The truth about salt.

For 40 years the dominant nutritional advice on blood pressure has been the same three words: cut the salt. It is on every food label, in every guideline, and in most of what your doctor has probably said to you if BP has ever come up.

The advice is not wrong, but it has been telling half the story. And for most people reading this, the half it has been leaving out is where the actual lever sits.

The PURE study by Mente and colleagues in Lancet 2016 pooled data from four cohorts and separated the sodium-cardiovascular link by starting blood pressure. In adults with hypertension, high sodium intake was clearly associated with more cardiovascular events and death. In adults without hypertension, the same relationship was not there. And in both groups, very low sodium intake carried its own risk signal.

That matters because the last four decades of universal salt-cutting policy assumed the sodium-BP-CV link applied equally to everyone. The evidence suggests it applies most cleanly to the roughly 30 percent of adults who are already hypertensive or salt-sensitive.

Meanwhile, on the other side of the ratio, the 2020 dose-response meta-analysis by Filippini and colleagues in JAHA of 32 randomized controlled trials found that increased potassium intake lowered systolic BP by up to 5 to 6 mmHg, with the largest effect in people with the lowest starting intake. The average American consumes around 2,600 mg of potassium per day. The recommended intake is 3,500 to 4,700 mg. Most adults are running a potassium deficit big enough that closing it would deliver a meaningful BP drop before they ever touched the salt shaker.

The physiologic story that ties it together comes from the Adrogué and Madias review in NEJM 2007. What blood pressure actually responds to is the ratio of sodium to potassium in the diet, not either number in isolation. Two people eating the same amount of sodium can have very different pressures depending on the potassium alongside it. The Western diet has broken the ratio from both ends, high on one side and low on the other.

Two things the standard advice keeps leaving out.

The first is where sodium actually comes from. Roughly 71 percent of daily sodium in the American diet comes from packaged and restaurant food, according to CDC data. Only about 11 percent comes from what people add during home cooking or at the table. The shaker in your kitchen has been carrying the reputation for a problem that is largely upstream of it. If you cut the shaker but keep eating the same bread, canned soup, deli meat, and takeout, your daily sodium barely moves.

The second is the salt itself. Sea salt, Himalayan, Celtic, kosher, and iodized table are all around 98 percent sodium chloride by weight. The trace minerals differ, but not at the doses that show up in your food. From a blood pressure perspective, salt is salt.

What does change when you switch from iodized table salt to any of the artisan salts is your iodine source. Iodized salt was a US public health intervention introduced in 1924 that essentially eliminated goiter in a generation. It is one of the cleanest public health wins on record. If you have moved entirely to pink or Celtic or sea salt without noticing, and you do not eat regular seafood, dairy, or eggs, you can drift into low iodine over time. That quietly affects thyroid function. In pregnancy, it can also affect fetal cognitive development.

The NIH Office of Dietary Supplements sets the adult recommended intake at 150 mcg per day. The American Thyroid Association recommends the full 150 mcg as a daily supplement for women planning pregnancy, pregnant, or breastfeeding.

The simpler move is to skip the supplement and keep iodized salt in rotation alongside whatever artisan salt you usually reach for.

Three moves this week, in the order that has the biggest effect.

Audit the packaged food. Look at the sodium labels on the six items that show up most often in your week (bread, deli meat, cheese, sauce, frozen meal, canned soup). If your daily sodium is coming from those items, the fastest lever is choosing lower-sodium versions or shifting from packaged to fresh foods, preferably whole foods, not putting the salt shaker down.

Add three potassium-forward foods to this week's shopping list. Spinach, sweet potato, white beans, salmon, avocado, plain yogurt, and bananas are all in the top tier. Two servings a day of any two of those closes most of the potassium gap for most adults.

Know your iodine source. If you have switched to artisan salt and do not eat regular seafood, dairy, or eggs, bring iodized salt back into rotation for cooking.

If you have been cutting salt for years as your BP strategy without shifting the packaged-food load or the potassium side, you have been doing about 15 percent of the available work.

Friday: three tools for this week's protocol.

Until Friday.

Longevity Daily / The Building Decades