Are you getting enough Vitamin D? Probably NOT!
Until recently, it was commonly believed that a daily dose of sunshine guarantees adequate vitamin D levels. Well, not anymore.
The latest studies are showing that most people are vitamin D deficient. Although our bodies do manufacture vitamin D when exposed to sunshine, how much depends on where you live and how much exposure you get. In fact, people who live in areas where the sun rarely shines make no vitamin D at all, and must depend entirely on dietary supplements and vitamin D-fortified foods.
On May 27, 2016, FDA issued a Final Rule on recommended daily intakes (RDIs) of vitamin D. Previously they were set at 200 IUs for people up to 50 years of age, 400 IUs for people between 51 and 70, and 600 IUs for over 70 years. According to a study published in the Journal of Nutrition (March 9, 2009) adults need at least four times the previously recommended dose. The new regulations set the level between 400 IUs and 800 IUs per day and also move to a weight based listing equivalent to 10 to 20 μg (micrograms).
In the study, young women (about 22.2 years of age) were given either a placebo or vitamin D3 supplement (200 IUs) between March and September of 2005, and then randomly assigned to receive either placebo or a daily vitamin D3 supplement (20 micrograms) until February 2006.
The researchers found that among the 86 women who completed the study, 80% of those receiving 20 micrograms (800 IUs) of vitamin D supplements achieved optimal concentrations of vitamin D (serum blood levels of at least 75 nmol/L) when compared to only 10.9 nanomoles per liter in the placebo group. The researchers concluded that this dose is adequate to optimize vitamin D levels in most, but not all, young women in Maine.
Why is Vitamin D important?
Vitamin D refers to two biologically inactive precursors—D3, also known as cholecalciferol, and D2, also known as ergocalciferol. Vitamin D3 is produced in the skin upon exposure to UVB radiation (290 to 320 nm), and is more bioactive.
Vitamin D deficiency may exacerbate osteopenia, osteoporosis, muscle weakness, fractures, some cancers, autoimmune diseases, infectious diseases and cardiovascular disease. There is also some evidence that vitamin D may reduce the incidence of several types of cancer and type-1 diabetes.
Vitamin D3 Prevents Fractures
A new study conducted by researchers at the University of Zurich recently published in the Archives of Internal Medicine (March 23, 2009) found that older people can prevent fractures by taking vitamin D3 supplements, as long as they use a high enough dose and continue taking it. The researchers did a meta-analysis, examining the results of 12 randomized controlled trials of vitamin D supplementation. A total of 42,279 people were included in the studies of non-vertebral fractures, with 8 of the studies addressing hip fractures.
The researchers concluded that the vitamin D3 supplements cut the risk of any non-vertebral fracture by 14 percent, and of hip fractures by 9 percent. It’s important to note that although quantities below 400 IU a day had no effect on fracture risk, people who consumed more than 400 IU daily had a 20 percent lower risk of any type of fracture and an 18 percent lower risk of hip fracture.
Can you get enough vitamin D3 through food?
The answer is no, for most people. In an interview with Reuters, Dr. Bischoff-Ferrari, one of the lead researchers of the meta-analysis, said you’d have to eat two servings of fatty fish like salmon or mackerel every day. She also recommends that younger adults increase their vitamin D3 supplementation.
So please take these new studies seriously, and start taking a high-dose vitamin D3 supplement today. It is an easy, inexpensive way to protect your bones, your overall health, and possibly extend your life.
Nelson, M.L. Blum, J.M, Hollis, B.W., Rosen, C., Sullivan, S.S. Supplements of 20 ug/d Cholecalciferol Optimized Serum 25-Hydroxyvitamin D Concentrations in 80% of Premenopausal Women in Winter. Journal of Nutrition, March 9, 2009, Volume 139, Pages 540-546, doi:10.3945/jn.108.096180
Heike A. Bischoff-Ferrari, et al. Arch Intern Med. March 23, 2009;169(6):551-561. Prevention of Nonvertebral Fractures With Oral Vitamin D and Dose Dependency: A Meta-analysis of Randomized Controlled Trials.
