A number of principles are foundational to maintaining good health. Over the years I have written about many of them. I have explained the importance of drinking pure water, of eating real food, of breathing clean air, and remaining physically active. I have written about the benefits of maintaining an alkaline environment in the body, the need for regular rest, and the importance of electromagnetic protection. I have described how free radical damage, inflammation, loss of methylation ability, and mitochondrial decline trigger aging and disease. I have not, however, written about the most fundamental health principle of all.

“Failure to thrive” is a phrase that is used to describe a condition of retarded growth in infancy and childhood. The term first appeared in the 1933 edition of The Diseases of Infancy and Childhood. A number of physical challenges including organ defects, anemia, malabsorption, chronic infections and other conditions can cause failure to thrive. There are instances, however, when the infant or child who has ceased growing is found to have no discernable physical defect. The reason for failing to thrive in many of those children is the absence of parental love and attention.

The degree to which lack of love can adversely affect growth is striking. It has been shown that lack of affection can cause the pituitary gland to stop producing growth hormone. An even more amazing finding is that the administration of human growth hormone is ineffective in restoring normal growth in children who have stopped spontaneously producing the hormone due to an absence of love in their lives!

In 1999 German physicians reported their experience with two 5 year-old children who had been found to be lagging in growth. Tests revealed that the children’s growth hormone levels were low. The children were therefore started on a series of growth hormone injections.

Both of the children responded to the administration of growth hormone initially, but their progress soon faltered and future shots were ineffective in stimulating growth. Evaluation of the children’s social situations revealed that they had been rejected by their parents and were not receiving love or affection. When they were removed from their homes and placed with caring foster parents their growth hormone levels spontaneously returned to normal and they began to grow at a normal pace.

While it is most obvious in children, the opportunity to love and be loved is foundational to good health at all ages. The Pittsburg Healthy Heart Project is a study designed to evaluate the effect of positive social interactions on the development of cardiovascular disease. The study found that healthy happily married men who reported frequent interactions with their spouses experienced less thickening in their carotid arteries over time than men who did not report such interactions.

Studies have consistently shown that married couples live longer, on average, than single individuals. The effect is particularly striking in men who lose their spouses. Widowers are more likely to die than other single men or married men of the same age. If they remarry, however, widowers tend to live even longer than other married men.

Because love is viewed as a complex phenomenon that does not yield itself to scientific investigation, few studies showing the affect of love on health exist. Studies do exist, however, looking at the health effects of relationships between animals and people. Animals are capable of showing unconditional love to their owners. Relationships with animals have been shown to promote feelings of self-worth, help offset loneliness, reduce anxiety, provide comfort, and create a feeling of being needed.

The ability of the unconditional love shown by animals to support healing has led UCLA Medical Center to introduce an animal assisted therapy and activity program called the People Animal Connection (PAC). Dog owners volunteer for the program. A dog-owner team undergoes an extensive screening and training process after which they regularly visit critically ill children and adults. Over 400 visits are made each month, and the program has become so successful that it is being emulated in other medical centers around the country. Similar programs are being used by nursing homes to ease loneliness and calm agitation in residents.

A University of Cambridge study looked at the health effects of obtaining a new pet, compared to individuals who did not do so. Individuals who obtained a new pet reported significantly fewer minor health problems in the months following the acquisition. Other studies have found a positive effect of pet ownership on survival following a heart attack, on the number of visits to physicians, on depression with AIDS, and on general cardiovascular risk factors.

The benefits of love are not limited to an emotional or psychological boost. As studies of growth hormone levels have demonstrated, loving affection evokes recognizable physical changes in the body. The area in which the effect appears to be the greatest is called the hypothalamic-pituitary-adrenal (HPA) axis.

The HPA axis is a complex relationship between the brain, the pituitary gland, and the adrenal glands. The HPA axis oversees the body’s reaction to stress, it regulates the digestion of food, modulates the immune system, affects mood, and determines energy usage. As such, it is critical to the maintenance of good health.

The hypothalamus is an almond-sized area of the brain that links the nervous system to the endocrine system through the pituitary gland. The hypothalamus is critical to the proper functioning of the autonomic nervous system, which controls automatic processes such as breathing, heart rate, and digestive activity.

The hypothalamus manufactures chemicals called neurohormones. Among these hormones are oxytocin and vasopressin, which regulate the activity of the posterior pituitary, and ACTH and TSH, which relate functions of the anterior pituitary.

The pituitary gland is often referred to as the “Master Gland” of the body. It secretes hormones that regulate the activities of other glands throughout the body. These include the adrenal glands, which produce a number of hormones including cortisol, epinephrine, and nor-epinephrine.

Loving affection has been shown to exert positive influences upon the HPA axis in animal studies. The positive effects on blood pressure, immune function, and energy production can explain many of the health benefits that are seen with loving relationships. These benefits appear to accrue from providing loving affection to others as well as from receiving loving affection from others. For example, dog owners who volunteer for the People Animal Connection program appear to receive as much from the program as the patients upon whom it is focused.

