The Pill 25,000 People Tested, And What It Didn't Do

Back in July I wrote about morning light and your body clock. Here's the other half of that story, and it's a stranger one.

Low blood vitamin D is tied to nearly every bad thing. Heart disease. Cancer. Broken bones. Low mood.

So researchers did the obvious thing. They handed out pills and waited.

What happened next is worth your time…

The Trial Built To Settle It

JoAnn Manson at Harvard ran a study called VITAL. It signed up 25,871 American adults and ran for more than five years.

Half took 2,000 units of vitamin D a day. The rest took a dummy pill, and nobody knew which.

Two questions came first. Would it stop cancer, and would it stop heart attacks and strokes?

The answer to both was no. That ran in 2019 in the New England Journal of Medicine.

And It Wasn't Alone

Australia ran its own, called D-Health. Rachel Neale and her team gave 21,315 adults over 60 a big monthly dose for five years. The main question was how many would die.

No difference. Published in 2022.

Bones came next, and this one caught people off guard. Meryl LeBoff's team looked at broken bones inside VITAL.

Among healthy adults, vitamin D didn't cut breaks at all. Not in total, and not at the hip. That ran in 2022, also in the New England Journal of Medicine.

Mood too. A study called VITAL-DEP tracked 18,353 people and found no effect on low mood. That ran in 2020 in JAMA.

Where There Was A Flicker

Two results kept the door open, and both need caveats.

Colds and flu first. A 2021 review pooled 37 trials and found a small shielding effect. It was strongest in people who were low to start with, and only with daily or weekly doses.

Small is the word. The benefit was real but barely cleared the bar.

Then autoimmune disease. Jill Hahn's team, using the same VITAL group, counted fewer new cases among those on vitamin D.

That ran in the BMJ in 2022. Read it closely though. It was a side question, not the main one, and the result sat right on the edge of counting at all.

Suggestive. Not proven.

So Why Does Low Vitamin D Look So Bad

Here's the puzzle. If the pills don't help, why do low levels track so tightly with illness?

Philippe Autier and his team laid out the likely answer in 2014, in Lancet Diabetes and Endocrinology.

They argue that low vitamin D is often the result of poor health, not the cause. Sick people go outside less. Swelling in the body lowers the level in your blood too.

People with high readings tend to walk, garden, and get out of the house. The vitamin may be a sign of that life, not the engine behind it.

Researchers have tried to settle this using genes, and those studies disagree with each other. Nobody should claim the case is closed.

Who Actually Benefits

Here the story turns useful, because the pills do help some people.

Children need it. Rickets is a disease of too little vitamin D, and stopping it is settled ground.

Older adults in care homes gain too, above all the frail and the truly low. Most of the benefit for falls and breaks sits with that group.

And anyone truly low needs fixing. The fight is about healthy, well-fed people topping up, not about real shortage.

On that note, the experts don't agree on where low begins. The National Academies set the bar at 20 nanograms per millilitre. The Endocrine Society prefers 30.

That gap is why one lab report calls you deficient and another calls you fine.

One Real Harm Worth Knowing

More is not better here, and there's evidence to prove it.

Kerrie Sanders and her team in Australia gave 2,256 women over 70 one huge dose of vitamin D each year. Falls went up. Broken bones went up too. That ran in 2010 in JAMA.

A Swiss trial led by Heike Bischoff-Ferrari found much the same with big monthly doses. More falls, not fewer. That ran in 2016.

The pattern holds up. Big rare doses look worse than small steady ones.

What Sunlight Does That A Pill Can't

Your skin makes vitamin D from strong sun. North of about Boston, it stops making any from November to February. We've known that since the 1980s.

But sunlight isn't only a vitamin D delivery system.

Richard Weller at the University of Edinburgh has studied a separate effect. Sun on skin frees a stored gas called nitric oxide. That relaxes blood vessels and nudges blood pressure down.

He showed it with light that makes no vitamin D at all. So whatever that gain is, no pill can copy it.

Which is more or less my whole point. The pill was never the same thing as the sun.

Three Things Worth Knowing

Vitamin D is the most studied pill of the last twenty years. Tens of thousands of people, huge sums of money, and mostly empty results.

All that work points quietly back to the thing it hoped to replace. Going outside.

Take the walk this week. The bottle can wait.

Stay well,
The Healing Plate