CIGARETTE SMOKING
Cigarette smoking is an important cause of death worldwide, accounting for more or less 5 million of the 57 million deaths globally, primarily through heart attacks, strokes and lung disease. In South Africa, smoking accounts for more than 25 000 deaths per year - roughly 5% of the total deaths.
The increased health risks associated with cigarette smoking are well-known and diseases which can be related to this risk include coronary heart disease, cancer and chronic obstructive pulmonary disease, which are among the major killers worldwide. In order to understand this increased risk better, it is necessary to refer to a process called oxidative stress. Oxidative stress is a process during which oxygen triggers the formation of oxidant compounds and free radicals, which have the ability to cause destructive changes in the body. These changes are suspected of initiating some of the early stages of many diseases, including cancer and heart disease.
Cigarette smoke contains an abundance of free radicals and other oxidants. Smokers therefore have a significant exposure to oxidative stress and this may be one of the pathways through which smoking contributes to the development of disease. The direct exposure from cigarette smoke, however, represents only a portion of the oxidative stress experienced by smokers. Emerging evidence indicates that cigarette smoke also contributes to additional oxidant formation in the body through effects on the inflammatory –immune response.
The word ‘antioxidant’ is well-known to most health-conscious individuals. In essence, antioxidants are nutrient substances which prevent the formation of excess harmful oxidants and free radicals in the body. In this way they impede the process of oxidative stress and prevent damage. Some micronutrients (vitamins and minerals) act as antioxidants and represent one line of defense against oxidative stress, such as that which stems from smoking. These micronutrients consumed in the diet may thus act to diminish some of the adverse effects of cigarette smoking. Antioxidant micronutrients that have been the topic of research in relation to smoking are vitamin C, vitamin E and carotenoids.
Vitamin C, also known as ascorbic acid, is a water-soluble vitamin and is essential for normal functioning of the body. Unlike most mammals, humans do not have the ability to produce their own vitamin C and, therefore, must obtain it through their diet. Apart from its antioxidant capacity, vitamin C may also be able to reactivate other antioxidants, such as vitamin E, so that they can be reused by the body. This vitamin is also involved in several enzyme systems for the synthesis of collagen (connective tissues, cartilage, teeth and skin), healing of wounds and conversion of nutrients into their functional forms. Furthermore, vitamin C is essential for immune system function, promotes resistance to infection, protects lung function, and enhances iron absorption from non-haeme food sources, which is found primarily in fruits, vegetables, dried beans, nuts and grain products.
When comparing smokers with non-smokers, evidence consistently indicates that current smokers have lower blood levels of vitamin C. Additionally, studies have shown decreasing vitamin C levels as the number of cigarettes smoked per day increases.
HOW DO WE EXPLAIN THIS DECREASE IN THE BLOOD LEVELS OF VITAMIN C?
One of the reasons smokers can be expected to have lower blood levels of antioxidant micronutrients is based on the simple observation that smokers tend to eat less healthy diets than non-smokers in general, and also specifically tend to consume fruits and vegetables, the major sources of vitamin C less frequently, than non-smokers.. However, this observation alone cannot fully explain the documented lower blood levels, since reduced blood vitamin C levels in smokers are present, even when adjustments are made for differences in vitamin C intake. More recent research findings indicate that the exposure of blood plasma to cigarette smoke depletes vitamin C present in the plasma. Essentially though, the complex interrelationships between smoking and dietary patterns and between dietary patterns and blood levels of vitamin C and other antioxidant micronutrients remain to be fully elucidated and specific mechanisms and pathways need to be clarified.
SMOKERS NEED MORE VITAMIN C
The Institute of Medicine, Food and Nutrition Board in the USA, have formulated the Dietary Reference Intakes (DRIs) with the aim at maximizing health and improving quality of life, which includes the reduction of risk of chronic disease. In view of the relationship between smoking, vitamin C and chronic disease risk, an additional intake of 35mg/day above the DRIs for gender and age has been recommended for individuals who choose to smoke, based on the available data (Table 1).
With prevention being an obvious better alternative than cure, it is clear that the focus and emphasis should be on interventions to stop and discourage cigarette smoking and in doing so, to promote a healthier lifestyle. However, since many people worldwide find it very difficult to stop smoking, it would be prudent to recognize the important interaction between smoking and vitamin C, and to act proactively according to current recommendations by increasing the dietary intake of this vitamin. Good food sources of vitamin C include citrus fruit, strawberries, tomatoes, peppers, cabbage, guava, potato, paw-paw and broccoli.
Smoking and Vitamin C
Scurvy Science – Antiscorbutic Foods and Vitamin C
What is scurvy?
