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Tag: Vitamin D

Published on Leave a comment on Vitamin D and Colorectal Cancer Risk

Long-awaited  vitamin D studies are finally appearing this year. A large international study found that higher levels of vitamin D in a person's blood is associated with a lower risk of colorectal cancer. Those with the highest vitamin D levels had a 21% lower risk (compared to the lowest group) of colorectal cancer after an average 5.5 years.

But the researchers generally do not recommend vitamin D supplements - saying that most people had adequate levels from foods and sunshine. However, they suggest that the risk for vitamin D deficiency is higher for those with very dark skin; for older adults (their skin may not be as efficient at synthesizing vitamin D); and for those who do not go outside at all - and that these groups may need supplementation (but not beyond 4000 IU per day - because higher levels have negative health effects). From Medical Xpress:

Large international study links blood vitamin D levels to colorectal cancer risk

A new study authored by scientists from the American Cancer Society, the Harvard T.H. Chan School of Public Health, the U.S. National Cancer Institute, and more than 20 other medical centers and organizations finds that higher circulating vitamin D concentrations are significantly associated with lower colorectal cancer risk. This study strengthens the evidence, previously considered inconclusive, for a protective relationship. Optimal vitamin D concentrations for colorectal cancer prevention may be higher than the current National Academy of Medicine recommendations, which are based only on bone health.  ...continue reading "Vitamin D and Colorectal Cancer Risk"

Published on Leave a comment on Study Finds No Benefit From Most Supplements

Another study has found that the most common vitamin and mineral supplements (multivitamins, vitamin D, calcium, and vitamin C), don't offer hoped for health benefits, and may actually carry some risks. This latest study was a review of other studies, and examined whether specific vitamins or minerals would  lower the risk of cardiovascular disease (including heart attacks and strokes) and death from any cause (referred to as all cause mortality"). [Posts discussing other research finding problems with supplements.]

In general, the review of studies of popular supplements (multivitamins, vitamin D, calcium, and vitamin C) show no consistent benefit (no significant effect) for the prevention of cardiovascular disease, heart attacks, or stroke, nor any lowering of death (all cause mortality). On the other hand, folic acid and B-vitamins with folic acid, B6, and B12 reduced stroke (folic acid showed a 20% reduction in stroke), but niacin and antioxidants were associated with an increased risk of death from any cause (10% increase). But overall the effects in the studies were small. Vitamin D did not show any benefits in reducing death, but the researchers pointed out that many vitamin D studies are now under way, and the results of vitamin D studies so far are mixed (e.g. 16 showing positive effects from vitamin D, 17 showing a more favorable effect in the control group, and 10 neither).

On the other hand, the researchers stressed that eating a well balanced diet has lots of health benefits and is recommended by the U.S. Dietary Guidelines Advisory Committee. Three dietary patterns are frequently discussed as beneficial: 1) a healthy American diet (sometimes called a "prudent diet") low in saturated fat, trans fat, and red meat, but high in fruit and vegetables, 2) a Mediterranean diet, and 3) a vegetarian diet. All 3 of these diets are rich in fruits and vegetables (which means increased fiber), are relatively rich in vitamins and minerals, and meet Dietary Reference Intake guidelines.  ...continue reading "Study Finds No Benefit From Most Supplements"

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Published on 1 Comment on Five Studies Looking at Vitamin D and Health

The last post was about several reviews of vitamin D studies, and how when people are put randomly into different groups and then followed for a while - that the studies generally are not finding the same wonderful effects of higher levels of vitamin D in the blood that observational studies are finding - instead finding no effect or mixed results. Some issues with observational studies: the groups are self-selected, some are a one time snapshot of a person (thus one can't tell what happens over time); and can't prove cause and effect (can only say there is an association or link). [See all posts about vitamin D.]

