1New data from a systematic review of almost 200 population-based studies shows that more than a third of populations worldwide may suffer from low levels of vitamin D.
The analysis, published in the British Journal of Nutrition, reviewed information from more than 168,000 people in 195 studies conducted in 44 countries - and is one of the first to investigate patterns of vitamin D status worldwide and in key population subgroups, using continuous values for 25(OH)D to improve comparisons.
Led by Dr Kristina Hoffmann from the Mannheim Institute of Public Health at Mannheim, Heidelberg University, Germany, the research team found that 37.3% of the studies reviewed reported mean serum vitamin levels - measured by 25-hydroxyvitamin D (25(OH)D) values - to be below 50 nmol/l; a value considered inadequate by health authorities worldwide.
"The strength of our study is that we used strict inclusion criteria to filter and compare data, using consistent values for 25(OH)D," said Hoffman. "Although we found a high degree of variability between reports of vitamin D status at the population level, more than one-third of the studies reviewed reported mean serum 25(OH)D values below 50 nmol/l."
In June 2008, a study published in the Archives of Internal Medicine found that low blood levels of vitamin D were associated with a doubled risk of death overall and from cardiovascular causes in women and men (average age 62) referred to a cardiac center for coronary angiography. At a scientific meeting in May 2008, Canadian researchers reported that vitamin D deficiency was linked to poorer outcomes in women with breast cancer. And a large study of aging in the Netherlands published in the May 2008 issue of Archives of General Psychiatry found a relationship between vitamin D deficiency and depression in women and men ages 65 to 95.
Many experts are now suggesting that the guidelines be doubled and even tripled to 60 ng/ml to prevent disease. Vitamin D has long been known to contribute to bone health by promoting the absorption of calcium. In recent years, much attention has been paid to its possible immune and inflammatory benefits.
Judy Stenmark, CEO of the International Osteoporosis Foundation (IOF) commented: "Given the global increase in the number of seniors and the almost fourfold increase in hip fractures due to osteoporosis since 1990, public health officials must address the impact of inadequate vitamin D status on fracture risk and overall health in their ageing populations as well as on children and adolescents.
"IOF urges further research as well as public health measures that would help to improve vitamin D status in these high-risk population groups."
Researchers from the University of California, San Diego School of Medicine had previously found that low serum vitamin D levels in the months preceding diagnosis may predict a high risk of premenopausal breast cancer.
The study of blood levels of 1,200 healthy women found that women whose serum vitamin D level was low during the three-month period just before diagnosis had approximately three times the risk of breast cancer as women in the highest vitamin D group. The study is currently published online in the journal Cancer Causes and Control.
The team, which included researchers from the IOF and DSM examined patterns of (25(OH)D) from the 195 studies in order to assess potential differences by age, sex and region.
"Vitamin D deficiency is associated with osteoporosis and is thought to increase the risk of cancer and CVD," said the team. "Despite these numerous potential health effects, data on vitamin D status at the population level and within key subgroups are limited."
Hoffman and her colleagues identified the 195 population-based studies - containing data from more than 168,000 people in 44 countries - using the Medline and EMBASE databases - finding that mean population-level 25(OH)D values varied considerably across the studies.
However, they noted that 37.3 % of the studies reported mean values below 50 nmol/l - a level that is generally classed as inadequate by health authorities worldwide.
"Although age-related differences were observed in the Asia/Pacific and Middle East/Africa regions, they were not observed elsewhere and sex-related differences were not observed in any region," added the team.
Further exploratory analyses did however suggest that newborns and institutionalised elderly from several regions worldwide appear to be at a generally higher risk of exhibiting lower 25(OH)D values, the authors said.
Other key findings from the study include:
- Vitamin D values were higher in North America than in Europe or the Middle-East.
- Only a limited number of studies for Latin America were available.
- Age-related differences were observed for the Asia-Pacific and Middle East regions, but not elsewhere.
- The substantial heterogeneity between the studies within each region precludes drawing conclusions on overall vitamin D status at the population level.
- There is a need for research designs which minimise potential sources of bias and thus strengthen understanding of vitamin D status in key subgroups worldwide.
Obtaining Vitamin D Naturally
Making vitamin D through sun exposure is the natural way to maintain D levels as shown through hundreds of thousands of years of human history.
To make vitamin D, you need UV-B rays to come into direct contact with your skin. UV-B rays cannot penetrate glass, so you don't make any vitamin D while you're sitting in a car or by a window at work or at home.
But creating enough vitamin D in your body isn't as simple as getting a certain number of minutes of sunlight exposure every day because the number and intensity of UV-B rays that reach your skin and lead to vitamin D production is affected by a number of different factors, the main ones being:
Your Skin Color
Lighter skin color allows deeper penetration by UV-B rays, which decreases the amount of sunlight exposure needed for adequate vitamin D production. If you have darker skin, it's harder for UV-B rays to penetrate your skin and create vitamin D, which means that you need greater exposure to sunlight than someone with lighter skin.
