calcium can be absorbed from foods (this link downloads a file containing a research paper explaining this).

Phosphorus Regulation

Just like calcium, vitamin D helps in intestinal phosphorous absorption from food as well as phosphorous reabsorption filtered by the kidneys. If one has vitamin D deficiency, only fifty to sixty per cent of phosphorus can be absorbed from foods.

Immunity

Vitamin D is needed in many immune system functions. It increases innate and adaptive immunity and suppresses autoimmunity.

Insulin Secretion

Vitamin D helps in insulin secretion. The deficiency of vitamin D can lead to poor blood sugar control in type 2 diabetes.

Blood Pressure Control

An enzyme called renin is involved in the production of a peptide (small protein fragment) called angiotensin II. This peptide increases blood pressure by constricting blood vessels as well as retaining water and sodium in the blood. Vitamin D reduces renin production as well as the risk of developing high blood pressure.

Central Nervous System Functions

Vitamin D helps in the development and functioning of the central nervous system. Vitamin D deficiency can lead to schizophrenia and multiple sclerosis. It is also linked to dementia, Alzheimer’s disease, Parkinson’s disease, and depression.

Cell Differentiation and Proliferation

A multicellular organism grows using cell division and multiplication. There are two critical processes involved in that: cell proliferation and cell differentiation.

Cell proliferation increases the total number of cells. It is required for wound healing as well as general growth. However, uncontrolled cell proliferation is not good. It can lead to a variety of tumours and cancers.

Cell differentiation is a fascinating process. In that, young, immature cells which is not specialised start taking up individual characteristics and as they mature, start doing more specialised functions that are different from those done by other types of cells.

This is similar to all the kids going to a primary school studying the same stuff. But after going to college, they specialise in science, accountancy, or law, maturing into individuals who perform distinct tasks in society.

Once the cells are differentiated, their rate of proliferation drops. Thus, cell differentiation is vital in reducing the risk of cancer development.

Vitamin D reduces cell proliferation and increases cell differentiation. So a deficiency of vitamin D can lead to cancerous tumours.

Blood Test for Vitamin D

Given so many benefits of vitamin D, its deficiency is a serious health risk. But for that, we should be able to measure it. As mentioned earlier, the vitamin D blood test does not check the actual vitamin D level but that of calcifediol. Why?

The blood levels of vitamin D are nearly a thousand times lesser than those of calcifediol. So measuring calcifediol is much easier.

Also, the real vitamin D has something called a half-life of 1 to 2 days, while calcifediol’s half-life is 2 to 3 weeks. So the blood vitamin D levels fluctuate every few hours while those of calcifediol are far more stable. Thus, measuring calcifediol is a better indicator of the body’s vitamin D status.

This is similar to measuring your blood glucose either as fasting blood glucose or glycated hemoglobin. The former fluctuates rapidly and is also affected by what you ate the previous night. The latter, on the other hand, is fairly stable and indicates your average blood glucose over a couple of months, unaffected by the changes in the immediate past.

Fasting blood glucose and glycated haemoglobin give different information about your blood glucose control. Similarly, calcifediol and calcitriol can give different information about your blood vitamin D control. But whatever calcitriol value tells you is of not much use unless the individual has kidney failure. So only calcifediol values are tested and quoted in the blood reports.

Safe Levels of Vitamin D

Your body is smart enough to make just about enough vitamin D from calcifediol based on its needs. But very high levels of calcifediol can be toxic and are best avoided. What are those levels?

Plus, if you are an engineer like me, you would wonder: if our blood tests are measuring calcifediol and not calcitriol (the real vitamin D), how do we know when we have developed a deficiency of the real vitamin D? After all, the body is supposed to make the same amount of calcitriol (based on its requirements) independent of the levels of calcifediol.

It turns out that the production of the actual vitamin D from calcifediol is very tightly controlled by our body’s endocrine system—its glands and hormones. A hormone called parathyroid hormone or PTH stimulates the conversion of calcifediol to the real vitamin D. So when the levels of actual vitamin D go down too low (as the body deems so), the levels of parathyroid hormone start rising rapidly. Measuring this increase, we can say that the body is signalling to us that its vitamin D levels are too low.

