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Who Needs Vitamin D and Why?

Beverley has a degree in science and additional certifications in nutrition and aromatherapy. She's published on and offline.

Provitamin D3

Provitamin D3

Did you know that vitamin D is not really a vitamin? It’s a prohormone. Our body converts it into the hormone it needs to perform necessary functions.

Vitamin D also isn’t one compound. It’s a cluster of five. D2 or ergocalciferol found in plants and D3 or cholecalciferol found in animals are the most active and the two compounds that may be most important to us.

Classified as fat-soluble, the vitamin occurs naturally in foods such as mushrooms, salmon, and other fatty fish. It is fortified in foods like milk, including the plant-based kind.

Synthesis of Vitamin D in the Body

Synthesis of Vitamin D in the Body

Is Vitamin D Needed?

The human body makes vitamin D3 when the skin is exposed to sunlight. The ultraviolet B rays of the sun convert compounds in the skin into D3. This is the reason it’s labeled “the sunshine vitamin.”

So, why do we need to consume it?

Most medical experts believe vitamin D or D3 is essential for good human health. Statistics found that at least one-third of Americans over the age of 60 are prescribed vitamin D supplements to lower the risk of diseases from the deficiency.

Individuals are deemed vitamin D deficient when their levels are within the range of less than 20ng per ml of 25-hydroxyvitamin D or (OH) D to less than 12ng per ml of 25 (OH) D.

Below-range levels of vitamin D in the body may cause osteoporosis, bone fractures, osteoarthritis, multiple sclerosis, cardiovascular issues, hypothyroidism, hyperparathyroidism, certain cancers, cognitive disorders, rickets, painful muscles, psoriasis, fatigue, and other diseases.

Some Health Professionals Believe Vitamin D Consumption Is Unnecessary

Based on the research over the past five years, some health experts conclude that consumption of vitamin D is unnecessary. One study titled VITAL was funded by the United States government. The results indicated that vitamin D did not reduce the risk of bone fractures in senior populations nor did it prevent cardiovascular issues and cancer.

A British medical journal also published results from 50 trials with over 70,000 subjects. They were given vitamin D supplements or a placebo to determine the vitamin’s effects on cancer and cardiovascular illness prevention. The results showed no significant difference in mortality rates.

Who Needs Vitamin D?

Data collected and analyzed through the National Health and Nutrition Examination Survey from a 2011- 2012 study concluded that vitamin D deficiency is greater in certain U. S. subpopulations. Those populations were subjected to factors that prevented the compounds or receptors in the skin from absorbing UV-B from the sun. This inhibited the body from making the active vitamin D it needs.

Factors That May Retard Vitamin D Production in Humans

The following factors could potentially disrupt the vitamin D conversion process:

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  1. Age
  2. Disease
  3. Complexion
  4. Obesity
  5. Lack of exposure to sunlight
  6. Infants who are breastfed


As we age our skin’s ability to make vitamin D decreases. However, our body still needs it to perform various functions. An intake can increase the vitamin level and may help keep older adults healthy by lowering the risk of diseases and conditions like osteoarthritis, osteoporosis, bone fractures, weak muscles, cognitive decline, and chronic illnesses such as breast, prostate, colon, and bladder cancers.

Also, older folks tend to stay indoors more and therefore are not exposed to sufficient sunlight.


A host of illnesses may cause a deficiency in vitamin D. They include liver disease, kidney disease, celiac disease, cystic fibrosis, Crohn’s disease, diabetes, tuberculosis, skin issues such as psoriasis, and individuals who had portions of their stomach or intestines removed.


Skin pigmentation, a result of melanin, interferes with or decreases the skin’s ability to absorb ultraviolet B rays from the sun. So, darker complexions or those with more melanin in their skin may have a greater need for vitamin D supplementation.


Body fat is measured by tools such as the Body Mass Index or BMI. A higher-than-normal body fat percentage may lower the body’s ability to absorb vitamin D.

Lack of Exposure to Sunlight

Individuals who work at night, people who live in regions where exposure to sunlight is limited, or citizens of heavily polluted areas may be more likely to suffer from a vitamin D deficiency.

Breastfed Babies

The American Academy of Pediatrics believes that breast milk does not provide babies with enough vitamin D. They determined that a newborn infant requires a daily dose of at least 400 IU to maintain proper health.

What Are the Natural Sources of Vitamin D?

Some food sources are naturally rich in vitamin D. They include several varieties of fish such as salmon, tuna, trout, swordfish, and sardines, cod liver oil, beef liver, eggs, and mushrooms.

Certain foods are fortified with vitamin D. They include whole milk, plant-based milk, cheese, other dairy products, cereals, and juices.

How Much Vitamin D Should One Take?

AgeDaily Supplemental Dose in International Units (IU)

From birth to one year old

400 IU

From one to 70 years

600 IU

From age 71 and older

800 IU

What Is the Appropriate Supplemental Dose of Vitamin D?

Vitamin D supplementation depends on the age of the individual. From birth to one year old, 400 IU per day is recommended. From one to 70 years, it’s 600 IU per day. Beyond 70, 800 IU is recommended.

Medical experts believe adults can safely take a maximum daily dose of 4,000 IU.

Maximum dosages for children range from

- 4,000 IU for age nine and older

- 3,000 IU for kids four to eight years old

- 2,500 IU from toddlers to three

- 1,000 IU from birth to six months old

Always consult your healthcare provider for diagnoses, accurate medical information, and permission before consuming any supplements. There’s no medical evidence to support vitamin D curing, treating, or preventing diseases.

Side Effects & Safety Concerns of Vitamin D

Overconsumption of vitamin D may cause digestive problems including diarrhea and constipation, loss of appetite, headaches, and fatigue due to an excess of blood calcium.

Hypercalcemic individuals can develop more serious hardening of bones, blood vessels, heart, lungs, and kidneys.

Certain medications may also interact poorly with vitamin D supplements.

Bottom Line

Do humans need vitamin D? Yes. Receptors in our skin absorb the sun’s ultraviolet-B rays and convert them into an active form called D3. Our body uses D3 to perform essential functions.

Some health professionals, however, believe vitamin D supplementation is unnecessary. Their conclusion is based on the past five years of research. Others in the medical field believe that certain subpopulations are affected by factors that may result in deficiency and diseases. Those factors include age, disease, darker skin hues, obesity, lack of exposure to sunlight, and breastfeeding infants.

A vitamin d deficiency in the elderly population, for instance, could cause osteoarthritis, osteoporosis, bone fractures, weak muscles, cognitive decline, and chronic illnesses, including several types of cancers.

Vitamin D occurs naturally in foods such as fatty fish and mushrooms. It’s fortified in others like juice, dairy, and cereal. Vitamin D 2 is the active form found in plants. D3 is found in animals, including humans. Supplementation is determined by an individual’s age. For example, a daily dose of 400IU is recommended for individuals one to 70 years old.

Overconsumption and certain medications may cause harmful reactions.

This content is for informational purposes only and does not substitute for formal and individualized diagnosis, prognosis, treatment, prescription, and/or dietary advice from a licensed medical professional. Do not stop or alter your current course of treatment. If pregnant or nursing, consult with a qualified provider on an individual basis. Seek immediate help if you are experiencing a medical emergency.

© 2022 Beverley Byer

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