High blood pressure–hypertension is a condition when blood pressure is higher than 130/85. 90% of the patients have high blood pressure because of unknown cause: so called essential hypertension.  Even though genetic factors can play some role, dietary, lifestyle and environmental factors are the underlying cause for the most of the patients: obesity, high sodium content in the food, low fiber-carbohydrates diet, low omega 3 fatty acids intake, not enough vitamin C, magnesium and calcium in your diet.
There are three main causes for essential hypertension:
1. Too much sodium in the diet.
2. Obesity.
3. Too much adrenaline, that is most likely related to him and him and himto heavy metal toxicity like mercury, lead, cadmium and arsenic.
Dietary suggestions for hypertension ( high blood pressure ):
1. Increase uptake of fruits and vegetables (1,2), fish, nuts and seeds, especially:
        – celery, that contains 3 n butyl phthalide, that brings blood pressure down,
        – garlic and onions (3),
        – nuts and seeds like walnuts, rich in omega 3 fatty acids,
        – cold water fish provided that it's not loaded with mercury,
        – green leafy vegetables because of their high magnesium and calcium content,
        – legumes and whole grains,
        – citrus, broccoli and other foods, rich in vitamin C because it takes lead out of your body.
2. Avoid alcohol, refined carbohydrates, salty foods like pickles, caffeine and smoking.

Of course diet alone cannot fix the problem.  It cannot fix Neurotransmitter Imbalance, it may not be able to fix minerals and vitamins deficiency because of maldigestion or malabsorbtion. It cannot fix Hormonal Imbalances either. To figure out what is going on you need to see Functional Medicine Doctor to go to the root cause of the problem and elimiate it.

References:
1.  Appel, Moore, Obarzanek.  A clinical trial of the effects of dietary patterns on blood pressure. DASH Collaborative Research Group NEJM 1997, 336:1117–1124.
2. Moore, Conlin, Ard, Svetkey.  DASH diet is effective treatment for stage I isolated systolic hypertension. Hypertension 2001, 38:155-158.
3. Silagy, Neil. A meta analysis of the effect of garlic on blood pressure. Journal of hypertension 1994, 12:463–468.