Short answer: We don’t know; the evidence is insufficient. Traditional Okinawans lived unusually long on a low-calorie, plant-heavy diet, but no study has linked that diet to cognition. A 1992 survey found dementia in 6.7 percent of Okinawans aged 65 and over, not dramatically low. The transferable lessons: fill up on low-calorie plant foods and stop before you’re full.

No study has tested whether the traditional Okinawan diet protects the brain, so the evidence is insufficient. What we have is strong longevity data, one dementia survey that didn’t show unusually low rates, and lab and animal studies of single Okinawan foods.

Okinawa is a chain of subtropical islands between mainland Japan and Taiwan. For much of the twentieth century it was poor and rural, and it had one of the highest rates of centenarians in the world. The Okinawan Centenarian Study, started in 1975 by Makoto Suzuki and later expanded by Bradley and Craig Willcox, has studied these elders for decades. Willcox and colleagues reported low death rates from age-related diseases such as heart disease in the older generation (Willcox 2007).

Lessons you can use

The traditional diet came from conditions you can’t recreate in a Western supermarket. But several of its habits transfer.

  1. Eat foods with fewer calories per bite. Build meals on vegetables, legumes, fruit, broth-based soups and whole tubers. You can eat filling amounts while taking in fewer calories. Calorie moderation protects the brain in animal studies; in people, it helps prevent obesity and type 2 diabetes, which are risk factors for dementia.
  2. Stop before you’re full. Okinawans call this hara hachi bu, eating until about 80 percent full. Smaller plates and eating slowly help. Mild calorie moderation over decades may support healthy aging, though its effect on the human brain hasn’t been tested.
  3. Eat purple and orange plant foods. Purple sweet potatoes, blueberries, red cabbage and purple carrots provide anthocyanins, the pigments that were plentiful in the Okinawan diet. Orange sweet potatoes are easier to find and offer beta-carotene, fiber and few calories.
  4. Include soy. Miso, tempeh, natto and tofu provide plant protein and isoflavones. Miso soup is an easy start. Natto is rich in vitamin K2; if you take warfarin, ask your doctor before eating natto, because its vitamin K can reduce the drug’s effect.
  5. Cook with turmeric. Modest daily turmeric in food, golden milk or tea fits the Okinawan pattern better than high-dose curcumin pills. Cooking it with fat may help absorption. Turmeric in food is not a concern; supplements are different (see the FAQ).
  6. Add some seaweed. Wakame in miso soup, nori as a snack or kombu in broth adds minerals and fiber. Go easy on kombu, which is very high in iodine, especially if you have a thyroid condition.
  7. Cut ultra-processed food. Okinawa’s health advantage faded as fast food, refined snacks and convenience meals arrived.
  8. Think in decades. The centenarians ate this way for 80 or 90 years. Any brain benefit would build over a very long time.

What traditional Okinawans ate

Sweet potato as the staple. Mainland Japan ate polished white rice, but Okinawa’s soil and climate suited the sweet potato, especially the purple-fleshed beni imo. Sweet potato supplied over half of daily calories in the traditional diet (Willcox 2014). According to USDA data, cooked sweet potato has about 90 calories per 100 grams, versus about 130 for cooked white rice, so people could eat their fill on fewer calories. Purple sweet potatoes are rich in anthocyanins, the same pigments found in blueberries. Terahara 2004 identified the specific anthocyanins in cell cultures grown from purple sweet potato; their effects on the brain have been seen only in lab and animal studies.

Very little fat or animal food. In a 1950 survey (Willcox 2014), fat supplied only about 6 percent of calories and protein about 9 percent, with carbohydrate, mostly sweet potato, about 85 percent. Fish, especially small reef fish and bonito, was eaten several times a week. Pork was eaten in small amounts, mostly at festivals.

Soy at almost every meal, mainly as tofu, miso and natto.

Seaweed every day, such as kombu, wakame and mozuku, in soups, side dishes and seasoning.

Bitter melon (goya), often stir-fried with tofu, egg and pork in goya champuru.

Turmeric (ukkon), used in cooking and as a traditional tea.

What the research says about these foods

None of these studies tested the Okinawan diet itself.

