While both whole lemons and lemon juice provide various vitamins and minerals, whole lemons are also a source of dietary fiber, notes Sara Ipatenco for SFGate. Other than this difference, both provide the body with vitamin C and limonoid compounds.
One whole lemon provides the body with 2.4 grams of dietary fiber, reports Ipatenco. The average human needs at least 20 grams of fiber daily, and a diet rich in fiber can prevent hemorrhoids and constipation. In addition, increased fiber intake can reduce the risks of diabetes and heart disease. Both whole lemons and lemon juice are sources of vitamin C. Vitamin C plays a pivotal role in the immune system and is required for healthy skin, blood vessels, teeth and gums. Lemons, like all citrus fruits, are a source of limonoid compounds, which give fruits their bitter taste and also have cancer-fighting properties. These organic compounds prevent cancer by protecting cells from damage. A 2004 study also found limonoids stunt further growth of oral tumors and prevent the propagation of new tumors.
Exercise caution when ingesting large amounts of lemons or lemon juice, adds Ipatenco. The acids in lemons can eat away at tooth enamel, leaving the teeth susceptible to decay. Eating whole lemons or drinking undiluted lemon juice causes the most damage; use a straw when drinking lemon beverages.