Polymyositis & Dermatomyositis Support Group
Polymyositis (PM) is a type of chronic inflammation of the muscles (inflammatory myopathy) related to dermatomyositis and inclusion body myositis. The inflammation is predominantly of the endomysium in polymyositis, whereas dermatomyositis is characterized by primarily perimysial inflammation.
I have noticed that my eating habits and the foods I get to eat have changed over time. I drink a lot of water too.
Regarding your neighbor who uses it for arthritis, it may have helped him if it detoxes one's liver as the article below claims.
http://rootandsprouts.com/benefits-of-lemon-water-according-to-science/
I too was told to avoid grapefruit but nothing about other citrus.