What Is The Average Vitamin D Level

Testing Your Patients For Vitamin D12

Many physicians recognize the importance of testing vitamin D levels in their high-risk patients, such as older adults and those who are dark-skinned or receive little or no sun exposure. Patients with low vitamin D levels are at risk of osteoporosis and cardiovascular disease, as well as cancer and respiratory disease. Patients who are pregnant or lactating should be tested too, since they represent another high-risk group. Deficiency in pregnancy can lead to preeclampsia, and deficiency while lactating can cause rickets in infants.

An important part of the testing process is advising patients on their vitamin D supplementation needs based on their test results. Heres what you need to know.

Why Is Vitamin D So Important

Vitamin D is one of many vitamins our bodies need to stay healthy. This vitamin has many functions, including:

• Keeping bones strong: Having healthy bones protects you from various conditions, including rickets. Rickets is a disorder that causes children to have bones that are weak and soft. It is caused by a lack of vitamin D in the body. You need vitamin D so that calcium and phosphorus can be used to build bones. In adults, having soft bones is a condition called osteomalacia.
• Absorbing calcium: Vitamin D, along with calcium, helps build bones and keep bones strong and healthy. Weak bones can lead to osteoporosis, the loss of bone density, which can lead to fractures. Vitamin D, once either taken orally or from sunshine exposure is then converted to an active form of the vitamin. It is that active form that promotes optimal absorption of calcium from your diet.
• Working with parathyroid glands: The parathyroid glands work minute to minute to balance the calcium in the blood by communicating with the kidneys, gut and skeleton. When there is sufficient calcium in the diet and sufficient active Vitamin D, dietary calcium is absorbed and put to good use throughout the body. If calcium intake is insufficient, or vitamin D is low, the parathyroid glands will borrow calcium from the skeleton in order to keep the blood calcium in the normal range.

What Is Vitamin D Deficiency

Vitamin D deficiency means that you do not have enough vitamin D in your body. Vitamin D is unique because your skin actually produces it by using sunlight. Fair-skinned individuals and those who are younger convert sunshine into vitamin D far better than those who are darker-skinned and over age 50.

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Causes Of Vitamin D Deficiency

Vitamin D deficiency can occur for a number of reasons:

You don’t consume the recommended levels of the vitamin over time. This is likely if you follow a strict vegan diet, because most of the natural sources are animal-based, including fish and fish oils, egg yolks, fortified milk, and beef liver. Here are the best vitamin d foods for vegetarians.

Your exposure to sunlight is limited. Because the body makes vitamin D when your skin is exposed to sunlight, you may be at risk of deficiency if you are homebound, live in northern latitudes, wear long robes or head coverings for religious reasons, or have an occupation that prevents sun exposure. Duirng the winter, vitamin D deficiency can be more prevalent because there is less sunlight available.

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You have dark skin. The pigment melanin reduces the skin’s ability to make vitamin D in response to sunlight exposure. Some studies show that older adults with darker skin are at high risk of vitamin D deficiency.

Your kidneys cannot convert vitamin D to its active form. As people age, their kidneys are less able to convert vitamin D to its active form, thus increasing their risk of vitamin D deficiency.

Your digestive tract cannot adequately absorb vitamin D. Certain medical problems, including Crohn’s disease, cystic fibrosis, and celiac disease, can affect your intestine’s ability to absorb vitamin D from the food you eat.

Are Vitamin D Levels Increasing In The United States Population

The results of a study comparing vitamin D levels in 1998-2000 vs. 2009-2011 among middle-aged women participating in the Study of Womens Health Across the Nation were published this month in the journal of Clinical Endocrinology. The researchers found that the average vitamin D level increased from 22 to 28 ng/ml among the 1,585 women in the analysis. The percent of women below 20 ng/ml decreased from 43% to 24%. Also, the percent of women using a supplement, which was defined as taking either a multivitamin or vitamin D supplement at least one day per week, increased from 41% to 67%.

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What Does Your Diet Have To Do With Getting Enough Vitamin D

Vitamin D doesnt occur naturally in many foods. Thats why certain foods have added vitamin D. In fact, newer food nutrition labels show the amount of vitamin D contained in a particular food item.

It may be difficult, especially for vegans or people who are lactose-intolerant, to get enough vitamin D from their diets, which is why some people may choose to take supplements. It is always important to eat a variety of healthy foods from all food groups. The vitamin content of various foods is shown in the following table.

Vitamin D content of various foods

It is important to check product labels, as the amount of added vitamin D varies when it is artificially added to products such as orange juice, yogurt and margarine.

Clinical Trials To The Rescue

Th is dearth of evidence is likely to change soon for vitamin D because large, randomized clinical trials are already in the pipeline. Manson is a principal investigator of the largest one. The VITamin D and OmegA-3 TriaL is testing the effects of taking 2,000 IU in supplements per day versus placebo in almost 26,000 adults over age 50.The primary focus is on prevention of cancer and cardiovascular disease, but data will be collected on a host of other disorders, including diabetes, hypertension, cognitive decline, depression, respiratory disorders, and autoimmune diseases. Its an ongoing five-year trial, with preliminary results expected in about three years.

