By Nick Gold

Table of contents

1. Study #1 - The link between 25-Hydroxyvitamin D, body composition and glucose tolerance in seniors

2. Study results

3. Study #2 – Seasonal variation of vitamin D in Danish adults and children

4. Study results

5. Study #3 – Vitamin D3 and interleukin 18 are closely linked with depression in men with psoriasis

6. Study results

7. Study #4 – The correlation between vitamin D, omega-3 fatty acids and trabecular bone score

8. Study results

9. Study #5 – The link between vitamin D supplementation, cardiorespiratory fitness and body composition in overweight men

10. Study results

11. Study #6 – The association between vitamin D deficiency and Hashimoto’s autoimmune thyroiditis in obese people

12. Study results

13. Study #7 – The link between MTHFR deficiency, sperm DNA hypomethylation and high doses of folic acid

14. Study results

15. Study #8 – the link between selenium status and the prevalence of prostate cancer

16. Study results

17. Study #9 – The relationship between vitamin D and carotid intima-media thickness (CIMT)

18. Study results

19. What is vitamin D?

20. What is the RDA of vitamin D?

21. Symptoms of vitamin D deficiency

22. Who might be at risk for developing vitamin D deficiency?

23. What to do next?

Study #1 - The link between 25-Hydroxyvitamin D, body composition and glucose tolerance in seniors

This study analyzes the connection between vitamin D deficiency and insulin resistance as well as body composition in men and women.

Study participants were 271 community-dwelling seniors over 60 years of age.

The study analysis focused on comparing the appendicular lean mass index and fat mass index based on serum vitamin D concentrations.

Multivariable linear regression as used depending on the BMI of the study participants, their physical activity level, smoking status, sex, and age.

Study results

The study concluded that those in the lowest serum vitamin D quartile had a higher fat mass in comparison with those in the third quartile and first quartile.

The highest serum vitamin D quartile was associated with better insulin sensitivity and less predisposition to develop type 2 diabetes.

The highest insulin resistance was seen in patients in the second serum vitamin D quartile

The study results indicate that a low serum vitamin D might be associated with impaired glucose metabolism and a higher fat mass index, regardless of BMI and other risk factors.

Study #2 – Seasonal variation of vitamin D in Danish adults and children

This study looks at the vitamin D variation in Danish children and adults depending on the season.

Three thousand ninety-two people participated in the study. The participants had ages between 2 and 69 years. Five hundred twenty-seven of those people were children, and 2565 were adults.

The study took place between 2012 and 2014.

A small portion of these participants had blood drawn each month for a year, and serum vitamin D was measured.

Information regarding vitamin D supplementation was also obtained using questionnaires.

The seasonal variations of vitamin D were measured and recorded based on age, sex and supplementation level.

Study results

The study concluded that approximately 86% of adults and children had sufficient amounts of vitamin D in the bloodstream during spring or autumn.

Many participants had spring concentrations below 50 nmol/L. The study also found out that women generally had better average concentrations of vitamin D in comparison with men.

Vitamin D supplementation was measured accurately, and it has been found that it had a profound effect on vitamin D concentrations in both adults and children, particularly during spring.

The study indicates that vitamin D variation among seasons is significant and bi-seasonal measurements are required to accurately determine the vitamin D concentration in Nordic populations.

Study #3 – Vitamin D3 and interleukin 18 are closely linked with depression in men with psoriasis

Psoriasis and depression have common traits including a deficiency of vitamin D3, systemic inflammation, and others.

This study looks at the link between the severity of the depression and certain inflammation biomarkers in men with psoriasis.

Eighty-five men participated in the study. The average age was 47 years, give or take 14 years. Sixty-five men without psoriasis also participated in the study and their average age was 44 years, give or take 13 years.

Both groups of men had their BMI and blood pressure measured as well as serum concentrations of lipids, interleukin 6 and 18, vitamin D3 and cortisol.

The participants filled the Beck depression inventory, and those who had psoriasis were assessed depending on psoriasis duration, severity and body area covered by lesions.

Study results

The study concluded that those patients who had psoriasis had a more severe depression status, they had higher cholesterol profiles, higher interleukin 6 and 18 levels, higher body mass indices and lower vitamin D3 concentrations in the bloodstream, in comparison with the control group.

