I just sent some links to someone who was looking for info about diet and blood pressure, and thought I might as well post them here. Note that the texts are only excerpts - you need to click on the links to see the full article.

....processes initiating atherosclerosis and high blood pressure are thought to start very early in life, and blood pressure and cholesterol levels have been shown to track from early childhood and to be related to childhood nutrient intakes(5,6). Body mass also tracks from early childhood, with obese children being at an increased risk of obesity in adulthood(7)
The high potassium and low sodium content of raw vegan diets reduces the need for calcium by reducing calcium losses and can be expected to reduce blood pressure and risk of stroke.
Not surprisingly, vegans in developed
countries are slimmer, with an average BMI
2 units (about 6 kg) below their meat eating
counterparts – a significant advantage in the
battle of the bulge. This markedly reduces
the risk of diabetes and high blood pressure.
At the very least, these results require any recommendation for increased fish consumption to be accompanied by a strong warning about the possible counterbalancing impact of methylmercury contamination. More disturbingly, Sorensen et al. (1999) found high prenatal methylmercury exposure to be associated with a 13 mm increase in both systolic and diastolic blood pressure at age 7. Without digressing into the many other ill effects of methylmercury exposure (including impaired neurological function in infants and reduced fertility in adults), it is clear that lifetime exposure to fish containing significant amounts of methylmercury cannot be recommended for the reduction of heart disease risk. This provides strong grounds to question the blanket recommendation of increased fish consumption.
Changes in diet should be the first strategy for anyone with high blood pressure, but most people will need to make drastic changes in their eating habits to succeed. Scientists at the National Institutes of Health have shown why the DASH diet lowers high blood pressure to normal in more than 80 percent of people with high blood pressure. On the DASH diet you eat lots of leafy green vegetables that are rich sources of nitrites, common salts that your bloodstream, can be converted to nitric oxide which opens blood vessels.

This means that nitrites could be a new treatment for high blood pressure, heart attacks, sickle cell disease, and blocked arteries leading the heart, brain and legs. Hemoglobin is the red pigment in red blood cells that carries oxygen in your bloodstream. When hemoglobin releases oxygen, it converts nitrites to nitric oxide, to widen blood vessels. Blood nitrite levels are low in patients with high blood pressure.

However, at high concentrations nitrites are toxic, so you must take limited amounts. Leafy greens are rich sources of safe amounts of nitrites. The nitrites go into the bloodstream, where exposure to oxygen converts nitrites to nitrous oxide which dilates arteries and lowers high blood pressure. Hypertensives should also eat lots of other plants for the same reason and cut back on meat and chicken, that are rich sources of sodium that can raise high blood pressure.
Another important component of any blood pressure lowering vegetarian diet is dietary fiber. Dietary fiber means everything in your food, which you cannot digest and which, therefore, passes through your body until it is expelled in your stools. Although the term "fiber", dietary fiber includes lots of materials which are not fibrous at all, such as gums and mucilages (a gummy substance from certain plants), which affect both the way in which your food is absorbed and the quantity you want to eat before you begin to feel full and tired of chewing.

As well as breakfast cereals whose fiber content you can hardly miss if you ever watch television, wholemeal bread and all fruit and vegetables have a high fiber content, although how much you actually get from your fruit and vegetables depends on whether you cook them and how much. Pulses like peas, beans and lentils have the highest fiber content of any cooked vegetables. Increasing the fiber content of your diet by eating more wholemeal bread, fruit and vegetables is one of the most effective steps you can take in any reduced-fat, weight reducing and cholesterol-free lowering diet, which in turn effectively reduces high blood pressure lowering blood cholesterol levels
Many studies have shown that vegetarians seem to have a lower risk of obesity, coronary heart disease (which causes heart attack), high blood pressure, diabetes mellitus and some forms of cancer.
What are the dangers of high blood pressure?

High blood pressure increases your risk of dangerous health problems, such as heart attacks and strokes – the higher the pressure the greater the risk.

How many people in the UK suffer from high blood pressure?

Around one in three men and women in the UK have high blood pressure.

What is the role of diet in causing high blood pressure?

Blood pressure rises as we get older but some people defy this seemingly inevitable development. Regular exercise, maintaining a healthy weight, a low fat (especially saturated animal fat) and low salt diet, quitting smoking and reducing the amount of alcohol consumed will all have an effect.

Even allowing for all that, the blood pressure of vegetarians doesn’t increase in the same way as meat eaters – in fact it goes up little with age. It’s not surprising, then, that a vegetarian diet can be used to treat high blood pressure. It is the totality of the vegetarian diet that works not any specific ingredient.

Vegetarians’ lower risk of high blood pressure is considerable and can be anywhere between 33-50 per cent. There is an inescapable link with meat and a Californian study as long ago as 1926 showed this. The vegetarians’ blood pressure was raised by 10 per cent simply by feeding them meat – and it happened in only two weeks.

