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All about vitamins, minerals and Tortoises

A C Highfield

There is a great deal of misunderstanding concerning the role of vitamins and minerals. Many people believe that the more you get of both the better - this is categorically not true, indeed, some vitamins and minerals can be positively dangerous if taken in excess. What is actually required is a balanced intake of essential vitamins and trace-elements - not massive doses of individual vitamins in isolation which serve only to upset the balance and may cause relative deficiencies elsewhere.
It is also important to dispense with the myths, common among tortoise keepers, that vitamin deficiencies are the cause of a great deal of frequently encountered diseases or that a vitamin injection is necessary to assist with hibernation. Both claims are totally incorrect. In fact, genuine cases of primary vitamin deficiency (that it a deficiency caused by a lack of the vitamin in the diet rather than as a consequence of inability to metabolise the vitamin due to some other health problem) are quite rare. In the last 7 or 8 years we have encountered maybe 5 or 6 cases of primary vitamin deficiency in tortoises. In all of the cases we have seen, the base-line diet of the animals concerned was by any standards grossly inadequate and limited in range. There is virtually no chance of vitamin deficiencies occurring in tortoises which are fed on a well balanced, varied diet.

There are two common ways in which additional vitamins may be given:

Oral vitamin supplements

These are useful as a guarantee that all necessary vitamins are being supplied - but again, they are not essential if the base-line diet is of high quality and is sufficiently varied. Animals on natural browse do not need vitamin supplements, although calcium supplements may still be necessary.

Vitamin injections

These should only be used to deliver specific vitamins in cases where a specific vitamin deficiency is known to exist. We are totally opposed to the routine use of vitamin injections - in most cases, they serve no useful purpose and indeed are a frequent cause of introduced infection via the injection site. Very few deficiencies are so acute that the much more effective and safer oral delivery route is not a satisfactory mode of treatment. Acute vitamin-A deficiencies may be dealt with by injection, but few other cases require this treatment. The use of a routine "vitamin booster" before or after hibernation is a complete waste of time.


Many people are unclear as to the difference between vitamins and minerals, and especially about how the two interact (many minerals, calcium for example, depend upon the presence of certain vitamins such as vitamin-D before they can be absorbed).

Vitamins are organic substances which help regulate bodily functions. Acting as co-enzymes, vitamins aid the action of enzymes during the metabolism of dietary nutrients. There are about a dozen major vitamins, a deficiency of any one of which will result in a serious deficiency disease. Vitamins are only required in relatively small quantities, but have a major effect upon the body's reproductive, digestive, nervous and muscular systems. Vitamins also affect tissue growth and anti-body production.

Some important vitamins are:


Important to the condition of the skin and mucous membranes, eye (especially retinal) condition, biochemical and reproductive functions. Plants contain carotene which is converted to true vitamin-A in the body.


The B-complex vitamins are water soluble and excesses are excreted in the urine. Vitamin B1, thiamine, is a regulator in the carbohydrate metabolism; Vitamin B2, riboflavin, is a co-enzyme in energy release and interacts with vitamin B6 and vitamin B12; Vitamin B3, niacin, is also crucial to the energy metabolism and is often obtained by converting the amino-acid tryptophan - this process requires the presence of thiamine, riboflavin and pyridoxine; Vitamin B6, pyridoxine, is involved in energy conversion from glycogen and in the synthesis of haemoglobin and antibodies; Vitamin B12 interacts with folic acid to govern the production of red blood cells. A deficiency causes pernicious anaemia and neurological symptoms. This vitamin is only produced within the gastro-intestinal tract when various micro-organisms act upon trace level cobalt. Deficiencies can occur following malabsorbtion syndrome or as a consequence of severe parasite infestations. The B-complex is just that. A matrix of interacting and inter-dependant compounds.


