Common Sense Health: A century-old problem we still ignore

By Diana Gifford-Jones on January 30, 2026.

In 1982, PubMed, a research database, indexed 740 papers with “vitamin D” in the title. In 2020, there were 5,566. Clearly interest has increased. Today, vitamin D is studied as a system-wide regulator and an essential component of skeletal, immune, metabolic, cardiovascular, neurological, and inflammatory processes.

But even a century ago, nutritionists feared the dangers of vitamin D deficiency. Warnings were dismissed as “alternative thinking.”

Vitamin D was discovered in the early 20th century, when researchers noticed that children deprived of sunlight developed rickets, a bone-softening disease that left them bow-legged and deformed. In 1903, Niels Ryberg Finsen, a Danish physician with Icelandic roots, received a Nobel prize for pioneering the therapeutic use of concentrated light. Sanatoriums, which emphasized sunlight exposure, and cod liver oil, rich in D, were common treatments for tuberculosis and other infections, but Finsen’s work explained it.

For decades afterward, vitamin D was viewed narrowly as a “bone vitamin” in spite of the success of sanatoriums. Once rickets was largely eliminated through supplementation of food, the medical profession lost interest. Blood levels were rarely tested. The assumption was that a normal diet and a bit of sunshine were enough.

More recent research has shown D is not just a vitamin, but a hormone, influencing hundreds of genes involved in immune function, inflammation, muscle strength, and brain health. Across the human lifespan, as much as 3-4% of the human genome is influenced by vitamin D. It’s confirmed what early advocates suspected – deficiency is the norm, not the exception.

With aging, skin becomes far less efficient at producing D from sunlight. An 80-year-old produces only a fraction that a 20-year-old can make with the same sun exposure. And if you live north of Atlanta, GA, you aren’t making enough D from sunlight in winter, period. Vitamin D is vital for mothers and developing children too.

Diet alone often isn’t enough. Very few foods naturally contain meaningful amounts of vitamin D. Unless someone regularly eats fatty fish or takes supplements, intake is usually inadequate. That means blood levels fall well below what researchers now associate with optimal health, 40 – 100 mg/mL.

Low vitamin D levels are strongly associated with increased risk of fractures and osteoporosis; loss of muscle strength and balance, leading to falls; impaired immune function and higher susceptibility to infections; chronic inflammation, which underlies heart disease, diabetes, and arthritis; and cognitive decline and mood disorders, including depression.

In other words, vitamin D deficiency worsens many of the conditions we attribute to “normal aging.”

Perhaps the greatest irony is this: vitamin D deficiency is easy to detect and inexpensive to correct. A simple blood test can reveal deficiency. Sensible supplementation can restore healthy levels. Yet many elderly patients are never tested, and when they are, the “acceptable” levels recommended by some authorities are likely too low to provide full protection. 2000 – 5000 IU or 50 – 125 mcg of D3 per day is a good start, guided by testing blood levels. Magnesium and Vitamin K2 are important companion nutrients to optimize vitamin D metabolism.

Medicine is very good at treating disease once it appears, but far less interested in preventing it. Vitamin D deficiency is a textbook example of this failure.

No vitamin is a magic bullet, and vitamin D is no exception. But ignoring a widespread deficiency that affects bones, muscles, immunity, and brain health makes no sense.

If there is a lesson here, it is one that’s been repeated in this column many times: when common sense, biology, and well-conducted research point in the same direction, it’s time to pay attention, no matter how long it takes conventional thinking to catch up.

This column offers opinions on health and wellness, not personal medical advice. Visit http://www.docgiff.com to learn more. For comments, diana@docgiff.com. Follow on Instagram @diana_gifford_jones

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