Therapeutic doses of supplements
Sometimes, in order to manage or treat a specific condition, nutritional supplements are prescribed in higher doses than the RDI. For example, you may be prescribed zinc to treat the common cold. This is known as a 'therapeutic dose' of that supplement.
Calcium has two essential roles in the body. Nearly all of the calcium in the body is found in our bones and teeth, where it combines with other minerals to form the hard crystals that give bones their strength. However, a small amount (less than 1%) of calcium circulates in the blood and throughout the body, since many of our body's cells – such as nerve, muscle and heart cells – need tiny amounts of calcium to work properly.
Since the body loses some calcium every day (mostly through the urine), if you do not consume enough calcium in your diet, the calcium level in your blood can fall. Your body will then compensate for this by drawing calcium out of your bones and into your blood. This can put you at higher risk of low bone density and osteoperosis, which can result in bone fractures.
Dietary sources of calcium
Less than half of Australian adults meet their daily recommended intake of calcium. Good dietary sources of calcium include:
- dairy foods
- canned fish with edible bones (sardines and salmon)
- tofu and fortified soy milk
Seeds (unhulled sesame seeds), nuts (almonds), legumes (chickpeas), broccoli and spinach contain small amounts of calcium.
How calcium is absorbed depends on what type of food it is in. Foods that are rich in oxalic acid (such as spinach and rhubarb) or phytic acid (seeds, nuts, grains and legumes) contain calcium, but the body doesn't absorb the calcium well. However, these foods are still healthy choices to increase the overall dietary calcium.
Too much protein in your diet can increase the amount of calcium lost in urine. Too little protein in the diet may contribute to poor bone health, possibly due to lowered calcium absorption.
Calcium needs are generally best met through diet, but for some women there may be times in their life when they need supplements to achieve their recommended dietary intake (see below).
Absorption of calcium from supplements depends on the type of calcium, the dosage and whether they are taken with a meal. Calcium absorption from supplements is at about 500mg or less.
The recommended dietary intake of calcium is:
- for women aged 19-50 = 1000mg per day
- for women aged 51 and over = 1300mg per day
For more information on calcium, including details of how much calcium different foods contain and RDI levels for all life stages, go to our calcium webpage.
|When should I take calcium supplements?|
Most calcium supplements in Australia contain calcium carbonate (eg. caltrate) or calcium citrate (eg. citracal)
Calcium supplements and heart disease
While calcium supplements can lower the risk of bone fracture, some evidence suggests that it may increase the risk of cardiovascular (CV) problems, such as heart attacks and stroke. Recent studies into the relationship between calcium supplements and CV problems have reached conflicting conclusions.
Knowing what to do can be confusing. Osteoperosis Australia stresses the importance of meeting the RDI of calcium, and recommends that if your diet is low in calcium, you need to take 500-600mg of calcium supplements a day. They state that the use of supplements at this level is considered safe and effective.
Folate is the naturally occuring form, and folic acid (also known as vitamin B9) is the form found in supplements. It is needed for healthy growth, particularly of the nervous system. Folate has a role in:
- forming red blood cells, which carry oxygen around the body
- cell growth
- DNA synthesis
- the develpoment of a baby's nervous system, both in the womb and while being breastfed
- reducing the risk of neural tube defects, such as spina bifida, in a baby
- along with vitamin B12, lowering the levels of the amino acid homocysteine – high homocysteine is a risk factor for atherosclerosis and cardiovascular disease
Dietary sources of folate
Folate is found in raw green leafy vegetables (especially cabbage and spinach), legumes, peanuts, eggs and cereals and other foods that are fortified with folate (such as Vegemite.) Cooking and heat causes considerable amounts of folate to be lost. Find more information about food and nutrition on our healthy living webpages.
Folic acid supplements
In order to increase the amount of folate available in the diet and reduce the risk of spina bifida, since 2009 in Australia, all flour used for breadmaking (except for organic bread) has been fortified with folic acid. Three slices of fortified bread will provide about 120µg of folate.
