It’s hard to believe that vitamin D deficiency is as pervasive a problem as it is in a country as developed as the US. But according to a recent report from the National Health and Nutrition Examination Surveys, 22% of Americans have moderate vitamin D deficiency and the deficiency is severe for 2.6%. Equally alarming is that more than 40% of Americans are vitamin D insufficient, meaning they’re falling short of adequate levels. Only one-third have levels considered sufficient, but even some of these people may not be getting enough D for their health.
Bottom Line Personal turned to pioneering vitamin D researcher Michael F. Holick, MD, PhD, of Boston University Chobanian & Avedisian School of Medicine for the facts about vitamin D deficiency.
Vitamin D Benefits
Most people associate vitamin D with the bone-making process and bone health. While this is true, there are other reasons you should get enough vitamin D. Here are just a few vitamin D benefits…
Optimizing cancer recovery
Analyses of the VITamin D and OmegA-3 Trial (commonly called the VITAL trial) and other vitamin D trials indicate a significant reduction in cancer mortality if you have sufficient levels of vitamin D. And vitamin D supplementation reduces risk for relapse or death in people with certain types of digestive tract cancer.
Decreasing autoimmune disease risk
The VITAL trial also looked at vitamin D’s link to autoimmune diseases, including rheumatoid arthritis, and found that vitamin D supplements reduced risk for an autoimmune disease by at least 22%.
Lowering diabetes risk
In adults with prediabetes, vitamin D can help keep it from progressing to diabetes, according to several studies.
Making pregnancy safer
Vitamin D supplement therapy in pregnancy reduces risk for premature births and helps reduce the incidence of gestational high blood pressure and preeclampsia. Also, when the mother has sufficient vitamin D, her baby’s risk for dental cavities in childhood is reduced.
What Causes Vitamin D Deficiency?
Until 1998, vitamin D deficiency was defined as blood levels below 10 nanograms per milliliter (ng/mL), but now we know that is dangerously low. The following are guidelines for the treatment and prevention of vitamin D deficiency now…
Vitamin D deficiency: 20 ng/mL or lower.
Vitamin D insufficiency: Between 20 ng/mL and 29 ng/mL.
Vitamin D sufficiency: Between 30 ng/mL and 100 ng/mL.
Optimal level: Between 40 ng/mL and 60 ng/mL. Note: People whose levels of vitamin D are above 60 ng/mL do not have to be concerned about toxicity.
Why do so many people fall short? Throughout evolution, sunlight was the primary source of vitamin D, but few of us spend enough time outside these days. If you live north of Atlanta in the US, your skin basically can’t make any vitamin D from about November through March because the sun’s rays are too low in the sky during those months.
For comparison: We determined that healthy adults in bathing suits exposed to enough simulated sunlight in our clinical research center to achieve what’s called a minimal erythemal dose—resulting in a light pinkness to their skin 24 hours after the exposure, not a sunburn—produced as much vitamin D as if they ingested between 15,000 international units (IU) and 20,000 IU of vitamin D. The body has a large capacity to produce vitamin D from sensible sun exposure (exposure of arms, legs, abdomen and back) for about half the time that it would take to provide a minimal erythemal dose (the amount of time depends on location, weather conditions, time of day, season and skin sensitivity). The amount of vitamin D that will be produced will depend on how much skin surface is being exposed.
Another problem: It is difficult for the body to obtain enough vitamin D simply from foods. Vitamin D foods are few and far between. There are no significant amounts of vitamin D in foods other than in wild-caught salmon and other oily fish, cod liver oil and mushrooms that produce vitamin D after being exposed to sunlight. Even fortified foods such as milk and other dairy products, orange juice and cereals deliver only 100 IU per serving, so it’s hard to be sufficient through diet alone.
What Does Vitamin D Deficiency Cause?
Vitamin D’s chief function is to maintain levels of calcium and phosphate in the blood so that these minerals can combine to mineralize bone. Vitamin D does this by increasing the intestine’s ability to absorb these minerals. Bone mineralization starts with cells called osteoblasts that appear on the bone surface and initiate production of the bone matrix collagen, which is then mineralized with calcium and phosphate to become calcium hydroxyapatite. It’s like creating a bridge with the matrix being the steel rebar and the calcium and phosphate complex as the concrete.