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Excess Weight Increases Need for Vitamin D
Heavier, older adults are known to have lower levels of vitamin D in their blood, an observation that was thought to be largely explained by the fact that heavier people often cover up more or spend less time outdoors in the sun.
But when Tufts researchers divided 381 men and women age 65 or older (who were participating in a study of calcium and vitamin D supplementation to prevent bone loss) into four groups based on their body fat percentage, they found no differences among the groups in the time spent outdoors, percent of skin exposed to the sun, or sunscreen use.
What they did find was that those with the highest percentage of body fat had 20% lower levels of vitamin D than those with the least body fat – a very significant difference.
This makes sense because vitamin D is a fat-soluble nutrient. “The idea is that somehow vitamin D is getting trapped in fat tissue, so it’s not available to the blood for circulation,” explained one of the study’s authors, Dr. Susan Harris.
“In general, it seems that heavier people may need more vitamin D…because a given intake is not going to lead to the same blood level,” Harris noted.
At what body fat percentage do vitamin D needs increase?
The American Council on Exercise guidelines state that men’s body fat should be in the range of 6-25%, and women’s body fat percentage should fall somewhere between 14-31%.
American Dietetic Association guidelines are more stringent. The ADA recommends that men’s body fat be in the range of 15-18%, and women’s in the range of 20-25%. Healthy male athletes might be as low as 5-12% body fat and healthy female athletes as low as 10-20%.
If your body fat percentage is higher than 25% (for men) or 31% (for women), you may need more vitamin D to prevent vitamin D deficiency than someone with a lower body fat.
How to determine your body fat percentage
A variety of affordable scales are now available for home use that measure body fat percentage along with weight. A good review of the options can be found at www.epinions.com. Your physician or fitness consultant at your gym may either use fat calipers or have a bioelectronic impedance machine to measure body fat.
Do you need more vitamin D3?
While higher body fat levels can predict vitamin D deficiency, checking your blood levels of D3 is the only way to determine your actual vitamin D status. Optimal blood levels of D3 range are thought to be 32 ng/mL (80 nmol/L). Anything lower than 30 ng/mL (75 nmol/L) indicates deficiency; levels greater than 150 ng/mL (375 nmol/L) indicate toxicity.
If your blood levels of D3 are below 30 ng/mL (75 nmol/L), ask your physician about taking 2,000 IU of vitamin D3 daily. Although recent recommendations suggest that in the absence of sun exposure, adults should ingest 1,000 IU of vitamin D3 per day, vitamin D3 supplements providing 2,000 IU/day may be more appropriate for heavier individuals.
Is taking 2,000 IU/day of vitamin D safe?
Currently, the tolerable upper limit for vitamin D set by the Institute of Medicine is 2,000 IU per day. However, many of the experts responsible for setting this limit now believe it needs to be substantially increased. Research published in the January 2007 American Journal of Clinical Nutrition reviewed dozens of vitamin D toxicity studies, including some in which volunteers took 100,000 IU a day without any adverse effects!
The authors of the vitamin D toxicity review concluded that the upper limit for daily intake of vitamin D could safely be set at 10,000 IU. This is not surprising when one realizes that just 10-15 minutes whole-body exposure to peak summer sun will generate and release up to 20,000 IU vitamin D3 into the circulation.
In the March 2007 issue of the American Journal of Clinical Nutrition, a group of 15 nutrition experts cited the vitamin D toxicity review in an editorial calling for an overhaul of vitamin D guidelines. The experts — including Dr. Walter C. Willett, chair of the Harvard School of Public Health’s nutrition department — noted that 400 IU only produces a very small increase in the amount of vitamin D circulating in the blood. Daily intake of about 2,000 IU is necessary before blood levels increase to 80 nmol/L (32 ng/mL), the level at which vitamin D is thought to have its full disease-fighting effects.
Hollis BW. Circulating 25-hydroxyvitamin D levels indicative of vitamin D sufficiency: implications for establishing a new effective dietary intake recommendation for vitamin D. J Nutr. 2005 Feb;135(2):317-22.
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Holick MF. The role of vitamin D for bone health and fracture prevention. Curr Osteoporos Rep. 2006 Sep;4(3):96-102.
