The yakuzen theory says that vegetables have "role to create a smooth path in the body system".
Spring ingredients with bitter taste like bitter gourd, edible wild plants, celery, and shiso leaves have a detoxifying effect and sooth irritation. Sweet taste from vegetables in season like pumpkin and carrots can help digesting what you eat.
Cucumbers and tomatoes can help fighting against heat in summer. Vegetables in a gourd group has a diuretic effect helping to get rid of excessive water from the body system and swelling. These vegetables take heat and humidity accumulated in the body system, resulting in making you feel cooler before eating such vegetables.
For the nutritional enhancement, Japanese yam and taro do great job. These veggies in the potato group help you to get in good physical shape, and help you stomach to absorb every nutrition from every single ingredient.
Further, yakuzen suggests that daikon radish and lotus root can moist skin and the intestines. Such vegetables are perfect for rough skin conditions and constipation.
What is the most important in the yakuzen theory is to intake vegetables and other ingredients by looking at how you feel and your physical conditions in each season. Try not to consume ingredients which are not in season.