If unconditional love conveys essential health benefits, what does it look like and how may it be obtained? It is not as though one can go to a local health food store and purchase love capsules. One cannot obtain a prescription from a physician and fill it at a local pharmacy. Is it practical to search for love, or is obtaining or demonstrating it a random occurrence based purely upon chance?

To answer those questions it is helpful to define love. If we do not know what it is we are seeking, how will we know when we find it? What is the love that protects against failure to thrive, slows the progression of atherosclerosis, and promotes longevity?

The Greek language has four words for love, and they are helpful in defining love as it relates to good health. One is eros. Eros refers to romantic love. It is the origin of the English word erotica. Eros refers primarily to sexual attraction. It is an emotional response. When the word love is used in our society it commonly refers to erotic love. This is not the type of love children are seeking, and I do not believe that it is the kind of love that accounts for most of the health benefits that accrue from long-term relationships.

Storge refers to the natural affection family members have for each other. It is the “blood is thicker than water” love. This is the type of love that is responsible for normal growth in children, and I believe it is the love that accounts for the increased longevity of married couples.

Philia is love between friends. It is “brotherly love”, the kind seen among members of fraternal organizations. Our term philanthropy is derived from this form of love. As in the case of a philanthropic donation the underlying motivation of philia may be a pure desire to support others or it may be selfish, seeking approval or recognition from others.

The fourth Greek word for love is agape. Agape refers to a selfless love that reaches out to others without regard to their appearance or actions. It is an unconditional love that always seeks the best for the object of its affection. Unlike erotic love, that is deeply emotional and comes and goes in mysterious ways, agape is a choice. It results from ones decision to act in a certain way toward others.

Romantic love may be elusive, and, if found, may fade over time. Families may or may not be rich sources of supportive love. Brotherly love may be a source of encouragement, or it may be superficial and fade when challenges come. Unconditional love is stable, not whimsical. It is under one’s conscious control.

The Apostle Paul described the attributes of unconditional love in some of the most eloquent words ever written. Love, he wrote, is patient. It is as willing to walk quietly beside an elderly person who moves slowly with the assistance of a walker as it is to encourage the first faltering steps of a toddler. It is able to encourage a child who is struggling with a homework assignment and not criticize a spouse who gets home late from work or doesn’t have dinner on the table at the appointed time.

Love is kind. It holds open the door for the person carrying a load of packages. It wipes away the tears of the child who has scraped a knee and takes time to apply a bandage. It says “please” and “thank you”.

Love is not jealous. It does not become upset when someone else is receiving attention, nor does it attempt to steal a piece of another’s glory. It rejoices when another does well and receives a reward.

Love does not brag, nor is it arrogant. It is as content to give an anonymous gift as it is to see its name on the marquee. It is content to sing backup or play rhythm guitar if it can help the lead singer shine.

Love does not act unbecomingly. It does not create a scene if a reservation was recorded incorrectly, nor does it berate the person behind the counter if a flight is delayed or cancelled. It awaits its turn at four way stops and doesn’t curse the slow driver in the fast lane.

Love does not seek its own. It is willing to play the game even when another person’s rules are not those to which it is accustomed. It is willing to serve without recognition.

Love is not easily provoked. It doesn’t explode when a glass is tipped over at the table. It doesn’t pick fights, but seeks ways to prevent them.

Love does not take into account a wrong suffered. It doesn’t keep a record of past hurts. It doesn’t bear grudges, nor does it take up the offenses of others.

Love is never glad to see injustice, but it rejoices in the truth. It doesn’t spread rumors, nor does it listen to them. It is sad when someone is falsely accused of doing wrong, even if he or she is a member of the opposite political party. It doesn’t seek to win on a technicality.

Love bears all things. It helps those who cannot help themselves. It does not seek to take advantage of others, but strives to protect the weak from harm. It is willing to sacrifice so that another can get ahead.

Love believes all things. It does not view people with suspicion. It is willing to give them the benefit of doubt. It looks for the good in others and encourages them.

Love hopes all things. Love is optimistic. It expects things to work out in the end. It wants others to succeed and do well.

Love endures all things. Love never gives up. It never becomes bitter. It doesn’t give in to discouragement, but rather looks for a brighter tomorrow.

Love never fails. Unlike romantic love, which can fade, familial love, which can grow cold, or brotherly love, which can prove fickle, unconditional love remains constant over time. It is permanent. It cannot be destroyed.

As important as the love and support of others is to one’s health, the benefits giving unconditional love are greater. Nothing can deflect stress more effectively. Nothing can make life more rewarding.

Unconditional love is the most powerful healing force in the universe. It may not be amenable to scientific study, but it is infinitely more powerful than the variables that can be measured in a test tube. The good news is that it is not beyond the reach of anyone. It is a gift of God to those who choose to accept it and exercise it.