Asthma, allergic rhinitis and chronic obstructive pulmonary disease, all caused by serious respiratory inflammation, affect millions of people across the world and there are about 15-20 million in India affected by these ailments.They are simply air pathway obstruction reversible by either spontaneously on their own or by treatment with medicines like beta agonists, corticosteroids or prednisolone. Typical signs include wheezing, prolonged expiration, rapid heart rate and some murmuring sound in the lungs. During severe attacks one can turn blue from lack of oxygen, experience some chest pain and loss of consciousness. Basic measurement of peak air flow rate can indicate whether one is suffering from such ailments. Stimuli for asthmatic and similar respiratory inflammation include allergens like house mite, cockroach, grass pollens, mold spores, pet epithelial cells, indoor air pollution, volatile organic compounds, perfumes, soaps, detergents, shampoo, hair sprays, lotion, paints, medications like aspirin, milk, peanuts, eggs, ozone, nitric oxide, sulfites, chlorine, hormonal changes, psychological stress, cold weather and exercise. Pathologically, the mucus glands in the airway get overdeveloped and respiratory passage progressively thickens due to scarring and frequent inflammatory conditions. Narrowing of the airway in the lungs caused by the tightening of the surrounding smooth muscles leads to bronchoconstriction.
Some of the phytochemicals present in cruciferous vegetables like broccoli have been identified as possible cure for asthma as they reduce the inflammation of the air pathways significantly. It was known that cruciferous vegetables are rich in sulfur containing organic compounds with many beneficial effects in human body and one of the major findings of the last decade was the presence of the isothiocyanate, Sulforaphane in these vegetables which has anti-cancer and anti-inflammatory properties. Besides they also contain Phenylethyl isothiocyanate (PEITC) and Indole-3-Carbinol(I3C), both with antioxidant properties capable of protecting against onset of many forms of cancer in humans. These chemicals have the potency to induce the activity of Type 2 detoxification enzymes which provide a defense mechanism triggering broad spectrum antioxidant activity that neutralize many free radicals responsible for cell damage and consequent mutation leading to cancer. Same hold good for inflammation of respiratory tract also and Sulforaphane triggers an increase in the level of antioxidant enzymes in the human airway. Increased activity of these enzymes offers protection against the onslaught of free radicals that one breathes every day in polluted air, pollens, diesel exhaust, tobacco smoke, etc. Free radicals, being supercharged forms of oxygen cause oxidative tissue damage resulting in inflammation and respiratory conditions like asthma.
Broccoli contains about 60 mg of Sulforaphane per serving. but three day old Broccoli sprouts are considered richest source of this chemical, the levels being 50-100 times higher than that in the vegetable. Glucoraphanin(SGS), a glucosinolate by nature, is the precursor of Sulforaphane which is formed by the action of the enzyme Myrosinase present in the cells. There appears to be some confusion as to whether SGS itself can induce the antioxidant enzymes or it has to be Sulforaphane, a product of Myrosinase enzyme action. If Sulforaphane is the real active principle, cooking of the vegetable will certainly inactivate the enzyme Myrosinase blocking the generation of Sulforaphane from SGS. There are Broccoli sprout extract tablets in the market made of a mixture of dry extract and Myrosinase enzyme extracted from watercress which on reconstitution or chewing is supposed to generate Sulforaphane. How far they are effective is not known.
Another issue that needs clarity is regarding the effectiveness of regular consumption of broccoli and other cruciferous vegetables, containing relatively low levels of SGS as compared to Broccoli sprouts. Probably to get the same effect one may have take more than 200g a day which may not be practical. This raises a fundamental question regarding the desirability of cooking of vegetables like Broccoli, if the active principles are destroyed at cooking temperatures. Some argue that the best way to get the full impact of the chemoprotectants in vegetables is to process them into fresh juice for consumption but one has to reconcile to loss of dietary fiber which will be left behind in the residues. Consumers will wonder whether such scientific studies could bring out more comprehensive, definitive and practical findings proven by clinical studies with large subjects so that they can practice what is preached with least reservation.