A weekly read on the gut, the brain, and the wiring in between. One clinical pearl, one paper, one product, one person. No hype, no selling, just the stuff I actually think about.
1. Practice
Six things the label will not tell you about the vitamin the country stopped measuring.
Thiamine, vitamin B1, is the vitamin that lets the body turn food into usable energy. The brain and the heart run short first. I have written here about who runs out and what it looks like. This week is about where it comes from. In an American diet the answer is mostly bread, cereal, and a law, and the law does more of the work than you think.
One. "Enriched" is a legal word. Refining wheat into white flour strips out the germ and the bran, and most of the thiamine leaves with them. In 1941, at a meeting called the National Nutrition Conference for Defense, the country decided that was a military problem and wrote a recipe to put some of it back. Every pound of enriched flour carries a set dose of thiamine, plus riboflavin, niacin, iron, and, since 1998, folic acid. In January 1943 enrichment of white bread became mandatory for the war. The order was repealed in 1946. No federal mandate has existed since. The FDA decided in the 1940s that it would not require fortification of any food, and that policy still stands. By 1952, when the FDA finally wrote its standard for enriched bread, 26 states had passed their own laws. Today the word means exactly this: if "enriched" is on the label, the vitamins are in the bag. If it is not, nobody promised anything.
Two. Enrichment overshoots the whole grain. A cup of cooked enriched egg noodles carries about half a milligram of thiamine, roughly 40 percent of a day's worth. A cup of cooked whole wheat pasta carries about a fifth of a milligram (NIH Office of Dietary Supplements food table). Whole grain is the better food for fiber and a dozen other reasons. It is not the better thiamine source. Trade every enriched food in your kitchen for whole grain and your thiamine can go down, not up.
Three. Do not rinse enriched rice. Federal rule: enriched rice has to carry the line "To retain vitamins do not rinse before or drain after cooking," unless the vitamins have been sealed into the grain. The vitamins sit on the outside of the grain, which is why the rule exists. Rinse, and they go down the drain. White rice that is not enriched has about one-tenth the thiamine of brown rice.
Four. It is in the water. Thiamine dissolves in water, and a meaningful share of it leaves in the cooking water you pour off. Heat takes some too. Steam vegetables, or cook them in the soup they are going into.
Five. Sulfites destroy it. Sodium bisulfite, the preservative in wine, dried fruit, and some shrimp, breaks thiamine apart. The federal rule that declares it safe carves out three exceptions. It may not be used in meats, on raw produce, or "in food recognized as a source of vitamin B1." The government knows what sulfites do to the vitamin. The "contains sulfites" line on the bottle is there for people with sulfite allergy, not for this. A glass of wine with dinner is not a crisis. A diet built on sulfited food is a subtraction nobody is adding up.
Six. Since 1993 the label has not had to list it at all. The 1973 nutrition label listed thiamine, riboflavin, and niacin by law. The Nutrition Facts panel that replaced it in 1993 kept vitamins A and C, calcium, and iron, and made the B vitamins optional. Most packages dropped them. You cannot add it up from the boxes in your pantry. As this week's paper shows, neither can the country.
2. Publication
Two documents, forty-four years apart.
On June 24 the CDC published its 2026 National Nutrition Report. It covers 24 years of blood and urine from the national health survey: 131 markers of what is in Americans' bodies, as opposed to what they say they eat. More than 2,700 tables. Folate, measured fifteen ways. Vitamins B6, B12, and C. Vitamins A, D, and E, the carotenoids, the omega-3s. Iron seven ways, then iodine, selenium, zinc, and copper. Fifteen markers for caffeine and what the body turns it into. A marker for the chemical that forms when starch is fried, and one for trans fats. It is a magnificent document, and I read the list twice to be sure. Thiamine is not on it.
It has not been on it since the survey took its current form in 1999. The report's own introduction notes that Americans eat foods fortified with "iron, thiamin, riboflavin, niacin, folate, vitamin A, vitamin D." Then it measures whether the folate worked, and it did. Blood folate rose about 50 percent after fortification began in 1998. The share of women of childbearing age running low fell from about one in ten to under one in a hundred. It is the best evidence in the world that putting a vitamin in flour changes bodies. Nobody has asked the same question about the vitamin the enrichment program was built for.
It was asked once. The first national health and nutrition survey, from 1971 to 1974, ran a urine test for thiamine. The results were published in 1982 (Kerr and colleagues, American Journal of Clinical Nutrition). Substandard values turned up in 3 percent of white subjects and 8 percent of Black subjects. Then the finding that matters more. In the authors' words, individual dietary recall data "were of limited value in predicting the laboratory indices." The same people were asked what they ate and had their urine tested, and the two did not line up.