Soy. White 2000 studied 3,734 Japanese-American men in the Honolulu-Asia Aging Study. Some men ate tofu two or more times a week at both midlife interviews. In late life, they had worse cognitive scores, larger brain ventricles and lower brain weight than men who ate little tofu. The odds ratios were mostly 1.6 to 2.0. This finding has been debated and not consistently replicated. A meta-analysis of 10 randomized trials in postmenopausal women (Cheng 2015) found that soy isoflavone supplements had a small benefit on overall cognitive scores (standardized mean difference 0.08). Fermentation can make isoflavones easier to absorb, and some fermented foods contain live bacteria, though their relevance to the brain is untested. See our page on fermented foods.

Seaweed. Seaweeds contain fucoidans, compounds with anti-inflammatory effects in lab research. Jhamandas 2005 found that fucoidan protected rat brain cells from amyloid-beta toxicity in a dish; this hasn’t been tested in people. Seaweed also provides iodine, which the thyroid needs. Iodine content varies hugely, from low in nori to very high in kelps such as kombu (Teas 2004). Some seaweed dishes may exceed the adult upper limit of 1,100 micrograms a day. In a Japanese study (Miyai 2008), eating 15 g of kombu daily raised TSH, a sign of suppressed thyroid function, until people stopped.

Bitter melon. It contains compounds studied for lowering blood sugar, and insulin resistance and type 2 diabetes are linked to faster cognitive decline. In mice fed a high-fat diet (Nerurkar 2011), bitter melon reduced markers of brain inflammation and oxidative stress. Human evidence on cognition is lacking, and human evidence on its metabolic effects is limited.

Turmeric. Ng 2006 studied 1,010 older adults in Singapore. Those who ate curry “occasionally” or “often or very often” scored better on a cognitive screening test than those who “never or rarely” ate it. The authors called this tentative evidence, and a one-time snapshot can’t show cause and effect. Curcumin, turmeric’s main compound, is poorly absorbed, and supplement trials on cognition have given inconsistent results.

Hara hachi bu and calorie moderation

Hara hachi bu is a Confucian-inspired habit of stopping at about 80 percent full, often reinforced by a phrase said before meals. It works as a cultural norm, not calorie counting.

Willcox 2007 analyzed six decades of archived population data. Older Okinawans had low calorie intake and ate fewer calories than they burned when younger, gained little weight with age and kept a low body mass index for life. The authors saw this as consistent with mild calorie restriction, which extends lifespan in many animal species.

In animals, calorie restriction of 20–40 percent extends lifespan and delays age-related brain changes. Mattson 2018 reviewed the mechanisms, such as stress-response pathways, less oxidative stress and better mitochondrial function. Okinawa suggests that mild, lifelong moderation, far gentler than the 20–40 percent used in rodent studies, is compatible with excellent health. Whether it protected cognition hasn’t been studied.

The low calorie density of the diet made this easier. Large volumes of sweet potato, vegetables, miso soup and seaweed, plus the habit of stopping early, meant people could feel satisfied on fewer calories.

Did Okinawans have less dementia?

Direct evidence is limited and doesn’t show dramatically low rates.

  • Okinawa survey (Ogura 1995): Researchers surveyed 3,524 randomly selected Okinawans aged 65 and over around 1992. Dementia prevalence was 6.7 percent. It rose steeply with age, to 41 percent of women and 21 percent of men aged 90–99.
  • Centenarians (Willcox 2007, Am J Geriatr Psychiatry): Of 22 centenarians, 82 percent were still living independently at an average age of 92, and almost two-thirds at 97, on a measure that included physical, sensory and cognitive function.
  • Japan trends (Dodge 2012): A review of eight dementia studies in Japan found that studies after the 1992 Okinawa survey reported higher prevalence, and that dementia appears to be rising in Japan. Differences in methods and regions make the comparison uncertain.
  • Hawaii (White 1996): Among 3,734 Japanese-American men in Hawaii, Alzheimer’s prevalence appeared higher than in Japan but similar to European-ancestry populations. This suggests environment matters, but says nothing directly about Okinawa.

No study has linked the traditional Okinawan diet itself to cognitive outcomes.

What happened when the diet changed

From the 1960s, and faster after Okinawa returned to Japan in 1972, the diet changed quickly. US military bases brought fast food, processed snacks, canned goods and more meat. Economic growth brought supermarkets and the mainland Japanese diet, with more white rice, refined food and animal products.

According to Willcox 2014, post-war generations, men in particular, ate more calories and a less nutritious diet. They were also less active and had a higher risk of obesity than earlier generations and other Japanese. Okinawa came to have the highest average BMI in Japan. White rice, bread and noodles largely replaced sweet potato, and hara hachi bu faded among younger people.