Other studies have produced similar results and a whole range of studies have shown vegetarians to have considerably lower blood pressure than meat eaters. It is also the finding of the World Health Organisation and American Dietetic Association.

Which strategies are effective in helping to prevent or treat high blood pressure?

Many studies have found that changing to a low-fat vegetarian diet can significantly lower blood pressure. The switch can also reduce the distressing symptoms associated with hypertension, according to a Swedish study. At the end of the trial period most patients had been able to give up their medication, 50 per cent felt ‘much better’, 15 per cent felt ‘better’ and 30 per cent felt ‘completely recovered’.
Click here for our tips for treating high blood pressure.
Top tips for treating high blood pressure:

Lose weight if necessary. A low-fat veggie diet is a successful aid to weight loss. Try the VVF’s V-Plan Diet;
Reduce salt in your diet. Adults should not exceed 6g of salt per day. Use less in cooking, avoid adding it at the table, avoid salty snacks, such as crisps, and canned foods with added salt. Try using fresh herbs and spices to flavour your food instead. It won’t be long before your taste buds adapt;
Choose more vegetarian foods – they protect and strengthen your heart and blood vessels:
Fruits – fresh or frozen, eg bananas, oranges, apples, pears, grapefruit, mango, strawberries and blueberries;
Vegetables – fresh or frozen, eg broccoli, kale, spinach, carrots, potatoes, tomatoes, squash and corn;
Wholegrains – eg brown rice, wholewheat bread or pasta, unsweetened cereal, millet, barley, buckwheat and quinoa;
Pulses (peas, all types of beans and lentils) – eg no added salt kidney beans, pinto beans, lentils, black-eyed peas, chickpeas, soya milk, textured vegetable protein and tofu;
Avoid meat and dairy – both contain saturated animal fat and cholesterol;
Eat ‘good’ fats – essential omega-3 from flaxseed, hempseed and their oils, walnuts and dark green leafy vegetables help protect your blood vessels;
Exercise regularly – set yourself a daily target of 10,000 steps. The VVF pedometer can help you on your way to health and fitness. Order from our webshop;
Stop smoking – after just one year you’ll have halved your risk of heart disease;
Reduce stress as much as possible – practice healthy coping techniques, such as muscle relaxation and deep breathing. Getting plenty of sleep can help, too;
Reduce your alcohol consumption to no more than one or two drinks per day.

The incidence of high blood pressure, as well as the average blood pressure, tends to be greater among meat eaters than among vegetarians. A recent Israeli study of nearly 200 people found that only 2 percent of vegetarians had high blood pressure, as against 26 percent of nonvegetarians of the same age and social circumstances. Furthermore, the average systolic pressure (when the heart beats) was 21 millimeters of mercury higher, and the average diastolic pressure (when the heart rests) was 11 millimeters higher among the meat eaters. In Finland a study published last January reported that switching to a low-fat diet (with more polyunsaturated vegetable oils than saturated animal fats) resulted in a significant decline in blood pressure. In this study, the benefits of fat reduction far outweighed those of cutting back on salt, which had no effect on the volunteers' blood pressure. And Australian researchers found that when healthy meat eaters switched to a lacto-ovo vegetarian diet for six weeks, their blood pressure dropped significantly, only to climb back when they resumed eating meat. The causes of these blood-pressure effects of vegetarianism are a matter of scientific debate. Some researchers believe that potassium, a protective nutrient prominent in fruits, is responsible for the blood pressure effect of vegetarianism, but others disagree.
One of the best things you can do is to add more potassium to your diet, especially if you're taking diuretics to lower your blood pressure. (These drugs make it harder for your body to hold onto potassium.) Large amounts of this mineral seem to reduce blood pressure, while low levels may lead to hypertension. Aim for at least 3,000 mg a day. That's a lot -- about what you'd get from six large bananas. But it shouldn't be too hard to manage if you're following the DASH diet and eating a variety of fruits and vegetables. Potatoes, avocados, tomatoes, citrus fruits, yoghurt, and tuna are also good sources of potassium. (Check with your doctor before increasing your intake of the mineral if you have kidney problems.)

You should also try to keep excess weight off. Meet with a dietician to plot out your calorie needs, and stay physically active. Losing weight will help lower your blood pressure. Finally, don't smoke, limit your alcohol intake to two drinks a day (hypertension is twice as high in heavy drinkers compared to light drinkers), reduce the amount of stress you're under, and get plenty of sleep.
What is high blood pressure?

Imagine that your arteries are pipes that carry blood from your heart to the rest of your body. High blood pressure (also called hypertension) occurs when your blood moves through your arteries at a higher pressure than normal.

What do the numbers mean?
Blood pressure is really two measurements, separated by a slash when written down, such as 120/80. You may also hear someone say a blood pressure is "120 over 80."

The first number is the systolic blood pressure. This is the peak blood pressure when your heart is squeezing blood out. The second number is the diastolic blood pressure. It's the pressure when your heart is filling with blood--relaxing between beats.

