Hypertension: Any significant salt reduction may lower blood pressure

• Any significant reduction in one’s consumption of dietary salt can improve high blood pressure, according to a new study.
• The study’s main focus was addressing primary aldosteronism, a common secondary cause of hypertension.
• The researchers also observed that a lower sodium intake reduced symptoms of depression and anxiety in participants.

A new study investigates the effect of a moderate reduction in dietary sodium intake on hypertension, or high blood pressure.

Dietary salt is a combination of two chemicals: sodium and chloride. The sodium in salt is closely linked to hypertension, and reducing its consumption is associated with a reduction in high blood pressure.

While the average American ingests about 3,600 milligrams (mg) of sodium each day, the American Heart Association recommends adults should consume no more than about a teaspoon, or roughly 2,300 mg, daily.

For people with hypertension, the recommended limit for daily sodium intake is lower, about 1,500 mg. This is roughly two-thirds of a teaspoon.

The study looks specifically at the benefits of sodium reduction on one specific cause of hypertension, primary aldosteronism.

In the study’s participants, cutting sodium consumption by half for 12 weeks significantly reduced high blood pressure values, as well as symptoms of depression and anxiety.

The 41 participants in the non-randomized, single-arm study monitored their sodium intake using a smartphone app that allowed them to track sodium levels in prepared, packaged, and fast foods.

The researchers found that using the app helped participants remain motivated through suggested low-salt recipes, a reward system, and a chat feature with which participants could reach out to experts with questions.

The study is published in the Journal of Internal Medicine.

Primary aldosteronism

“Most people suffer from essential hypertension, i.e., hypertension without a specific and treatable underlying cause,” said study lead author Dr. Holger Schneider.

However, he said, “up to 15% of cases can be attributed to secondary hypertension. Primary aldosteronism is the most common endocrine cause of secondary arterial hypertension.”

For people whose high blood pressure does not adequately respond to medication, primary aldosteronism may be the reason. With primary aldosteronism, adrenal glands produce an excess of the hormone aldosterone, which balances sodium and potassium levels. Aldosterone excess together with a high dietary sodium intake aggravates cardiovascular damage.

The diagnosis of primary aldosteronism requires a blood test that is too infrequently ordered, according to preventive cardiologist Dr. Yu-Ming Ni at MemorialCare Heart and Vascular Institute at Orange Coast Medical Center in Fountain Valley, California, who was not involved in the study.

“This is not something that people hear much about, but it’s certainly something that is more common than we think. We often get patients on blood pressure medications, and we’re getting their blood pressure under control, and then we’re satisfied,” Dr. Ni said.

How salt affects blood pressure

For decades, said Dr. Schneider, numerous large population-based studies have established an association between salt consumption and hypertension. Even so, the mechanistic link between the two is not yet fully understood.

Dr. Ni explained the classic Guyton model, which asserts that salt draws water — and therefore blood from the heart — into the blood vessels in the arteries, increasing the pressure pushing out against their walls.

“But it also affects your kidney hormone function,” he said.

The kidneys should be able to manage this, restoring blood pressure to healthy levels, but “[d]efects in this feedback mechanism would promote salt-sensitive hypertension,” said Dr. Schneider.

Still, Dr. Schneider cautioned:

“It should be noted that even the most basic assumptions stated above — for example, salt increases cardiac output — are still contested and not fully resolved, as illustrated by a very recent study which showed that rats actually reduced cardiac output and increased their peripheral resistance when switched from a low- to a high-sodium diet.”

Even a small reduction in sodium helps

The authors of the study hoped to ascertain whether even moderate sodium reduction was beneficial and found that lowering one’s intake even to a moderately high level of sodium indeed carries benefits.

Study participants’ sodium consumption dropped from a baseline of over nine grams per day to just over five grams, or 5,000 mg. Even that amount, however, is double the recommended amount of daily sodium.

“That’s a lot of salt,” said Dr. Ni.

Improved depression and anxiety

One of the study’s surprising findings was that reducing sodium intake helped reduce participants’ depression and anxiety.

Dr. Schneider explained that anxiety and depression are common in patients with primary aldosteronism.

“The study showed that pathological scores for depression normalized at the end of the moderate salt intervention,” said Michelle Routhenstein, heart health dietitian at EntirelyNourished.com, who was also not involved in the study.

“Previous studies have shown that high sodium can contribute to depression through direct effects on neurotransmitters, neural function, and possibly the gut microbiome,” she said.

Salt — and sodium — hidden in plain sight

“It’s incredible how much salt is in food,” said Dr. Ni.

Routhenstein, meanwhile, pointed out all the foods that people wouldn’t often think of as containing salt.

“Sodium is often added to the foods we eat in prepared and packaged foods, and can appear in unexpected places like breakfast cereals, certain spice rubs, instant pudding mix packs, baked goods, breads, and salad dressings,” she said.

Dr. Ni pointed out that restaurants — fast food and otherwise — as well as food product manufacturers “are adding more salt than you would add if you were to make the same meal because they want the food to taste good.”

As a result, individuals cannot accurately assess their sodium intake simply according to the salt they manually add to foods during cooking or at the table.

Salt alternatives

Routhenstein also cautioned against replacing salt with salt alternatives, since they may also carry health risks. Too much potassium chloride, for example, may raise potassium levels dangerously, increasing the chances of sudden cardiac arrest and arrhythmias, particularly in people with heart disease and kidney failure.

“Instead, I would focus on adding in more fresh herbs and spices like cumin, basil, turmeric, and oregano to not only help reduce the salt content in the diet but to also add antioxidants and anti-inflammatory compounds,” Routhenstein advised.

Try replacing high-salt flavorings such as soy sauce with coconut aminos that provide a similar umami flavor with half the sodium, suggested Routhenstein.

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