What 'oils' does a gastroenterologist keep in their home kitchen?

In my daily practice, I am often asked, "What oil is actually good for the body?"

The oils I actually use are

extra virgin olive oil
flaxseed oil, perilla oil, and fish oil (DHA/EPA)
MCT oil
rice bran oil

(as of 2026/03/23).

Why do I choose them?
This time, I will focus on olive oil.

I will explain the reasons from the perspective of a gastroenterologist, while also incorporating medical data.

Why is olive oil "special"?

There are several types of fatty acids, which are the main components of oil, but the star of olive oil is "oleic acid" (a monounsaturated fatty acid).

A "natural lubricant" that regulates the intestinal environment

From a gastroenterological perspective, the intestinal regulating effect of oleic acid cannot be overlooked.

Because oleic acid is difficult to absorb in the small intestine, it moderately stimulates the large intestine and promotes peristalsis.

Furthermore, as is true for all oils, it also acts as a physical "lubricant" to improve bowel movements.
For those suffering from constipation, this is an easy self-care method to try.

In my practice, I have seen many people who consume olive oil as a constipation remedy, and I have the impression that the response is quite good.

Recently, papers have also been published regarding its effects on the intestinal environment.

It is said to trigger an increase in short-chain fatty acid-producing bacteria, a decrease in inflammatory bacteria, and the regulation of the intestinal mucosal barrier and immunity.

Polyphenols that provide health benefits

What sets olive oil apart from other vegetable oils is the strength of its antioxidant properties.

There are research papers reporting that the Mediterranean diet, which frequently incorporates olive oil, has health benefits.

The polyphenols contained in olive oil have antioxidant and anti-inflammatory effects, which are considered to be a major factor in the health benefits of olive oil.

Polyphenols are abundant in young green olives and are perceived as a spicy or bitter taste.

• Early-harvest green olives: Contains a very high amount of polyphenols.

• Fully ripened olives: Has a milder flavor, but the polyphenol content is reduced.

If you prioritize health benefits, it is important to choose this type of high-freshness oil that has a 'peppery' kick.

There are many olive oil products at the supermarket, but I recommend extra virgin olive oil.

Extra virgin olive oil has regulations regarding 'acidity,' which indicates the quality of the oil, and it is said that this label represents products that have met those standards.

While olive oils other than extra virgin are more affordable, some are processed or blended.

The risks of 'heating' as shown by medical data and how to deal with them

Oleic acid, the main component of olive oil, is resistant to heat, so I use olive oil when cooking with heat.

The main component, oleic acid, is stable and resistant to oxidation, but it has the property that valuable polyphenols are sensitive to heat.

It is known that the amount of polyphenols decreases during the 120ºC to 170ºC heating processes we use in our daily cooking.

Cooking methods recommended by a gastroenterologist

1. Ideally, consume it 'raw': Drizzle it directly over salads, natto, tofu, or bread. This is the most efficient way to ingest polyphenols.

2. For stir-frying, keep it 'short': Take advantage of the stability of oleic acid and finish quickly. Studies examining health benefits also use olive oil for heating. However, to benefit from the polyphenols, a short cooking time is better.

3. For deep-frying, use 'low temperature and short time': If you must deep-fry, you need to take care not to raise the temperature too high to minimize the loss of polyphenols.

While it is considered more heat-resistant than common oils, the principle is to keep it short and, ultimately, 'enjoy deep-fried foods only occasionally.'

What is the appropriate intake?

No matter how healthy an oil is, lipids contain 9 kcal of energy per gram.

Referring to the Ministry of Health, Labour and Welfare's 'Dietary Intake Standards,' a good balance for edible oil intake is
about 1 tablespoon (approx. 12g) per day.

On days when you eat fried food, it is easier to maintain balance if you have the peace of mind to adjust your intake over the course of a week rather than a single day, such as by cutting back on oil in your other two meals or the following day.

A small cupful protects your blood vessels 10 years from now

The health of the internal organs that we gastroenterologists examine is built upon the accumulation of our daily meals.

Try rethinking olive oil not just as a 'cooking oil,' but as a 'perishable food that must be handled with care regarding heat.'

The polyphenols contained in that single bite will surely become a powerful ally in protecting your blood vessels and intestines.

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May your dining table become healthier and more enriched.