I was eating well by every standard measure. I still felt like something was missing. It turned out something was.
The food itself has changed — the minerals in fruit, vegetables and meat have been falling for eighty years, and why that happened is the subject of Part 1, The Vanishing Minerals. This article is about the other end of it: what the body does when the supply runs thin, and how a person would ever know.
Why Minerals Matter More Than Most People Know
Minerals are not optional accessories to nutrition. They are structural and functional essentials. Magnesium alone is required as a cofactor in more than 300 enzymatic reactions — energy production, protein synthesis, nerve transmission, blood sugar regulation, and DNA repair among them. Zinc drives immune response and wound healing and is involved in the production of over 300 enzymes. Selenium is essential for thyroid function and a potent antioxidant in its own right. Copper, often overlooked, is needed to form hemoglobin, maintain connective tissue, and support the nervous system. Chromium and boron are both still under study — boron for calcium handling, bone formation and brain function, chromium for its effect on insulin.
Linus Pauling, who won two Nobel Prizes and spent the later decades of his career studying nutrition and its relationship to disease, put it plainly: “You can trace every sickness, every disease, and every ailment to a mineral deficiency.” That is a strong statement, and a deliberately provocative one, but the underlying point — that mineral insufficiency is a root, not a footnote — is supported by a significant body of research.
When the body is running low on even one mineral, compensations begin. Enzymes work less efficiently. Immune responses slow. Hormonal signaling becomes imprecise. These effects are rarely dramatic enough to name as a disease. They are more often felt as fatigue that does not make sense, sleep that does not restore, a vulnerability to illness that seems out of proportion.
What the Country Is Actually Short Of
In June 2025, a team led by Carlene Starck published an analysis in Nutrients of what Americans eat, using national survey data gathered between 2017 and 2020. They set out to name the nutrients the country is genuinely short of. Calcium and magnesium came out at the top of the list, alongside vitamin D, vitamin E and fiber. Iodine and potassium were short in every group they measured — every age, both sexes.
The magnesium figure is worth seeing on its own. A woman between 19 and 50 is recommended 360 milligrams a day. American women take in between 254 and 294.
The National Institutes of Health has a name for the ground this article stands on: inadequacy. It is the stretch where intake sits below the recommended amount but above the level that produces a named deficiency disease. Most people live there.
Mineral by Mineral
Magnesium. The first signs are loss of appetite, nausea, fatigue and weakness. As the shortfall deepens, numbness and tingling follow, then muscle contractions and cramps, then abnormal heart rhythms.
Potassium. Constipation, fatigue, muscle weakness, and a flat, unwell feeling with no obvious cause. A low intake also raises blood pressure, raises the risk of kidney stones, and increases the calcium the body loses in urine.
Calcium. This one shows itself late. The body holds the calcium in the blood steady by taking what it needs from the skeleton, so the shortfall is paid out of bone, unseen, for years. It surfaces decades later as osteoporosis — and as a fracture from a fall that a sound bone would have survived.
Zinc. Taste and smell dull first, and food loses its edge. Wounds close slowly. Infections arrive often and stay. Hair thins and appetite drops. In older adults, thinking and mood shift as well.
Iron. Weakness, fatigue, difficulty concentrating, and a body that struggles to hold its own temperature. Immune response weakens with it. The World Health Organization estimates that approximately half of the world's 1.62 billion cases of anemia come from a shortage of iron. American women are moving the wrong way: a 2024 analysis in JAMA Network Open of 9,737 women aged 20 to 44 found iron shortfall rising across the two decades to 2018, with vitamin A and vitamin C falling further still.
Selenium. The thyroid feels this one. Selenium is required to convert thyroid hormone into its active form, and a shortage of selenium deepens a shortage of iodine — the thyroid carries both losses at once.
Selenium also holds the clearest proof that the ground beneath a crop reaches the person who eats it. In 1935, in districts of China where the soil holds little selenium, physicians identified a disease of the heart muscle now called Keshan disease. Adults in those districts were taking in no more than 10 micrograms of selenium a day; 20 is enough to protect against it. The disease struck women of childbearing age and preschool children hardest, and it receded where selenium was put back.
Copper. Anemia that persists through iron supplements. Pale skin. Bone that thins and weakens. Unsteady walking. Infections that take hold more easily.
