1.8 Test your learning
The following activities relate to the whole of this section about vitamins.
Use Table 1 to identify which vitamins are likely to be lost (a) when a piece of frozen beef is defrosted and the water, some of which comes from inside the meat, is thrown away and (b) when fat drips from meat during the roasting process.
(a) Any of the water-soluble vitamins could be lost in the water that drips from the thawed beef. The water-soluble vitamins found in beef are niacin (vitamin B3 ) and some vitamin B12 and pantothenic acid (vitamin B5 ).
(b) The fat-soluble vitamins could be lost in the fat that drips from the meat during cooking, but beef contains very few of the fat-soluble vitamins, just perhaps a small amount of vitamin K.
Which vitamins can be synthesised by cells in the body?
Which vitamins are groups of compounds?
Which three vitamins act as antioxidants? Are any of these synthesised in the body?
Vitamin D can be made in the skin, provided that it is exposed to sufficient sunlight. Vitamin A can be made from β-carotene in the diet, obtained from carrots and from dark green leafy vegetables. Niacin (vitamin B3 ) can be made from the amino acid tryptophan.
Vitamins A, E and K are groups of compounds, as is the vitamin B complex, through the members of this group are given separate names.
Vitamins A, C and E are the vitamins that act as antioxidants. Vitamin A can be made from β-carotene (see above), but the others must be obtained through the diet.
Devise a table to show the similarities between the following pairs of vitamins: (a) riboflavin and niacin; (b) folate and vitamin B12; (c) vitamins E and C.
Consider their sources, functions and signs of deficiency.
Table 3 The similarities between some pairs of vitamins
|Vitamins||Sources||Functions||Signs of deficiency|
|(a) riboflavin and niacin||Both found in milk and eggs.||Both involved in cell metabolism.||Both affect the skin. Riboflavin deficiency causes cracks around the mouth, etc. and niacin deficiency causes dermatitis (one of the symptoms of pellagra).|
|(b) folate and vitamin B12||Both found in yeast extract and breakfast cereals.||Both important in cell division.||Both deficiencies result in anaemia. Folate is linked to megaloblastic anaemia and vitamin B12 to pernicious anaemia.|
|(c) vitamins E and C12||Both found in some vegetables.||Both act as antioxidants by destroying free radicals.||No clear symptoms related to vitamin E. Lack of Vitamin C causes scurvy.|
A mother of three children under 5 is concerned that she is not giving them a balanced diet, since they mostly eat prepared convenience foods. What foods would you suggest that she introduces to their diet to boost their intake of vitamins?
A bowl of cereal with milk at breakfast time, together with eggs sometimes and fresh fruit regularly eaten at other meals would provide a good source of almost all the vitamins. Additionally, introducing some fresh, easy to prepare vegetables, such as broccoli, into their diet would be beneficial.
Have a look at labels on food packets, tins, etc., to see which have information about vitamins. Can you tell whether the food contains the vitamins naturally or whether they have been added by the manufacturer (fortified)?