Are You Vitamin D Deficient?

by , | Last updated Jan 11, 2024 | Foods, Immune Efficiency, Nutrition

Vitamin D deficiency is quite common in the U.S. A 2011 study found 41.6% of adults in the USA have either an outright deficiency or an insufficient amount of vitamin D. This number goes up to 69.2% in Hispanics and 82.1% in African-Americans. 1

What Is Vitamin D?

Even though it is termed “vitamin D,” this interesting substance is, in reality, not a true vitamin. Biochemically speaking, bioactive D3 or calcitriol is a steroid hormone that our bodies start to synthesize when sunlight strikes our skin. It takes a whole series of intricate biochemical reactions in the skin, liver, and kidneys to finally produce the active form of this prohormone, alias “vitamin.” Thus, the food we eat is not the only source of this unique substance with steroidal actions.

What Does Vitamin D Do for Us?

We have all heard that vitamin D enables us to have strong, resilient bones. However, is that all it does? Vitamin D has other roles in the body, including neuromuscular and immune function, cancer-fighting activities, and reduction of inflammation. 2

Vitamin D does even more than this. In its hormone form, it acts as a molecular “switch” that targets and activates more than 200 human genes in a wide variety of tissues, many of which are involved with “upkeep” and repair of cells and tissues. 3 In other words, prohormone D activates certain genes and enables them to manufacture their specific proteins, which in turn, modify cell and tissue function. Vitamin D plays a role in maintaining gut integrity so less food-associated pathogens get into the blood stream. 4

Vitamin D Deficiency Linked to Disease

Scientists are also finding connections between vitamin-D deficiencies and asthma, COPD (Chronic Obstructive Pulmonary Disease), 5, weakened immune systems in offspring, 6 insulin resistance, and type 2 diabetes 7, and even how well you recover after periodontal surgery.8 Metabolites of vitamin D seem to have protective benefits against brain atrophy or “shrinkage,” and disability in persons suffering from multiple sclerosis.9

Vitamin D & Respiratory Infections

Vitamin D stimulates immune cells to secrete these anti-bacterial and antiviral compounds in immune cells and the epithelial cells in the lungs. 10 Vitamin D appears capable of inhibiting pulmonary inflammatory responses while enhancing innate defense mechanisms against respiratory pathogens. 11 Specifically in respiratory health, vitamin D deficiency has been shown to increase the risk of upper respiratory tract infections and tuberculosis and improve asthma. 12 Vitamin D inhibits several important pro-inflammatory compounds that push complications from respiratory infections.

Vitamin D and COVID-19

Adequate amounts of vitamin D may reduce the risk for Covid-19 and its complications. Hospitalized COVID-19 patients who had optimal levels of vitamin D, as defined by a blood level of 25-hydroxyvitamin D of at least 30 ng/mL (a measure of vitamin D status), had a significant decreased risk for adverse clinical outcomes. These included becoming unconscious, hypoxia (body starved for oxygen), and death. In patients older than 40 years, they observed that those patients who were vitamin D sufficient were 51.5 percent less likely to die from the infection compared to patients who were vitamin D deficient or insufficient with a blood level of 25-hydroxyvitamin D less than 30 ng/mL.13

Vitamin D and Cancer

Higher blood levels of vitamin D have been linked to a lower risk of having colon cancer and a decreased risk of dying from colorectal cancer. Low levels of vitamin D may increase the risk for breast cancer. Vitamin D plays a key role in preventing the initial stage of cancer by exerting anti-inflammatory and antioxidant defenses and DNA damage repair processes. Additionally, vitamin D can help to produce the changes in the microenvironment of the tissues so to discourage the growth of cancer cells and encourage the destruction of cancer cells. 14

Vitamin D and Cardiovascular Health

Low levels of vitamin D increase the risk for inflammation and reduce the ability of the blood vessel to manufacture nitric oxide. 15 In moderation, nitric oxide helps to keep the blood flowing and discourages the platelets from sticking together. Individuals who have low levels of vitamin D are more likely to have an increase in certain hormones (renin, angiotensin 2) that increase blood pressure. 16

A 1921 study also shows that people with vitamin D deficiency are more likely to suffer from heart disease and higher blood pressure than those with normal levels of vitamin D. In this study, the participants who had the lowest concentrations of vitamin D, the risk of heart disease was more than double that seen for those with sufficient concentrations.17

Signs & Symptoms of Vitamin D Deficiency

Many times there are no obvious symptoms, but as the D deficiency continues, the parathyroid hormone increases and secondary hyperparathyroidism occurs. This hormone causes the bones to release calcium into the blood. Bone, joint, and muscle pain, twitching and spasms, fatigue and weakness are common signs of D deficiency. If the vitamin D deficiency is not corrected, then osteoporosis eventually occurs and the risk of calcified arteries increases. In children, irritability, lethargy, delayed development, bone fractures or deformities may occur. With extra calcium in the blood, the risk of kidney stones increases.

How Much Do We Have?