Blood calcifediol is measured in ng/mL. When its level dips below 30 ng/mL, the PTH levels start rising significantly above their normal values. High PTH levels also cause calcium from the bones to be pulled out into the blood. So calcifediol levels below 30 ng/mL can lead to osteoporosis or fragile bones. Those levels are called vitamin D insufficiency.

Table 1 shows various calcifediol level cutoffs indicative of the body’s vitamin D status. Interestingly, the Institute of Medicine, USA has set vitamin D level cutoffs based on calcium absorption and bone mass maintenance needs. On the other hand, the US Endocrine Society has set vitamin D level cutoffs based on its effects on the development of various chronic disorders.

In some countries, vitamin D values are mentioned in units of nmol/L. The conversion is 1 nmol/L = 0.4 ng/mL. So you should multiply the nmol/L value by 0.4 to get the value in ng/mL before using the above table.

Which of the two cutoffs is my own preference? Well, do you just want healthy bones or do you also want to prevent problems from disorders such as high blood pressure, cancers, and type 2 diabetes? I would go with the US Endocrine Society’s cutoffs.

Daily Requirements of Vitamin D

In 2010, the Institute of Medicine, USA set the recommended dietary allowance or RDA of vitamin D at 600 IU a day. That is equal to 15 µg of vitamin D since 1 µg = 40 IU of vitamin D. We will use IU or international units in this article.

The vitamin D RDA of 600 IU is based on our body’s bone health needs. However, for preventing overactive thyroid or hyperthyroidism, that number bumps up to 800 to 1,000 IU a day. Further, if you consider the preventive role of vitamin D in many chronic disorders, that number could be even higher. In fact, many experts suggest 2,000 to 5,000 IU of vitamin D intake a day for optimal health.

Daily intakes of up to 10,000 IU of vitamin D have not been found to cause toxicity or other side effects, even when taken for an extended period of time. However, conservatively, 4,000 IU a day is considered a safe upper limit for the intake of vitamin D.

In my view, 2,000 IU a day is a good number for everyone and a higher number might be fine for brown- or dark-skinned people. This is the table I follow:

Food Sources of Vitamin D

As discussed, foods containing vitamin D₃ come from non-vegetarian sources such as fish oils or fatty fish. Another interesting and humane way of making vitamin D₃ is using lanolin, which is the yellowish fat obtained from sheep wool. When lanolin is exposed to ultraviolet rays, vitamin D₃ is produced. So animals are not harmed in this method of production. If you get vitamin D₃ from lanolin, you can consider it to be vegetarian in nature because it does not involve killing any animal. However, it will still not be a vegan source.

Vitamin D₂ is found in wild mushrooms and algae. So vitamin D₂ food sources will be acceptable for vegans. The only challenge is vitamin D₂ is roughly half as effective as vitamin D₃ in raising your blood vitamin D levels.

The Sunshine Vitamin

Our skin makes vitamin D in the presence of sunlight. Unfortunately, this method of production needs exposure to sunlight for a significant period of time. As a rule of thumb, the daily exposure needed will be equal to one-half to one-fourth of the duration that causes the skin to burn. Since darker skin tones take a longer time to start burning on sun exposure, exhibit 1 shows the sun exposure duration needed for various skin tones.

Issues with Sun Exposure

Most of the medical literature comes from the Western world. So it shows the requisite sun exposure duration as that which is needed by white-skinned people. As you can guess, fair-skinned people need very little time (about 10 minutes) to get adequate sun exposure to produce enough vitamin D. As a result, many articles on vitamin D talk about the virtues of going out in the sun.