A normal blood pressure is 120/80 or lower. High blood pressure is 140/90 or higher. If your blood pressure is between 120/80 and 140/90, you have something called "prehypertension."

How is high blood pressure diagnosed?
Blood pressure is measured by putting a blood pressure cuff around your arm, inflating the cuff and listening for the flow of blood. Your doctor will measure your blood pressure at more than one visit to see if you have high blood pressure.

How often should I have my blood pressure checked?
Even in children, blood pressure should be checked occasionally, beginning at about age 2. After age 21, have your blood pressure checked at least once every 2 years. Do it more often if you have had high blood pressure in the past.

What problems does high blood pressure cause?
High blood pressure damages your blood vessels. This in turn raises your risk of stroke, kidney failure, heart disease and heart attack.

Does it have any symptoms?
Not usually. This is why it's so important to have your blood pressure checked regularly.

How is it treated?
Treatment begins with changes you can make to your lifestyle to help lower your blood pressure and reduce your risk of heart disease (see the box below). If these changes don't work, you may also need to take medicine.

Even if you must take medicine, making some changes in your lifestyle can help reduce the amount of medicine you must take.

Lifestyle changes
Don't smoke cigarettes or use any tobacco product.
Lose weight if you're overweight.
Exercise regularly.
Eat a healthy diet that includes lots of fruits and vegetables and is low in fat.
Limit your sodium, alcohol and caffeine intake.
Try relaxation techniques or biofeedback.

How do tobacco products affect blood pressure?
The nicotine in cigarettes and other tobacco products causes your blood vessels to constrict and your heart to beat faster, which temporarily raises your blood pressure. If you quit smoking or using other tobacco products, you can significantly lower your risk of heart disease and heart attack, as well as help lower your blood pressure.

What about losing weight and exercising?
If you're overweight, losing weight usually helps lower blood pressure. Regular exercise is a good way to lose weight. It also seems to lower high blood pressure by itself.

Is sodium really off limits?
Not everyone is affected by sodium, but sodium can increase blood pressure in some people. Most people who have high blood pressure should limit the sodium in their diet each day to less than 2,400 mg. Your doctor may tell you to limit your sodium even more.

Don't add salt to your food. Check food labels for sodium. While some foods obviously have a lot of sodium, such as potato chips, you may not realize how much sodium is in things like bread and cheese.

Do I need to quit drinking alcohol altogether?
In some people, alcohol causes blood pressure to rise quite a lot. In other people, it doesn't. If you drink alcohol, limit it to no more than 1 or 2 drinks per day. One drink is a can of beer, a glass of wine or 1 jigger of liquor. If your blood pressure increases with alcohol, it's best not to drink any alcohol.

Does stress affect my blood pressure?

Stress may affect blood pressure. To help combat the effects of stress, try relaxation techniques or biofeedback. These things work best when used at least once a day. Ask your family doctor for advice.
What is a good high blood pressure diet?
A good high blood pressure diet is not only rich in important nutrients and fiber but also includes foods that contain far more electrolytes, potassium, calcium, and magnesium, than are found in the average American diet. Avoid saturated fat (although include calcium-rich dairy products that are no- or low-fat). When choosing fats, select monounsaturated oils, such as olive or canola oils. Choose whole grains over white flour or pasta products. Choose fresh fruits and vegetables every day. Many of these foods are rich in fiber, which may help lower blood pressure. Important foods include most fruits (especially potassium-rich fruits including bananas, oranges, prunes, and cantaloupes) and vegetables (especially carrots, spinach, celery, alfalfa, mushrooms, lima beans, potatoes, avocados, broccoli).
Everyone, regardless of their blood pressure, should consume less than 2,400 milligrams (about one teaspoon) of sodium each day. People with hypertension should strive for even lower intake
Omega 3 fatty acids (docosahexaenoic and eicosapentaenoic acids) are found in oily fish. Studies are indicating that they may have specific benefits for many medical conditions, including hypertension. They appear to help keep blood vessels flexible and may also help protect the nervous system. The fatty acids are also available in supplements, although over-the-counter supplements are not regulated and their effects on health are not known. The long-term effects on blood pressure are not known. Calcium regulates the tone of the smooth muscles lining blood vessels, and population studies have found that people who have sufficient dietary calcium have lower blood pressure than those who do not. Hypertension itself increases calcium loss from the body. Some, but not all, studies have found modest beneficial effects on blood pressure from calcium supplements. Sufficient calcium is important, in any case, for strong bones.
Some antioxidant supplements, including vitamins C and E and alpha-lipoic acid, are being studied for possible benefits in protecting against hypertension by preventing injury in the blood vessels. Alpha-lipoic acid for example prevented elevated blood pressure in rats. Vitamin C apparently also has specific benefits for hypertension by preventing dangerous effects on nitric acid, the substance that keeps arteries flexible.