Pregnant women need more folate, so the National Health and Medical Research Council (NHMRC) recommends that all women should take a supplement containing 500µg for at least one month before pregnancy and then for the first three months of pregnancy. The pre-conception supplement is vital, because the critical period for the development of the foetal neural tube is between day 17 and day 30 of pregnancy – when most women are not yet aware that they are pregnant.
To metabolise folic acid, your body also needs B2, B6 and B12. It is therefore essential that these nutrients are taken with folic acid. Many of the over-the-counter multivitamin supplements and B complexes in Australia do contain these nutrients with folic acid, as do many of the formulas recommended for pregnancy. To make sure you are getting what you need, read the labels and consult a health practitioner specialising in antenatal nutrition.
Folate deficiency is one of the most common vitamin deficiencies in Australia. Those at risk of low folate include elderly people in care, chronic alcoholics and pregnant women. Folate deficiency is also seen in people with malabsorption syndromes and in people taking certain medications, such as the anti-tumour drug methotrexate, the anti-malarial drug pyrimethamine, the antibiotic trimethoprim (commonly prescribed for urinary tract infections), sedatives and barbiturates.
The recommended dietary intake of folate for adults is 400µg per day. For pregnant women the recommended dietary intake (RDI) is 600µg per day, so women planning pregnancy are advised to supplement with 500µg of folate per day (in a formula also containing vitamins B2, B6 and B12).
The thyroid gland needs iodine to make hormones. In early pregnancy, the mother's thyroid gland becomes about 50% more active, supplying enough thyroid hormones to regulate the baby's development.
Like folate, iodine is essential for normal development of a baby's brain and nervous system, in utero and after birth. If you have low levels of iodine before you get pregnant you may not have enough iodine to support you and your developing baby in the first trimester (first 12 weeks) of pregnancy. Iodine deficiency, which is unfortunately common in pregnancy in Australia, can lead to stillbirths, miscarriages and congenital abnormalities such as cretenism (an irreversible form of developmental and mental retardation). Iodine deficiency can also cause lowered intelligence; low iodine in a pregnant woman can lead to her child's IQ score dropping by 7-13 points.
Dietary sources of iodine
Iodine can be found in sea-water, in marine plants such as kelp, and in soil, though this varies by region. The main dietary sources of iodine are seafood and bread containing iodised salt, but it is difficult to get enough iodine through diet alone.
Iodine supplements and doses
Most of the damage caused by iodine deficiency occurs early, before the woman realises she is pregnant. This is why iodine supplements are essential for women considering pregnancy.
The recommended dietary intake of iodine is 150µg per day for adults and 220µg per day in pregnancy.
The National Health Medical and Research Council (NHMRC) recommends iodine supplementation of 150µg per day for all women who are pregnant, breastfeeding or considering pregnancy. Even if your dietary intake of iodine is sufficient, taking a supplement is not likely to make you exceed the upper limit of 1100 micrograms (1.1µg). However, there is an exception to this: avoid kelp-based and seaweed-based supplements, as their iodine content has been found to be highly variable and could exceed the upper limit.
Adverse effects of iodine
Women with known thyroid disease should consult their doctor before taking an iodine supplement.
Iron is involved in the transport of oxygen in the blood, and has a role in the health of your immune system. Low levels of iron can make you feel fatigued or tired and lowers your immunity.
The Australian recommended dietary intake (RDI) for iron is 18mg for women aged 19-50 years and 8mg for women over the age of 51.
|Iron in your food comes in two forms:|
Iron levels in women are often low. It's a balancing act of correct intake and maintenance of desired levels. Inadequate iron intake or an increase in blood loss, for example in heavy periods, may result in iron deficiency. It's important to have a blood test to check the levels of both haemoglobin (a protein in red blood cells that contains iron) and ferritin (a protein that serves to store iron in the body) before taking iron supplements.
Calcium makes it harder for the body to absorb iron from food and supplements. For people who have enough stored iron, this probably isn't a problem. However, if you are iron deficient and take iron supplements, take them at a different time of the day to calcium supplements and at a meal with little or no dairy.
Omega-3 fatty acids are a type of polyunsaturated fat. They play a vital role in the brain's function, growth and development and in lowering the risk of heart disease. Research also suggests that omega-3 may help reduce inflammation and support the immune system.
