Yom Kippur: Science & Spirit

higher purpose

Yom Kippur is called the holiest day of the year. But what does holy really mean?

In Hebrew, the word is קֹדֶשׁ (kodesh), from the root קדש which means “set apart.” Something holy is separated from the ordinary so it can be dedicated to a higher purpose.

Shabbat is holy because it is set apart from the six weekdays. The Torah is holy because it is set apart from ordinary writings. Yom Kippur is the holiest day because it is completely set apart — a day of no work, no food, no distractions, only soul and return.

Holiness is not outside of us. It is within us. On Yom Kippur, when the body quiets, the holiness that is always there rises to the surface.

Science & Spirituality

Yom Kippur is a day when body and soul come together. What is powerful is how both science and spirituality agree: when we stop eating, something profound begins to happen. Science shows us how the body repairs itself during a fast, and spirituality shows us how the soul awakens in the quiet. Together they reveal why Yom Kippur is not only a day of atonement, but a day of deep renewal.

Atonement means cleansing and repairing the relationship between us and Hashem, and also between us and other people. In Hebrew it is called kapparah, from the same root as Kippur. It is not about punishment but about starting fresh.

Alongside kapparah is the word teshuvah, which means “return.” Teshuvah is the process of turning back toward our essence, toward our truest self, and toward Hashem. Yom Kippur is not only about being forgiven for what went wrong. It is about coming home.

pause & reset

In English, the word “fasting” comes from the Old English word fæstan, which means “to hold firmly, to observe, to keep.” To fast is to stand firm against desire and to dedicate oneself to something higher. That is why we call it fasting.

In Hebrew the word is צום (tzom). Its root means to withhold, to refrain, to hold back. Litzom is the act of not eating and drinking for the sake of something higher. It is not simply skipping meals. It is choosing to pause the body’s usual rhythm in order to reveal what is deeper.

On Yom Kippur it is called tzom ha-asiri, the tzom of the tenth day of Tishrei. The day itself is defined by this act of refraining. In the quiet created by this tzom, we sense more clearly that life is not sustained only by bread and water but by the breath and presence of Hashem.

The verb לצום (litzom) means to refrain, to step back from the body’s needs so the soul can come forward.

The Body in Renewal

When we go without food, our body enters repair mode. Digestion is one of the body’s most energy-demanding processes. Once digestion rests, that energy shifts into cellular cleaning and rebuilding. Scientists call this autophagy. During autophagy, old and damaged cells are broken down, and fresh, healthy ones take their place. It is a natural recycling process that strengthens immunity and supports longevity.

Research has shown that fasting can lower inflammation, balance blood sugar, and even trigger protective mechanisms that help the body resist disease. Some doctors are exploring how fasting cycles may help with cancer.

The spiritual practice of fasting is mirrored by a real physical cleansing inside our cells.

The Spirit Awakened

Spiritually, fasting softens us. Without meals to anchor the day, time feels different. Our emotions rise closer to the surface. Prayer feels more raw, sometimes more honest. Hunger itself becomes a teacher. It shows us that we are not only sustained by food, but by something deeper, by the life force that flows through us at every moment.

There are different ways we return. Some people are moved by fear — fear of judgment, fear of consequences, fear of what happens if we keep going down the same road.

Others are drawn by love — the pull to reconnect, to be close, to live from the heart. In recovery language, fear can get our attention, but love is what keeps us moving forward. Yom Kippur touches both. We may feel shame for mistakes, but the day is an invitation to let love be stronger than shame. Shame keeps us stuck in the past. Love carries us into healing.

The Rhythm of the Fast

For me, the fast has a rhythm. The first half of the day is the hardest, when the body still expects its usual meals. But by the second half, something shifts. The hunger eases. The body quiets down and I feel more spacious inside. Usually by the time we reach the end, I no longer even feel hungry. Breaking the fast becomes less about desperation and more about gently re-entering the ordinary world.

On Yom Kippur, fasting is both physical and spiritual healing. The body repairs itself in silence. The soul is awake and unburdened. And in that space, we can feel what is always there: unconditional love, radical acceptance, and the highest version of ourselves.

Staying Comfortable During the Tzom

Although Yom Kippur is about stepping back from physical comforts, there are ways to move through the day more gently so hunger does not overwhelm you. Preparation is key. Before Yom Kippur, drink plenty of water so your body is well-hydrated. Eat fruits and vegetables with high water content, like cucumbers, melons, and grapes. Choose complex carbohydrates such as rice or oats, and pair them with protein like fish, chicken, or legumes to give steady energy. Avoid salty foods that create thirst and minimize caffeine so your body is not dealing with withdrawal during prayer.

Once the tzom begins, shift your focus from what you are not eating to the subtler ways your body is still being nourished. Science shows that sunlight and breath provide real support. Sunlight stimulates vitamin D and helps regulate the body’s rhythms, steadying both mood and energy. Deep breathing increases oxygen flow, which calms the nervous system and helps your cells function more efficiently. In this sense, light and air become food for the body in a quieter way.

Grounding is another way to steady yourself. Walking barefoot on earth, grass, or stone allows the body to absorb natural electrical charges from the ground, a process known as earthing. Research has shown this can reduce inflammation, regulate stress hormones, and bring balance to the body’s systems. Spiritually, it reminds us that when we humble ourselves and come down to the ground, we actually draw closer to life itself.

By the second half of the day, many people notice that the hunger eases and the body grows quiet. When it is time to end the tzom, break it gently. Begin with water or tea to rehydrate. Many have the tradition of eating dates first, restoring natural sugars, then moving to a warm soup or broth that soothes the stomach before eating a fuller meal. The idea is not to rush but to re-enter the ordinary world with kindness to the body.