Even when your food intake is good, inefficient digestion can limit your body's uptake of vitamins. Some common causes of inefficient digestion are not chewing well enough and eating too quickly. Both of these result in larger than normal food particle size, too large to allow complete action of digestive enzymes. Many people with dentures are unable to chew as efficiently as those with a full set original teeth.
Habitual drinking of liquids that are too hot, or consuming an excess of irritants such as coffee, tea, pickles and spices can cause inflammation of the digestive linings, resulting in reduced digestive fluids which are minerals from the food we eat.
Drinking too much alcohol is known to damage the liver and pancreas, which are vital to the digestion and metabolism process. It can also damage the lining of the intestinal tract and adversely affect the absorption of nutrients, leading to sub-clinical malnutrition. Regular heavy use of alcohol increases the body's need for the B-group vitamins, particularly thiamin, niacin, pyridoxine, folic aid and vitamins B12, A and C as well as the minerals zinc, magnesium and calcium. Alcohol affects the availability, absorption and metabolism of nutrients.
Smoking, apart from being an irritant to the digestive tract, increase the metabolic requirements of vitamin C all else being equal, by at least 30mg per cigarette over and above the typical requirements of a non-smoker. Vitamin C, which is normally present in such foods as papayas, oranges and bell peppers, oxidizes rapidly once these fruits are cut, juiced, cooked or stored in direct light or close to heat, Vitamin C is important in boosting the body's immunity.
Overuse of laxatives can result in poor absorption of vitamins and minerals from food, by hastening the intestinal transit time. Paraffin and other mineral oils increase looses of fat-soluble vitamins A, E and K. Other laxatives used to excess can cause large looses of minerals such as potassium, sodium and magnesium.
Fad diets that miss out on whole groups of foods can be seriously lacking in vitamins. Even the popular low-fat diets, if taken to an extreme, can be deficient in vitamins A, D and E. vegetarian diets, which exclude meat and other animal sources, must be very skillfully planned to avoid vitamin B12 deficiency, which may lead to anemia.
Lengthy cooking or re-heating of meat and vegetables can oxidize and destroy heat-susceptible vitamins such as the B-group and c, as well as many minerals. Light steaming is preferable. Some vitamins such as vitamin B6 can be destroyed by irradiation from microwaves.
Freezing food containing vitamin E can significantly reduce its levels once defrosted. Foods containing vitamin E exposed to heat and air can turn rancid. Vitamin E is an antioxidant, which protects our tissues from oxidative damage. Other vitamin losses from food processing include vitamin B1 and C. Highly processed refined foods and convenience foods are usually lower in nutrients than unprocessed natural whole foods.
The B group vitamins are essential for the proper functioning of the nervous system. Chemical physical and emotional stresses can increase the body's requirements for vitamins B2, B6, folic acid and C. air pollution increases the requirements of vitamin E.
Some antibiotics, although valuable in fighting infection, also kill of friendly bacteria in the gut, which would normally be producing B-group vitamins to be absorbed through intestinal walls. Such B-vitamin deficiencies may lead to a variety of nervous conditions. Therefore, it may be advisable to supplement with B-group vitamins, or a good multivitamin, when on a lengthy course of broad-spectrum antibiotics.