Moreover, the depression severity in patients with psoriasis was positively correlated with the duration and severity of psoriasis and negatively correlated with vitamin D3 concentrations.

The study results indicate that there is a link between high concentrations of interleukin 18, low concentrations of vitamin D3 and the severity of depression in men with psoriasis.

This is an important finding because it opens up the path to investigate whether vitamin D3 supplementation or anti-inflammatory treatments might be effective in treating depression in men.

Study #4 – The correlation between vitamin D, omega-3 fatty acids and trabecular bone score

This study looks at the association between trabecular bone score, vitamin D and omega-3 trial in men and women.

The trabecular bone score represents a method to determine bone density based on bone microarchitecture. It is a marker for osteoporosis.

This research analyzed TBS (trabecular bone score) to determine if it differs based on sex, age, race or BMI.

The effects of vitamin D and omega-3 fatty acid supplementation was analyzed to determine its effectiveness in reducing risks for cardiovascular disease and cancer.

Six hundred seventy-two people participated in this study. Three hundred sixty-nine of them were men, and 303 were women. The average age was 63 years, give or take six years.

Study results

The study concluded that TBS was higher in men in comparison with women, but lower in those who had high BMI, drank too much alcohol, used SSRI or had diabetes.

It has also been found that a low TBS is correlated with a history of fragility fractures.

The TBS didn’t vary depending on caffeine use, race or smoking habits.

More studies are required to determine if vitamin D supplementation might help improve TBS and prevent osteoporosis in seniors.

Study #5 – The link between vitamin D supplementation, cardiorespiratory fitness and body composition in overweight men

This study looks at the relationship between vitamin D deficiency and health problems such as adiposity and impaired cardiorespiratory fitness.

It was a placebo-controlled, double-blinded study which took place throughout six months.

Forty obese or overweight people participated in the study. Their BMI was higher than 25, and their vitamin D deficiency was ≤ 55 nmol/L.

The study participants received 2000 IU vitamin D pills or placebo.

Body composition data and the level of cardiorespiratory fitness were assessed, and blood samples were drawn from the participants.

Bioelectrical impedance analysis was used to measure body composition, and a cardiopulmonary exercise test was used to measure cardiorespiratory fitness.

Study results

The first results observed were changes in body fat percentage as well as oxygen uptake. However, there was no important difference between the placebo and intervention groups when it comes to BMI and oxygen uptake at anaerobic threshold.

This means that supplementing with 2000 IU of vitamin D per day doesn’t influence body composition in overweight or obese men who are deficient in this vitamin.

Study #6 – The association between vitamin D deficiency and Hashimoto’s autoimmune thyroiditis in obese people

Insufficient amounts of vitamin D has been correlated with autoimmune diseases, including Hashimoto's disorder.

Obesity is a primary risk factor for developing autoimmune diseases because it is associated with low vitamin D levels.

This study looks at the possible link between low levels of vitamin D and Hashimoto's autoimmune thyroiditis.

Participants in the study were 261 healthy overweight and obese men and women. Their average age was 41 years, give or take approximately 16 years.

These were healthy people with no signs of chronic diseases and completely drug-free.

The study measured multiple health parameters such as fasting levels of vitamin D, antibodies, free triiodothyronine, free thyroxine, TSH, thyroid peroxidase, glucose, cholesterol levels, triglycerides, and uric acid.

Other parameters measured include BMI, waist circumference and blood pressure.

Study results

Approximately 55% of the study participants were deficient in vitamin D. Almost 20% of them had autoimmune thyroiditis.

The number of people with vitamin D deficiency who also had autoimmune thyroiditis was significantly higher than those who didn’t have AT.

The levels of thyroid stimulating hormone (TSH) was also higher in patients with AT, compared with patients who didn’t have AT.

The study concluded that those who had AT had a higher chance of being `deficient in vitamin D, in comparison with people who didn’t have AT.

Approximately 76% of people with vitamin D deficiency were obese, in comparison with 59% of people who didn’t have vitamin D deficiency and were also obese.

These results indicate that vitamin D deficiency is linked to AT in obese people. Moreover, obesity is also associated with low levels of vitamin D in the bloodstream.

The study recommends testing for AT in all overweight and obese patients who have vitamin D deficiency.

