07. Health — The Step Count and the Salt Packet

Overrated · The 10,000-steps-a-day target

Fitness trackers and wellness apps treat 10,000 steps a day as a scientifically grounded minimum for health. The number traces to "manpo-kei," Japanese for "10,000-steps meter." Yamasa Clock and Instrument Company sold a pedometer under that name in Japan in 1965. It was a product name, not a research finding. I-Min Lee and colleagues tracked 16,741 US women, mean age 72, by accelerometer for seven days between 2011 and 2015, in the Women's Health Study. Mortality risk fell steadily with more steps but leveled off at about 7,500 steps a day. Women averaging roughly 4,400 steps a day already had about 41% lower mortality than those averaging roughly 2,700.

Underrated · Oral rehydration therapy

Before the 1970s, hospital-based IV fluids were the assumed treatment for severe childhood diarrhoea. A home-mixed sugar-salt solution seemed too simple to matter. Global annual deaths from diarrhoea in children under five fell from an estimated 4.6 million in 1980 to under 500,000 by 2018. World population grew by 70% over the same span. By 2007, oral rehydration therapy alone was estimated to have prevented 54 million diarrhoeal deaths since its introduction. In Bangladesh, BRAC ran a national "Lobon-Gur," salt-sugar, home-mix campaign. By a 1993 assessment, 70% of Bangladeshi mothers could correctly prepare the solution at home.

The gap

A round number on a wrist display is easy to see, repeat, and sell; a dose-response curve in a study appendix is not. Walking still lowers mortality — the plateau sits well below 10,000, not at zero. The 1965 marketing origin does not make walking useless; it means this specific target number was never derived from evidence. Oral rehydration therapy is cheap and mixed at a kitchen table, so it earns no place on a screen.

Example: A 1965 Tokyo pedometer's brand name still sets the default goal on phones sold sixty years later, while a sachet of salt and sugar that helped prevent tens of millions of deaths has no icon on any app.

Verdict. The step count is marketing wearing the coat of medicine; the salt packet is medicine that never needed marketing.

Overturned if: a larger, more diverse cohort finds mortality still falling in a straight line past 10,000 steps a day, with no plateau below it.

Sources. 2019 · I-Min Lee et al., "Association of Step Volume and Intensity With All-Cause Mortality in Older Women" — JAMA Internal Medicine · 2018 · David R. Nalin & Richard A. Cash, "50 years of oral rehydration therapy: the solution is still simple" — Lancet31488-0/abstract)