Information about dietary supplements
Dietary supplements have become a popular part of people’s daily routines with a vast array available on the market. This article discusses important information on the supplementation of vitamins A, D, E and K. This information can help you to make an informed decision when purchasing a supplement.
Table of contents
- What is a dietary supplement?
- Do I need a dietary supplement?
- Fat soluble vitamins
- Are there any negative health effects of taking a dietary supplement?
- Vitamin A
- Vitamin D
- Vitamin E
- Vitamin K
- What to do if you are planning to take a dietary supplement
Dietary supplements come in many different forms such as capsules, pills, drinks and powders [1,2]. A dietary supplement can consist of the following:
- Vitamins e.g. multivitamins, vitamin D, vitamin E
- Minerals e.g. Calcium, iron
- Amino acids
- Herbs and botanicals e.g Echinacea, ginger
In Australia, these products are classed as ‘complementary medicines’, alongside homeopathic and aromatherapy preparations . They are regulated under the Therapeutic Goods Act 1989 . A dietary supplement does not have to undergo the same level of testing for effectiveness as drugs do .
There are strict guidelines that a dietary supplement must follow under the therapeutic goods act (TGA). The product is only able to make claims that the company has been able to verify and no unrealistic expectations of the product are allowed to be made . The TGA as well states that a product must not declare that it is safe or cannot cause harm/ side effects .
Dietary supplements may be useful for individuals with a certain condition that makes it difficult to meet nutritional requirements . They may also be beneficial during some stages in life, for example, women during pregnancy require folate supplements. However, a healthy individual should be able to obtain all of their required vitamins and minerals from a healthy, balanced diet . Additionally, they can be an unnecessary added expense and many foods are now fortified with extra nutrients.
It is important to remember that a dietary supplement may be able to assist in meeting your essential nutrient requirements but they cannot replace a healthy diet that incorporates lots of variety, just as they cannot make up for a poor diet [5,6].
Additionally, dietary supplements do not serve the same purpose as drugs. They should not be used as a substitution for prescribed medication. As a result, they are prohibited from making claims to treat, prevent or cure a disease or illness [4, 7].
Supplementation of the fat soluble vitamins will be discussed in this article.
Fat soluble vitamins consist of vitamins A, D, E and K. They are stored (in the liver and adipose tissue- fat) for longer periods of time than water soluble vitamins and therefore present a greater risk for toxicity, when consumed in excess . However, it is also possible for some diseases and conditions to impair fat absorption and hence the absorption of these vitamins .
Whilst it is uncommon for someone to ingest toxic levels of a nutrient, it is possible. This occurs mostly from supplementation – it is very hard to have too much of a nutrient from dietary means, unless there is an underlying condition.
Important information about the supplementation of fat soluble vitamins is discussed below – this information is based on the current, available evidence and can help you to make an informed decision about taking a dietary supplement.
Background information: Vitamin A comes in the following forms – retinol, retinal, retinoic acid, and retinyl esters.
Beta carotene is part of a group of colour pigments called carotenoids, it can be converted into vitamin A (known as proformed vitamin A). Preformed vitamin A (or retinol) is the active form of vitamin A and does not require conversion.
Toxicity (known as hypervitaminosis A) can occur from excess intake of preformed vitamin A . It is rare for toxicity to occur from diet alone, the main cause is excess consumption of supplemental vitamin A .
Chronic intakes of excess vitamin A can lead to the following symptoms or conditions:
- General symptoms: Intracranial pressure, dizziness, nausea, loss of appetite, blurred vision, headaches, poor muscle coordination, skin irritation, pain in joints and bones, coma and death in severe cases [9, 10].
- Liver abnormalities (abnormal liver pathology) 
- Individuals with pre- existing liver disease, a high alcohol intake, hyperlipidaemia or protein malnutrition may be at a higher risk of accumulating excessive levels of vitamin A . Damage caused to the liver is not always reversible .
- Higher risk of bone thinning/ osteoporosis [10, 12]
- Potentially interferes with the positive roles of vitamin D 
- Teratogenicity (ability to cause birth defects). Pregnant women should not take supplements with high levels of preformed vitamin A .