Unfortunately, for the rest of the world, sun exposure is not a great option. Here is my detailed article on this website: What is ‘adequate’ sun exposure for vitamin D? Below is the summary of the main points:

1. Longer sun exposure: Most brown-skinned people in countries such as India have skin tones that need three to seven times the sun exposure that a fair-skinned person needs. So most Indians need to stand for thirty to seventy minutes daily in the afternoon sun. That is not practical for white-collared people who work inside offices.
   
2. Skin darkening: While fair-skinned people desire a tanned look, brown-skinned people—many women and some men—are conscious of their skin colour and prefer fairer skin. Any prolonged sun exposure darkens the skin. So doing that on a daily basis is undesirable for such individuals.
   
3. Cultural sensitivities: The exposure time calculated above assumes that the face, arms, legs, and back are exposed to sunlight. It is impossible to expect that in a culturally conservative country such as India, especially women.
   
4. Food fortification: In the developed world, food items such as milk and cereals are fortified with vitamin D. In developing countries, fortification is not the norm. So the only option for most people there is to take vitamin D through unfortified food or supplementation.
   
5. Winter cold: During harsh winters, standing outdoors to expose your arms, legs, and back will be extremely difficult. As a result, it is practically impossible to get adequate sun exposure so that your skin makes enough vitamin D for your daily needs.
   
6. Summer heat: In many places during summer, the days are extremely hot and one does not want to be out in the sun. Now, if you think sitting behind the glass windows of an AC room will solve that problem, it won’t. A specific part of the sunlight called UV-B rays is needed for the production of vitamin D in the skin. The glass windows absorb exactly these rays. Read on this website: Can skin make vitamin D from sunlight through glass? A short, summary video about this:

Vitamin D Supplementation

Foods high in vitamin D are non-vegetarian in nature. The best sources of it are cod liver oil and fatty fish such as trout and salmon. Unfortunately, they are not part of typical Asian staple food. In India, the closest food item high in vitamin D is an egg, which gives 44 IU of vitamin D. For 2,000 IU daily needs of a person, this is barely 2% of the requirement and even then, it won’t suit a vegetarian person. As a result, vitamin D supplementation is recommended.

Supplemental vitamin D is available in two forms: a mega-dose once a week of 50,000 to 60,000 IU and a daily dose of 1,000 to 2,000 IU. There are a few nuanced things you need to understand about these options.

If blood levels of vitamin D are very low, a norm is to give the megadose of ergocalciferol (for vegetarians) or cholecalciferol. This is usually 50,000 to 60,000 IU. It is meant to be taken once a week. So effectively, you are giving 7,000 to 8,000 IU a day.

These mega-doses are prescribed by doctors in the developed world. They should be taken strictly under such medical guidance. The guideline is to use that dose only once a week for 8 to 12 weeks to raise the blood vitamin D (calcifediol) levels. At the end of that period, the blood levels of calcifediol need to be checked before the prescribing doctor decides on whether to continue with the mega-dose.

Fat-Soluble Vitamin

Now, vitamin D is a fat-soluble vitamin. So once it is inside your body, it stays there until it is used. As a result, any excess of vitamin D is likely to harm you.

Water-soluble vitamins such as vitamin C are excreted through urine if taken in more than needed quantities. So they rarely cause any problem with excess intake.

In other words, you need to be careful about your intake of fat-soluble vitamins. The mega-dose of 60,000 IU is high enough that excess or incorrect use of it can elevate your blood vitamin D beyond safe levels.

Unfortunately, in many countries, people simply go to a local chemist and ask for a mega-dose. That is a risky proposition as one may slip into toxic levels of vitamin D unless they are routinely checked.

On the other hand, the vitamin D lab test is fairly expensive—far more than the cost of a few months of vitamin D supplementation. Thus, taking a mega-dose every week and then checking blood vitamin D levels every three months is an expensive affair. So my preference is for a daily dose of vitamin D, which can be safely taken for life.