But anyway, today's post is about some more vitamin D studies, all published in 2018. All of them find health benefits from higher blood levels of vitamin D. What is an ideal level of vitamin D varies from study to study, and some are observational - thus can only say "find an association with" in the findings. The fifth study finds beneficial effects from higher doses of vitamin D, and the participants were randomly assigned to the groups (good!). Click on links to read details. All excerpts are from Science Daily:

Vitamin D deficiency linked to greater risk of diabetes

An epidemiological study conducted by researchers at University of California San Diego School of Medicine and Seoul National University suggests that persons deficient in vitamin D may be at much greater risk of developing diabetes. The findings are reported in the April 19, 2018 online issue of PLOS One.  ...continue reading "Five Studies Looking at Vitamin D and Health"

Published on Leave a comment on Best to Eat Calcium Rich Foods, Not Calcium Supplements

Once again, a study found an association between a worrisome health problem (intestinal polyps) with a dietary supplement (calcium), but no problems with eating the foods (calcium rich foods). The large multi-center study specifically looked at serrated polyps (SPs) because they are considered precursor lesions for colorectal cancer - that is, that while they are not cancerous, some of them will develop into cancer. Persons invited to join the study had a recent colonoscopy with at least one adenomatous polyp detected and removed, and then were scheduled for another colonoscopy 3 to 5 years later. This was considered a "chemoprevention study" to see if certain supplements help prevent polyps (and thus cancer).

People in different parts of the US were randomly assigned to either receive calcium supplements (1200 mg/day of elemental calcium), vitamin D (1000 IU/day of vitamin D3),  both supplements (calcium supplement plus vitamin D), or neither. Supplement treatment continued for 3 to 5 years and then there was an observational period that was 6 to 10 years after the person first started supplementation. The higher incidence of serrated polyps was a "late effect" (6 to 10 years later) and not seen during the treatment time (the first 3 to 5 years). They found that women and current smokers had higher risks of serrated polyps when exposed to supplemental calcium. Vitamin D alone was not linked with polyps.

Other studies have also found an association between calcium supplements and increased risk of certain health problems, and a lower incidence of polyps with a higher intake of dietary calcium (real food). The researchers said: "Patients with a history of premalignant serrated polyps, especially women and smokers, may wish to avoid vitamin D and calcium supplementation." BOTTOM LINE: General guidelines should be to eat foods, not supplements, to get your nutrients, vitamins, and minerals. There are many studies also at this point that a high fiber diet with lots of fruits, vegetables, whole grains, legumes (beans), nuts, seeds are associated with better intestinal health and fewer polyps (here, here). Another way to view it is: feed your beneficial gut microbes with good, real food. And especially not highly processed junk. From Medical Xpress:

Calcium supplements may boost risk of abnormal bowel growths

Calcium supplements, taken with or without vitamin D, may increase the risk of small growths in the large bowel (colon) called polyps, suggest results from a large US trial published online in the journal Gut. Polyps are small growths in the lower part of the large bowel. They are non-cancerous, but some could eventually turn into cancer if they are not removed. Polyps come in different shapes and sizes, and this study specifically focused on the risk of serrated polyps, which are less common than conventional "adenomatous" polyps, but likely have the same risk of developing into cancer. 

...continue reading "Best to Eat Calcium Rich Foods, Not Calcium Supplements"

Published on Leave a comment on Vitamin D, Breast Cancer, and Melanoma

Two more studies found that higher levels of vitamin D in the blood are associated with better health outcomes - one study found a lower risk of breast cancer, especially among postmenopausal women, and in the other - better outcomes after a metastatic melanoma diagnosis.

The breast cancer study suggested that a fairly high blood level of vitamin D (25(OH)D serum level>38.0 ng/mL) was associated with a lower risk of breast cancer. But overall they found that women supplementing with vitamin D (more than 4 times a week) at any dose had a lower risk of breast cancer over a 5 year period than those not supplementing with vitamin D. From Environmental Health Perspectives:

Serum Vitamin D and Risk of Breast Cancer within Five Years

Vitamin D is an environmental and dietary agent with known anticarcinogenic effects, but protection against breast cancer has not been established. We evaluated the association between baseline serum 25-hydroxyvitamin D [25(OH)D] levels, supplemental vitamin D use, and breast cancer incidence over the subsequent 5 y of follow-up. From 2003-2009, the Sister Study enrolled 50,884 U.S. women 35-74 y old who had a sister with breast cancer but had never had breast cancer themselves. Using liquid chromatography-mass spectrometry, we measured 25(OH)D in serum samples from 1,611 women who later developed breast cancer and from 1,843 randomly selected cohort participants.

