I'm a Greek Mediterranean diet expert. Here's my best advice for Americans who want to eat better on a budget.

• A Greek doctor and nutrition scientist says it is possible to eat healthy on a budget.
• She cooks beans a few times a week, and recommends choosing small portions of meat.
• At home, she uses a DIY spread made from 50% butter and 50% olive oil, to make her toast healthier.

This as-told-to essay is based on a conversation with Dr. Artemis Simopoulos. It has been edited for length and clarity.

Former chair of the nutrition coordinating committee at the National Institutes of Health, Dr. Simopoulos is founder and president of the Center for Genetics, Nutrition and Health in DC, a nonprofit focused on nutrition education.

I have dedicated my life to studying and eating good food. It's the dearest topic to me.

Scientifically, there is no confusion about how to eat to promote health and longevity. I think all the conflicting and overhyped diet advice you see has been created strictly for financial and political reasons.

So I want to tell you a little bit of my history, and what I've discovered over my 68-year career studying diet and chronic disease.

I hope this information will help you choose foods that will nourish your body, in an affordable, sustainable, delicious way.

In Greece, traditional diets included fresh produce, fish from the sea, lots of olive oil and sourdough bread

As a girl growing up in Kalamata, on the southwestern edge of the Peloponnesian peninsula, I found fresh food everywhere. On the weekends, we would visit our family farm, about 15 minutes outside the city. Traditionally, most Greeks had something like that, a place they could go to pick up fresh food, whether it was their own farmland or a daily market.

At our farm, we had olive trees, figs, pomegranates, walnuts, anything you can imagine. It was very easy for us to have fresh vegetables, fruit, and fish from the Messenian Gulf on the table. Greek people are very proud of their food, and like to make it very fresh. This was especially true when I was growing up, in the 1940s and 50s, as there wasn't much refrigeration outside the big cities.

We'd supplement local foods with some fatty tinned fish from Norway, like smoked herring or cod. That was especially useful on Fridays, when most Greeks, following the Greek Orthodox church tradition, don't eat any meat. But in general, our diet was pretty low on meat back then. We would eat small quantities of lamb, and some chicken. There was no beef. The backbone of our diet was legumes, like chickpeas, black eyed peas, and northern beans, great for soups and cold salads, plus lots of sourdough bread. People would also hunt and eat some wild birds, which are rich in iron, fostering healthy hemoglobin.

We also had many protein-rich snacks, like lupin beans, which people would often turn into a pickled snack with a little salt. My favorite sweet treat was a Kalamata dried fig stuffed with walnuts and almonds. What a shock it was when I arrived in America for college!

When I arrived in the US for college, I was shocked to find white flour everywhere

When I arrived in New York for college, snow wasn't the only thing that was new, fluffy, and bright white. I discovered that white flour was everywhere in the American diet. Chocolate-chip cookies, chicken à la king, and bread that tasted like cotton to me. I wasn't used to this, and it was a difficult adjustment.

In Greece, I was raised on thinner sauces created with lemon, olive oil, white wine, and maybe some butter. All of this rich, thick, floury food in the US was so different. I couldn't eat half of the meals they served in my dormitory. Sometimes I'd just have Swedish rye crackers with some cheese on them for dinner.

On the weekends, the Greek students would ride the subway downtown to a restaurant near Times Square called The Pantheon. What a great time we'd have, sitting around dishes of lamb and potatoes, big fresh Greek salads, and sharing fruit for dessert.

Once I moved to Boston for medical school, it was easier to get fresh, good food. There were plenty of Greek markets within walking distance of where I lived, and I had my own little kitchenette where I could prepare meals.

I have developed some traditional recipes, which I share in my Omega-3 diet book, but I tell people you don't have to be Greek to eat well, which is why I also have a new book called "The Healthiest Diet for You: Scientific Aspects," which I've made available for free online.

History tells us you can eat well and save money

For thousands of years, people around the world have found their own ways to eat a balanced, nutrient-rich diet that's aligned with their genetics.

While it's true the traditional Greek eating plan is great for health and longevity, naturally staving off many chronic diseases, the Greeks were not alone in figuring out how to source local, abundant items that were good for their hearts and minds. In South America, there are Chia seeds, in China, Camellia trees.

The key thing everyone has in common in these traditional eating plans is a focus on fresh foods, like omega-3-rich leafy greens, plus plenty of other vegetables and a base of legumes for protein.

Most traditional diets are rounded out with small amounts of meat, and fatty fish, as well as plenty of nuts.

It's an inexpensive, and sustainable way to eat. We don't need to buy into all these new highly-processed meat-free alternatives, or vegan and gluten-free packaged treats, which are not health foods.

I always advise my friends to select the freshest local meats and fish they can find. Some complain that this is a pricey strategy, so I tell them 'eat half as much.' You don't really need to spend so much money. Replace a third of the meat you eat with beans on the plate. We ought to be a lot more conscious and respect food.

It's this issue of imbalance, piling oil, sugar, and white flour into everything we eat, that I believe is at the core of the modern chronic disease epidemic in the US. Our processed foods are to blame. But I don't want people to lose hope. You can eat a healthy diet.

I take care to ensure, for example, that my eggs are rich in omega-3 — an essential fatty acid our brains need to thrive. In the late 1980s I did some studies comparing American chicken eggs to Greek eggs from my farm and found the ratio of essential fatty acids, which should be 1:1, was in complete balance on the farm, while in the US it was higher than 20:1! I couldn't believe it.

Even in Greece things are rapidly changing, and it's really sad. We all need to get back to our plant-based diets. For the Greeks, these were diets rich in local greens, extra virgin olive oil, and sourdough bread.

My simple trick: add olive oil into your diet — you can even mix it with butter

My recommendation: Cook beans at least a couple of times a week. Snack on nuts and seeds instead of processed foods filled with sugar and white flour, which are stripped of the nutrients and plant compounds that our bodies need to function well.

And if you can only start with one thing, may I recommend one of my favorite home cooking hacks? Mix your butter or your canola oil in a 1 to 1 ratio with extra virgin olive oil.

My butter and olive oil mix makes a great healthy spread for toast, while my go-to cooking oil mixture of 50% organic canola and 50% EVOO is a science-backed way to balance nutrition by improving the polyphenol composition of your meals and the anti-inflammatory properties of the dish.

Enjoy!