Our being is comprised of three elements: the body, the mind, and the spirit. If one of these elements is out of balance, our whole being is out of balance. True radiance is possible when all three elements are in accord and are also in perfect harmony with each other. Only then we truly become radiant beings that are full of light, that are healthy, youthful, happy, and content. Only then we can fulfill our full potential.
These elements are supported by the three “pillars”, which are physical purification practices (Body), positive thinking & affirmations (Mind), and spiritual practices (Spirit).
According to Yogananda, the author of “Autobiography of a Yogi”, our body is a physical manifestation of the five vibratory elements, which is entire Universe is also composed of: earth, fire, water, air, and ether (same elements as used in Ayurveda and Chinese medicine).
To keep the body healthy you have to address the elements and keep them all in balance.