VITAMINS

The basic nutrients of food include carbohydrate, protein, fat, vitamins, and minerals. The body needs to obtain appropriate vitamins from food to maintain the normal functions of cells and organs, and to promote growth and development. Any lack or excess amounts of vitamins in the body may have side effects.

Functions and Categories

• Vitamins have various functions that help to regulate metabolism, to prevent chronic diseases (such as heart disease and cancer), and to maintain normal appetite, mental health, and immunity.
• Vitamins can basically be classified into the following two categories:
  

  (1)	Fat-soluble vitamins
  	* Include Vitamins A, D, E and K; dissolve in fats; and are absorbed with the help of fats that are in the diet * Excessive fat-soluble vitamins are stored in the liver and will not be eliminated from the body
  (2)	Water-soluble vitamins
  	* Include Vitamins B and C, and dissolve in water * Excessive amount of water-soluble vitamins are excreted through urine and sweat.

  
  
• The amount of vitamins in food is affected by the ways in which food is stored or cooked. Vitamins A and C and some Vitamins B can be destroyed under strong light, so food rich in those vitamins should be stored in dim places or in the fridge.
  
• Vitamin C and some Vitamins B are soluble in water and can be destroyed under heat, and thus we should avoid
  
  1. washing them too much
     
  2. cooking them too long time
  
  

Vitamin	Function	Food sources	Symptom of deficiency	Symptom of excess
Vitamin A	Maintains eye health Promotes growth and development, maintains healthy bones and teeth Enhances the protection and regeneration of cells and mucous membrane Maintains healthy respiratory and intestinal tracts Maintain healthy hair, nails and skin	Dairy products, cod liver oil, liver, dark green and yellow vegetables and fruits	Night blindness, dry eyes Dry skin Stomach discomfort Poor growth Weak bones and teeth	Dry, scaly, peeling, and itchy skin, rash Hair loss Poor appetite, fatigue Vomiting, stomach discomfort Liver injury Headache, bone pain Nervousness, irritability
Vitamin D	Helps body absorb and utilize calcium and phosphorus, so as to maintain bones, teeth and brain healthy Maintains normal calcium level in blood	Egg yolk, liver, cod liver oil, fish. Our skins also produces Vitamin D when exposed to sunlight	Children: rickets Adults: osteoporosis	Calcified cartilage High calcium level in the blood causes abnormal heart beat and damage to organs such as kidneys Vomiting, diarrhea Sore eyes Itchy skin
Vitamin E	Maintains normal conditions of cells, and healthy skin and tissues Protects red blood cells Antioxidation Enhance immunity	Green leafy vegetables, whole-wheat cereals, nuts, egg yolk	New born infants: haemolytic anaemia Adults: weakness	Low thyroxine level Headache, dizziness, fatigue Stomach discomfort, poor appetite
Vitamin K	Helps blood clotting, prevent over bleeding Maintains health of the liver	Green leafy vegetables, soya beans. The human body can also produce Vitamin K through germs in the colon	Uncontrol bleeding from wounds due to clotting difficulty	Can lead to liver damage
Folic acid	Helps produce cells and red blood cells Promotes growth and reproductive functions	Dairy products, liver, whole-wheat cereals, beans, banana	Anaemia Decreased immunity Fatigue Stomach discomfort	Uncommon
Vitamin B1	Helps carbohydrate and protein metabolism, thus enabling the body to get energy from food Helps maintain normal function of the heart, muscles and digestive system Promotes growth and development	whole-wheat cereals, fish, meat, various vegetables, beans, yeast	Beriberi Listlessness, insomnia, vomiting Nervous system problems, depression Growth retardation in children	Uncommon
Vitamin B2	Helps in carbohydrate, protein and fat metabolism, enables the body to get energy from food Maintains healthy mouth, lips, tongue, and eyes Maintains healthy skin, hair and nails	Dairy products, eggs, meat, green leafy vegetables, liver, whole-wheat cereals, nuts, yeast	Inflammation of the oral cavity, mouth corner and tongue Itchy, dry and bloodshot eyes Dry skin Weakness	Uncommon
Vitamin B3	Helps in carbohydrate and fat metabolism, enabling the body to get energy from food Regulates cholesterol level Maintains healthy skin, mucous membranes, tongue and the digestive system	Dairy products, fish, meat, poultry, vegetables, whole-wheat cereals	Dyspepsia Rough and inflamed skin Listlessness	Stomach discomfort, vomiting Listlessness, headache, fatigue
Vitamin B6	Helps in protein metabolism Helps produce red blood cells, hormones, enzymes and antibodies Helps in transmission of nervous impulse	Dairy products, meat, whole-wheat cereals, green leafy vegetables, fish	Anaemia Nervousness, insomnia, depression Muscle cramps	Limb numbness, partial loss of sensation
Vitamin B12	Helps produce red blood cells Maintains healthy nervous system Promotes appetite Helps in protein metabolism	Dairy products, fish, eggs, liver, meat	Anaemia Slowness in thinking, emotional chaos, poor memory Weakened sensation	Uncommon
Vitamin C	Helps synthesize collagen; promotes the growth and repair of cells, gum, teeth, blood vessels and bones Helps healing after operation and injury Helps calcium and iron absorption Enhances immunity	Citrus fruits (mandarin, orange, grapefruit, lemon), strawberry, black current, kiwi fruit, tomato, green leafy vegetables, green pepper	Scurvy Gum inflammation and bleeding, fall of teeth Susceptibility to skin bleeding, burst of capillary vessels Weakness, fatigue Bone pain, swollen and aching joints	Abdominal pain Diarrhea Kidney stone

Should we take vitamin supplements?

There are various kinds of vitamin supplements available on the market. Should we take these "tonics" to maintain good health?
We should maintain a balanced diet and should not be food picky. Food Pyramid provides general guideline for healthy eating and you will absorb sufficient and appropriate vitamins from your daily intake. There is no need to take extra nutritional supplements to stay healthy.
If you need to have diet control because of any diseases, you should consult a doctor or dietitian. Never take any vitamin pill or supplement on your own.