It is important to be aware that Vitamin D is vital for optimal health, and its insufficiency increases the risk of serious health conditions.
There are 2 major types among several forms of vitamin D3 and D2, and several skin types that influence the amount of the vitamin produced by our body (individuals with dark skin produce less vitamin D than individuals with light skin!).
Other important factors that affect levels of vitamin D are age (aging cause malabsorption), and lifestyle in general (dietary habits, sun exposure or avoidance, clothing, weight/obesity), as well as environmental factors such as climate and air pollution.
D3 is a type of vitamin D produced by our skin and skin of animals/vertebrates during the exposure to UVB sunlight; and the flesh of oily fish ( salmon, mackerel, herring) is particularly rich in this vitamin. It can also be found in a limited amount in egg yolks, meat, and offal.
The second form – D2 is “created” by plants (fungi and yeasts) via sunlight exposure; unfortunately, fruit and vegetables contain little amounts of naturally present vitamin D, and that is the reason why vegetarians need to take fortified foodstuff or take dietary supplements to maintain the appropriate level of the vitamin.
Both types of vitamin D (D3 and D2), are metabolized in the liver (25 hydroxy Vitamin D) and kidneys* to finally reach the active form (1,25 hydroxyvitamin D), which then can bind vitamin D receptors present in each cell of our body.
*the final hydroxylation to the active form, can also occur in other organs (as well as cancer tissues).
Crucial for healthy bones
Vitamin D is immensely important for our skeleton because it participates in calcium homeostasis (i.e., the balance of the internal body environment ). The first discovery of its beneficial effects was around 1920, when scientists from the UK and Austria found that rickets in children can be cured by exposing them to (summer) sunlight and artificially induced UV light.
This fascination went a bit extreme in the late 19th century when prominent U.S. pediatrician Luther Emmett Holt advised parents to attach wire cages to the windows so babies could benefit from the sun!
Although vitamin D is well-known for maintaining healthy bones and preventing osteoporosis, according to the latest research – its role goes far beyond.
Health risks of vitamin D deficiency
Accordingly to the latest science low levels of vitamin D in the blood correlate with many chronic illnesses, such as various types of cancer, cardiovascular, autoimmune (multiple sclerosis) as well as neurodegenerative disorders such as Alzheimer’s.
Vitamin D for longevity
A recent meta-analysis of 22 clinical trials conducted the researchers from the University of Cambridge and Harvard Medical School, suggests that giving vitamin D3 supplementation alone can significantly improve the lifespan (up to 11%). Some previous studies at the University of Copenhagen have also found very similar results.
The possible mechanism includes the prevention of the accumulation of toxic proteins in the cell, which is linked to aging and age-related chronic diseases.
But, it doesn’t mean that taking this vitamin alone would make us healthy and fit. It needs to be coupled with other healthy routines and lifestyles in general, such as adequate nutrition, and most importantly outdoor physical activity.
Vitamin D for cancer prevention
While the role of Vitamin D in the prevention of cancer is still being debated in the scientific communities, researchers do agree on one thing: Vitamin D supplements can significantly increase survival rate (17%) in cancer patients; possibly by slowing the tumor growth, and inhibiting metastasis.
It is, however, necessary to investigate which types of cancer respond better to vitamin D considering inter-individual differences in genetics which might influence response to vitamin D treatment.
Chron’s disease and vitamin D
In patients with Chron’s disease, clinical trials confirmed that patients who received 2000 IU per day of Vitamin D had a drop in inflammation and relapse rate comparing to the placebo group.
Asthma patients who regularly took vitamin D supplements reported a lower number of remissions.
Vitamin D suppresses inflammation
The vitamin can protect us from bacterial and viral infections through several mechanisms:
– By reducing the production of proinflammatory cytokines (chemical messengers)
– By inducing the production of cathelicidin, a polypeptide with antimicrobial and antioxidative properties.
Self-help for common cold/Influenza
In 2006, scientists claimed that the influenza virus was largely seasonal due to seasonal variations in solar UVB doses (the less of vitamin D during the winter, the lower its anti-inflammatory effect).
Shortly after, two clinical trials supported this claim. Participants taking 2000 IU per day had very few influenza or cold events, unlike those who were taking 800IU or 400 IU.
Vitamin D for better athletic performance
Peak sports performances are reported at concentrations of 25 OH vitamin D levels near 50 nmol/L, and full-body exposure to summer sunlight. Concurrently, Vitamin D can reduce the risk of stress fractures.