Study #7 – The link between MTHFR deficiency, sperm DNA hypomethylation and high doses of folic acid

High doses of folic acid (vitamin B9) are used to improve the sperm quality of infertile men. Folic acid is an important factor in the DNA methylation process.

The researchers who conducted this study discovered a decrease in DNA methylation in the sperm of infertile men who took 5mg of folic acid a day for six months.

The epigenomic impact of folic acid on male germ cells was investigated on mice. These mice were given high doses of folic acid (ten times more than the recommended daily intake) or control diets for up to 6 months.

Study results

There were no significant changes in overall health markers or sperm quality at the end of the study. DNA hypomethylation was detected in mice which received high doses of folic acid.

Wild-type mice were given even higher doses of folic acid (20 times the RDI), and they showed signs of DNA hypomethylation only with these very high doses and after 12 months of supplementation, in comparison with other mice.

The amount of testicular MTHFR protein levels was decreased in wild-type mice which received 20 times the RDI of folic acid, but not in those who received just ten times the RDI.

This finding might suggest that MTHFR deficiency plays an important role in the DNA hypomethylation of sperm.

The results of the study indicate that high doses of folic acid might be responsible for sperm DNA hypomethylation and MTHFR deficiency might play an important role in this process.

Study #8 – the link between selenium status and the prevalence of prostate cancer

The amount of selenium in the body is inversely correlated with prostate cancer, but supplementing with selenium hasn’t been shown to reduce the incidence of this type of cancer.

This study looks at the relationship between selenium status, prostate cancer and the genotype of selenoproteins.

The gene which encodes selenoprotein 15 is called SELENOF. Tissue microarrays of SELENOF were analyzed to determine its levels and the location of cells in prostate tissue.

The study participants were people from the Chicago-based Adiposity Study Cohort. DNA samples from these patients were used to determine genotype frequencies of SELENOF and SELENOP (selenium-carrier protein) as well as baseline selenium levels.

Study results

The study concluded that SELENOF is significantly decreased in tumors from African-American men in comparison with tumors from Caucasian men.

The SELENOF genotypes were linked with higher tumor grades, while the polymorphism in SELENOP was linked with increased serum PSA.

Study #9 – The relationship between vitamin D and carotid intima-media thickness (CIMT)

There is an increasing amount of data linking low serum vitamin D levels with cardiovascular diseases.

Based on this evidence, the purpose of this study is to analyze if low levels of vitamin D would be correlated with the progression of vascular disease in Canadian adults who are HIV positive.

The researchers looked at the link between baseline vitamin D levels and carotid intima-media thickness (CIMT). This assessment took place between 2002 and 2011.

The study was performed using stored blood samples from the Canadian HIV Vascular Study.128 people participated in this study and the average age was approximately 47 years, give or take eight years.

Study results

Approximately 94% of the study participants were white and nearly 37% of them were smokers. About 14% of the total number of participants was deficient in vitamin D.

These people were monitored for up to 8 and a half years on an annual basis, and the CIMT was accurately assessed.

The study concluded that baseline levels of vitamin D were inversely associated with CIMT progression. Further studies are required to determine if supplementation might be a good treatment option for this Canadian population.

What is vitamin D?

Vitamin D is a secosteroid required for absorbing calcium, phosphate, and magnesium in the intestinal tract.

Vitamin D as a whole consists of a group of secosteroids. The most popular ones are vitamin D3 (aka Cholecalciferol) andvitamin D2 (Ergocalciferol).

The human body synthesizes vitamin D from sunlight through the skin. This vitamin is also present in very few foods, but one can use supplementation to get the required daily allowance of vitamin D.

What is the RDA of vitamin D?

The recommended dietary intake of vitamin D depends on age, but most adults and teenagers need approximately 500-600 IU of vitamin D a day.

However, a plethora of researchers agree that it is safe to get more than 600 IU of vitamin D per day since this substance is very important for optimal health.

Vitamin D can be taken from certain types of foods such as:

· Cod liver oil – important source, approximately 1,300 IU per tablespoon

· Salmon – approximately 450 IU per 3 ounces of cooked salmon

· Tuna – approximately 150 IU per 3 ounces

· Eggs – nearly 40 IU of vitamin D are found in the yolk

· Sardines

· Milk

· Yogurt

· Orange juice

Vitamin D can also be taken from exposure to sunlight, but the amount synthesized by the skin depends on a lot of factors.

