The reasons why fruits and vegetables lower blood pressure are many and not always completely understood.
The fact is, vegetarians have strikingly lower blood pressure.
And many studies show that switching to a vegetarian diet typically lowers blood pressure.
In the Dietary Approaches to Stop Hypertension (DASH) study, 459 people with and without high blood pressure were randomly assigned to one of three diets:
1) A typical American diet that provided about 3 servings/day of fruits and vegetables and 1 serving/day of a low-fat dairy product
2) A fruit and vegetable diet that provided 8 servings/day of fruits and vegetables and 1 serving/day of a low-fat dairy product, or
3) A combination diet (now called the DASH diet) that provided 9 servings/day of fruits and vegetables and 3 servings/day of low-fat dairy products.
After eight weeks, the blood pressures of those on the fruit and vegetable diet (8 servings/day) were significantly lower than those on the typical American diet, while blood pressures of those on the combination (DASH) diet (9 servings/day of fruits and vegetables) were lower still.
Frank M. Sacks, M.D., professor of medicine at Harvard Medical School, says that there are two obvious possibilities as to why fruits and vegetables lower blood pressure:
1) Something in plant foods depresses blood pressure or
2) Something in meat forces it up
At first Dr Sacks thought meat raised blood pressure, but he scrapped that theory after he tested vegetarians by having them add meat to their diet.
In one group of vegetarians who ate eight oz./225 grams of lean beef a day for a month, systolic blood pressure rose very slightly, diastolic blood pressure not at all.
Neither did a heavy egg diet for three weeks boost blood pressure. Nor could he get blood pressure to budge in response to different kinds of fats.
Dr Sacks concluded that curbing total fat or saturated animal fat doesn't affect blood pressure at all (although it might affect other measurements, i.e. cholesterol levels).
On the other hand, he's convienced that agents in vegetables and fruits have 'mysterious' powers to reduce blood pressure.
One blood-pressure lowering component may be fiber, especially from fruit.
A recent Harvard study of nearly 31,000 middle-aged and elderly men found that those who ate very little fruit were 46% more likely to develop high blood pressure over the next four years than men who ate the equivalent fiber in five apples a day.
For unknown reasons, fiber in fruit had the strongest anti-hypertensive effect, more so than fiber in vegetables or cereals.
Another possibility is antioxidants in fruits and vegetables that increase amounts of a hormone-like substance, prostacyclin, which is a special prostaglandin eicosanoid that prevents clotting and induces the dilation of blood vessels, lowering blood pressure.
Vitamin C present in fruits and vegetables lowers blood pressure and a lack of vitamin C in your diet can send your blood pressure up.
According to Dr Christopher J. Bulpitt of Hammersmith Hospital in London, an expert on hypertension, vitamin C in fruits and vegetables is a powerful preventive against high blood pressure.
He points to a string of evidence showing that high blood pressure and stroke fatalities are highest among people who eat the least vitamin C.
Also researcher Paul F. Jacques, at the U.S. Department of Agriculture's Human Nutrition Research Center on Aging at Tufts University, agrees that a low intake of foods rich in vitamin C predicts high blood pressure.
In one study he found that elderly people who ate the vitamin C in a single orange a day were twice as likely to have high blood pressure as those who ate four times that much.
Systolic pressure was eleven points higher and diastolic pressure six points higher among the skimpy vitamin C eaters.
In another research, Dr. Jacques concluded that low blood levels of vitamin C raised systolic pressure about 16% and diastolic pressure 9%.
There's no doubt that potassium present in fruits and vegetables lowers blood pressure and taking it away can raise it.
To demonstrate this fact, a test was carried out at the Temple University School of Medicine in Philadelphia.
Ten men with normal blood pressure ate a potassium-adequate diet for nine days, then a potassium-restricted diet, again for nine days.
Deprived of potassium, the men experienced an average jump in arterial pressure (including both systolic and diastolic) of 4.1 points and it shot even higher when the men's diets were loaded with sodium.
