What one food makes up 67% of the Okinawan diet?

October 15, 2025 •

4 min read

The traditional Okinawan diet is renowned for its association with human longevity, and for decades, one food item dominated this dietary pattern. In the mid-20th century, the purple sweet potato, known locally as beni imo, provided approximately 67% of the total daily calories for Okinawan centenarians. This vibrant, antioxidant-rich tuber is the singular food that makes up the largest proportion of the Okinawan diet, contributing significantly to their historic health advantages.

Quick Summary

The staple food that historically dominated the traditional Okinawan diet is the purple sweet potato, or beni imo, providing about 67% of total caloric intake. This nutritious, antioxidant-rich tuber was central to the eating patterns linked to the region's high number of centenarians. Beyond just the sweet potato, the diet emphasized a wide range of vegetables, legumes, and soy products, with minimal meat and processed foods.

Key Points

The Purple Sweet Potato is Key: The beni imo, or purple sweet potato, historically made up 67% of the calories for Okinawan centenarians.
Rich in Anthocyanins: Its vibrant purple color is due to powerful antioxidants, which fight inflammation and cellular damage associated with aging.
Low Glycemic Index: Despite its sweetness, the purple sweet potato does not cause significant blood sugar spikes, unlike many other carbohydrate sources.
A Broad Plant-Based Diet: The overall diet is 90% plant-based, with other vegetables, soy products, and legumes playing significant roles.
Minimal Meat and Processed Foods: Traditional Okinawans consumed very little meat, fish, and dairy, and avoided processed foods.
The 'Hara Hachi Bu' Principle: Mindful eating, or stopping when 80% full, complements the high-fiber diet to aid digestion and weight management.
Modern Shift in Diet: With the introduction of Western foods, the traditional diet has changed, impacting the health outcomes of younger generations.

The Purple Sweet Potato: A Longevity Secret

In the Blue Zone region of Okinawa, Japan, where people have historically enjoyed some of the longest life spans in the world, the traditional diet held a surprising secret: a single food item accounted for a massive portion of daily caloric intake. That food is the purple sweet potato, or beni imo. Unlike common orange sweet potatoes, the Okinawan variety is a vibrant purple inside, a hue that signals its powerful antioxidant content.

Historically, especially up until the 1950s, the purple sweet potato was the dietary workhorse for Okinawan centenarians, making up about 67% of their total calories. This reliance on the sweet potato was largely due to necessity, as the subtropical climate and frequent storms of Okinawa made it difficult to cultivate rice reliably. Imported rice was also too expensive for many families, leading them to rely on the resilient, nutrient-dense sweet potato.

The Nutritional Powerhouse: Why the Sweet Potato?

The purple sweet potato is far more than just a calorie source; it is a nutritional powerhouse packed with health-promoting compounds. Its intense purple color comes from anthocyanins, powerful antioxidants also found in blueberries and red wine. Anthocyanins have been linked to reducing inflammation and protecting against age-related diseases.

Other notable nutrients in the beni imo include:

Antioxidants: In addition to anthocyanins, they contain high levels of vitamin A, C, and E.
Fiber: High fiber content promotes healthy digestion and provides a feeling of fullness, which supports the Okinawan practice of eating only until 80% full, known as hara hachi bu.
Potassium: Rich in potassium, the sweet potato helps balance the body's fluids and blood pressure.
Low Glycemic Index: Despite their sweet taste, purple sweet potatoes have a surprisingly low glycemic index, meaning they do not cause sharp spikes in blood sugar.

The Broader Traditional Okinawan Diet

While the sweet potato was the caloric backbone, it was part of a larger dietary pattern rich in whole, plant-based foods. The remainder of the traditional Okinawan diet was composed of other vegetables, soy products, legumes, and grains, with only minimal amounts of meat and fish.

Vegetables: Beyond the sweet potato, the Okinawan diet includes a variety of green and root vegetables like bitter melon (goya), cabbage, and seaweed.
Legumes and Soy: Tofu, miso, and edamame are regular components, providing essential protein and isoflavonoids.
Grains: Rice and other grains constituted a smaller portion of the diet compared to mainland Japan.
Minimal Meat: Fish and occasional pork were consumed in very small quantities, often for special celebrations.

Comparison: Traditional Okinawan vs. Modern Western Diet

To understand the full impact of the traditional Okinawan eating pattern, a comparison with the average modern Western diet is illuminating. The stark differences highlight why the Okinawan diet is associated with such impressive health outcomes.


Feature	Traditional Okinawan Diet	Modern Western Diet
Caloric Source	Predominantly from sweet potatoes (approx. 67%) and other vegetables	High proportion from processed foods, meat, and dairy
Carbohydrates	High (around 85%), from complex carbs	Variable, often from refined grains and sugar
Fat Intake	Very low (around 6%), mostly unsaturated fats	Significantly higher, often with more saturated and trans fats
Antioxidants	Very high, especially from purple sweet potatoes	Lower, varies based on individual vegetable and fruit intake
Fiber	High, from a wide range of plants	Often insufficient due to low plant intake and processed foods
Processed Foods	Minimal, relies on fresh, whole foods	Very high, with added sugars, salt, and unhealthy fats

A Shift in Dietary Patterns

It is important to note that the traditional Okinawan diet has changed in recent decades due to globalization and Western influence. The consumption of processed foods, meat, and refined carbohydrates has increased, leading to a decline in some health metrics for the younger generation compared to their centenarian predecessors. This shift underscores the significance of the ancestral eating habits that were centered on the simple, yet potent, purple sweet potato.

Conclusion

The purple sweet potato is the single food that once comprised an impressive 67% of the Okinawan diet, a key component in a lifestyle associated with exceptional longevity and health. Its rich antioxidant content, low glycemic load, and dense nutritional profile made it an ideal dietary cornerstone. While other factors like community, physical activity, and mindful eating are also crucial, the unique dietary foundation of the Okinawan people cannot be overstated. The legacy of the beni imo serves as a potent reminder that simple, nutrient-rich, whole foods can have a profound impact on human health.

To learn more about the research behind the Okinawan diet and other longevity secrets, explore the resources available at the Blue Zones project.

Frequently Asked Questions

The primary food source in the traditional Okinawan diet is the purple sweet potato, known as beni imo, which historically provided around 67% of daily caloric intake.

Okinawans relied heavily on the sweet potato due to geographic necessity. The crop thrived in their subtropical climate, which was prone to storms that damaged rice paddies, and it was a more affordable and reliable staple than imported rice.

No, the traditional Okinawan diet is not strictly vegetarian, but it is primarily plant-based (around 90%), with very small amounts of pork, fish, and other animal products consumed, often during special occasions.

Other foods include a wide variety of vegetables (like bitter melon and seaweed), soy products (such as tofu and miso), legumes, and some whole grains, alongside minimal meat, fish, and dairy.

Okinawan sweet potatoes, particularly the purple variety (beni imo), contain higher levels of anthocyanin antioxidants, which provide their deep purple color and additional health benefits.

Health benefits linked to the traditional Okinawan diet include exceptional longevity, lower rates of heart disease, and a reduced risk of certain cancers, largely attributed to its high antioxidant and nutrient content.

Yes, in recent decades, Western influences have led to an increase in processed foods and meat consumption in Okinawa, causing a decline in the health and longevity of younger generations compared to their elders.