अपांसोम्य पीयमानानां योऽणिमा स उर्ध्वः समुदीषति सा प्राणो भवति ॥ ६.६.३ ॥
apāṃsomya pīyamānānāṃ yo’ṇimā sa urdhvaḥ samudīṣati sā prāṇo bhavati || 6.6.3 ||
3. O Somya, the finest part of water that is drunk rises to the surface and becomes our prāṇa.
Anna means the food that you eat—any food. Wheat, rice, fish, meat, vegetables, milk, and so on—all this is anna. The Upaniṣad says, that which is the finest part of the food rises to the surface, like the butter in curd. It then becomes the mind. It is the subtlest part of the food, the essence. According to Vedānta, the mind is material. It is a by-product of food and is nourished by food.
Somya, O Somya; apām pīyāmānānām, of the water that is drunk; yaḥ aṇimā, that which is the finest part; saḥ ūrdhvaḥ samudīṣati, it rises to the surface; saḥ prāṇaḥ bhavati, that becomes prāṇa, the vital force.
Similarly, if you drink water, the finest part of that water becomes separated from the rest and rises to the surface to become prāṇa, the vital force. This is why in Sanskrit water and life (jala and jīvana) are synonymous. Without water, life cannot exist. In fact, science says that life first appeared in water.