- Excess beta-carotene intake can lead to carotenodermia (a yellow/ orange tinge to the skin) however this is harmless and reversible [9, 11].
Long-term use of high dose supplements of beta carotene have been shown to have a possible link with lung/ prostate cancer in smokers or previous smokers. Some individuals also believe it may interfere with cancer treatment and recovery from angioplasty (a heart procedure) .
With the exception of these sub groups, large amounts of beta-carotene have not been linked with adverse health effects.
If you decide to take a vitamin A supplement, find one that contains all of its vitamin A or the vast majority of it from beta carotene opposed to preformed vitamin A [12, 11].
It is not recommended that you take vitamin A supplements whilst pregnant or if you have a history of smoking/ asbestos exposure.
- Retinoids – These medications are a synthetic form of vitamin A. Individuals on retinoids should not take additional supplements containing high doses of vitamin A – this can lead to vitamin A toxicity and the symptoms described above .
- Tetracyline antibiotics –vitamin A can interact with some types of antibiotics. Taking high doses of vitamin A along with tetracycline antibiotics can increase the risk of intracranial hypertension. Normal doses of vitamin A when taken with tetracylines do not appear to present an issue .
- Hepatoxic drugs (medications that can be harmful to the liver) – As large doses of vitamin A can affect the liver; they should not be taken in conjunction with medication that can also have harmful effects. Taking vitamin A supplements with these drugs can increase the risk of liver damage .
- Anticoagulants (Warfarin) – Taking vitamin A supplements with Warfarin (Coumadin) can increase the risk of bruising and bleeding. It is best to check with your doctor if you are planning on taking a vitamin A supplement .
Background information: Vitamin E comes in different forms known as tocopherol and tocotrienol. Tocopherol is an oily compound. α tocopherol is the most biologically available form of vitamin E.
There has been much debate over the potential health concerns high doses of vitamin E can cause . The following points discuss the potential negative health effects that numerous studies and meta analyses have found .
- Some adverse symptoms of long term, high dose vitamin E supplementation may include malaise (general feeling of being unwell), fatigue and gut disturbances 
- There has been a link between supplemental vitamin E intake and an increase in all causes of mortality [9, 15, 17].
- Clinical trials have found that individuals taking alpha- tocopherol supplements are at a heightened risk of haemorrhagic stroke. This could be due to the effect high doses of vitamin E have on blood coagulation by inhibiting platelet aggregation .
- One study published in 2007 showed a significant increase (17%) in the incidence of prostate cancer in men who were taking vitamin E supplements .
- After a review of the available data, the NHMRC came to the conclusion that the main health concerns include: a slight increase in the risk of stroke, subarachnoid haemorrhage in smokers and a greater risk of haemorrhage in aspirin takers . Apart from these results, the NHMRC did not conclude there to be any other health concerns with taking vitamin E supplements.
- Vitamin E supplements should be avoided prior to surgery. This is because of their blood thinning properties that can result in a haematoma (collection of blood) that may lead to complications .
Vitamin E has the potential to interact with a number of different drugs. Prior to taking a vitamin E dietary supplement, it is important to ensure that any drugs you are taking are not affected by vitamin E. Common drugs to be aware of include:
- Anticoagulant and antiplatelet medication (e.g. Warfarin) – Vitamin E can increase the risk of bleeding by inhibiting platelet aggregation (blood clotting). This is particularly the case when combined with a low vitamin K diet, which is recommended for those who take Warfarin .
- Simvastatin and niacin- Vitamin E when taken in conjunction with other antioxidant vitamins (e.g. vitamin C, beta-carotene) can limit the rise in HDL cholesterol (good cholesterol) which has beneficial cardio protective properties . It can therefore, partly interfere with the role of Simvastatin and Niacin that aim to decrease LDL cholesterol (bad cholesterol) and increase HDL. Consumption of grapefruit and grapefruit juice should also be minimised whilst taking these drugs as it affects their metabolism.
- Chemotherapy and radiotherapy – Some oncologists advise against antioxidant supplementation during these treatments as it may interfere with their effectiveness –potentially by protecting cancer cells from the same extent of damage .
