Many people think about health in terms of physical health and longevity. (See the section on Nutrition for more information about physical health).
Being vegan is more expansive than our physical health. It is also important for our psychological wellbeing, and for our social and emotional relations with each other. As you are becoming aware, animal rights (and therefore veganism) is the most important social justice issue of our time. Social justice is an essential component of healthy functioning for everyone, at many interrelated levels.
The Power of Compassion, (Higgins, S in How to be Happy and Healthy, The Seven Natural Elements of Mental Health, Second edition, ed Halpin, M. Ashfield Press: Dublin).
Educating ourselves on the harm we cause to other animals when we use them reveals shocking information that has the potential to traumatise. Yet, at some level the information is not new. The depths of the horrors we inflict on other animals might be new, but everyone is aware that animals are killed so that we can use them. While the information about suffering on smallholdings or organic farms might be new, few people are unaware of the horrific conditions on factory farms.
We are not unaware; information on the suffering of other animals is not in our unconscious minds; rather it is in our subconscious minds. In order to continue using other animals without causing ourselves psychological stress and anxiety, we have to suppress that knowledge.
Continually suppressing that knowledge does not make for good psychological health. It is a waste of our mental energy and it prevents us living the truth. Many new vegans describe a type of lightness or a sense of peace as there is no need to hide from the consequences of their lifestyle.
As long as we sanction harm against defenseless, sentient others, we will live in a violent society that is predicated on inequality. Evidence suggests that the rate of violent crime (as measured in arrest rates for violent crime, rape and sex offences) is higher in slaughterhouse employees than in other industries and that this is directly attributable to the violent nature of slaughterhouse work (Fitzgerald et al, 2009).