Sometimes called 'the sunshine vitamin', vitamin-D is a fat soluble vitamin which is essential to the absorption and utilisation of calcium and phosphorous, as such, it plays a major role in bone formation. It can be obtained either naturally, by the action of ultra-violet light on sterols in the skin, or orally by supplementation - virtually all specialist calcium/mineral supplements intended for reptile use contain vitamin D in sufficient quantity.


Vitamin-C has many functions, but as it is present in almost all fruits and green vegetables, deficiencies are extremely unlikely in tortoises.


Many plants contain vitamin-E which is an antioxidant and works in conjunction with vitamins A and C.


A fat-soluble coagulation vitamin. This vitamin is synthesised in the gut by bacterial action and is also found in plant foods. It is especially abundant in green, leafy plants.


Minerals are quite different from vitamins and are both chemical regulators and construction materials - Calcium forms a major part of a tortoise's body, more than any other mineral. Calcium deficiency is also extremely common as a growing tortoise requires substantial quantities of this mineral in order to build its skeleton.
The building of healthy bone tissue is the result of many vitamins and minerals acting in cooperation with each other.
It is essential to note that calcium is poorly absorbed by the body whereas phosphorus is readily absorbed - if a diet is heavy in phosphorus in relation to calcium, the excess phosphorus will prevent the uptake of calcium to the bone. It is very easy to feed a diet too concentrated in phosphorus because it is available in nearly every foodstuff whereas calcium is relatively rare. We must knowingly choose calcium bearing foods when designing diets for captive animals.
Calcium and phosphorus together account for three-fourths of the mineral elements in the body, and five other elements account for most of the rest. It is important to note that their actions are interrelated; no one mineral can function without affecting the others.
The major function of calcium is to act in cooperation with phosphorus to build and maintain bones. Calcium is essential for healthy blood and also helps to regulate heartbeat. In addition, calcium assists in the process of blood clotting and helps prevent the accumulation of too much acid or too much alkali in the blood. It also plays a part in muscle growth, muscle contraction and nerve transmission. Calcium aids in the body's utilization of iron, helps activate several enzymes (catalysts important in metabolism), and helps regulate the passage of nutrients in and out of cell walls.
Calcium absorption is very inefficient. Two factors effect absorption directly; the availability of calcium in the diet and the current body need. Unabsorbed calcium is excreted.
Certain substances interfere with the absorption of calcium. When excessive amounts of fat combine with calcium, an insoluble compound is formed which cannot be absorbed. Other substances that can disrupt this process include oxalates and phytic acid.


Phosphorus is the second most abundant mineral in the body. It functions along with calcium. A balance of calcium and phosphorus is needed for these minerals to be effectively used by the body.

Phosphorus plays an important part in almost every chemical reaction within the body. It is important in the utilization of carbohydrates, fats and protein for growth, maintenance, and repair of cells and for the production of energy. It aids in the transference of heredity traits from parents to offspring. It is also necessary for proper skeletal growth, kidney function and transference of nerve impulses.
If phosphorus content is high, additional calcium must be taken to maintain proper balance. Phosphorus is available in a wide variety of foods and further supplementation is not necessary.

Miscellaneous trace elements

Calcium, chlorine, phosphorus, potassium, magnesium, sodium, and sulfur are present in relatively high amounts in the body tissues. Other minerals are present in the most minute quantities but are essential for proper body functioning. Iron, copper, and fluorine are present in sufficient quantities from deep green leafy plants. Iodine is needed to maintain a positive calcium balance, so a multi-mineral mixture containing iodine should be provided in addition to supplementation of raw calcium.


Try to ensure that all diets are as varied as possible - in this way, a wide cross-section of trace elements will be made available.
Do not dose with 'pure' vitamins unless under veterinary direction - some pure vitamins (such as vitamins A & D are highly toxic if taken in excess). These should only be used as part of a treatment program to correct a properly diagnosed specific deficiency.

Provide vitamins orally rather than by injection for preference.

The regular use of a safe, properly formulated multi-vitamin and mineral preparation will ensure that dietary deficiencies do not occur.

Aim for a high calcium - low phosphorous

balance in tortoise diets