For example, the amount of skin exposed to sunlight, whether there are clouds in the sky or not, current season, as well as applied sunscreen, can increase or decrease the amount of vitamin D absorbed by the skin.

It's important to know a few things when it comes to producing vitamin D through the skin:

· Exposure to sunshine through windows doesn’t allow the skin to produce vitamin D

· A sky covered with clouds can reduce the absorption rate by 50%

· Sunscreen prevents most of the skin from producing vitamin D, but the shielding is not 100% effective. Some vitamin D is produced even if sunscreen is applied

· Exposing the legs, arms, face or back from 5 to 30 minutes twice a week might provide the body with sufficient amounts of vitamin D

· Using commercial tanning beds can also help the skin produce some vitamin D, but the amounts are minimal

Symptoms of vitamin D deficiency

The cells in the body have receptors for vitamin D and this substance acts as a hormone.

Unfortunately, it is believed that approximately 1 billion people are deficient in vitamin D. Almost 41% of US citizens have low levels of vitamin D in their bodies, according to a 2011 study.

Here are some of the most common signs and symptoms of vitamin D deficiency:

1. Excessive fatigue – chronic tiredness can have multiple causes, and a deficiency in vitamin D might be one of them. For example, people who have vitamin D levels below 20 ng/ml might experience excessive fatigue regularly

2. Depression – depressed people might have low levels of vitamin D in their bloodstream. Observational studies discovered an important relationship between vitamin D deficiency and symptoms of depression and anxiety.

3. Moreover, vitamin D supplementation has been shown to improve seasonal depression symptoms

4. Bone deterioration – since vitamin D is involved in the absorption of calcium in the intestinal tract, too little vitamin D might lead to bone loss in people of all ages. Low levels of vitamin D have been associated with fragility fractures regularly

5. Back pain – studies show that vitamin D deficiency might also be correlated with severe back pains as well as joint and leg pains

6. Getting sick regularly – vitamin D plays an important role in protecting the body against viruses and bacteria. It stimulates the immune system and prevents colds and flu. People who have a deficiency in vitamin D usually get sick more often and are more sensitive to seasonal viruses and bacteria

7. Slow healing of cuts and bruises – vitamin D is necessary to create new skin tissue and complete the healing process of wounds and cuts. If there isn’t enough vitamin D in the body, injuries might heal slower than usual, and this can be a sign of vitamin D deficiency

Who might be at risk for developing vitamin D deficiency?

Some people are more likely to havetoo little vitamin D in their bodies. These people are known as groups at risk for vitamin D inadequacy.

For example, people who have darker skin are less likely to get enough vitamin D from sunlight, even if they spend a lot of time outdoors.

Studies show that the black population is consistently deficient in vitamin D in comparison with white populations.

This happens because the extra melanin in the skin of black people prevents the skin from absorbing enough amounts of vitamin D.

In such cases, supplementing with vitamin D is a viable option as well as taking this vital nutrient from certain foods such as sardines and tuna.

People who spend most of their times indoors are also more likely to develop vitamin D deficiency, for obvious reasons.

For example, business professionals who work full-time jobs in office buildings and potentially spend extra time at home working don’t get much exposure to sunlight.

Similarly, many children spend a lot of time playing computer games indoors these days, and this can affect their vitamin D absorption. Parents should make a habit of sending their kids outside to get fresh air and a healthy dose of vitamin D from sunlight.

Lastly, obese people are commonly associated with low amounts of vitamin D in the bloodstream. This might happen because men and women with a BMI of over 30 have higher amounts of subcutaneous fat.

This fat is likely to prevent the release of vitamin D in blood circulation and trap absorbed vitamin D in fat tissues.

What to do next?

Now you understand the importance of getting adequate amounts of vitamin D in your body.

The next logical step would be to become more aware of your vitamin D intake and try to increase it, if possible.

For example, consider eating more foods rich in vitamin D as well as exposing your skin to sunlight more often.

Vitamin D supplementation is also a good idea, but make sure you speak with your physician first. You might want to assess your vitamin D levels with a blood test before beginning supplementation.