In short, the weekly megadose of 50,000 or 60,000 IU should only be by prescription of a doctor. On the other hand, a daily dose of 1,000 IU, or preferably 2,000 IU, could be taken by every adult, independent of her vitamin D deficiency status. The daily dose does not lead to toxic levels because the body typically uses that much vitamin D on a daily basis anyway. That is why such daily dose supplements are available in OTC (over-the-counter) format around the world and you do not need any prescription to take them. A short, summary video about this:

Benefits of Vitamin D Supplementation

There are three aspects of vitamin D for our health. The role of vitamin D in:

1. Various body functions;
2. Preventing diseases; and
3. Treating diseases.

So far, most of our understanding of vitamin D is how it helps in calcium and phosphorus balance, blood pressure control, insulin secretion, cell differentiation, and immunity. The research is ongoing about the disease prevention and treatment parts.

Many trials have been conducted but each one used a different patient profile, dosage, and study duration. Some trials were on animal models and some others were just observational studies. The results show a wide range of conclusions. To understand this aspect better, I have a detailed article on this website: How to understand the evidence from clinical trials of nutrients?

Below is a summary of some of the findings.

Bone Health

A vitamin D deficiency reduces the absorption of calcium in the intestines. This can cause low levels of blood calcium. But since calcium is needed for heart and muscle functioning, its blood levels are controlled very tightly. When blood calcium levels dip low, the body stimulates the secretion of parathyroid hormone (PTH) above its normal levels. High PTH levels force calcium to come out of the bones into the blood, weakening them. Thus, a deficiency of vitamin D can lead to fragile bones.

This has led to a misconception that vitamin D helps make bones stronger. Indeed, some trials have shown that if one is deficient in vitamin D, taking its supplements helps prevent fractures. However, once the blood vitamin D levels are in the normal range, taking extra vitamin D does not increase calcium absorption further.

Similarly, vitamin D’s role is not to increase the level of calcium in the bones. It is to raise the level of calcium in the blood. If your diet is deficient in calcium, the blood (figuratively) seeks other sources of calcium such as the bones. So if you take vitamin D supplements but you don’t have enough calcium in your food, you will actually end up with weaker bones and fractures.

Taking 800 to 1,000 IU a day of vitamin D reduces falls and fractures in adults. But one should have 1,000 to 1,200 mg of dietary or supplemental calcium a day to get this benefit for bone health.

Autoimmune Conditions

Autoimmune disorders are triggered when the body’s immune system attacks its own tissues mistakenly. When the immune system is working properly, it acts against foreign substances and pathogens. Certain cells called T-cells spearhead this attack. But too aggressive an attack causes collateral damage to the body. So the immune response of T-cells needs to be controlled or muted. The technical term is modulation of the immune response. Vitamin D helps with that.

Vitamin D deficiency may cause or aggravate rheumatoid arthritis.

Type 1 diabetes is an autoimmune condition often caused in the early years of life. Low vitamin D levels in the mother during pregnancy are associated with a higher risk of developing type 1 diabetes in babies. Supplementing with vitamin D during pregnancy is found to reduce the risk of developing type 1 diabetes in infants.

Vitamin D deficiency is associated with the risk of developing multiple sclerosis. Of course, that does not mean that one causes the other.

Many patients of lupus or systemic lupus erythematosus (SLE) are found to be deficient in vitamin D.

There are many trials conducted with various doses to see the effect of vitamin D supplementation on different autoimmune conditions. The results are all over the place—from improvement and prevention to no effect at all. But I did not find any trial that showed a negative effect, i.e., the vitamin D supplementation worsened the condition.

Higher vitamin D intakes were associated with a reduced incidence of ulcerative colitis and Crohn’s disease, two types of inflammatory bowel autoimmune diseases.

One study suggested that supplementation of vitamin D to increase blood levels above 30 ng/mL may help reduce intestinal inflammation and improve patients’ quality of life.

In summary, we cannot say that vitamin D supplementation can prevent or treat autoimmune conditions. However, correcting a deficiency of vitamin D can reduce the risk of developing autoimmune conditions.

Cancer

Multiple studies have shown that a deficiency of vitamin D is associated with the incidence of many cancers. Similarly, some other studies have shown that vitamin D can limit the progression of cancer cells by reducing multiplication (proliferation), increasing cell specialisation (differentiation), or inducing cell death (apoptosis).

