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Posted by Margy Squires on 6/1/2026 to
Vitamin D3
Around 1920 in wintry England, a dog loving researcher concluded that his dogs were developing rickets (bone deformation) due to a missing nutrient because when fed cod liver oil, they recovered. He named the nutrient vitamin D. It wasn’t until a decade later that scientists learned vitamin D could be synthesized in the skin with adequate exposure to sunlight. They thus determined lack of sunlight caused the D deficiency and subsequent rickets. Vitamin D earned the nickname “the sunshine vitamin” but lost its “essential” status since a nutrient is defined as “essential” only if it cannot be produced in our bodies
What is D, then?
About a decade ago, scientists and researchers discovered that D’s activity fell more in line as a hormone after they isolated the vitamin D receptor (VDR) and saw how different cells were influenced. As a hormone, D’s benefits extend beyond its accolades as a bone builder to impact many body functions.
The Facts.
Structurally related to cholesterol, vitamin D3 (cholecalciferol) is produced in the body with the help of the liver and kidneys to the active hormone form, calcitrol. All you need, as we learned, is adequate exposure to ultraviolet sunlight. In its bone role, vitamin D regulates body levels of calcium and phosphorous to affect bone buildup and breakdown. According to the National Osteoporosis Foundation, “vitamin D plays a major role in calcium absorption and bone health… similar to that of a locked door and a key. Vitamin D is the key that unlocks the door and allows calcium to leave the intestines and enter the bloodstream. Vitamin D also works in the kidneys to help reabsorb calcium that otherwise would be excreted or deposited in non-bone places like arteries and organs.
Vitamin D’s role in bone health is solidly established. An estimated 54 million Americans have osteoporosis, a loss of bone density, and low bone mass or osteopenia, putting them at risk for fractures. Many studies show a direct link between vitamin D, stronger bones and reduced falling and fractures in the elderly.
Vitamin D appears to play a role in pain modulation, too, although the exact mechanism is not clear. A 12-week clinical study looked at the relationship of active D3 to widespread musculoskeletal pain in 56 patients with fibromyalgia, headaches, spinal arthritis and failed spinal surgery. Moderate to severely low levels were found in over half of the patients, regardless of age (26-80 years). Similarly, low levels of D3 are found in arthritis, diabetes, heart disease and multiple sclerosis. Restoring D3 levels was an important part of the treatment for these conditions.
Are you getting enough D?
Ideally, only 10-15 minutes of sunlight three times a week should be enough time to “make” vitamin D. However, the time of day, amount of sunlight available, the season and latitude, and even the fairness of your skin affect the outcome. Sunblock, pollution, clothing, age, and darker skin color also decrease the skin’s ability to make vitamin D. Your health also p ays a factor. Disorders of the parathyroid, kidneys and intestines will adversely affect your ability to maintain D levels. Any problem with fat absorption or synthesis also puts a person at risk since D is a fat soluble vitamin.
You can also get some vitamin D in food sources: Cod liver oil, saltwater fish (salmon, mackerel, tuna, sardines), egg yolks and beef liver. Due to an epidemic of rickets in school age children in the 1930s, vitamin D was added to milk, a practice which is still continued today. But D is also advertised on bread and cereal labels, range juice cartons and in other foods where D is not typically found. Unfortunately, it may not be the active form of vitamin D or in such small quantities that it would be hard to obtain your daily quota without supplementing.
Supplementing with oral vitamin D, especially in cases of deficiency, seems to be the easiest and fastest way to increase or maintain healthy levels. Take the right form. An oral dose of D3 (cholecalciferol) results in 70-80% higher levels of vitamin D in the bloodstream compared to an oral dose of (synthetic) D2.
Dosages.
The Institute of Medicine, which sets vitamin daily values “determined that there was insufficient scientific information to establish an RDA for vitamin D”. Instead, the recommended intake is listed as an Adequate Intake (AI) to maintain normal calcium metabolism in healthy people. The 400 IU commonly cited is based on the amount found in a teaspoon of cod liver oil, a daily dose of which prevents rickets in children. The dose does not account for adult age, size and deficiencies.
Toxicity.
Reports of 400-800 IU intake daily as “massive” and “toxic” are old news. In fact, in a 2006 published paper, Dr. Michael Holick of the Mayo Clinic states, “Vitamin D toxicity has not been reported from long term exposure to sunlight and has only been observed from dietary intake when daily doses exceed 10,000 IU. Doses of 4,000 IU for 3 months and 50,000 IU/wk for 2 months have been administered without toxicity”. The real issue seems to be in getting enough, not too much.
Vitamin Testing.
Inactive vitamin D3 is stored in fat cells for future use so levels are easily checked with a simple blood test, a 25-hydroxy vitamin D. With osteoporosis on the rise as the population ages (and increased pollution and bad diet prevail), most doctors will order the test for you. Some states allow you to order D test for yourself from labs like Quest and LabCorp, although it may be self-pay so check the costs first.
Summary.
Although the role of vitamin D’s influence on bone health is well documented, its impact on other disease processes is just beginning to emerge. Whether you think of D as a vitamin or a hormone, you’ll want to check your levels as its benefits are unquestionable.
Resources
- National Osteoporosis Foundation www.nof.org
- Office of Dietary Supplements, NIH Vitamin D Fact Sheet
- Gostine ML, David FN. Vitamin D deficiencies in pain patients. Practical Pain Management J/A 2006.
- Holick, MF. High prevalence of vitamin D inadequacy and implications for health Mayo Clin Proc 2006:81:353-373.
Caution: Consult your doctor before supplementing with vitamin D if you are planning a pregnancy or are pregnant; have elevated calcium levels, and/or disorders of parathyroid, GI tract or liver.
©TyH, Inc. For informational purposes only.
