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Fruits, vegetables, whole grains, nuts, seeds, legumes, low-fat dairy products, and foods high in potassium naturally help improve heart health and lower diastolic blood pressure. Start consuming more whole foods, and cut back on foods that are processed and high in sugar and fat.  On a daily basis, try to get 6 to 8 servings of whole grains (1 slice of bread is one serving), 4 to 5 servings of vegetables (½ cup cooked veggies is one serving), and 4 to 5 servings of fruits (½ cup fruit juice is one serving).  You should also aim for 2 to 3 servings of dairy (1 cup fat-free milk is one serving), 6 servings or fewer of lean meat/poultry/fish (3 oz. of cooked meat is one serving), and 4 to 5 servings of nuts/seeds/legumes per day (2 tbsp peanut butter is one serving) per day.  Limit your consumption of sweets to 5 servings or fewer per week.  Foods rich in potassium can help balance out the effect of sodium, so consider eating more potassium-rich fruits and vegetables in particular, including oranges, avocados, beans, greens, potatoes, and tomatoes. Excess sodium consumption causes water retention and forces your heart and arteries to work harder to pump blood throughout your body. Consume no more than 1,500 mg of sodium per day. Use sea salt instead of table salt, which often contains man-made additives that can worsen your health.  Keep in mind that one teaspoon of table salt contains 2,300 mg of sodium on average. The average person consumes about 3,400 mg of sodium daily--more than twice the recommended amount. Excess sodium can cause your body to retain water, which increases the amount of work your heart and blood vessels must do. As a result, excess sodium increases your diastolic blood pressure just as it increases your systolic blood pressure. Check food labels and recipes, and stick with foods that contain 140 mg or less of sodium per serving. Limit salt, MSG, baking soda, baking powder, disodium phosphate, and any compound with "sodium" or "Na" in it. Rely on other herbs, spices, and naturally flavorful ingredients to enhance the taste of food instead of reaching for the salt. Studies show that moderate alcohol consumption can improve heart health, but consuming more than one or two alcoholic beverages per day increases blood pressure and has adverse health effects. Lower your alcohol intake, and consult with your healthcare provider for recommendations on alcohol consumption. Note that "one drink" equals 12 oz of beer, 5 oz of wine, or 1.5 oz of 80-proof liquor. Caffeine is linked to higher diastolic blood pressure levels, which occurs when caffeine blocks the hormone responsible for keeping arteries widened. Reduce your current caffeine intake, and switch from drinking coffee, energy drinks, and sodas to natural white, green, and black teas when you need an energy boost.  Technically, caffeine may or may not have a significant effect on your blood pressure. If you don't drink it often, caffeine can cause a dramatic spike in overall blood pressure, but it generally has a less significant effect if you've been consuming it regularly for an extended period of time. Check your blood pressure within 30 minutes of drinking a caffeinated beverage; if either diastolic or systolic blood pressure increases by 5 to 10 mmHg, that's too much, and you should look at cutting back. If you decide to reduce your caffeine, take several days to do so and lower your average consumption to about 200 mg daily--roughly two 12 oz (355 ml) cups of coffee. Regular consumption of red meats increases diastolic blood pressure and your risk for developing heart disease. This is due to the high fat content in meat, which raises cholesterol and increases your blood pressure. Stop eating red meats such as beef and steak, and switch to eating healthier meats such as chicken, turkey, and fish. Foods rich in omega-3 fatty acids can improve heart health and are effective at lowering blood pressure and reducing your risk for heart disease. Examples of foods rich in omega-3 fatty acids are walnuts, salmon, tuna, mackerel, sardines, and tilapia.  Ideally, you should get 2 to 3 servings of healthy fat daily. While omega-3 fatty acids are a good choice, just about any monounsaturated or polyunsaturated fat can help your diastolic blood pressure. This includes many plant-based oils, including olive oil, canola oil, peanut oil, safflower oil, and sesame oil.  Avoid foods containing saturated fats and trans fats, since these have a negative effect on your blood pressure. This includes fried and heavily processed foods.
Eat a diet comprised of healthy whole foods. Reduce your sodium intake. Consume less alcohol. Reduce caffeine intake. Avoid consuming red meats. Increase your intake of omega-3 fatty acids.