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Kimball SM, Ursell MR, O’connor P, Vieth R. Safety of vitamin D3 in adults with multiple sclerosis. Am J Clin Nutr. 2007 Sep;86(3):645-51.
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Vieth R, Bischoff-Ferrari H, Boucher BJ, et al. The urgent need to recommend an intake of vitamin D that is effective. Am J Clin Nutr. 2007 Mar;85(3):649-50.
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Vitamin D Supplements Reduce Risk of Death from All Causes
A meta-analysis published in the September 2007 issue of the AMA journal Archives of Internal Medicine reveals vitamin D supplementation is linked with reduced risk of death from any cause.
Researchers analyzed 18 randomized, controlled clinical trials involving a total of 57,311 participants. Subjects given supplemental vitamin D received doses ranging from 300 to 2000 IU (averaging 528 IU) daily over a 5.7 year average follow-up period.
Subjects who received vitamin D were found to have a 7% lower risk of dying of any cause compared to those who did not supplement with the vitamin. In half of the studies, blood levels of vitamin D were measured and were found to be 1.4 to 5.2 times greater among participants who received vitamin D supplements than in those who did not.
The Many Health Benefits of Vitamin D Supplementation
Hypothesizing an explanation for vitamin D’s wide-ranging protective effects, the authors noted vitamin D’s ability to inhibit the proliferation of cancer cells, improve blood vessel function and boost immunity. They also suggest that statin drugs’ ability “to decrease all-cause mortality could partly be due to increases in vitamin D levels they would provoke or through acting as vitamin D analogues on vitamin D receptors.”
In an accompanying editorial, Edward Giovannucci, MD, ScD, of the Harvard School of Public Health questioned: “Would even a greater reduction in mortality accrue than that suggested in this meta-analysis if intakes of vitamin D were higher, if compliance was improved, if higher levels of 25-hydroxyvitamin D [vitamin D3] were attained, and if the duration of supplementation was longer?”
“From a broader public health perspective, the roles of moderate sun exposure, food fortification with vitamin D, and higher-dose vitamin D supplements for adults need to be debated,” Giovannucci urged.
While scientists debate, one thing is clear: ensuring intake of vitamin D in amounts sufficient to produce blood levels in the range of 70-80 nmol/L, which research now indicates should be around 2,000 IU of vitamin D3 per day, helps protect against all causes of death.
Autier P, Gandini S. Vitamin D Supplementation and Total Mortality: A Meta-analysis of Randomized Controlled Trials. Arch Intern Med. 2007 Sep 10;167(16):1730-7.
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Giovannucci E. Can vitamin d reduce total mortality? Arch Intern Med. 2007 Sep 10;167(16):1709-10.
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Vitamin D Supplements May Lower Mortality Rates
The September 10, 2007 issue of Archives of Internal Medicine reported the results of a meta-analysis that examined 18 previously published studies which had suggested that deficiencies in vitamin D lead to a higher risk of death from cancer, heart disease and diabetes.
The report stated that those individuals isolated from the studies who took vitamin D supplements had a seven percent lower risk of death than those who did not take supplements.
“If the associations made between vitamin D and these conditions were consistent, then interventions effectively strengthening vitamin D status should result in reduced total mortality,” wrote the researchers from the International Agency for Research on Cancer in France and from the European Institute of Oncology in Italy.
The meta-analysis looked at randomized controlled trials of vitamin D supplements published before November 2006. They found and analyzed 18 separate trials involving 57,311 individuals.
The average vitamin D dose was 528 iu (international units), but ranged from 300 to 2,000 iu. Commercially available vitamin D supplements typically range from 400 to 600 iu.
Over a follow-up period of 5.7 years, 4,777 of the participants died. In the nine trials that had collected blood samples, those individuals who took vitamin D supplements had an average of between 1.4 and 5.2 times higher blood levels of vitamin D than those who didn’t.
“In conclusion, the intake of ordinary doses of vitamin D supplements seems to be associated with decreases in total mortality rates,” said the authors.
However, the relationship between vitamin D status and supplementation remains to be fully understood and the authors are calling for additional population-based, placebo-controlled randomized trials to further investigate their findings.
“Mechanisms by which vitamin D supplementation would decrease all-cause mortality are not clear,” said the researchers.