Another multi-year trial based at Tufts University will test whether daily supplements of 4,000 IUs will prevent or delay the onset of type 2 diabetes in people with prediabetes. Both trials are sponsored by the National Institutes of Health.

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Interval Target Level And Dose

For some time, bolus dosing was en vogue because it was thought to be interesting for practical reasons. With the exception of critical care, bolus doses with long dosing intervals are not used. They are no longer recommended because of the higher risk of adverse effects associated with them . Moreover, the 2017 individual patient data meta-analysis by Martineau et al. showed a clear benefit for vitamin D on acute respiratory infection when daily or weekly dosing was used, but not with longer dosing intervals . In the intensive care, however, a typical daily dose is inefficient, and an upfront loading dose is necessary to improve vitamin D levels rapidly .

It is also important to note that different dosing regimes may have different effects on clinical outcomes. Because a daily dose leads to stable availability of various vitamin D metabolites, this could be an important explanation for many of the negative vitamin D intervention trials .

As there is no evidence that increasing the recommended daily dose of vitamin D supplementation up to 50g would cause severe side effects in the general population, and considering that 20g is the lowest dose consistently associated with a bone benefit, it seems reasonable to recommend a daily dose of 2050g . In general, a daily vitamin D of 800IU appears to be sufficient to achieve a target 25D level of at least 50nmol/L in most healthy individuals, whereas 2000IU is sufficient to achieve a level of at least 75nmol/L .

How Much Vitamin D Should We Take

If everyone took 2,000 units of vitamin D a day, it could shift the curve from average blood levels in the mid-50s to about a 110 nmol/L , which some estimate could add years to our life expectancy. Data derived from randomized clinical trials have convinced some influential experts, such as Harvards Chair of Nutrition, that we should shoot for this kind of range, levels that about nine out of ten people fail to reach because it may necessitate taking 1,800 to 4,000 units of vitamin D a day.

The Institute of Medicine , however, considered blood levels of 50 nmol/L to be sufficient and therefore recommended only 600 to 800 units a day for those with little or no sun exposure. Why so low? Because the IOM was only considering bone health. Even if we cared just about our bones and not our lifespan, wed still probably want to shoot for a 75 nmol/L threshold, because theres evidence from hundreds of autopsies of people who died in car accidents, for instance, showing osteomalacia, or softening of the bones, in 18 to 39 percent of people who reach the IOM target of 50 nmol/L, but failed to make it to 75 nmol/L.

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Definition Of Vitamin D Deficiency

Serum 25D is considered to be the best marker for assessing vitamin D status, and reliably reflects the free fractions of the vitamin D metabolites, despite the fact that, in theory, the bioavailable fractions may be more clinically informative . A range of below 75nmol/L of serum/plasma 25D concentration is considered vitamin D deficiency by most authors . A cutoff of < 25 or < 30nmol/L increases the risk of osteomalacia and nutritional rickets dramatically, and therefore is considered to determine severe vitamin D deficiency . The clinical practice guidelines of the Endocrine Society Task Force on Vitamin D have defined a cutoff level of 50nmol/L as vitamin D deficient. Furthermore, different societies and expert bodies have defined 50nmol/L as vitamin D requirement of nearly all normal healthy persons, by using bone health as the main basis. For example, a cutoff level of 50nmol/L is recommended by the Institute of Medicine in their Dietary Reference Intakes. Vitamin D levels of < 30nmol/L should likely be prevented with a public health approach . There are many large and relevant risk groups for vitamin D deficiency .

Table 1 Risk groups for vitamin D deficiency including high-risk medications.

Prevalence Of Vitamin D Deficiency Worldwide

Prevalence rates of severe vitamin D deficiency, defined as 25D < 30nmol/L , of 5.9% , 7.4% , and 13% have been reported. Estimates of the prevalence of 25D levels < 50nmol/L have been reported as 24% , 37% , and 40% . This may vary by age, with lower levels in childhood and the elderly , and also ethnicity in different regions, for example, European Caucasians show lower rates of vitamin D deficiency compared with nonwhite individuals . Worldwide, many countries report very high prevalences of low vitamin D status. 25D levels < 30nmol/L in > 20% of the population are common in India, Tunisia, Pakistan, and Afghanistan. For example, it has been estimated that 490 million individuals are vitamin D deficient in India .

Specific categories of patients have a very high prevalence of vitamin D deficiency. Often, they are characterized by an insufficiency or failure of organs involved in vitamin D metabolism. Patients with chronic renal failure and on hemodialysis, renal transplant recipients affected with liver disease or after liver transplantation may have a prevalence of vitamin D deficiency ranging from 85 to 99% .