Vitamin D in pregnancy
Clinical trials in South Carolina found that pregnant women have better pregnancy and birth outcomes by taking 4000 IU-6500I U/day vitamin D3 and reaching serum blood levels above 40 ng/L of Vitamin D3 (Improved gene expression which is essential during fetal development).
Studies also showed a lower risk of autism and pregestational diabetes.
Again, taking dietary supplements, especially in pregnancy and lactation, and in doses that are greater than (officially) recommended, should not be taken unless prescribed by a doctor.
Too much Vitamin D is highly toxic!
Taking excessive dose (than the officially recommended dose of 4000 IU/day) might cause acute toxicity and, rarely, lethal effects via calcium buildups in the blood, the state known as hypercalcemia. Symptoms include vomiting, frequent urination, the formation of kidney stones, and others.
However, obese children and adults on medications such as anticonvulsants, glucocorticoids, or those on AIDS medications need at least two to three times more vitamin D for their age group to satisfy their body’s vitamin D requirement! But, again, only prescribed by the doctor.
Are we getting enough vitamin D through sun exposure?
The most natural way to get enough vitamin D is from the sun. No wonder, because we all had evolved and emigrated from Africa, hunting for foods and roaming around half-naked. Well before (during the course of evolution) we settled first agricultural communities to work in the fields; in a word, we have always been exposed to sunlight naturally.
Nowadays, as work shifted from farms to offices, about 1 billion people worldwide are estimated to suffer from vitamin D deficiency regardless of ethnicity and age groups.
Something must be wrong with modern times because this world is getting better, no doubt about that, but somehow people seem to suffer more. The major contributors might include unhealthy habits and lifestyle in general, population density, and air pollution in larger cities. This is especially true for serious health conditions associated with a lack of vitamin D.
But, it is as important to say that overexposure to UV radiation, can be particularly problematic.
The main reasons include premature aging of the skin and much worse – increases the risk for developing skin cancer.
Fishing for good rays
The ratio of UVA and UVB (responsible for making vitD) changes during the day, and the proportion of UVB is the highest in the midday, so it is advisable to try to catch some midday sun few times a week.
The lack of sunlight in the North
However, those living up North (Canada, Russia, Norway, etc.) may struggle to make enough of the vitamin D in the winter due to weaker sun rays and no sunlight in the winter months. That’s why regular intake of vitamin D supplementation is so important.
How much vitamin D supplementation we should take?
The current daily recommended dose of 600-800 IU/day made by the Institute of Medicine in 2010 is now considered incorrect.
Because these guidelines were focused on the protective effect related to bones, not for optimal health.
The latest studies clinical trials will hopefully provide more precise information regarding the recommended dose. Now, it is estimated that adults should take between 2000-4000 IU/day, which can secure the steady levels of 75-150 nmol/L (30 – 40 ng/ml) of serum 25OH Vitamin D.
(However, we should keep in mind that that scientific studies might be flawed and that dietary supplementation guidelines are regularly updated).
Groups at risk of vitamin D deficiency
People who spend most time indoors, like shift work, especially these days and months of coronavirus lockdown, seem to be at higher risk.
Dark-skinned people are also predisposed to lack this vitamin, because melanin reduces the production of vitamin D in the skin; they should spend more time on the sun to produce the right amounts of vitamin D.
The overweight and obese people are particularly at risk of vitamin D deficiency, because when vitamin D is made in the skin, it is also absorbed in the fat, and it doesn’t really reach the circulation.
Elderly people, because aging reduce our ability to produce and absorb the vitamin via diet. Vitamin D production decreases due to the lower production of 7-dihydro cholesterol, a precursor of Vitamin D.
Check to test whether you have the “right” level of vitamin D?
The simplest step is to check the serum levels of 25OH vitamin D which is considered the biomarker of vitamin D status.
So, get tested and talk to your doctor about getting the right amount of supplements in case you are deficient. Levels of vitamin D below 20 ng/ml are considered insufficient, and many scientists claim that Vit D levels should be above 40-50 ng/ml (100-125 nmol/l) to express its protective effect.
We all need to keep in mind that the prevention of chronic diseases is hugely important.
So, go on, bring out your old bones to the sun, but do it rationally and safely!
- Chowdhury Rajiv, Kunutsor Setor, Vitezova Anna, Oliver-Williams Clare, Chowdhury Susmita, Kiefte-de-Jong Jessica C et al. Vitamin D and risk of cause specific death: systematic review and meta-analysis of observational cohort and randomised intervention studies BMJ 2014; 348 :g1903
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- “Vitamin D may help prevent a common side effect of anti-cancer immunotherapy.” ScienceDaily. ScienceDaily, 22 June 2020. <www.sciencedaily.com/releases/2020/06/200622095018.htm>.