How to eat your way to lower blood pressure

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If you need to lower your blood pressure, consider swapping bread, crackers and cookies for foods like milk, yogurt, tofu and soy beverages.

According to a U.S. study published this week in Circulation: Journal of the American Heart Association, partly replacing refined carbohydrate with foods high in soy or milk protein may help prevent and treat high blood pressure.

In the study, 352 adults with high-normal blood pressure or mild hypertension were assigned to take 40 grams of either soy protein, milk protein, or a refined carbohydrate supplement, every day for eight weeks.

The supplements had a similar sodium, potassium and calcium content and were taken twice daily in water or juice.

Compared with the carbohydrate supplement, using soy protein and milk protein significantly lowered systolic blood pressure. (Systolic blood pressure is the top number in a blood pressure reading and measures the pressure when the heart contracts.) Refined carbohydrate supplements did not change blood pressure.

The reduction in blood pressure was small on an individual level, but was considered important on a population level. It's a decrease that could lead to 6 per cent fewer stroke-related deaths and a 4 per cent lower rate of heart-disease deaths.

Earlier studies have found that daily soy protein helps lower blood pressure. Soy protein's blood pressure-lowering effect may be due to its phytochemical (isoflavone) and phosphorus content.

The well known DASH diet, rich in low-fat dairy products, has also been shown to guard against hypertension, presumably because of its calcium and potassium content - two minerals linked with healthy blood pressure. (DASH stands for Dietary Approaches to Stop Hypertension.)

The results of this week's study demonstrated that milk protein also has a blood pressure-lowering effect. Milk protein contains enzymes and amino acids that have been shown to lower blood pressure.

One in five Canadians has high blood pressure, a condition that can cause heart attack, stroke, heart failure and kidney damage. High blood pressure is defined as 140/90 mm Hg or higher. If you have diabetes, 130/80 mm Hg is considered high.

An equal number of Canadians have pre-hypertension, a blood pressure reading between 130-139/85-89 mmHg. Unless lifestyle changes are made to bring blood pressure down, 60 per cent of people with pre-hypertension will develop high blood pressure in four years.

The following diet modifications can help you prevent hypertension, or lower your blood pressure if you already have it.

Limit refined carbs

A steady intake of white starches and sugary foods can cause salt retention and elevate blood pressure. Switch to 100-per-cent whole-grain foods such as whole-grain whole wheat bread and crackers, brown rice, whole-grain pasta, large flake or steel-cut oats, quinoa and unhulled barley.

Avoid sugary drinks; limit dessert to once or twice per week. Get used to adding less sugar or honey to coffee and tea and breakfast cereal.

Add milk or soy protein.

The DASH diet includes two to three low-fat dairy servings per day. One serving includes 1 cup skim or 1 per cent milk, 1 cup of 0.1 to 1 per cent milk-fat (MF) yogurt and 1.5 ounces of 7 per cent MF cheese.

To increase your intake of soy protein, use unflavoured or unsweetened soy beverages in place of, or in addition to, milk. Add firm tofu to stir-fries, toss soy beans into salads and snack on roasted soy nuts or edamame.

Increase fruit and vegetables

The DASH diet is also plentiful in fruit and vegetables: seven to 12 servings each day. These foods are excellent sources of potassium, a mineral that helps blood vessels relax and causes the kidneys to excrete more sodium. In fact, studies show that people with a low daily intake of the mineral are more likely to develop high blood pressure and suffer a stroke.

Adults need 4,700 milligrams of potassium each day. Excellent sources include bananas (1 medium = 422 milligrams), apricots (4 = 362 mg), prune juice (½ cup = 373 mg), cantaloupe (1 cup = 440 mg), spinach (½ cup cooked = 443 mg), Swiss chard (½ cup cooked = 508 mg) and sweet potato (1 small = 285 mg).

Eat legumes and nuts

Include beans and/or nuts in your diet four times per week. These foods are a good source of vegetable protein and they're rich in magnesium, a mineral that promotes normal blood pressure.

Add chickpeas, kidney beans, black beans and lentils to salads, soups, pasta sauces, tacos and chilies. Snack on a small handful of unsalted, raw or dry roasted nuts.

Watch sodium

Excess sodium has been linked with elevated blood pressure in many studies. Canadians, aged nine to 50, require 1,500 milligrams of sodium each day. With age, our body becomes more sensitive to the blood pressure-rising effect of sodium and daily requirements drop to 1,300 milligrams for adults aged 50 to 70 and 1,200 milligrams for people over 70.

For most adults, the daily upper sodium limit is 2,300 milligrams. If you're over 50 or have high blood pressure you should consume less.

Limit or avoid alcohol

If you drink, limit yourself to one to two drinks per day or a weekly maximum of 7 for women and 9 for men. Drinking more than two drinks per day increases blood pressure and escalates the long-term risk of developing hypertension.

Lose excess weight.

If you're overweight and have hypertension, losing five kilograms will lower your blood pressure. In some cases, weight loss can reduce or eliminate the need for blood pressure medication. If you need to cut calories, replace refined grains and sweets with more fruit and vegetables.

Leslie Beck, a Toronto-based dietitian at the Medcan Clinic, is on CTV's Canada AM every Wednesday. Her website is lesliebeck.com.