It is widely known that vitamin D deficiency can lead to osteoporosis, osteopenia, muscle weakness, fractures, common cancers, infectious diseases, autoimmune diseases, and cardiovascular diseases.
Median adult intake of vitamin D in the US is said to be only 230 iu per day, much lower than what nutrition experts have said should instead be 2,000 iu per day.
Autier, Philippe and Sara Gandini. “Vitamin D Supplementation and Total Mortality: A Meta-analysis of Randomized Controlled Trials.” Arch Intern Med. 2007;167:1730-1737.
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Optimal Vitamin D Levels Protective Against Colorectal Cancer
Previous studies, including the Women’s Health Initiative, found that a low dose of vitamin D (400 iu/day) was not protective against colorectal cancer, but new research shows that vitamin D offers significant protection when taken at a higher dose (1,000 – 2,000 iu/day).
The new research reviewed 5 studies involving a total of 2,896 subjects. Study participants with blood levels of D3 of at least 33 ng/mL (nanograms per mililiter)—the equivalent of 82.5 nmol/l (nanomoles per liter) were found to have a 50% lower risk of colorectal cancer compared to those whose blood levels of D3 were 12 ng/mL (30 nmol/l) or less.
The authors of this review recommend a daily intake of 2,000 iu/day of vitamin D3 to reduce incidence of colorectal cancer with minimal risk. This supports their recommendation by referring to an analysis of 30 studies, that found no reproducible toxicity when blood levels of D3 were below 100 ng/mL (250 nmol/l).
In addition, a “No Adverse Effect Level” (NoAEL) level of 2,000 iu/day of vitamin D3 has been established by the National Academy of Sciences (NAS). The NAS reported that no illness from vitamin D intoxication has been described for intakes <3,800 iu/day. One study reported that no cases of toxicity have ever been documented at doses <40,000 iu per day.
A vitamin D3 intake of 1,000–2,000 iu/day, with a target of 33 ng/mL (82.5 nmol) for blood levels of D3 are safe, practical recommendations to reduce risk of colon cancer.
Gorham ED, Garland CF, Garland FC, Grant WB, Mohr SB, Lipkin M, Newmark HL, Giovannucci E, Wei M, Holick MF. Optimal vitamin D status for colorectal cancer prevention: a quantitative meta analysis. Am J Prev Med. 2007 Mar;32(3):210-6.
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Vitamin D – Protective Against Breast Cancer
A review of two studies involving 1,760 women found that those who had blood levels of vitamin D3 of at least 52 ng/ml (the equivalent of 130 nmol/l) had a 50% lower risk of breast cancer than those whose blood levels of D3 were <13 ng/ml (32.5 nmol).
Since a vitamin D3 blood level of 52 ng/ml (130 nmol/l) would necessitate an intake of 4,000 iu of D3 daily, which exceeds the National Academy of Sciences upper limit of 2,000 iu per day, the researchers recommend supplementing with 2,000 iu/day plus 12 minutes of sun exposure.
Moderate exposure to sunlight (about 12 minutes during late spring, summer and early fall in northern latitudes [above 51º] or throughout the year in southern latitudes [below 35º]) is thought to produce an amount of D3 equivalent to supplementing with 3,000 iu.
Women who are at high risk for breast cancer and who live in northern latitudes may wish to talk to their health care provider about supplementation with doses higher than 2,000 iu/day of vitamin D3 during the winter.
Garland CF, Gorham ED, Mohr SB, Grant WB, Giovannucci EL, Lipkin M, Newmark H, Holick MF, Garland FC. Vitamin D and prevention of breast cancer: pooled analysis. J Steroid Biochem Mol Biol. 2007 Mar;103(3-5):708-11.
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Insufficient Vitamin D – the Principal Cause of Preeclampsia
In preeclampsia, the most common, dangerous complication of pregnancy, blood pressure rises along with the appearance of significant amounts of protein in the urine. The condition can cause significant damage to the blood vessels, kidneys and liver of the mother, and has no known cure apart from ending the pregnancy.
A recent study involving 1,198 women in their first pregnancy has shown that vitamin D deficiency is a strong, independent risk factor for preeclampsia.
