The fat soluble vitamins consist of vitamins A, D, E and K. As their name suggests, they are soluble in fat. These vitamins are stored in the liver and adipose (fat) tissue – this means that it is not essential to consume them every day though they are still great to have! Having too much of these vitamins can be toxic and supplements are not normally necessary or recommended for healthy individuals. This is different to water soluble vitamins that do not get stored. Eating a healthy diet should not lead to toxicity in healthy individuals.
Deficiency is most common with conditions that interfere with normal fat absorption and as a result, the absorption of A, D, E and K. The table below discusses the function, source and presentation of deficiency for each of the fat soluble vitamins.
Retinol (Vitamin A)
Different forms of Vitamin A include:
Retinol
Retinal
Retinoic acid
Retinyl ester
Function
- Necessary for healthy growth and development
- Aids with good vision, particularly night vision
- Essential in normal development of teeth and bone
- Essential for immune function
- Regulates the expression of genes
- Antioxidant – protects cells from free radical damage
- Embryogenesis – the formation and development of an embryo. Particularly for the spinal cord, limbs, heart, ears and eyes.
- Maintains healthy skin and skeletal/ soft tissue
Source
- Liver
- Full cream milk
- Carrots
- Pumpkin
- Pink grapefruit
- Sweet potato
- Egg yolk
- Dried apricot
- Mango
- Cheddar cheese, ricotta cheese
- Herring
- Spinach and other dark green, leafy vegetables
Deficiency
- Blindness
- Softened cornea (keratomalacia)
- Night blindness (nyctalopia)
- Xerophthalmia – inability to produce tears
- Abnormal development of embryo
- Poor immune system
- Skin disorders – ‘goose flesh’, ‘toad skin’, follicular hyperkeratosis
At risk
- Pancreatitis
- Malabsorption of fat
- Cystic fibrosis
- Laxative abuse
Cholecalciferol Vitamin D3
Function
- Vital for growth and development
- Aids in the absorption of phosphorus and calcium
- Pro – hormone. As the name suggests, this is like a precursor of a hormone
- Helps to maintain healthy skin, muscle strength and immune system
Source
The best source of vitamin D is sun exposure. Small amounts can be obtained from your diet but it is not enough to meet your requirements.
- Herring
- Sardines
- Canned tuna/ salmon
- Fortified margarine
- Egg yolk
- Vitamin D mushrooms
Deficiency
Rickets
Clinical features of Ricket’s include:
- Bone abnormalities e.g. bowing of the legs
- Bone pain, impaired mineralisation of the skeleton
- Osteomalacia (a reduction in the density of bones)
- Tender muscles
- Tetany secondary to hypocalcaemia. This results in the involuntary contacting of muscles.
Tocopherols Vitamin E
Function
- Acts as an antioxidant – protecting poly unsaturated fatty acids from oxidation
- Protect against haemolysis (the early break down of red blood cells)
- Maintenance of epithelial tissue
- Synthesis (production) of prostaglandins – these carry out important functions within the body
Source
Fats and oils are the main source
- Sesame seeds
- Almonds
- Vegetable oil
- Margarine
- Egg yolk
- The fats of meats, fish and poultry
Deficiency
- Disturbances in vision
- Muscle weakness
- Impaired deep tendon reflexes
- Alterations in balance and coordination
Vitamin K
Function
- Helps to produce prothrombin which is responsible for normal blood coagulation (clotting)
- Plays a role in the metabolism of bone
Source
- Liver
- Green leafy vegetables e.g. spinach, kale, broccoli, salad greens
- Vegetable oils e.g. canola, soybean
- Milk
- Menaquinones (synthesised by bacteria)
Deficiency
- Delayed clotting time
- Haemorrhage
- Lipid malabsorption
- Liver disease
- Need to be aware of vitamin K when on Warfarin (medication for blood pressure). Vitamin k can make Warfarin less effective
The above table was adapted from the Griffith Handbook of Clinical Nutrition and Dietetics1
By incorporating foods from each of the vitamin categories, you can work towards achieving a balanced diet. Many of the foods overlap which makes it easier to get a range of vitamins!
References
1. Stewart R.Griffith Handbook of Clinical Nutrition and Dietetics. 4th ed. Queensland: Griffith University; 2011.
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This article was written by our dietitian Belinda Elwin who is a Dietitians Association of Australia member and Accredited Practising Dietitian and Nutritionist.
If you have questions about water soluble vitamins or other nutrition related issues, make an appointment. We‘ll provide you with a simple and effective routine targeted to your concerns. Contact us today.