We found that 25(OH)D levels were associated with a 21% lower breast cancer hazard (highest versus lowest quartile). Analysis of the first 5 y of follow-up for all 50,884 Sister Study participants showed that self-reported vitamin D supplementation was associated with an 11% lower hazard. These associations were particularly strong among postmenopausal women.

In this cohort of women with elevated risk, high serum 25(OH)D levels and regular vitamin D supplement use were associated with lower rates of incident, postmenopausal breast cancer over 5 y of follow-up. These results may help to establish clinical benchmarks for 25(OH)D levels; in addition, they support the hypothesis that vitamin D supplementation is useful in breast cancer prevention.

The first sentence in the melanoma study lays out what is widely known: "Vitamin D deficiency (≤20 ng/mL) is associated with an increased incidence and worse prognosis of various types of cancer including melanoma." Studies show that the relationship between vitamin D, sunlight exposure, and melanoma is complicated in a number of ways, including: sun exposure may be associated with increased survival in patients with melanoma. which may mean that vitamin D has a protective role in patients with melanoma. Several studies suggest that vitamin D may delay melanoma recurrence and improve overall prognosis. The study also found that metastatic melanoma patients with vitamin D deficiency who are unable to or don't raise their vitamin D blood levels (25(OH)D3) have a worse outcome compared to those who are are able to markedly increase (by greater than >20 ng/mL) their 25(OH)D3 levels. From Oncotarget:

Vitamin D deficiency is associated with a worse prognosis in metastatic melanoma

Vitamin D deficiency (≤20 ng/mL) is associated with an increased incidence and worse prognosis of various types of cancer including melanoma. A retrospective, single-center study of individuals diagnosed with melanoma from January 2007 through June 2013 who had a vitamin D (25(OH)D3) level measured within one year of diagnosis was performed to determine whether vitamin D deficiency and repletion are associated with melanoma outcome.

A total of 409 individuals diagnosed with histopathology-confirmed melanoma who had an ever measured serum 25(OH)D3 level were identified. 252 individuals with a 25(OH)D3 level recorded within one year after diagnosis were included in the study .... A worse melanoma prognosis was associated with vitamin D deficiency, higher stage, ulceration, and higher mitotic rate. In patients with stage IV metastatic melanoma, vitamin D deficiency was associated with significantly worse melanoma-specific mortality. Patients with metastatic melanoma who were initially vitamin D deficient and subsequently had a decrease or ≤20 ng/mL increase in their 25(OH)D3 concentration had significantly worse outcomes compared to non-deficient patients who had a >20 ng/mL increase. Our results suggest that initial vitamin D deficiency and insufficient repletion is associated with a worse prognosis in patients with metastatic melanoma.

Published on Leave a comment on Some Health Benefits of Sunlight

 I'm starting to see studies questioning whether some of the beneficial health effects that many attribute to vitamin D may actually be due to sunlight. In the first study, researchers said that sunlight also has low levels of "blue light" which energizes T cells. T cells are a type of white blood cell, are part of the immune system, and help protect the body from infection and cellular abnormalities (cancer). So the blue light in sunlight had a positive effect on the T cells.

The second study examined whether it was low levels of vitamin D that is linked to multiple sclerosis (which is the widely accepted medical view) or was it low exposure to sunlight? They found that vitamin D is not associated with multiple sclerosis risk in blacks or Hispanics (but is in whites). But sun exposure is protective in all three racial/ethnic groups (blacks, Hispanics, whites). Thus it was the sunlight that was important in protecting against multiple sclerosis rather than vitamin D. Bottom line: for various beneficial health reasons, go out in sunshine frequently (20 minutes a day is fine). Remember, sunlight is the "natural source" for vitamin D (the ultraviolet light hitting our bare skin allows us to make vitamin D).

From Dec. 2016 in Science Daily: Sunlight offers surprise benefit: It energizes infection fighting T cells

Sunlight allows us to make vitamin D, credited with healthier living, but a surprise research finding could reveal another powerful benefit of getting some sun. Georgetown University Medical Center researchers have found that sunlight, through a mechanism separate than vitamin D production, energizes T cells that play a central role in human immunity.

Their findings, published today in Scientific Reports, suggest how the skin, the body's largest organ, stays alert to the many microbes that can nest there. They specifically found that low levels of blue light, found in sun rays, makes T cells move faster -- marking the first reported human cell responding to sunlight by speeding its pace.

