Incorporating vegetables naturally high in nitrates into the diet can help lower blood pressure in patients with hypertension as they relax the blood vessels.
There are several studies that suggest that over-consumption of nitrates in the form of preserved meats, are linked to cancer. It is not a simple issue but in general vegetable and fruit sources of nitrates are considered healthy whereas preserved meat sources are not. 70-80% of human consumption of nitrates is thought to be from plant sources as well as from water.
Nitrates (and their precursors nitrites) are both naturally occurring substances and are produced by living cells. They’re involved in many important chemical reactions in the body. In themselves they are not dangerous, but they can react with other compounds found in food or in the body to form carcinogenic compounds
called nitrosamines. These reactions are more likely to occur in the presence of protein, which is why preserved meats can be problematical.
The formation of nitrosamines is much less likely in the presence of antioxidants such as vitamin C which is found in vegetables. This is thought to be one reason why a diet high in vegetables is good for the heart and is helpful in lowering the risk of certain cancers.
CAUTION In early life nitrate-rich foods can cause blue baby disease (methemoglobinemia). They are fine for babies over 4 months of age, but spinach and beetroot should be fed in moderation until the infant reaches the age of one year. Symptoms of blue baby syndrome are shortness of breath, the skin will turn blue due to lack of oxygen in the blood) and the baby may lose consciousness.