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date: 20 May 2019

smoking

Source:
Food and Fitness: A Dictionary of Diet and Exercise
Author(s):

Michael Kent

smoking 

Many smokers claim that their habit helps them to relax, but there is no doubt that smoking is harmful to health and has a detrimental effect on athletic performance. Tobacco smoking is a major, preventable factor leading to death. Almost 20 per cent of deaths in the USA have been attributed to diseases associated with inhaling the products of combustion from the tobacco plant, Nicotiana tobacum. These products include nicotine, carbon monoxide, and tars.

The psychological and addictive effects of smoking cigarettes are attributed to nicotine, a drug that stimulates the central nervous system and enhances arousal. Nicotine affects blood pressure and heart rate directly, increasing the risk to smokers of coronary heart disease. It also affects hormone production. For example, cigarette smoking lowers blood oestrogen levels and therefore reduces bone mineralization. When inhaled, the carbon monoxide passes into the bloodstream where it combines with haemoglobin, reducing the ability of blood to transport oxygen. Among heavy, chronic smokers the reduction may be as much as 10 per cent, reducing their ability to take part in strenuous exercise, and accounting for the breathlessness experienced by most smokers. Tars inhaled during smoking are microscopic, organic substances which can stick onto cells in the lungs. Some tars release free radicals that may be carcinogenic and increase the risk of lung cancer. The high production of free radicals in smokers may explain why they break down vitamin C faster than non-smokers (vitamin C is one of the antioxidants that mops up free radicals). It is estimated that the vitamin C requirements of smokers may be twice as much as non-smokers. In the UK, the RNI for adult non-smokers is 40 mg but smokers require more vitamin C (possibly as much as an extra 80 mg); in the USA, the RDAs are 60 mg for non-smokers and 100 mg for smokers.

Smoking is highly addictive. Smokers who try to give up may suffer withdrawal symptoms including a persistent craving for tobacco, irritability, poor concentration, and weight gain. The weight gain is popularly attributed to eating more to compensate for the lack of oral gratification provided by smoking. However, the gain may also be due to metabolic changes because nicotine increases metabolic rate, particularly during exercise. It is sensible for ex-smokers to moderate the effects of weight gain by increasing their aerobic activity. They should also control their feeding habits carefully. For example, snacks should consist of nutritious, low calorie foods such as raw vegetables and fruit.