"T cells, whether they are helper or killer, need to move to do their work, which is to get to the site of an infection and orchestrate a response," Ahern says. "This study shows that sunlight directly activates key immune cells by increasing their movement."

"We know that blue light can reach the dermis, the second layer of the skin, and that those T cells can move throughout the body," he says. ...."We found that sunlight makes hydrogen peroxide in T cells, which makes the cells move. And we know that an immune response also uses hydrogen peroxide to make T cells move to the damage," Ahern says. "This all fits together." Ahern says there is much work to do to understand the impact of these findings, but he suggests that if blue light T cell activation has only beneficial responses, it might make sense to offer patients blue light therapy to boost their immunity.

From Medscape: Is It Time to Rethink Low Vitamin D as a Contributor to MS?

The idea that vitamin D deficiency may contribute to multiple sclerosis (MS) has been well established in the literature and has, for the most part, been etched into recent neurology dogma. Yet, research by Annette Langer-Gould, MD, PhD—a clinical assistant professor at the University of Southern California's Keck School of Medicine in Los Angeles—suggests that the association might not be that simple. ....As background, the vitamin D–multiple sclerosis hypothesis originated from the observation that the prevalence of MS increases with increasing distance from the Equator, as ultraviolet radiation (UVR) from the sun becomes less intense. But this is also where more white people live.

The main result of our study is that vitamin D is not associated with MS risk in blacks or Hispanics, regardless of genotype. In contrast, sun exposure is protective in all three racial/ethnic groups.

Published on Leave a comment on High Dose Vitamin D Does Not Prevent Cardiovascular Disease

A recent study looking at high dose supplementation of vitamin D found that it did not prevent cardiovascular disease. This study came about because of earlier studies observing that there is a higher incidence of cardiovascular disease in persons with low vitamin D levels (as measured in their blood). But such results from observational studies need rigorous testing in studies where people are randomly assigned to groups, and that are "double-blind" (no one knows who is getting the vitamin D until the end of the study) to eliminate bias. And this is what was done in this study, with the result that monthly high doses of vitamin D3 for 3 years did not prevent cardiovascular disease (including stroke, heart attacks, hypertension, etc) - as seen in that there were no group differences between the vitamin D and placebo groups. Finding no effects are "null findings".

But note that the subjects in the study got monthly high doses, and not daily or weekly vitamin D. It is unknown whether daily dosing would have made a difference in the results. However, the vitamin D levels in the blood soon reached levels (about 51.725 ng/mL) that many view as a desirable "protective" level. So we'll see what other studies find. But these results are definitely disappointing for those wanting an easy "magic bullet" for preventing cardiovascular disease. Bottom line: focus on lifestyle (diet, exercise, not smoking, etc) for heart health. From Science Daily:

Monthly high-dose vitamin D supplementation does not prevent cardiovascular disease

Results of a large randomized trial indicate that monthly high-dose vitamin D supplementation does not prevent cardiovascular disease, according to a study published by JAMA Cardiology. Studies have reported increased incidence of cardiovascular disease (CVD) among individuals with low vitamin D status. To date, randomized clinical trials of vitamin D supplementation have not found an effect, possibly because of using too low a dose of vitamin D. Robert Scragg, M.B.B.S., Ph.D., of the University of Auckland, New Zealand, and colleagues randomly assigned adults (age 50 to 84 years) to receive oral vitamin D3 (n = 2,558; an initial dose of 200,000 IU, followed a month later by monthly doses of 100,000 IU) or placebo (n = 2,552) for a median of 3.3 years.

Of the 5,108 participants included in the primary analysis, the average age was 66 years; 25 percent were vitamin D deficient. Cardiovascular disease occurred in 303 participants (11.8 percent) in the vitamin D group and 293 participants (11.5 percent) in the placebo group. Similar results were seen for participants with vitamin D deficiency at study entry and for other outcomes such as heart attack, angina, heart failure, hypertension, and stroke.

The authors write that the results of this study do not support the use of monthly high-dose vitamin D for the prevention of CVD. "The effects of daily or weekly dosing on CVD risk require further study." [Original study.]