This shift is consistent with diet playing a part in Okinawan longevity, but physical activity, income and health care changed at the same time. Whether dementia rates will rise in younger Okinawans isn’t yet known, though rising metabolic disease would be expected to increase risk.

Okinawan vs Mediterranean diet

Both are plant-heavy, low in processed food and moderate in animal protein, and both are linked to low rates of heart disease and some cancers. The main differences:

  • Fat: The Mediterranean diet gets 35–40 percent of calories from fat, mostly olive oil. The traditional Okinawan diet got about 6 percent in 1950, rising to about 26–28 percent in later Okinawan diets. Healthy aging seems possible with very different fat intakes.
  • Starch: Mediterranean meals rely on grains, bread and pasta; Okinawan meals relied on sweet potato.
  • Calorie density: The traditional Okinawan diet was much lower.
  • Evidence: The Mediterranean diet has far more evidence for cognition, including trial sub-studies from PREDIMED. Okinawan evidence is almost entirely observational and population-level, and about longevity rather than the brain.

Both share plenty of plant foods, fish, anti-inflammatory foods, little processed food and habits that prevent overeating. That two such different diets are both linked to long lives suggests the overall pattern matters more than any single food.

Frequently asked questions

Can I take curcumin supplements instead of eating turmeric?

Trials of curcumin supplements on cognition have given mixed results. In one trial of 40 adults without dementia (Small 2018), a well-absorbed curcumin product (90 mg twice daily) improved memory and attention over 18 months compared with placebo. Brain scans for amyloid and tau gave mixed results. Other trials haven’t replicated this. Supplements are not a substitute for a healthy diet, and they carry risks food doesn’t. Cases of liver injury have been reported with curcumin and turmeric supplements, more often with high-absorption or piperine-containing products. Avoid them if you have liver disease, and ask a doctor or pharmacist first if you take blood thinners or other medication.

How much is genetics?

Genetics plays a role. Willcox 2008 showed that variants in the FOXO3 gene, involved in stress resistance, are strongly associated with human longevity, a finding since replicated in other populations. But health has worsened within the same gene pool as the traditional diet disappeared, so genetics alone can’t explain the Okinawan advantage. How much is genetic isn’t known precisely.

Is calorie restriction safe for everyone?

Mild moderation, eating low-calorie-density foods and stopping at 80 percent full, is generally safe for healthy adults. Calorie restriction is not appropriate for children, teenagers, pregnant or breastfeeding people, people with a history of eating disorders, underweight people or those with certain medical conditions. People taking insulin, sulfonylureas or SGLT2 inhibitors should cut calories only under medical supervision, because of the risk of low blood sugar or ketoacidosis. Talk to a healthcare provider before making big changes to how much you eat.

Sources

  • Willcox, B. J., Willcox, D. C., Todoriki, H., Fujiyoshi, A., Yano, K., He, Q., Curb, J. D., & Suzuki, M. (2007). Caloric restriction, the traditional Okinawan diet, and healthy aging: the diet of the world’s longest-lived people and its potential impact on morbidity and life span. Annals of the New York Academy of Sciences, 1114, 434–455. doi:10.1196/annals.1396.037

  • Willcox, D. C., Willcox, B. J., Todoriki, H., & Suzuki, M. (2009). The Okinawan diet: health implications of a low-calorie, nutrient-dense, antioxidant-rich dietary pattern low in glycemic load. Journal of the American College of Nutrition, 28(Suppl), 500S–516S. doi:10.1080/07315724.2009.10718117

  • Willcox, D. C., Scapagnini, G., & Willcox, B. J. (2014). Healthy aging diets other than the Mediterranean: a focus on the Okinawan diet. Mechanisms of Ageing and Development, 136–137, 148–162. doi:10.1016/j.mad.2014.01.002

  • Willcox, D. C., Willcox, B. J., Shimajiri, S., Kurechi, S., & Suzuki, M. (2007). Aging gracefully: a retrospective analysis of functional status in Okinawan centenarians. American Journal of Geriatric Psychiatry, 15(3), 252–256. doi:10.1097/JGP.0b013e31803190cc