Dietary sources of omega-3
Omega-3 is found in marine, plant and animal sources including:
- fish such as salmon, tuna, mackerel, herring, anchovies, sardines and trout
- oils such as flaxseed, canola and walnut
- nuts and seeds such as flaxseed, walnuts and chia seed
- leafy green vegetables
- foods with added omega-3 fatty acids, such as milk, yoghurt, eggs and bread
- eggs, chicken and beef (the amounts of omega-3 vary depending on whether the animals are grass-fed or not)
Alpha-linolenic acid (ALA) is the essential omega-3 fatty acid. It cannot be made in the body and must come from the diet. The most abundnant source of ALA is flaxseed oil. Chia seeds, walnuts, and pepitas (pumpkin seeds) are also good sources of ALA.
Eicosapentaenoic acid (EHA) and docosahexaenoic acid (DHA) are the omega-3 fatty acids found in fish. The body can also use ALA to make EPA and DHA.
Fish oil supplements are a source of omega-3 fatty acids. However, the quality, type and strength of fish oils varies between products. Ideally, look for a supplement containing at least 300mg of EPA and 150-200mg of DHA per capsule for adults, and take 1-4 capsules a day. Higher doses may be prescribed in certain situations. It is vital that fish oil supplements are from a 'clean' source; that is, the manufacturer has ensured the product has been tested for heavy metals such as mercury, and ideally for environmental contaminants such as dioxins and polychlorinated biphenyls (PCBs).
The Western diet is often low in omega-3 fatty acids. The best sources of omega-3 are fresh and canned salmon, sardines, mackerel and herring. Two or three serves per week of a 150g piece of oily fish are recommended.
Omega-3 fatty acids and heart health
Omega-3 fatty acids in fish and fish oils have been found to improve heart health, helping to protect healthy people against heart disease, as well as reducing the incidence of cardiac events and death in people with existing heart disease.
The Heart Foundation of Australia recommends taking 500mg of combined DHA and EPA a day. They recommend that people with high levels of triglycerides (detected in a blood test) should take up to four capsules of 1000mg fish oils daily. They also recommend eating 2g of alpha-linolenic acid (ALA) a day.
Omega-3 fatty acids and pregnancy
DHA is very important during pregnancy as it is essential for the development of the baby's brain and nervous system. The amount of DHA recommended during pregnancy is 200-300mg per day. However, pregnant women in Australia are only consuming an average of 99mg of DHA a day. To consume enough DHA, eat three serves of oily fish (salmon, mackerel, sardines) a week, or take a daily fish oil supplement containing 300mg. Avoid fish known to be high in mercury – shark (flake), broadbill, marlin, swordfish, orange roughy (sea perch) and catfish.
A recent review showed that pregnant women who ate one or more servings of fish per day, had babies with better neurodevelopment than babies of women who ate no fish. Conversely, a review of clinical trials in which omega-3 supplementations were taken, showed that there were no clear association between the supplement and cognitive outcomes of the infant. Based on these results, 2-3 serves per week of fish (low mercury sources) during pregnancy is recommended, but supplementing with 200-300mg of DHA daily, as recommended may be appropriate.
There is some concern about the use of fish oil supplements and whether they can increase bleeding time due to blood thinning. However, research shows this isn't the case. People on blood-thinning medication, such as warfarin, should seek advice before taking fish oils.
Vitamin B12 is important for energy, for producing and maintaining nerve cells and red bloods cells, and for DNA synthesis in the body's cells.
If the body does not get enough B12, the production of nerve cells and red blood cells eventually suffers. However, because the body can normally absorb and use B12 quite efficiently, a person can go for months and years without enough B12 before any symptoms of deficiency are apparent.
Vitamin B12 deficiency can be a serious health issue. It can cause:
- weakness and fatigue
- cognitive problems such as dementia, memory and thinking problems, depression, psychosis and hallucinations
- problems with balance and walking
- numbness and tingling sensations in the hands and feet
- problems with bowel and bladder control
- digestive system problems such as diarrhoea and constipation
Vitamin B12 can also lead to an increase in homocysteine (a naturally occuring amino acid associated with cardiovascular disease).