Published on Leave a comment on Vitamin D and Frequent Headaches

 I saw mention of this study in a number of places - that low vitamin D levels are linked to chronic headaches. A little too soon to know if that is really true -  the researchers in this study looked at the blood vitamin D levels of 2601 men just one time, and did not give vitamin D supplements to the men to see if this changed the frequency of migraine headaches. The researchers themselves pointed out that other studies looking at this same issue have had mixed results. And they themselves pointed out that low blood levels of vitamin D (serum 25(OH)D concentration) was associated with a markedly higher risk of frequent headache in men. Associated does not mean caused.

Yes, low vitamin D levels is linked to a number of health problems (see all vitamin D posts). But at this point I think that it's a case of "wait and see" to see if vitamin D levels have something to do with headache frequency. Perhaps other micronutrients are important, perhaps something else. Note that in the study they used below 50 nmol as the measure for low vitamin D levels. In the USA, that translates into below 20 ng/ml, which everyone agrees is too low (a deficiency). The best source of vitamin D is sunlight - which is why it's called the "sunshine vitamin". From Science Daily:

Vitamin D deficiency increases risk of chronic headache

Vitamin D deficiency may increase the risk of chronic headache, according to a new study from the University of Eastern Finland....The Kuopio Ischaemic Heart Disease Risk Factor Study, KIHD, analysed the serum vitamin D levels and occurrence of headache in approximately 2,600 men aged between 42 and 60 years in 1984-1989. In 68% of these men, the serum vitamin D level was below 50 nmol/l, which is generally considered the threshold for vitamin D deficiency. Chronic headache occurring at least on a weekly basis was reported by 250 men, and men reporting chronic headache had lower serum vitamin D levels than others.

When the study population was divided into four groups based on their serum vitamin D levels, the group with the lowest levels had over a twofold risk of chronic headache in comparison to the group with the highest levels. Chronic headache was also more frequently reported by men who were examined outside the summer months of June through September. Thanks to UVB radiation from the sun, the average serum vitamin D levels are higher during the summer months.

The study adds to the accumulating body of evidence linking a low intake of vitamin D to an increased risk of chronic diseases. Low vitamin D levels have been associated with the risk of headache also by some earlier, mainly considerably smaller studies.

Published on Leave a comment on Low Vitamin D Levels and Bladder Cancer

 Another study finding a link with low levels of vitamin D and a health problem - this time an increased risk of bladder cancer. Vitamin D is frequently called the "sunshine vitamin" because sunlight is the best source of vitamin D (our body makes vitamin D3 from sunlight exposure on our bare skin). If you take vitamin D supplements, look for vitamin D3 (rather than D2). From Medical Xpress:

Low vitamin D levels linked to increased risk of bladder cancer

Vitamin D deficiency is associated with an increased risk of developing bladder cancer, according to a systematic review of seven studies presented today at the Society for Endocrinology annual conference in Brighton. Though further clinical studies are needed to confirm the findings, the study adds to a growing body of evidence on the importance of maintaining adequate vitamin D levels.

Vitamin D, which is produced by the body through exposure to sunshine, helps the body control calcium and phosphate levels. Vitamin D can also be obtained from food sources such as fatty fish and egg yolks. Previous studies have linked vitamin D deficiency with a host of health problems including cardiovascular disease, cognitive impairment, autoimmune conditions, and cancer.

In this work, researchers from the University of Warwick and University Hospital Coventry and Warwickshire, Coventry and the investigated the link between vitamin D and bladder cancer risk. They reviewed seven studies on the topic which ranged from having 112 to 1125 participants each. Five out of the seven studies linked low vitamin D levels to an increased risk of bladder cancer.

In a separate experiment, the researchers then looked at the cells that line the bladder, known as transitional epithelial cells, and found that these cells are able to activate and respond to vitamin D, which in turn can stimulate an immune response. According to lead author of the study Dr Rosemary Bland, this is important because the immune system may have a role in cancer prevention by identifying abnormal cells before they develop into cancer. "....our work suggests that low levels of vitamin D in the blood may prevent the cells within the bladder from stimulating an adequate response to abnormal cells," said Dr Bland. 

