Acidic food means usually foods that make our bodies shift to be acidic media especially blood pH become more acidic and as well known cancer cells grow very quickly in acidic pH as well as pathogens also any disease can propagate easier in acidic media

Refer: pH Gradient reversal: An Emerging Hallmark of Cancers.

http://www.chimachine4u.com/AA.html

An acid body is a magnet for sickness, disease, cancer and aging. Eating more alkaline foods helps shift your body's pH and oxygenates your system. Alkaline foods keep your body healthy and functioning correctly, preventing and combating cancer.

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