For the last 2,000 years or so, many have considered Hippocrates to be a wise ancient Greek who had plenty to say about staying healthy. From the Hippocratic Oath taken by every doctor, swearing to “do no harm,” to universal wisdom that applies to everyone, he is considered to be an important contributor to modern science to this day.

David Katz, M.D., of Yale University, states, “Hippocrates was a visionary who figured out the most important ways we can stay healthy, all of which have been proved by modern science,” and his opinion is shared by many, even though he lived from 460 BC to 370BC.

Here are five important contributions, credited to Hippocrates, that were all true thousands of years ago and still apply today:

1. Walking is the healthiest form of exercise.

Hippocrates observed that the healthiest people were those who exercised. For his patients, he regularly prescribed exercise as a treatment for ailments. He was one of the first to note that those who remained sedentary had far more chronic health problems than those who were living active lifestyles.

Today, physicians continue to prescribe exercise for their patients, understanding that physical activity on a regular basis can help to prevent and treat many conditions, as well as improve overall life expectancy. Walking is an all-natural medicine, tried and true for centuries.

2. Disease affects different people in different ways.

Not everyone with the same disease will have the same symptoms, the same progress and the same outcomes. Much depends on the actual person—not just their overall health and risk factors, but their personality, their relationships and other things that affect their lives. Treating the whole person was something Hippocrates was known for, and this continues to be an important part of medicine today.

Physicians need to take into account whether or not a person with any disease has toxic issues in their life—relationships, career problems, sleep issues or any other extra problems that can make them sicker than the actual disease. Understanding all of the problems and how they affect someone makes a difference in the treatment and outcome.

3. What you put into your body matters.

Even Hippocrates recognized that those who overate became overweight and were more likely to have serious health problems as a result. One of his first steps when treating any patient was to evaluate what they ate and try to make improvements in their diet.

Today, physicians are still using this method of treatment, understanding that what a person eats, and how much, can have a dramatic effect on their health. Avoiding processed foods, eating plenty of fruits and vegetables and avoiding unhealthy things like alcohol and smoking leads to a healthier life, both then and now.

4. Moderation matters.

A famous quote by Hippocrates, “Everything in excess is opposed to nature,” is now basically translated into “everything in moderation.” For those who enjoy sweet treats or the occasional glass of wine, serious health concerns are not a serious risk. It is when those things are taken to an extreme, and not properly controlled, that health problems will develop.

5. Not every problem needs medical treatment.

Even in the days of Hippocrates, there were plenty of medical “professionals” who prescribed treatments that were unnecessary, and even potentially harmful. Hippocrates believed that sometimes, doing nothing was a better treatment than using unnecessary treatments.

Physicians today are held accountable to certain standards and certain practices, based on the needs of the patient and the presentation of symptoms. It can be hard to resist trying something that “might” work, but physicians have a responsibility to be cautious and appropriately conservative when treating patients, and, of course, to avoid causing harm.

The ideas that Hippocrates put forth thousands of years ago have helped to shape modern medicine, and they continue to guide physicians through treating patients and developing new ideas and cures. It is essential that patients work with their doctors, being honest about symptoms and following up with prescribed treatment, in order to obtain the best health outcomes.