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How To Prevent And Treat Vitamin D Deficiency

Many patients and physicians think that adequate vitamin D intake can be obtained via diet alone. This assumption is erroneous. With the exception of fatty fish, the vitamin D content of most foods, including fortified dairy products, is relatively low to nonexistent. Even some dairy products in the United States are not fortified, making it important to read food labels to ensure the vitamin D content of foods.

Why Maintain Normal Vitamin D Levels

Maintaining normal vitamin D levels is very extremely important since this vitamin plays a vital role in the absorption of phosphorus and calcium and ensures that they are in healthy levels. Phosphorous and calcium are needed in the production and mineralization of bones and this can only happen if calcium is absorbed in the intestines. Babies need normal levels of vitamin D for optimum growth while adolescents need them to be fit and active. Older people must also maintain normal vitamin D levels to avoid bone fractures.

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How To Take Vitamin D

For best results take vitamin D once a day, with a meal, because it is a fat-soluble vitamin. If you take it on an empty stomach it is unlikely to be absorbed.

You can take it in the morning or at night, but if you tend to skip breakfast, take it in the evening, just before your evening meal.

It may be best to take it early in the evening, as there is a suggestion vitamin D can interfere with the production of melatonin. However, there is no evidence to support the fact that vitamin D disrupts sleep patterns.

Make sure you drink plenty of fluids.

If you miss a dose, skip it, but take the next one on time.

Based On Years Of Patient Testing And Data Analysis We Have Updated Our Laboratory Report Reference Range To Reflect That Values Between 20

This raises the issue: is normal the same thing as optimal? Not necessarily. The Vitamin D Council places the ideal level between 40 and 80 ng/mL with levels below 20 ng/mL as deficient. The Endocrine Society has a Clinical Practice Guideline on the evaluation, treatment, and prevention of vitamin D deficiency. This guideline recommends a minimum vitamin D level of 20 ng/mL, but to guarantee sufficiency they recommend between 30 and 50 ng/mL for both children and adults. In contrast, the Vitamin D Council states that even levels between 30 and 40 ng/mL are still not quite sufficient. On the other end of the spectrum, results that fall between 80 and 100 ng/mL are not achievable naturally that is, they are only reached with some form of vitamin D supplementation. So, while they are not harmful levels, they are instead reflective of supplementation and therefore not what would be detected in a “normal” patient population.

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What Role Is Played By Calcium Nutrition

Maintenance of normal serum calcium levels results from an array of interrelated processes, including intestinal calcium absorption, calcium uptake and release from the skeleton, and renal calcium handling. As previously noted, vitamin D plays a critical role in each of these processes. Hypovitaminosis D impairs intestinal calcium absorption and leads to secondary HPT and risk of bone loss. Heaney et al found that maximal calcium absorption in men occurs when 25D levels are in the range of 30 to 40 ng/mL, consistent with vitamin D levels needed to suppress PTH. However, even in the presence of vitamin D sufficiency, inadequate oral calcium intake may cause secondary HPT. The National Osteoporosis Foundation guidelines recommend that men and women younger than 50 years ingest 1000 mg/d of elemental calcium, and those older than 50 years ingest 1200 mg/d .

Clinicians should be mindful of several important caveats when considering calcium supplementation.

First, up to 500 to 600 mg of elemental calcium can be efficiently absorbed in any single dose, with excess calcium passing unabsorbed through the gut.

Pinpointing A Healthy Vitamin D Level Is Tricky

So, what is the current cutoff value at which people are considered “low,” and thus at risk for developing bone thinning and having fractures? Ah. This is where there is a lot of argument.

In 2010, the venerable Institute of Medicine issued a report based on lengthy examination of data by a group of experts. To sum up, they estimated that a vitamin D level of 20 ng/mL or higher was adequate for good bone health, and subsequently a level below 20 was considered a vitamin D deficiency.

In my practice, and in most, it is not uncommon to see a vitamin D level less than 20. When that happens, we tell the patient that they are deficient and recommend fairly aggressive replenishment, as well as ongoing supplementation. The majority of folks have a level between 20 and 40, in my experience, and this is corroborated by the IOMs findings in that 2010 report.

But in 2011, the respected Endocrine Society issued a report urging a much, much higher minimum blood level of vitamin D. At that time, their experts concluded: “Based on all the evidence, at a minimum, we recommend vitamin D levels of 30 ng/mL, and because of the vagaries of some of the assays, to guarantee sufficiency, we recommend between 40 and 60 ng/mL for both children and adults.”

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How To Keep Vitamin D Levels In Check

Normal vitamin D levels can be maintained through healthy diet, vitamin supplementation, regular exercise and adequate sunlight exposure. Those with high levels of the vitamin should consult their physicians for proper dosage of vitamin D supplements so as to avoid toxicity.

Maintaining normal vitamin D levels is important for all sorts of people for optimum health and to avoid the dreadful health problems that may result due to abnormal amounts of vitamin D in the body.