Citrus Fruits

Oranges, grapefruits, lemons, limes etc. are one of the most concentrated sources of vitamin C. Vitamin C increases the number of chemical messengers - specially interferon - which are vitally important in the process of fighting infection.
Antibiotics are powerless against cold which is caused by a virus. A three day high anti oxidant diet may help zap it out.
D - limonene, in citrous skin, can leach into the juice and may detoxify cancer promoters.
Carotenoids may also fight cancer which is present in the above foods.
Another phytochemical - flavonoids act as antioxidant and may inhibit blood clotting.
These fruits are rich in vitamin C (a powerful antioxidant) and fibre.