They concluded that potassium also helps keep a high-sodium diet in check.
Dr. G. Gopal Krishna, the study's senior author, thorizes that too little potassium leads to sodium retention, which over time may trigger high blood pressure.
If you alreaday are on medications for hypertension, getting enough potassium can lessen the doses of medication you need.
A study at the University of Naples in Italy, discovered that after a year on high-potassium diet, 81% of a group of patients needed only half their original dosages of drugs to control their high blood pressure.
Further, 38% of the high-potassium group was able to stop medication entirely. They simply ate 3 to 6 servings of high-potassium foods a day, boosting their average intake of potassium about 60%.
I'll mention next just a few examples of how some foods actually work to lower blood pressure, but they're not the only ones with this amazing healing power. Throughout this website you'll find countless other fruits and vegetables that are just as powerful.
Eating spinach and bitter greens (including beetroot greens, chicory, dandelion, endive, fenugreek, horseradish, lettuce and nettle) to lower blood pressure is a very sensible strategy and not just because they're rich in vitamin C or potassium.
One of the reasons these greens lower blood pressure is because they spur production of nitric oxide, a molecule that helps blood vessels to relax, remain smooth, regulating blood flow, inflammation and blood pressure.
Other edible greens such as amaranth, chard, lamb's-quarters, purslane and sorrel can also work.
You can use them in salads, sauté them with diced onion and garlic or toss as many as you can find into a soup with other blood pressure-lowering foods such as celery, broccoli, carrots, garlic, onions, saffron and tomatoes, just before you're ready to serve it.
They all have different benefits for treating high blood pressure.
For instance, dandelion roots and leaves are highly diuretic, with high levels of potassium and sometimes used by naturopathic physicians in place of the common prescription diuretic furosemide.
Meanwhile, fenugreek, which is served as part of Indian dish alu methi, is a fabulous source of choline and beta-carotene, both of which help reduce high blood pressure.
Overall, fenugreek seeds contain eight different diuretic agents, which not only help reduce blood pressure but also help control cholesterol and regulate blood glucose.
In addition to their cardio-protective B vitamins, collard greens are a very good source of potassium and a good source of magnesium, two minerals that have both been shown to reduce high blood pressure.
Many people argue over the debates whether tomatoes are to be considered fruits or vegetables. Don't worry, I'm not going to join in.
What matters is that either way, tomatoes are a fabulous source of lycopene, an antioxidant carotenoid compound which gives them their red colour.
Tomatoes also contain vitamin C, potassium and folate as well as beta carotene and vitamin E, which help protect cells from oxidative damage.
In a study of 31 people with hypertension who didn't require medication, researchers gave them a tomato-like placebo for 4 weeks, followed by 8 weeks of a tomato extract and then another 4 weeks of the placebo.
During the tomato extract period, their systolic readings dropped by 10 mmHg and their diastolic readings by 4 mmHg; no changes were seen during the placebo phases.
Apart from tomatoes, apricots, guava, watermelon, papaya, and pink grapefruit are also significant sources of lycopene.
Fava beans, also known as broad beans, are amongst the richest natural sources of L-dopa, a precursor of the chemical dopamine, which, amongst other things, act as a diuretic.
In one study, eating 40 grams of freshly chopped fava beans significantly increased the amount of sodium and dopamine in the urine - a good thing when it comes to reducing blood pressure.
As we've seen, a number of compounds may contribute to the cardioprotective effects of fruits and vegetables, including vitamin C, folate, potassium, fiber, and various phytochemicals.
However, supplementation of individual micronutrients or phytochemicals has not had the same effect on lowering blood pressure and protecting from heart disease.
So in the case of fruits and vegetables, the benefit of the whole may be greater than the sum of its parts. In other words, it's much better, and more enjoyable, to eat the real thing, i.e. fruits and vegetables to lower blood pressure, than relying entirely on supplements.
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