Given the qualifier "unless you have existing cardiovascular or renal issues" they probably understand the relation between sodium and blood pressure. (Dare I say understand it better than you?)
Trans fats (more specifically partially hydrogenated vegetable oils) are understood to be harmful in any amount. Sodium is essential in some quantity and only harmful in excess. It really doesn't make sense to group them together as "harmful nutrients."
When there’s extra sodium in your bloodstream, it pulls water into your blood vessels, increasing the total amount (volume) of blood inside them. With more blood flowing through your blood vessels, blood pressure increases. It’s like turning up the water supply to a garden hose — the pressure in the hose increases as more water is blasted through it.
Over time, high blood pressure may overstretch or injure the blood vessel walls and speed the build-up of gunky plaque that can block blood flow. The added pressure tires out the heart by forcing it to work harder to pump blood through the body. And the extra water in your body can lead to bloating and weight gain.
High blood pressure is known as the “silent killer” because its symptoms are not always obvious. It’s one of the major risk factors for heart disease, the No. 1 killer worldwide. Almost no one gets a free pass. Ninety percent of American adults are expected to develop high blood pressure over their lifetimes.
Did you know that sodium can affect your blood pressure even more dramatically if you’re sensitive to salt? Recent science explains that certain factors may influence how your blood pressure changes when you eat salt, such as:
Age Weight Race/ethnicity Gender Some medical conditions (like diabetes or chronic kidney disease) Even if you don’t already have high blood pressure, eating less sodium can help blunt the rise in blood pressure that occurs with age. It can also reduce your risk of heart attack, heart failure, stroke, kidney disease, osteoporosis, stomach cancer and even headaches.
That's not about sodium - its about high blood pressure, which is not in dispute.
Your body is exquisitely designed to balance sodium. Sweat, tears, urine remove excess very quickly. Blood pressure is affected by sodium, sure. A point or two for an hour or two.
Unless you have a health issue related to sodium, lets quit demonizing it. The worst thing about salt is, folks use it to distract from real improvements they could make in their health.
Sodium is considered to more problem than trans fats for Japanese people because average Japanese takes more sodium than recommended and takes less trans fats than it meaningfully harm.
Trans fats (more specifically partially hydrogenated vegetable oils) are understood to be harmful in any amount. Sodium is essential in some quantity and only harmful in excess. It really doesn't make sense to group them together as "harmful nutrients."