Scurvy is a disease caused by lack of vitamin C in the diet, causing symptoms of bleeding gums, painful joints and raised red lesions on the skin. Vitamin C is used along with an enzyme in the body to produce collagen. Collagen is like a protein ‘glue’, holding tissue together, especially when healing wounds. When collagen production is low due to vitamin C deficiency, tissues break down and severe cases of scurvy can result in death.
History of scurvy treatment on sea voyages
Many sailors died from scurvy on long voyages, until ship captains experimented with different types of food. On long sea voyages, they needed to carry preserved food rather than fresh food to prevent supplies from rotting. These preserved foods (such dried ship’s biscuit) contained low levels of vitamin C, so scurvy often developed in the crew. Certain foods called antiscorbutics, with high concentrations of vitamin C were experimented with during long voyages.
Vitamin C breaks down easily, particularly in warm environments, on exposure to air and in alkaline environments (such as during cooking). This caused problems during long voyages as the antiscorbutics gradually lost their nutritional value during storage.
Eventually, the Dutch, Germans and British worked out how to eliminate crew deaths from scurvy. The Dutch and Germans served 500 grams of raw or boiled sauerkraut per crew member twice a week. This seemed to be enough to ward off scurvy and was served more frequently when scurvy symptoms surfaced. James Lind from Scotland concluded in 1753 that lemon juice was an effective cure for scurvy and James Cook was renowned for convincing his crew to eat sauerkraut. Cook used a little psychology in persuading his crew to eat the sauerkraut by suggesting that it was only good enough for the officers. So, the lower ranked crew insisted that they should also receive a ration of sauerkraut!
Although they were not aware of the existence of vitamin C during the 18th century, they understood that antiscorbutic foods prevented the development of scurvy. Green vegetation such as grass was also collected on stops along the way to supplement their diet and were important supplies of vitamin C. For example, while Cook circumnavigated New Zealand in HMB Endeavour, they often stopped to collect wild celery and scurvy grass (Lepidium oleraccum), which were viewed as antiscorbutics. They also ate the young hearts of the cabbage palms (Cordyline australis) which contains significant amounts of vitamin C.
Antiscorbutics carried on HMB Endeavour included: malt, sauerkraut, marmalade of carrots, mustard, portable soup, rob of lemon and orange. The malt infusion was thought to be a good treatment for scurvy, but modern measurements show that it has a very low level of vitamin C. Rob of lemon is simply concentrated lemon juice. It was used sparingly on those who showed symptoms of scurvy. While limes and lemons have good vitamin C content, it tends to break down easily and degenerated over the course of the voyage.When sailing on HMS Resolution I and II, Cook stocked the same antiscorbutics as he had on HMB Endeavour. The malt was hopped on board and allowed to ferment into wort and evaporated into a thick syrup. The wort was mixed as one part to ten parts of water to form beer. Weekly antiscorbutics served included fermented or fresh cabbage and reconstituted portable broth with peas. The portable broth was reconstituted from a stored thick gel and cut with boiling water.
Vitamin C levels of foods
Listed below are the Vitamin C contents of foods which would have been consumed during a typical voyage. Values are in milligrams per 100 grams of food.
Lemon (raw, peeled) = 48mg
Lemon juice concentrate = 230mg
Lime (raw, peeled) = 47mg
Sauerkraut = 10 to 15mg
Cabbage (white, raw) = 45mg
Cabbage (unsalted, boiled) = 36mg
Biscuit (oatmeal, wheatmeal) = 0 mg
Malt = 0.1mg
Whiting (fish raw or steamed) = 1mg
The biochemistry of scurvy
When the body does not have enough vitamin C, collagen is not produced properly. This causes blood capillaries to haemorrhage blood and cause weakness and joint pain. Raised red spots on the skin turn into lesions after five months of a lack of vitamin C. Teeth become loose and gums bleed – making it difficult to eat. Eventually – the body’s tissues break down and the sufferer may die. As well as preventing tissue breakdown, vitamin C helps the body to absorb iron. While vitamin C has been popularly suggested to prevent colds and flu, it has not yet been scientifically proven.
The chemical name for vitamin C is ascorbic acid. Ascorbic acid is water soluble and is absorbed into the blood in the upper part of the small intestine and excreted in the urine.
Humans need less than 300mg of vitamin C stored in their body before scurvy will develop. Depending on age and pregnancy, recommended vitamin C intakes range from 30 to 95mg per day. Vitamin C poisoning can occur in humans if too much is consumed. The upper safe limit is about 2 000mg for adults.
Normally, ascorbic acid is synthesised from simple sugars by plants and most animal species. Only humans, monkeys, guinea pigs, fruit eating bats, and two species of Indian birds do not have the enzyme to produce vitamin C or ascorbic acid and must obtain it from their diet.