Calcium plays a critical role in almost all the body’s metabolic functions and neuromuscular activity—vitamin D and the parathyroid glands are tasked with regulating calcium. If you’re vitamin D deficient and not absorbing enough calcium, the parathyroid glands will make more parathyroid hormone and set off a chain of events. The parathyroid hormone…
- Helps the kidneys reabsorb as much calcium as possible so that it is not lost in urine
- Instructs the kidneys to activate more vitamin D, which induces the intestine to be more efficient in absorbing calcium.
- Causes the kidneys to lose phosphate in the urine. The decrease in blood phosphate compromises the body’s ability to mineralize new collagen matrix, resulting in rickets in children and osteomalacia (softening of bones) in adults.
- Removes calcium and matrix from your bones which, in turn, creates holes within the structure of bones, decreasing bone mineral density and causing osteopenia that can progress to osteoporosis. The compromised skeletal architectural integrity increases risk for fractures.
Since a 2010 study done by German researcher and surgeon Matthias Priemel, MD, of University Medical Center Hamburg-Eppendorf, we have known that osteomalacia starts when vitamin D falls below 30 ng/mL. Dr. Priemel and his team examined bone biopsies from healthy people who had died in accidents. Though he couldn’t identify at exactly what level osteomalacia starts, he found no signs of it when blood vitamin D levels (25-hydroxyvitamin D) were 30 ng/mL or higher. Identifying vitamin D deficiency before this happens is critical because osteomalacia can cause throbbing aching bone pain and increased risk for fracture. The good news is that treating vitamin D deficiency will result in the mineralization of the collagen matrix, resolving rickets and osteomalacia and improving bone mineral density. But when the mineral and collagen matrix is removed from the skeleton, vitamin D is not able to reestablish the bone and does not treat osteoporosis, but it does help prevent it from occurring.
Osteoporosis does not cause bone pain or symptoms unless there is a fracture. In osteomalacia’s early stages, there could be subtle symptoms. In winter, you might notice that your joints feel stiffer, you have aches and pains in your bones and muscles, and you feel more tired. Some people blame those symptoms on lack of sunshine, cold weather or working too hard, but they can signal vitamin D deficiency. In later stages, the chief vitamin D deficiency symptom is throbbing, aching bone pain (often misdiagnosed as fibromyalgia) along with muscle weakness and fatigue (often misdiagnosed as chronic fatigue syndrome) .
Checking and Correcting Your Vitamin D Status
If you are not obtaining enough vitamin D from dietary and supplemental sources, get a blood test to find out your vitamin D status (blood level of 25-hydroxyvitamin D), especially if you’ve never had one. Keep in mind: Your vitamin D status will be highest at the end of summer and lowest at the end of the winter, with an average variable of 9 ng/mL—enough to mask a deficiency or insufficiency. Consider being tested in early spring for accuracy. If you’re deficient or insufficient, work with your doctor who likely will recommend vitamin D supplemention.
How do you get to optimal levels? If your starting point is 20 ng/mL or less—in other words, you are vitamin D deficient—for every 100 IUs of vitamin D you ingest, your level will rise by about 0.6 to 1 ng/mL. That means you need 4,000 IUs to 6,000 IUs a day to get to the optimal level between 40 ng/mL and 60 ng/mL. Alternative to a daily vitamin D pill: A once-a-week dose of 50,000 IUs of vitamin D-2 or vitamin D-3 for eight weeks and then 50,000 IUs every two weeks indefinitely. It should be recognized that vitamin D-2 and vitamin D-3 are equally effective in accomplishing the treatment and prevention of vitamin D deficiency. If you are obese with a BMI greater than 30, you require two to three times as much vitamin D as a normal-weight person to maintain the same vitamin D status.
There are three more important lifestyle steps to take…
Get enough calcium every day
Best: 900 milligrams (mg) to 1,000 mg of highly available calcium daily. Most of my patients drink three glasses of milk a day (300 mg of calcium in eight ounces of skim milk) to meet that need. Enriched nondairy alternatives are an option. If you don’t get enough dietary calcium, take calcium supplements to reach that amount.
Exercise
Walk at least three to five miles a week. Exercise helps to maintain bone mineral density in the hip and spine…improves muscle tone, reducing risk for falling…and can provide some vitamin D from sensible sun exposure.
Get out in the sun at optimal times
Knowing exactly when that is varies. To personalize this for your circumstances, download the free app DMinder (dminder.ontometrics.com, available on Apple or Google Play). It shows you how to optimize sun exposure to get enough vitamin D based on your location, body and skin type and time of day, and it warns you of any risk for sunburn. You can also use the app to track the amount of vitamin D you’re getting from the sun.
