Experts say that different types of cooking oils are better for you than others, and a new study suggests that the number of times you reuse cooking oils can also affect your health. Spanish researchers found that people whose kitchens contained any type of oil that had been reused many times over were more likely to have high blood pressure than people whose cooking oils were changed more frequently. People who ate foods cooked with sunflower oil also showed a higher risk of high blood pressure, while consuming more olive oil appeared to protect people from high blood pressure. Based on the findings, study author Dr. Federico Soriguer of the Hospital Civil Plaza in Malaga recommends that people cook with olive oil whenever possible, and discard any oils after using them up to two or three times. Although olive oil is generally considered to be a healthy addition to meals, the findings suggest that repeatedly reusing the oil may invalidate its favorable effects on health, Soriguer says. Many of the study participants consumed the so-called Mediterranean diet, which features liberal use of olive oil and has been linked with numerous health benefits. Soriguer explained that followers of the Mediterranean diet often use an "oil bath," or deep fryer, to fry foods. However, when the same pot of oil is repeatedly reheated, the oils begin to degrade, releasing substances known as polymers and polar compounds that can become absorbed by food. To measure the effects of repeated use of cooking oils, Soriguer and his team measured levels of polymers and polar compounds from oil samples taken directly from the kitchens of 538 adults. The more polar compounds and polymers present in oil samples taken from a participant's house -- a sign the oil had been reused repeatedly -- the more likely it was that participant had high blood pressure. However, people whose blood samples contained a relatively high concentration of fats predominantly found in olive oil were less likely than others to have high blood pressure, Soriguer and his team report in the American Journal of Clinical Nutrition. Olive oil that had been repeatedly reused tended to show a lower concentration of polymers and polar compounds than other types of oil, suggesting that olive oil degrades more slowly than other types, Soriguer explained. He added that although the Mediterranean diet features heavy use of olive oil, its rising cost is inducing some followers to substitute other types of oil, or to use a mixture. Soriguer noted that his findings have induced him to make a personal change. "I have removed the fryer out of my house," he revealed.