Vitamin B12 deficiency is most common in elderly people, and for those on a 'tea and toast' diet. For elderly people low in B12 the risk of cognitive problems is especially high.
High levels of folate can mask B12 deficiency. This is a concern for vegetarians and vegans whose folate intake is generally high and B12 low. Because nearly all natural sources of B12 are animal-derived products (see below), breastfed babies of vegan mothers are also prone to B12 deficiency.
Some medications, can also lower B12, as can medications that lower stomach acid. Vitamin B12 deficiency can also be seen in people who have had surgery for weight loss.
Testing for vitamin B12 deficiency
Vitamin B12 is found in the blood in two forms – active and inactive. It is the amount of active B12 that interests us, but previous tests could not distinguish between the two forms. However, in recent years, a new test has been developed that can measure active vitamin B12, making it more accurate than previous tests.
Dietary sources of B12
Vitamin B12 is naturally found only in animal products. Good sources include fish, poultry, liver, meat, milk, cheese and eggs. Because B12 is produced by bacteria in the large intestines of the animal, it is generally not found in plant foods. Traces of B12 have been found in white button mushrooms, but an average serve of mushrooms contains only about 5% of the recommended daily dose, so they are not a significant source of B12.
Vitamin B12 supplements are usually given as an under-the-tongue supplement, although oral supplements work just as well. Some people may lose the ability to absorb vitamin B12, or have such low levels that they need B12 injections. If you are worried that you might have a vitamin B12 deficiency, see your doctor.
The recommended daily dose of vitamin B12 for adults is 2.4µg per day, though supplement doses can vary between different kinds of tablets. The body can only absorb small amounts of B12 at a time, so small doses (1-5µg) more often is recommended.
Adverse effects of B12
If you are healthy, taking too much vitamin B12 in food or supplements will not harm you.
Vitamin D is not a nutrient in the usual sense; it is actually made by the skin, then metabolised in the kidneys to its active form. Vitamin D is essential for bone health. Its most understood role is helping the body absorb calcium and phosphorus.
Vitamin D also assists with:
- bone development and strength
- cell growth
- maintaining a healthy immune system
- hormone function
- nervous system regulation
Observational studies show that vitamin D may have a role in preventing many diseases, including diabetes and cancer. The evidence for this is still not strong, but large scale trials are ongoing to provide better evidence.
Vitamin D deficiency
The amount of sunlight your body needs to make enough vitamin D depends on many factors, including your skin tone, body weight, medical conditions you may have, and where you live in Australia. See the below table for details and recommendations.
Even though Australia has one of the highest UV radiation levels in the world and is well known for its sunshine, research has found that many Australians are deficient in vitamin D because of the amount of time they spend indoors. A recent survey showed that 23% of the Australian population aged 12 and over had low levels of vitamin D. Those most at risk of having a vitamin D deficiency include:
- older people and people living in care (such as hospitals or rehabilitation), particularly those who stay indoors or cannot walk and have limited exposure to sunlight
- people with gastrointestinal disease
- people taking certain medication (for example anti-epileptics)
- people who cover or veil their skin for cultural or religious reasons
- people with darker skin
- pregnant women
- people who are overweight or obese
- postmenopausal women
- breast-fed babies of mothers deficient in vitamin D
Finding out your vitamin D level
Vitamin D levels can be measured with a simple blood test. The test measures the level of the active form of vitamin D (known as 25-OHD) in the blood. Vitamin D levels are classified into ranges:
|Level of vitamin D deficiency||Range (in nmol/L)|
|Severe||Less than 12.5|
Classification: The Australian and New Zealand Bone and Mineral Society, the Endocrine Society of Australia and Osteoporosis Australia
The number of vitamin D tests given to Australians has skyrocketed in recent years. The significant cost to the health system ($143 million) led medical authorities to suggest tests be limited only to people at high risk of vitamin D deficiency.