Published on Leave a comment on Vitamin D Levels and Mental Decline In Older Adults

 A new study conducted in China found an association between low vitamin D levels and future cognitive decline in older adults. The lower the vitamin D levels at the initial screening (the baseline), the more people with cognitive decline at a 2 year follow-up. There were were no gender differences. (Another study with similar results.) Vitamin D is produced naturally in the skin when exposed to sunlight, and also found in smaller amounts in food such as fish (e.g. salmon) and eggs. Vitamin D helps maintain healthy bones and muscles, but it also plays a key part in brain function and is viewed as neuroprotective. Low levels are associated with greater risk of cardiovascular and neurodegenerative diseases.

The 1,202 participants (60 years or older) in China had their baseline vitamin D levels measured at the start of the study, and their cognitive abilities assessed over two years. What I found interesting in this study was that the vitamin D levels in the people was in general pretty low - this was without any supplementation, thus from sunlight. The researchers specified vitamin D levels (25-Cholecalciferol) in nmol/l, but in the United States values are generally specified in ng/ml. In the study the median level of vitamin D levels in the lowest quartile converted to ng/ml was 10.0 ng/ml, and in the highest quartile the median level was 26.4 ng/ml. With those low numbers, all 4 groups in the United States would be advised to supplement daily with vitamin D (specifically vitamin D3). From Journals of Gerontology: Medical Sciences:

Vitamin D Levels and the Risk of Cognitive Decline in Chinese Elderly People: the Chinese Longitudinal Healthy Longevity Survey

Vitamin D has a neuroprotective function, potentially important for the prevention of cognitive decline. Prospective studies from Western countries support an association between lower vitamin D level and future cognitive decline in elderly people.

This community-based cohort study of elderly people in China follows 1,202 cognitively intact adults aged ≥60 years for a mean duration of 2 years. Plasma vitamin D level was measured at the baseline. Cognitive state of participants was assessed using the Mini-Mental State Examination (MMSE). Cognitive impairment was defined as an MMSE score <18. Cognitive decline was defined as ≥3 points decline from baseline....Participants with low vitamin D level had an increased risk of cognitive decline. This first follow-up study of elderly people, including the oldest-old, in Asia shows that low vitamin D levels were associated with increased risk of subsequent cognitive decline and impairment.

Vitamin D is a secosteroid hormone necessary for maintaining good musculoskeletal health; its deficiency is associated with increased risks of cardiovascular and neurodegenerative diseases. Vitamin D is primarily synthesized in the skin upon exposure to sunlight; smaller amounts are obtained through dietary intake. More recently, enzymes responsible for the synthesis of its active form have been found to be distributed throughout the human brain.... This growing body of evidence suggests that vitamin D has a neuroprotective function that is potentially important for the prevention of cognitive decline. Although the importance of vitamin D cannot be disregarded, there is still no consensus on its optimal level. This is especially pertinent in the elderly people, the oldest-old in particular, as cutaneous synthesis of vitamin D decreases with age. Moreover, their impaired mobility and limited outdoor activities can further exacerbate vitamin D deficiency.

Cross-sectional studies have generally found a positive association between vitamin D status and cognitive performance in older adults. Recent prospective studies from United States and Europe support an association between diminished vitamin D status and future cognitive decline. Since cutaneous synthesis is the main source of vitamin D, there exists great variability in vitamin D levels across populations due to differences in latitude, seasons, and race/ethnicity, such as level of skin pigmentation.

Our findings were consistent with previous cohort studies showing that vitamin D status predicts cognitive decline....A notable observation in the present study is that the association of vitamin D status and cognitive decline were similar in both oldest-old and less elderly people. In this study, there was a clear association between lower 25(OH)D3 level and cognitive impairment in subjects aged ≥80....An additional difference from previous studies is that the current study indicates that the association between vitamin D and cognitive impairment is not gender specific.

The observation of temporal association between 25(OH)D3 levels and subsequent cognitive function supports the notion that vitamin D has a clinically important neuroprotective effect. A wide variety of mechanisms for this effect has been proposed and is supported by animal studies. Vitamin D has been found to modulate neuronal calcium homeostasis, cerebral process of detoxification, immunomodulation, and beta-amyloid clearance.....Further, it was unlikely that vitamin D supplementation would explain the association in this study, as 87% of the participants reported no use of vitamin supplements....In conclusion, our longitudinal study indicates that low 25(OH) D3 levels are associated with subsequent cognitive decline and cognitive impairment.