How You Would Know
A blood panel names iron and copper reliably, and any doctor can order one. Magnesium is harder. Less than 1 percent of the body's magnesium is in the blood, and the body defends that number by drawing on bone and tissue, so a magnesium result taken from the liquid part of your blood can read normal while the stores behind it run low. The National Institutes of Health states this plainly: the level in the blood does not reflect the magnesium in the whole body.
That leaves the reading your own body gives you — the list above, in a person who eats well and still feels the way this article describes.
Iodine: Too Little, and Too Much
Iodine deserves its own section, because it is the one mineral where the ceiling matters as much as the floor.
The United States began adding iodine to table salt in the 1920s, and that addition has carried the country's thyroid health ever since. Iodine is added to table salt alone. Celtic, Himalayan, Redmond, kosher and fleur de sel are sold as they come from the sea or the mine. A quarter teaspoon of iodized table salt carries 78 micrograms of iodine, over half a day's requirement. The USDA measures plain sea salt at zero. Anyone moving from one salt to the other is moving their iodine source, by intention or by accident.
The country has already felt this. In November 2025, Harris Lieberman, Rebecca Mathews and Victor Fulgoni published an analysis in the Journal of Nutrition of 22,851 Americans aged 14 and over, tracked through national survey data from 2001 to 2018. The proportion falling short of iodine nearly doubled over those years. By 2017 and 2018, 35 percent of women of reproductive age and 46 percent of pregnant women were below the requirement. The authors name the causes directly: changes in iodized salt, in dairy, and in bread.
The thyroid runs on iodine, and it is the organ that sets the pace of everything else — temperature, weight, energy, the speed of thought. Food covers the need: two tablespoons of dried nori carry 116 micrograms, three ounces of baked cod 146, a cup of milk 84, a container of Greek yogurt 87, an egg 31.
How Much Is Too Much
The thyroid is as sensitive to excess as it is to shortage. Too much iodine produces several of the same signs — a goiter, which is a swelling of the thyroid at the front of the neck; a raised TSH, the hormone the brain sends to switch the thyroid on; and an underactive thyroid — along with an overactive one and inflammation of the gland itself. The upper limit for adults is 1,100 micrograms a day. Food alone rarely reaches it. Seaweed does: dried seaweed runs from 16 to 2,984 micrograms per gram depending on the species, so one generous serving of the wrong kind can carry a week's worth. Kelp capsules are the other place people overshoot, and some carry more than the daily limit in a single dose. Anyone with an autoimmune thyroid condition can react at amounts considered safe for everyone else.
How to Check
Periodic checking belongs in the routine. A spot urine test measures a whole population. The National Institutes of Health states that one sample cannot diagnose a single person. The test that answers the question is thyroid function — TSH, and T4, the hormone the thyroid itself makes — drawn by your doctor. Worth asking for after you change salts, and worth having in hand before you begin any iodine or kelp supplement.
So the practice has three parts: unrefined salt on the food, iodine from the sea and the dairy shelf, and a number from your doctor confirming you landed between the floor and the ceiling.
Where the shortage begins — in the soil, and in eighty years of measurements — is Part 1, The Vanishing Minerals.
The body speaks in small signs: a cramp, a restless night, a wound slow to close. It repeats them until someone listens.
Sources & Inspiration: Carlene S. Starck et al., “Identification of Priority Nutrients in the US: Targeting Malnutrition to Address Diet-Related Disease Across the Lifespan,” Nutrients, 2025. Harris R. Lieberman, Rebecca S. Mathews and Victor L. Fulgoni III, “Iodine Inadequacy Is Prevalent and Has Continuously Increased from 2001 to 2018 in the United States,” Journal of Nutrition, 2025. Derek Miketinas et al., “Macronutrient and Micronutrient Intake Among US Women Aged 20 to 44 Years,” JAMA Network Open, 2024. Deficiency signs, upper limits and food iodine figures from the National Institutes of Health Office of Dietary Supplements fact sheets for magnesium, potassium, calcium, zinc, iron, selenium, copper and iodine. Anemia figures from the World Health Organization.
This article is for informational and educational purposes only. If you live with high blood pressure or kidney disease, or take medicine for either, speak with your doctor before adding salt, potassium or any mineral supplement. Minerals interact with one another and with prescription medicine, and iodine in particular has both a floor and a ceiling. Speak with a qualified healthcare provider before beginning a mineral or iodine supplement, before changing salts if you have a thyroid condition, and before making any change to your supplement routine or health plan.