Another misconception of the Warburg Effect is that cancer cells can only use glucose. This is not true. There are two main molecules that can be catabolized by mammalian cell — glucose, but also the protein glutamine. Glucose metabolism is deranged in cancer, but so is glutamine metabolism. Glutamine is the most common amino acid in the blood and many cancers seem to be ‘addicted’ to glutamine for survival and proliferation.