If you live above 35 degrees latitude north or below 35 degrees latitude south, you receive little to no UV-B rays from some point in autumn to some point in spring. During this time, your body has to rely on the vitamin D that it has created during warmer months, or on intake of vitamin D through food and supplements.
Altitude and Latitude
The further north or south you live from the equator, the less exposure you have to UV-B rays.
The higher you live above sea level, the greater exposure you have to UV-B rays.
Pollution and Clouds
Both decrease the number of UV-B rays that reach you.
With each passing year, natural degenerative changes that occur in your skin make it harder for UV-B rays to convert cholesterol in your skin into vitamin D. It's a known fact that elderly people need to rely more on food sources than sunlight for their vitamin D. At 70 years of age, the average person has approximately 30% of the capacity to generate vitamin D from sunlight that a 20-year old has.
10 REASONS YOU NEED VITAMIN D ALL YEAR ROUND
1. Improves Muscle Function
If you have chronic pain you may want to reassess your vitamin D levels.
New research shows, for the first time, a link between vitamin D and muscle function -- including recovery from exercise and daily activities. It also explains why lower levels can lead to physical fatigue. Similar research done with adolescent girls found that vitamin D is positively related to muscle power, force, velocity and jump height.
And while you may not be too worried about your jump height, this research is relevant if you find it hard to even get to the gym -- let alone hit your personal bests while you’re there.
2. It Blunts Your Appetite
Beyond the clear impact on our mood, gloomy pre-spring weather can indeed make us fat. We produce vitamin D when our skin is exposed to the ultraviolet B (UVB) rays in bright sunlight. Beyond the established immune-enhancing benefits, rising vitamin D levels are also known to activate the production of leptin, which helps us slim down by signalling our brain and our stomach.
A study from Aberdeen University found that adequate levels of sunlight can significantly reduce obesity. After monitoring more than 3,100 post-menopausal women living in northeast Scotland over a two-year period they discovered that women who had the highest BMI also had the lowest amounts of vitamin Din their blood.
3. It Can Protect Lung Function
The sunshine vitamin will not only help you feel better, you’ll breathe easier too. According to a new study from researchers in Boston, vitamin D deficiency is associated with worse lung function and more rapid decline in lung function over time in smokers. This research suggests vitamin D may protect against some of the effects of smoking on lung function. The number one protector? Not smoking!
4. Can Help You Shed Weight
Vitamin D has been proven to lower insulin, improve serotonin levels, enhance the immune system, control appetite and even improve fat-loss efforts.
A study completed by a team at Massey University showed women who were given a daily dose of 4,000 IU of vitamin D3 showed improvements in their insulin resistance after six months of supplementation.
If that’s not enough, research from the University of Minnesota found that higher vitamin D levels in the body at the start of a low-calorie diet improved weight-loss success. Scientists determined that as vitamin D increased in the blood, subjects ended up losing almost a half-pound more on their calorie-restricted diet.
5. Lowers Blood Pressure
A 2012 study, presented at the European Society of Hypertension meeting in London, shows that vitamin D supplementation can help lower blood pressure in patients with hypertension. Similarly, additional research found that vitamin D deficiency in premenopausal women may increase the risk of developing high blood pressure even 15 years later -- certainly a great reason to your levels optimized today for healthy aging.
6. Shuts Down Cancer Cells
Researchers at McGill University have discovered a molecular basis for the cancer preventive effects of vitamin D, whereby its active form essentially shuts down cancer cells.
Direct Link Between Low Levels of Vitamin D and Mortality
Low levels of vitamin D and high levels of parathyroid hormone are associated with increased mortality according to a study in The Endocrine Society's Journal of Clinical Endocrinology and Metabolism (JCEM). The study also indicates that the potential impact of remediating low vitamin D levels is greater in African Americans than Caucasians because vitamin D insufficiency is more common in African Americans.
The highest average intakes of the sunshine vitamin were associated with a 77% decrease in the risk of Alzheimer's, report researchers in the The Journal of Gerontology: Medical Science.
9. Affects Hundreds of Genes in Disease Preventing Potential
Vitamin D has a significant effect on at least 229 genes some of which have been associated with Crohn’s disease and type 1 diabetes, according to UK and Canadian researchers.
Reduces Risk of Osteoporosis
If you are a woman, you need to pay special attention to your vitamin D status to protect your bones. Using state-of-the-art technology, researchers from the University Medical Center Hamburg in Germany, and the University of California, Berkeley found that vitamin D deficiency was associated with less mineralization on the surface of the bone, as well as structural characteristics of older and more brittle bone.