Heart Disease

Vitamin D levels are inversely proportional to the presence of high blood pressure.

Another trial found that every 10 ng/mL increase in blood vitamin D levels was associated with a 12% lower risk of high blood pressure.

A study suggested a link between vitamin D deficiency and endothelial dysfunction, which leads to an increased risk of heart disease.

Type 2 Diabetes

Vitamin D deficiency is found to be fairly common in type 2 diabetes patients.

Some recent trials suggest that vitamin D supplementation may reduce insulin resistance in patients with glucose intolerance or type 2 diabetes.

Dementia and Alzheimer’s Disease

In 70% to 90% of older patients, vitamin D levels are insufficient or deficient. Many of these people also have impaired memory functions. It is believed that vitamin D supplementation can improve brain functions such as remembering details, planning, and organising.

Parkinson’s Disease

Vitamin D deficiency is more common among Parkinson’s patients. Supplementation with vitamin D was found to reduce the worsening of Parkinson’s disease.

Respiratory Disorders

The risk of developing an upper respiratory tract infection or URTI was 24% higher in individuals with vitamin D levels between 10 and 29 ng/mL and 36% higher in individuals with levels below 10 ng/mL compared to that in normal individuals (vitamin D levels of 30 ng/mL or above).

Vitamin D supplementation reduces the severity and mortality (chances of dying) in COVID-19.

My Views

Many of the research papers quoted in this article were published between 2012 and 2018. That tells us that the current understanding of the role of vitamin D in various conditions is based on research in the last ten years. As we go forward, this sliding 10-year window of time will give us more clarity on the full extent of the vitamin D benefits. However, this much is clear:

1. The blood levels of vitamin D of 30 to 60 ng/mL are optimal for preventing many health disorders; and
2. A daily intake of vitamin D of 2,000 IU is recommended for most adults, especially the elderly and darker-skinned people.

Importance of Vitamin K₂

As discussed, vitamin D supplementation does not increase calcium in the bones; it increases calcium in the blood. However, the levels of calcium in the blood are very tightly controlled by the body as it is needed for heart and muscle functioning. So when the blood calcium levels rise, the body immediately starts removing them from the blood leading to calcium deposits.

In general, such deposits go into soft tissues. We can get calcium deposition in the kidneys, leading to kidney stones and in blood arteries, leading to calcified arteries, heart attacks, and stroke.

Therefore, with vitamin D supplementation, we need to ensure that the excess blood calcium is steered into hard tissues such as the bones instead of soft tissues such as the kidneys and arterial walls (the endothelium).

That task is fulfilled by vitamin K₂, which steers the calcium deposits into the bones. But for that, one needs to get adequate vitamin K₂ from the diet. The daily requirement of vitamin K₂ for the body is about 100 to 300 µg, a good part of which can come from the food.

However, there is always a possibility of getting insufficient vitamin K₂ through the diet. So a good idea would be to have vitamin K₂ included in the daily supplement of vitamin D. Here is a short video explaining this point:

People who are on blood thinners for heart conditions are advised to consult their doctors because vitamin K₂ has an active role in blood clotting.

However, given that our body needs 100 to 300 µg of vitamin K₂ a day, having a small amount of vitamin K₂ such as 20 to 30 µg in a tablet is quite safe. Still, you must consult with your doctor if you are going to take a vitamin D plus vitamin K₂ combination supplement if you are on blood thinners.

To Read More

• Nature: Vitamin D supplementation: cholecalciferol, calcifediol, and calcitriol;
• Oregon State University: Vitamin D;
• Harvard School of Public Health: The Nutrition Source: Vitamin D;
• National Institutes of Health: Vitamin D: Fact Sheet for Health Professionals;
• WebMD: Vitamin D – Uses, Side Effects, and More.

First published on: 5th June 2022
Image credit: fwstudio on Freepik
Last Updated on: 29th May 2023