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All You Need to Know About Vitamin D

Vitamin D is an essential nutrient that should be included in our diet, not only obtained through synthesis from sun exposure. Vitamin D is fat-soluble, meaning that we can usually find it in foods that contain fats. However, diet alone may not provide sufficient amounts of this vitamin. 
In this article, we will examine this vitamin’s relevance on human health, how to obtain it and why an adequate supplementation is crucial.

Top Foods High in Vitamin D

There are foods high in vitamin D, but the amounts are insufficient to meet our daily needs (approximately 10% of what we get from sun exposure). 
However, in cold seasons or geographical locations where it’s impossible to obtain it, it can be useful to increase the consumption on foods high in vitamin D.

We will take a look at which foods are high in vitamin D:

  • Fish and seafood: Blue fish, in particular, has a high amount of vitamin D. If possible, choose wild-caught fish.
  • Mushrooms: As María Bascuñana recommends in her book (VitaminaDos), if you expose mushrooms to sunlight (laminated or with their hymenium facing upwards), you can benefit from the vitamin D that this food brings to your diet.

We have to consider the low nutritional density of today’s food. Additionally, cooking and preserving food affects the amount of vitamin D it contains.

Sun and Vitamin D

A question that has been debated many times is: Is the vitamin D from sun exposure sufficient for us? Let’s see what science tells us.

Sun and vitamin D are two powerful allies, but even if we spend hours under the sunlight in the summer, it may not be enough. 
There are different factors that can affect significantly the amount of vitamin D that we obtain from the sun.

First of all, latitude. 
The further we are from the equator, the less efficient that production of vitamin D will be. Specifically, obtaining vitamin D from the sun is challenging at latitudes above 33º. Considering that the southernmost point of the Iberian Peninsula is around 36º, it can be really hard to achieve adequate vitamin D levels at these latitudes without significant lifestyle changes or supplementation.

If we mention sun and vitamin D, we also have to consider the seasons and time of the day. At latitudes above 33º, winter makes it almost impossible to produce this vitamin. In the summer, we should get exposure at central times, but that increases the risk of sunburn. Even if there exist different strategies to increase sun tolerance, it can be challenging or hard to accomplish for most people, because of our current lifestyles.

There are other key factors that connect the sun and vitamin D. For example, skin pigmentation (the darker it is, the most exposure time that will be needed), exposure time, skin surface and cloudiness, among others.

Symptoms of Vitamin D Deficiency

Recent epidemiological studies have proven that vitamin D deficiency affects between 35% and 55% of the world’s population. 
In Spain, the percentage is even higher than 60%.

Patients with extended vitamin D deficiency can experience symptoms like bone, head and joint pain, fatigue, weakness and involuntary muscle spasms.

However, consequences of vitamin D deficiency go even further. Low vitamin D levels have been linked to a higher risk of depression and anxiety. Additionally, they can also affect bone metabolism, pain response, hormonal balance and fertility, skin health, insulin resistance, and even development and onset of autoimmune diseases, as we will discuss next.

Benefits of Vitamin D

You may be asking yourself what the benefits of vitamin D are, so we will examine them in detail.

One of its benefits that you may already know is its importance in bone health, including teeth. 
It’s essential for calcium absorption, and it also helps maintain a balance of calcium levels. 
There are contradictory results about the role of vitamin D in bone health, but that has a simple explanation: the secret is in the dosage, as we will learn later on.

One of its most interesting functions is its impact on insulin resistance. Vitamin D improves sensitivity to insulin, as well as its secretion.

Its benefits extend well beyond bone and metabolic health.

  • Vitamin D’s usefulness in managing pain has been proven. For example, it’s beneficial for various types of pain, including menstrual pain, headaches (migraines), neuropathic and musculoskeletal pain, and osteoarthritis.
  • Vitamin D is also crucial for reproductive health, so it’s interesting to know that its benefits affect both feminine and masculine fertility. Its importance is key in gestation and lactation periods. It contributes to a healthy pregnancy and it helps prevent conditions like pre-eclampsia, gestational diabetes, preterm labour, abortion, and even post-partum depression. Later on, vitamin D will have a huge impact on the baby’s health during the early years. A deficiency in vitamin D during this period can lead to certain conditions such as dermatitis, asthma, allergies, neurodevelopmental disorders, and bone diseases.
  • It has positive effects on the immune system. Vitamin D supplementation can be very useful for patients with infections and respiratory diseases such as asthma, or with autoimmune diseases such as multiple sclerosis, hypothyroidism, psoriasis, inflammatory bowel disease, type 1 diabetes, and even in cases of cancer.
  • Vitamin D may have positive effects in brain health, particularly in cases of depression (especially those related to magnesium). There is also scientific evidence suggesting that it may have positive effects on neurodevelopmental disorders, such as Autism Spectrum Disorder, cognitive impairment and multiple sclerosis. Recent studies have highlighted molecular mechanisms that explore vitamin D’s potential for treating depression and anxiety.

Vitamin D Supplementation

When choosing a vitamin D supplement , we need to consider several factors.

Firstly, vitamin D supplementation should be in the form of vitamin D3 (cholecalciferol), rather than vitamin D2 (ergocalciferol).

It’s also necessary to adjust the dosage
The reason there are contradictory results in many studies about vitamin D is partly due to the varying dosages used. 
Excessively low dosages lack significant effects, which is the case in most vitamin D supplements. It’s also important to highlight that there are people who are resistant to vitamin D. This means that patients may need higher doses of vitamin D supplementation, which should be prescribed by health care professionals.

What’s more, excessively high or unique dosages may have side effects, such as intoxication. The effects of vitamin D toxicity are a rare side effect that dates back to the 1930s-1950s, when this vitamin was introduced in the dietary industry through fortified foods. At that time, mistakes in production led to intoxication due to extremely high doses, from 50,000 IU to 2,640,000 IU per day.

Today, the safe maximum dose has been set at 10,000 IU by the Institute of Medicine (IOM) in 2011. 
However, that study was reviewed 3 years later due to an statistic error. 
That was crucial in establishing a new safe and effective dose: the recommended daily supplementation turned out to be around 8,000 IU, indicating that the safe maximum dose is likely much higher. Subsequently, other authors referred to this same error, which opened the door to using higher doses. From 2018 onwards, patients with autoimmune diseases were treated with doses exceeding 30,000 IU. This treatment lasted for years, and no side effects were found.

How do I Take vitamin D?

Besides the dosage of your vitamin D supplement, it’s important to also consider other components that can help maximize its benefits.

  • Of course, there is a strong relationship between vitamin D and the microbiota. This supplement can modify the populations of our microbiota, but the relationship is bidirectional. The use of 4th generation probiotics can be beneficial, as these microbial communities are involved in lipid metabolism (the metabolism of fats) and fatty acid synthesis. This means that the microbiota plays a crucial role in the absorption of vitamin D, since it’s a fat-soluble vitamin (meaning it dissolves in fats).
  • Magnesium is closely related to this vitamin. This mineral is essential for the activation and transportation of vitamin D, and even for the expression of its receptors. The percentage of magnesium deficiency in general population is high (this mineral is primarily found in the soil, and its content in foods has considerably decreased due to intensive farming), and it can occur without presenting any apparent symptoms.
  • On the other hand, it’s important to highlight the role of iron, which is vital for the functioning of vitamin D. In cases of anaemia, lactoferrin supplementation can be useful.

Assessing your nutritional status with regard to other micronutrients is also important, so we recommend consulting a health care professional before starting any supplements.