Yes, magnesium deficiency will create high and low blood pressure.
Thyroid or adrenal malfunction will create it also.
Toxic burden that affects the central nervous system can affect it.
I think doctors advise salt reduction because it interferes with the prescription drugs that they put the person on. But if the person is not on a blood pressure precription, I think drastically limiting salt is a mistake. Your body NEEDS salt. Not processed garbage salt, but naturally occuring sea salt. A pinch in a glass of water does wonders for health. SALT IS A NECESSITY OF LIFE. People on my iodine group do salt loading to help detox metals.
Blood pressure issues are an indicator that something is wrong in the body-the body is trying to send you a message. blood pressure medicine is a forced squelching of that signal. It makes people think the body is now running normally, but the underlying disease process is still there, it has just been silenced.
I have given my medical files to a freind for review, or I could give you more info.
Go on wrongdiagnosis.com and type in the symptoms, it will give you a list of all (usually all) the possible causes.