As a rule, most healthy people with sufficient ultraviolet exposure should not require any additional supplementation of vitamin D during the summer months, provided they have a healthy liver and at least one viable kidney and get adequate sun exposure.  (Elderly or dark skinned individuals may not produce enough vitamin D from sun exposure.) Vitamin D insufficiency can easily surface in the autumn and fall and in those who have risk factors for vitamin D deficiency. 

Six Factors that Affect Your Vitamin D Status

A number of factors can affect the amount of vitamin D synthesized in the skin. 18 Any of these factors can affect the amount of vitamin D circulating in our bloodstream. For example:

Exposure to Sunshine

How much ultraviolet light are you being exposed to? This will be affected by latitude and time of year, among other variables. How much of your skin is exposed to the ultraviolet rays? How old are you? The elderly manufacture less vitamin D from sunlight.  The higher content of  melanin in dark skin reduces the skin’s ability to make vitamin D from sun exposure. Some studies suggest that sunscreen applications decrease the amounts of vitamin D you will get from sunshine.

Weight and Fat Status

Are you obese? People with a body mass index of 30 or greater often have low blood levels of vitamin D. Vitamin D is less bioavailable in obese individuals. Did you know that healthful weight loss, by means of a calorie-reduced diet or increased exercise, is associated with higher serum levels of 25(OH)D? 19

Diet and Vitamin D Deficiency

Any or all of these factors can affect the amount of vitamin D circulating in our bloodstream. We get most of our vitamin D from exposing our skin to sunshine. Since dietary vitamin D comes from animal products, those who eat a total vegetarian diet may be at risk for deficiency especially if they do not get sufficient sun exposure, are elderly, or have bowel, kidney, and liver diseases.20,21,22

Health Status

The capacity to absorb vitamin D into the bloodstream depends on the health of the digestive tract. Crohn’s disease, celiac disease, and other digestive problems may limit your ability to benefit from supplementation.

Kidney and Liver Function

These organs play a key role in vitamin D hormone formation. If they are compromised, one’s vitamin D levels will probably decrease.

Environmental Factors

The closer you live to the North or South Pole, the lower the angle of the sun in winter. At these high latitudes, it is difficult for you to make your own vitamin D since the amount of UVB light is decreased. Vitamin D synthesis is triggered in the body when these rays strike your skin. Furthermore, when the days are short and the weather is cold, nearly all of the skin is covered by layers of warm clothing and thus remains unexposed to the sun. The amount of air pollution in your locale can affect how much UVB radiation reaches you.

How Much Vitamin D Do You Need?

Have you ever had your vitamin D levels checked? Especially the elderly, those with dark skin, and those with other risk factors for deficiency would do well to be tested annually. Pregnant women should be tested also. The current recommendation for vitamin D is 400 IU per day for infants from birth to 1 year; 600 IU per day for children and adults up to 71 years old, and 800 IU per day for those age 71 years and older. The upper limit for vitamin D is 2,500 IU/day for 1-3 year olds, 3,000 IU/day for 4-8 year olds, and 4,000 IU/day for those 9 years and older.

Vitamin D is stored in the liver. Persistent excess amounts can lead to kidney damage. High vitamin D concentrations have been implicated in promoting vascular calcification and arterial stiffness that contribute to arteriosclerosis and hypertension. 23

Defining Deficiency, Insufficiency, and Optimal

The 25-hydroxy vitamin D blood test is the most accurate way to measure how much vitamin D is in your body. 24

  • Deficiency: A level less than 12 ng/mL (or <30 nmol/L) indicates vitamin D deficiency. Deficient amounts of vitamin D results in rickets in infants and children, osteomalacia in adults. ⦁ Insufficiency: The range between 12 to 20 nanograms (30-50 or nmol/L) is considered insufficient. Vitamin D insufficiency generally considered inadequate for bone and overall health in healthy individuals. ⦁ Adequacy: A level above20 ng/mL (>50 nmol/L) is considered adequate for healthy people.
  • Optimal: Levels between 40 to 60 ng/mL are consistent with those reported in population studies to be associated with the lowest risk of several types of cancers, cardiovascular diseases, autoimmune diseases, and all-cause mortality. 25
  • Unsafe: Levels >60 ng/mL (at >150 nmol/L ) are linked to potential adverse effects. 26

The Linus Pauling Institute (Micronutrient Research for Optimum Health at Oregon State University) recommends aiming for a serum 25-hydroxyvitamin D level of at least 32 ng/ml to adjust for individual differences and ensure adequate body vitamin D status.


Vitamin D is vitally important for cellular, respiratory, immune, gut, and lung health. Get your vitamin D level checked promptly and annually if you have any risk factors for deficiency. For those who need vitamin D supplement, be sure to get vitamin K2 either from plain non-dairy yogurt or supplement. Why? Some studies indicate that taking a vitamin D supplement without getting enough vitamin K2 can lead to calcified arteries. Unlike vitamin K1 in leafy greens, K2 is found in fermented foods.



© 2024, Wildwood Sanitarium. All rights reserved.

Disclaimer: The information in this article is educational and general in nature. Neither Wildwood Lifestyle Center, its entities, nor author intend this article as a substitute for medical diagnosis, counsel, or treatment by a qualified health professional.


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