Janet, I've been thinking about what Tom wrote, specifically the insulin thing. At first, it makes no sense, insulin doesn't regulate BP, it regulates fuel systems, protein metabolism, etc. Then we gotta understand what BP actually is, what kind of pump the heart actually is, and the fact that the heart simply cannot push blood through the smaller vessels cuz its pressure output is just too low (several orders of magnitude too low in fact), and we gotta look at some obscure yet quite recent experimental research on water.
Two kinds of pumps. Pressure pumps, flow pumps. Pressure pumps typically have low flow. For example a hydrolic pump for machinery. Very high pressure but low flow so that the pistons move slowly when charged, but produce high force to move very heavy things. In my computer, I have water cooling, there's a flow pump with low pressure (centrifugal design), but high flow. Same with air pumps where there's pressure pumps (piston design) for air tools like in a garage, and flow pumps (simply called fans) for air cooling a computer for example.
Blood pressure is technically what's called back pressure, i.e. the pressure resulting from resistance. The higher the resistance, the higher the back pressure, we can measure this at the arm, where blood vessels and arteries are much larger than where the resistance is down the line. The higher the back pressure, in a flow pump system, the lower the flow. Since the heart's mode of action is akin to a reciprocating pump (with a one-way valve, like some aquarium pumps for example), the back pressure manifests as pulses rather than continuous. This means the heart is a flow pump, not a pressure pump.
Resistance comes primarily from smaller blood vessels, which the heart's pressure output simply cannot overcome, and secondarily from what's called hydrolic or viscosity resistance due to the size of the arteries, i.e the smaller the arteries the higher the resistance. If vessels are constricted (become smaller) or somehow restricted (blocked by some obstruction), back pressure rises.
So the question is how would insulin either constrict or restrict the smaller blood vessels so that back pressure rises?
We know about vessel constriction due to stress hormones like epinephrine and cortisol for example. Does insulin have an effect like this, or on those hormones? Maybe. We know about obstructions like atherosclerotic plaque and the likely causal role of insulin here, but the time scale is too short to blame this, we're talking days and months here not years and decades.
Now for the water stuff. Here's a link to a lecture by the guy who figured out a fourth state of water: https://www.youtube.com/watch?v=TPvYxDDpAgo
(check part 2 as well) This explain how, even though the heart simply cannot push blood through the smaller blood vessels, blood nevertheless gets pushed through anyways. It's the blood vessels themselves, and the water contained within the blood, that form a very effective pressure pump but with very low flow evidently. It's so effective it can push red blood cells through even though they're bigger than the vessels. The cells get squished literally.
So this means two things. Either red blood cells get bigger and can no longer fit even if squished, or become less flexible, or both. We got HbA1c, where red blood cells actually get bigger because they're now stuck to a glucose molecule (or more than one). It's also likely that they become less flexible as well. If we watched the above video carefully, we'll note that the mechanism involves a hydrofilic surface, i.e. water sticks to it, and accumulates and gets thicker. The lining of blood vessels aren't the only place where this occurs (the basis for the pumping action), it also occurs with blood content like glucose molecules for example. In effect, the molecules become larger due to accumulation of that gel-like water around it. In effect, the more glucose goes in the blood, the more viscous the blood becomes, the harder it gets to push it through smaller blood vessels, the higher the back pressure.
So, it's also about glucose, not just insulin. In one of the comments, Tom repeated that they controlled for blood glucose level to find the link with insulin, implying that glucose does not play a role, when in all likelihood it does as illustrated by the above.
It's also likely that due to the action of insulin on fatty acids probably through the enzyme lipoprotein lipase or some such - the formation of triglycerides right in the blood, and triglycerides are bigger than fatty acids - this also contributes to obstructing the smaller blood vessels.
Finally, if I use my paradigm to explain the ways where insulin is involved with dietary carbs, the liver, insulin-degrading enzyme, hyperinsulinemia, hyperglycemia, and so forth, we can deduce that insulin will be much higher than blood glucose level should warrant. The reason is that there's much more glucose being kept from spilling out, in storage in the liver in the form of glycogen, and little ketones to activate insulin receptors and in turn insulin-degrading enzyme to degrade insulin and cause insulin to drop. Excess glucose - i.e. excess glycogen in the liver - must first be cleared before insulin even begins to drop.
So, plausible, yay or nay? To me, yay.
Personally, I remember having BP in the 120/80 range before I went LC. Then it dropped in the 90/60 range when I was full-on all-meat. Then it rose in the 120/80 range when I first got sick, and remains in this range still. My personal experience says what Tom wrote about the insulin link with BP must be real and must indicate a causal role, and that dietary carbs ain't the only thing that can do that to insulin and in turn to BP. And my personal experience with docs trying to figure out why I've been sick says these docs have no clue about any of it. Therefore, it's my opinion that none of them can make any determination about BP for any purpose whatsoever, let alone write official recommendations about it.