Women with low blood levels of vitamin D (>45.4 nmol/l) in early pregnancy were much more likely to develop preeclampsia than women whose vitamin D levels were higher (<53.1 nmol). Early pregnancy blood levels of vitamin D <37.5 nmol/l were associated with a 5-fold increase in risk of developing preeclampsia.
Babies born to mothers with preeclampsia were much more likely to be deficient in vitamin D, despite the widespread use of prenatal vitamins, which provide 400 iu of vitamin D.
On the positive side, as mothers’ blood levels of vitamin D increased, their risk of pre-eclampsia strikingly decreased, as did their babies’ risk of vitamin D deficiency.
A recent review study found that blood levels of vitamin D3 needed for bone mineral density, dental health, and to lessen risk of falls, fractures and colorectal cancer, begin at 75 nmol/l, and are best between 90 and 100 nmol/l. Many experts now recommend daily intake of 1,000 iu of vitamin D3 to bring blood levels up to 75 nmol/l.
Women who are pregnant or hoping to conceive should ask their doctor to check their blood levels of vitamin D3 and to consider supplementation (D3, 1,000 iu/day) if their blood levels are lower than 75 nmol/l.
Bodnar LM, Catov JM, Simhan HN, Holick MF, Powers RW, Roberts JM. Maternal vitamin D deficiency increases the risk of preeclampsia. : J Clin Endocrinol Metab. 2007 May 29; [Epub ahead of print]
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Vitamin D Levels Affect Cardiovascular Risk
Low blood levels of vitamin D are strongly associated with risk factors for cardiovascular disease, reveals data on 7,186 men and 7,902 women from the Third National Health and Nutrition Examination Survey. (Martins D, Wolf M, Arch Intern Med 2007 June)
Vitamin D refers to two biologically active precursors: D2, which is known as ergocalciferol and is derived from foods such as fatty fish, egg yolk and liver, and D3, cholecalciferol, which is produced in the skin upon exposure to sunlight. Both D2 and D3 are processed in the liver and kidneys to form 25(OH)D, the “storage” form in which vitamin D circulates in the bloodstream.
Compared to higher blood levels of this storage form of vitamin D, 25(OH)D, (at least 37 ng/mL [92 nmol/L]), low levels (less than 21 ng/mL [52 nmol/L]) were associated with greatly increased odds of:
- Hypertension (130% or 1 + times the risk)
- Diabetes mellitus (198%, double the risk)
- Obesity (229% or 2 + times the risk)
- High triglycerides (147%, 1½ times the risk)
According to researchers, this study indicates it is time to reassess the current position on the levels of vitamin D considered adequate and optimal. Current recommended blood levels of vitamin D [25(OH)D] are primarily based on levels needed to maintain bone health and prevent rickets, but do not address the levels necessary to minimize cardiovascular risk factors.
Since prevalence of CVD risk factors continued to decline as vitamin D levels reached and surpassed 37 ng/mL (92 nmol/L), researchers think higher levels may confer additional benefits.
Prevalence of Insufficient Vitamin D Levels “Alarmingly High”
In the UK, British researchers measured vitamin D levels in 7,437 adults over age 45 and found the prevalence of low levels of vitamin D “alarmingly high.”
In winter and spring, 87.1% of subjects had vitamin D levels less than 75 nmol/L (30 ng/mL). Even during the summer and fall, vitamin D levels in 60.9% of subjects were below 75 nmol/L (30 ng/mL). Low vitamin D levels (<40 nmol/L or 16 ng/mL) were twice as likely in obese subjects. (Hyppönen E, Power C., Am J Clin Nutr 2007 March)
Daily Dosage Recommendations for Vitamin D Should Be Greatly Increased
Researchers who conducted a review of numerous well-designed human clinical trials published since 1997 feel that the upper tolerable limit (UL) of 2,000 iu per day set for vitamin D by the Food and Nutrition Board at that time, is way too low and should be increased five-fold.
They are confident that, in healthy adults, even a dose of vitamin D3, the most biologically active form of the vitamin, of up to 10,000 iu per day can be safely recommended. (Hathcock JN, Shao A. et al. Am J Clin Nutr 2007 Jan)