The general consensus is that vitamin E is best obtained from dietary sources alone. A Vitamin E dietary supplement only needs to be taken when recommended by a health professional but if you are looking to take one; a lower dose supplement is advised.
Background information: Cholecalciferol, ergocalciferol
- Long term intake of high dose Vitamin D can lead to toxicity. Non-specific symptoms can include Weight loss, loss of appetite, fatigue, weakness, headache, vomiting, dry mouth, metallic taste, heart arrhythmias, polyuria (excessive production of urine) [21, 22, 23].
- Excessive vitamin D intakes can significantly raise the levels of calcium in the blood (hypercalcaemia) by increasing the uptake of calcium from the intestines. This can result in vascular and soft tissue calcification which can damage the heart, kidneys, lungs and blood vessels [21,22,23,24]. Additionally, the risk of kidney stones is also increased .
- Bone disease ( causing fractures and falls) has also been linked with hypervitaminosis D 
- Infants with excessive vitamin D intake can experience mental and growth retardation and kidney failure .
It is advised that a dietary supplement that is very high in vitamin D be avoided in the long term . In particular, those with the following conditions should ensure they are monitored well whilst taking high doses of vitamin D :
- High blood calcium or phosphorus levels
- Kidney disease
- Heart disease
If you are taking any of the following medications, it is advised that you first speak to your doctor before taking a vitamin D dietary supplement.
- Statins (Atorvastatin – Lipitor): These drugs aim to lower cholesterol levels. Taking vitamin D supplements can impact how much of this drug is absorbed by the body, therefore making it less effective . Consumption of grapefruit and grapefruit juice should also be minimised whilst taking these drugs.
- Digoxin (lanoxin): Treats heart failure and abnormal heart arrhythmias. Taking this drug in conjunction with a vitamin D dietary supplement may cause levels of calcium in the blood to get dangerously high .
- Thiazide diuretics: These drugs remove excess fluid from the body. They can increase vitamin D activity and decrease calcium excretion which may result in higher blood calcium levels. A Vitamin D dietary supplement should therefore be taken with precaution, if at all. This is particularly the case for those with compromised renal function or hyperparathyroidism 
- Diltiazem: Large doses of vitamin D may interact with this drug, making it less effective. You should check with your doctor before taking a vitamin D supplement.
Background information: Vitamin k is important for blood clotting. It comes in 2 forms – vitamin K1 (phylloquinone, phytomenadione, or phytonadione) and K2 (menaquinones). There are also synthetic forms known as K3 , K4, K5.
Most evidence suggests there to be no harmful effects associated with excessive intake of vitamin K. This is why the NHMRC has not set an upper limit of intake.
However, studies have shown that the following may occur with the over consumption of a synthetic form of vitamin K – menadione (K3):
- Excess consumption of menadione can cause oxidative damage to cell membranes . This is said to occur when menadione interferes with another antioxidant in the body (glutathione). The breakdown of red blood cells can cause liver damage and haemolytic anaemia.
Due to the above finding, menadione has stopped being used as a dietary supplement in most countries.
If you are taking an anticoagulant drug, you should first consult with your doctor if considering a vitamin K supplement.
- Anticoagulants (Warfarin) – Vitamin K plays a big role in blood clotting. By taking vitamin K supplements in conjunction with blood – thinning medication, the effects of that medication can be negated. Even foods that are high in vitamin K must be reduced when taking blood – thinners 
If you would still like to take a supplement, the following precautionary steps should be taken:
- Notify your health care provider of the supplements you are taking/ plan to take. Do not assume they are safe for you.
- Do not take over the recommended dose.
- If you are scheduled to have surgery, it is important to discuss the supplements you are taking with your doctor.
- Tell your doctor if your situation changes whilst you are on the dietary supplement e.g. if you fall pregnant.
- Tell your doctor if you start to experience any adverse effects.
- Do not take a dietary supplement in place of medication.
This article was written by our nutritionist Belinda Elwin who is a Dietitians Association of Australia member and Accredited Practising Dietitian.
If you have any nutrition related questions, contact your local doctor or ENT Wellbeing and they will arrange for you to see Belinda. For healthy eating advice, Contact us today!
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