  • Willcox, B. J., Donlon, T. A., He, Q., Chen, R., Grove, J. S., Yano, K., … & Curb, J. D. (2008). FOXO3A genotype is strongly associated with human longevity. Proceedings of the National Academy of Sciences, 105(37), 13987–13992. doi:10.1073/pnas.0801030105

  • Ogura, C., Nakamoto, H., Uema, T., Yamamoto, K., Yonemori, T., & Yoshimura, T. (1995). Prevalence of senile dementia in Okinawa, Japan. International Journal of Epidemiology, 24(2), 373–380. doi:10.1093/ije/24.2.373

  • White, L., Petrovitch, H., Ross, G. W., Masaki, K. H., Abbott, R. D., Teng, E. L., … & Curb, J. D. (1996). Prevalence of dementia in older Japanese-American men in Hawaii: the Honolulu-Asia Aging Study. JAMA, 276(12), 955–960. doi:10.1001/jama.1996.03540120033030

  • White, L. R., Petrovitch, H., Ross, G. W., Masaki, K., Hardman, J., Nelson, J., Davis, D., & Markesbery, W. (2000). Brain aging and midlife tofu consumption. Journal of the American College of Nutrition, 19(2), 242–255. doi:10.1080/07315724.2000.10718923

  • Ng, T. P., Chiam, P. C., Lee, T., Chua, H. C., Lim, L., & Kua, E. H. (2006). Curry consumption and cognitive function in the elderly. American Journal of Epidemiology, 164(9), 898–906. doi:10.1093/aje/kwj267

  • Small, G. W., Siddarth, P., Li, Z., Miller, K. J., Ercoli, L., Emerson, N. D., … & Barrio, J. R. (2018). Memory and brain amyloid and tau effects of a bioavailable form of curcumin in non-demented adults: a double-blind, placebo-controlled 18-month trial. American Journal of Geriatric Psychiatry, 26(3), 266–277. doi:10.1016/j.jagp.2017.10.010

  • Mattson, M. P., Moehl, K., Ghena, N., Schmaedick, M., & Cheng, A. (2018). Intermittent metabolic switching, neuroplasticity and brain health. Nature Reviews Neuroscience, 19(2), 63–80. doi:10.1038/nrn.2017.156

  • Cheng, P. F., Chen, J. J., Zhou, X. Y., Ren, Y. F., Huang, W., Zhou, J. J., & Xie, P. (2015). Do soy isoflavones improve cognitive function in postmenopausal women? A meta-analysis. Menopause, 22(2), 198–206. doi:10.1097/GME.0000000000000290

  • Dodge, H. H., Buracchio, T. J., Fisher, G. G., Kiyohara, Y., Meguro, K., Tanizaki, Y., & Kaye, J. A. (2012). Trends in the prevalence of dementia in Japan. International Journal of Alzheimer’s Disease, 2012, 956354. doi:10.1155/2012/956354

  • Terahara, N., Konczak, I., Ono, H., Yoshimoto, M., & Yamakawa, O. (2004). Characterization of acylated anthocyanins in callus induced from storage root of purple-fleshed sweet potato, Ipomoea batatas L. Journal of Biomedicine and Biotechnology, 2004(5), 279–286. doi:10.1155/S1110724304406056

  • Jhamandas, J. H., Wie, M. B., Harris, K., MacTavish, D., & Kar, S. (2005). Fucoidan inhibits cellular and neurotoxic effects of beta-amyloid (A beta) in rat cholinergic basal forebrain neurons. European Journal of Neuroscience, 21(10), 2649–2659. doi:10.1111/j.1460-9568.2005.04111.x

  • Nerurkar, P. V., Johns, L. M., Buesa, L. M., Kipyakwai, G., Volper, E., Sato, R., … & Nerurkar, V. R. (2011). Momordica charantia (bitter melon) attenuates high-fat diet-associated oxidative stress and neuroinflammation. Journal of Neuroinflammation, 8, 64. doi:10.1186/1742-2094-8-64

  • Teas, J., Pino, S., Critchley, A., & Braverman, L. E. (2004). Variability of iodine content in common commercially available edible seaweeds. Thyroid, 14(10), 836–841. doi:10.1089/thy.2004.14.836

  • Miyai, K., Tokushige, T., & Kondo, M. (2008). Suppression of thyroid function during ingestion of seaweed “Kombu” (Laminaria japonica) in normal Japanese adults. Endocrine Journal, 55(6), 1103–1108. doi:10.1507/endocrj.k08e-125