That was the last time. Every statement since about thiamine in Americans is a recall statement. People report what they ate yesterday. A computer looks each food up in a table. The total is compared against a requirement set in 1998 and not revisited. By that method, only about 6 percent of Americans fall short (NHANES 2003 to 2006). The one time the method was checked against bodies, the authors called it of limited value. The country kept the recall and dropped the bodies. The NIH fact sheet on thiamine says it plainly today: "No current data on rates of thiamin deficiency in the U.S. population are available."
The honest ceiling. A urine test in 1974 reflects recent intake more than reserves. Three and eight percent is not an epidemic. Nothing in the CDC report says thiamine status is bad; it says nothing at all. A country that measures caffeine fifteen ways can measure this.
3. Product
This week's pick: a book. Kenneth Carpenter's Beriberi, White Rice, and Vitamin B: A Disease, a Cause, and a Cure (University of California Press, 2000). Unsponsored, no affiliate relationship. Used copies are easy to find, and the press sells it as an ebook.
Carpenter was a Berkeley nutrition scientist who turned historian, and this is the definitive account of the disease that gave us the word vitamin. It reads as a detective story in which the detectives keep getting the answer wrong for good reasons. Beriberi looked like an infection. It looked like a poison in the rice. A Japanese navy surgeon showed in the 1880s that changing sailors' rations made it disappear, and credited the protein. A Dutch physician in Java gave chickens the disease by feeding them polished rice, cured it with the polishings, and drew the wrong conclusion from his own experiment. The molecule was not isolated until 1926 or made in a lab until 1936.
Why it earns the slot this week: it is the story of what happens when a country decides a problem is solved. The vitamin was found, the flour was enriched, the disease left the wards, and the measuring stopped. Carpenter is careful and plain, and he is not selling anything.
4. Person
One person worth knowing in this space.
Christine Pfeiffer, the chemist who runs the CDC's Nutritional Biomarkers Branch in Atlanta. The CDC laboratory division she works in produced the 131 markers in this week's report, and much of what the country knows about folic acid fortification comes out of her group.
In 2021 she wrote an editorial in the American Journal of Clinical Nutrition about measuring thiamine. Her sentences, not mine. Dietary intake data say most Americans get enough, "however, biochemical status is not directly monitored by the NHANES." Because the signs of deficiency are so variable, "the measurement of a suitable biomarker of thiamine status is essential." For years the field was held back because the molecule falls apart in a blood sample and the lab methods were neither simple nor reliable.
Then she describes what changed. Mass spectrometry, the lab technique that weighs molecules, can now measure the active form of the vitamin directly in a drop of dried blood from a finger prick. The sample is stable for a month at room temperature and travels in an ordinary envelope. She lays out three steps to make results comparable across labs: agree on one marker, agree on one way to report it, and set up outside quality checks. The editorial's focus is the world's poorest countries, where the need is most urgent. The same tools work in Atlanta.
I have no idea whether thiamine is on her list for the next survey cycle. I do know that the person who could put it there has already written down why it matters and how it could be done. That is further than the field has been in fifty years. Her papers are free to read on PubMed under her name, and the report is at cdc.gov/nutrition-report.
The survey has run for fifty years since, and the question was never asked again. All that time, the blank where the number should be has been read as reassurance.
The same thing happens one person at a time. "Your labs were normal" means the things on the panel were normal. Thiamine is not on the panel, for the same reason it is not on the national list: nobody put it there. If you want it checked you have to ask for it by name, and it helps to be able to say why: how long the appetite has been gone, how many weeks the stomach has been wrong, when the energy left.
That is what MeNome is for, our free app at menome.belly-md.com. It does not measure any vitamin. It keeps the record of what you can see, a minute a day. When you ask for the test, you can say what has been happening and for how long.
A blank is not a zero.
That's the four. See you next week.
Rick
From BellyMD
MeNome is our free app for keeping your own record. A minute a day on your gut, sleep, mood, and energy, and over time it shows you what shows up together. It lives at menome.belly-md.com.
I also make MGB+, a small line of gut-brain supplement formulas: Clear, Cool, and Calm, at belly-md.com. Structure-function support, not a treatment for any disease.
If you want to talk through your own gut-brain picture with me directly, I offer a gut-brain consultation. Details at belly-md.com.
Not medical advice. This newsletter is for education and does not create a physician-patient relationship. Nothing here is a diagnosis or a prescription. Talk to your own physician before starting, stopping, or combining any medication or supplement, including over-the-counter ones.