I've had to deal with this same thing. I was told to avoid MSG, OTC meds that contain ibuprofen, diet soft drinks, preservatives, sugar substitutes, soy sauce, and baking soda to name a few. I must wash all canned vegetables before cooking. Don't drink soft water from the tap.
I was told to eat a diet high in fiber, plus I take Oat Bran capsules, and plenty of fresh vegetables and fruits. On my own I started taking Coenzyme Q-10, 100 mg daily, 400 iu vitamin E, 500 mg Hawthorn Berries, Vitamin C, and a Vitamin B-6 capsule daily.
Parsley, rosemary, cayenne, garlic, and onions are also good for high blood pressure. I think one of the best things a person can do is cut back on the salt. I was totally amazed at the amount of salt that was in different products when I investigated. Sometimes it is really hard to not put that little dab of salt on something when you are used to it. And, sometimes I fudge a little. LOL If I can think of anything else I'll post it.
Here are a couple exerpts from the following link that are very informative.
http://www.health.gov/dietaryguidelines/dga2005/document/html/chapter8.htm
Reducing salt intake is one of several ways that people may lower their blood pressure. The relationship between salt intake and blood pressure is direct and progressive without an apparent threshold. On average, the higher a person's salt intake, the higher the blood pressure. Reducing blood pressure, ideally to the normal range, reduces the risk of stroke, heart disease, heart failure, and kidney disease.
Another dietary measure to lower blood pressure is to consume a diet rich in potassium. A potassium-rich diet also blunts the effects of salt on blood pressure, may reduce the risk of developing kidney stones, and possibly decrease bone loss with age. The recommended intake of potassium for adolescents and adults is 4,700 mg/day.
Individuals With Hypertension, Blacks, and Middle-Aged and Older Adults. Some individuals tend to be more salt sensitive than others, including people with hypertension, blacks, and middle-aged and older adults. Because blacks commonly have a relatively low intake of potassium and a high prevalence of elevated blood pressure and salt sensitivity, this population subgroup may especially benefit from an increased dietary intake of potassium. Dietary potassium can lower blood pressure and blunt the effects of salt on blood pressure in some individuals. While salt substitutes containing potassium chloride may be useful for some individuals, they can be harmful to people with certain medical conditions. These individuals should consult a healthcare provider before using salt substitutes.
Good Luck!