Where to get vitamin D
Your body makes vitamin D when it is exposed to sunlight, so sunlight is one of the best sources of vitamin D. Plant and animal foods, as well as fortified foods, such as milks and breads, can all be dietary sources of vitamin D.
Vitamin D comes in two forms: D3 (also called cholecalciferol) is produced by the action of sunlight on the skin. D2 (also called ergocalciferol) is found in some foods - fatty fish such as salmon, herring and mackerel, eggs and fortified foods. One cannot rely on diet alone to ensure adequate vitamin D levels.
|What you need||What to be careful of|
The body usually needs 10-15 mins a day of exposure to outdoor sun to produce enough vitamin D. As a guide expose the face, arms, hands or legs for:
Check the map of Australia for guidelines on the recommended amount of sun exposure based on your location, the season and your skin pigmentation.
You can get daily updates on the UV index at sunsmart.com.au
Dietary sources of vitamin D are limited and can come from:
It is very hard to get enough vitamin D from these sources alone.
For elderly people in care, taking additional vitamin D supplements and calcium supplements may lower the risk of bone fractures.
Get your doctor's advice about whether to take a vitamin D supplement.
Vitamin D supplements
Supplemental doses for adults range from 600-4000IU per day.
High doses of vitamin D can be harmful. A 2011 Institute of Medicine (IOM) report concluded that doses below 10,000IU/day are not usually associated with toxicity, whereas doses of 50,000IU/day or more for several weeks or months are often associated with toxic side effects. Most of the reports of vitamin D toxicity have documented vitamin D intake of more than 40,000IU/day
Zinc is an essential mineral that:
- supports a healthy immune system
- helps synthesise DNA
- is essential for wound healing
- is a key component in many cellular processes
- supports the healthy growth and development of the body during:
Zinc reduces the replication of the cold virus and boosts the immune system. Taking zinc supplements at the first sign of a cold may shorten your cold by about a day.
Dietary sources of zinc
Zinc can be found in oysters, meat and fish, and in lesser amounts in wholegrain cereals, legumes, dairy foods and seeds such as pumpkin and sunflower.
Zinc is found more in animal-based foods than in plant-based foods; an antioxidant compound called phytate, found in plant foods such as legumes, unrefined cereals, seeds and nuts, binds to zinc during digestion, making the zinc less able to be absorbed. When baking bread, heat destroys much of the phytate in the grains. Soaking and sprouting beans, grains and seeds also reduces phytates (this is why some people like to 'activate' seeds and nuts).
The RDI of zinc for adult women is:
Not all zinc supplements are absorbed equally. The best absorbed forms are zinc picolinate (not readily available in Australia) and zinc citrate. Most supplements contain 20-30mg of elemental zinc.
Zinc supplements are not recommended for general cold prevention (unless your doctor prescribes them) because too much zinc can interfere with absorption of other nutrients such as copper and iron.
Taking an iron supplement may inhibit zinc absorption. However, dietary iron in a meal that also contains zinc does not reduce absorption.
Unless prescribed do not take more than 40mg of elemental zinc per day.
Taking zinc on an empty stomach can cause nausea.
Sean R Lynch (2000). The effect of calcium on iron absorption. Nutrition Research Reviews, 13, pp 141-158.
Papadimitropoulos E, Wells G, Shea B, Gillespie W, Weaver B, Zytaruk N et al. Meta-analyses of therapies for postmenopausal osteoporosis. VIII: Meta-analysis of the efficacy of vitamin D treatment in preventing osteoporosis in postmenopausal women. Endocr.Rev. 2002;23(4):560-9.
Hilakivi-Clarke, L. Andrade, JE. Helferich, W. 2010. 'Is Soy Consumption Good or Bad for the Breast?' J Nutr 140(12):2326S-2334S
Messina, M. 2010. 'A Brief Historical Overview of the Past Two Decades of Soy and Isoflavones Research'. J Nutr 140(7):1350S-1354S
Last updated 27 February 2017 — Last reviewed 16 December 2016
This web page is designed to be informative and educational. It is not intended to provide specific medical advice or replace advice from your health practitioner. The information above is based on current medical knowledge, evidence and practice as at December 2016.