Ever wondered why some people live to 100 or more? Yes, genes play a part – but diet and nutrition play an even bigger one.

Centenarians are they are the fastest-growing age segment of the population. In fact, it’s estimated that by 2020 there will be more than 12,000 in Australia. Hotspots, or “blue zones” around the world where clusters of centenarians live, include Okinawa in Japan, Ogliastra in Sardinia, Italy, Ikaria – nicknamed “the island where people forget to die” - in Greece, and California’s Loma Linda. What makes these people unique is not just their ability to live to 100-plus: it’s their ability to do so with healthy bodies and minds. Here are 10 dietary secrets we can learn from centenarians.

1. Put carbs on the menu

The diet of Okinawan and Sardinian centenarians is high in carbohydrates, according to a study published in the Journal of the American College of Nutrition. For example, traditional Okinawans consume 90 percent of their calories from carbohydrates like vegetables and legumes, rather than highly processed carbohydrate foods, such as sugary breakfast cereals. And centenarians still stay slim, suggesting that the type rather than the quantity of carbohydrate eaten – that is, whole food versus refined - is vital.

2. Indulge gently

While the words ‘alcohol’ and ‘healthy’ are not often seen together, centenarians often do drink alcohol. For example, Ikarians have three to four small glasses of antioxidant-rich red wine every day. Ikarian wine is very rich in flavonoids, which have been shown to help protect against cancer and inflammation. Okinawans also imbibe a small amount of locally brewed awamori, or rice liquor. So enjoy a tipple, but do so with moderation.

3. Say “Haru hachi bu”

For centuries, Okinawan grandmothers have wisely advised, “Haru hachi bu” - which translates as “Eat until you are only 80 percent full”. Today, people habitually overeat, and find it to exercise self-restraint. Aim to eat with your eyes, practise mindfulness at meal times, and don’t feel obliged to clean your plate.

4. Pick a dainty plate

A study published in the Indian Journal Community Medicine has reported that the Okinawans consistently eat from quite small plates. Plate sizes in the West, on the other hand, have grown dramatically in the last 50 years, which naturally equates to larger servings. One cue for fullness is seeing an empty plate, so stock your cupboard with smaller plates and watch your portion sizes decrease, too.

5. Make it mostly plants

Current recommendations are that Australians eat two serves of fruit and five of vegetables daily – but most of us find even that difficult. Despite eating widely varying foods in their respective diets, all centenarians have in common the fact that they eat a mostly plant-based diet. For example, Loma Linda centenarians are vegetarians while the Sardinians and the Ikarians follow the famous Mediterranean diet, which contains only small quantities of meat and oily fish, but lots of vegetables.

6. Eat a rainbow

Still on the topic of veggies, eating a wide range of them, rather than the same-old peas and potatoes every day, is particularly valuable. A study published in the Indian Journal Community Medicine showed the Okinawans eat a minimum of 300g of mixed vegetables a day, including large amounts of antioxidant-rich sweet potato. Another vegetable that features widely in their diet is hijiki seaweed, which they eat daily. Seaweed is rich in dietary fibre, omega-3 fatty acids, minerals, and vitamins A, C and E. Nutrient-rich wild greens, like dandelion and the spinach-like horta, also make up a large portion of the Ikarian diet. Numerous studies reveal the protective nature of antioxidants and phytochemicals in vegetables against cancer and heart disease, providing another reason for centenarian longevity.

7. Sip miso soup

According to a Journal of Clinical Nutrition study, Okinawans start most meals with miso soup, consisting of water, miso paste, seaweed, tofu, sweet potato, and green leafy vegetables. Miso is an antioxidant, plus it contains isoflavones, constituents which have been shown to protect against bone loss associated with osteoporosis.

8. Cut calories

A centenarian’s diet is typically low in calories. For example, the energy intake of Okinawans is about 1,100 kcal/day for both sexes; however, the average recommended caloric consumption for Aussies is 2,000 to 2,500 - and many people eat much more than this. Even at 2,000 calories per day, we're still consuming double the amount of the Okinawans. We don't need to eat as much as we think we do.

9. Be unrefined

What centenarians don’t eat is equally important. A common theme is that they avoid calorie-dense refined sugars, saturated fats and processed foods. Simply replacing them with nutrient-dense, low calorie whole foods can lengthen your life.

10. Stay trim

Centenarians seldom take formal exercise, but they do stay active. It is not uncommon to see people in their nineties riding mountain bikes in Okinawa, while Sardinians typically work in their vegetable gardens and walk several kilometres daily. Another healthy habit seen in Ikarian centenarians is their noon siesta. The lesson? Move your body more but don’t forget to rest.

Lisa Costa Bir is a Sydney based naturopath specialising in adrenal fatigue and thyroid disorders such as Graves disease and Hashimoto’s.