For many people eating a well-balanced diet can be a difficult task particularly when trying to stay healthy.  For example, vegetarians and vegans need to select foods more carefully to ensure they get all the nutrients they need, while some people – such as pregnant or breastfeeding women – need more of certain nutrients.

If your diet is lacking in a particular nutrient, one option is to use dietary supplements. Supplements can help you meet your recommended dietary intake (RDI), which is the daily amount of a nutrient your body needs in order to function and remain healthy.

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 is an essential nutrient for many body functions. It is especially important for strong teeth and bones.
  • Good sources of calcium include dairy foods, canned fish with edible bones, tofu and fortified soy milk
  • Diet is usually the best way to get your daily calcium, but for some women there may be times in their life when they will need to take calcium supplements
  • If you do not get enough calcium in your diet, your body will draw calcium from your bones, which can put you at risk of conditions such as osteoporosis
  • Less than half of adults meet their daily recommended intake of calcium, which is 1000mg per day for women aged 19-50, and 1300mg per day for women 51 and over

There is some controversy about what levels of calcium supplements are healthy; some studies suggest a link between high calcium levels and cardiovascular problems. The current recommendation is that if you are not getting enough calcium in your diet, you should take 500-600mg of calcium supplements a day.

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 osteoporosis, which can result in bone fractures.

Dietary Sources of Calcium

Less than half of 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 Supplements

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


Most calcium supplements contain calcium carbonate (eg. caltrate) or calcium citrate (eg. citracal)

  • Calcium carbonate requires an acidic environment for maximum absorption and should therefore be taken with meals
  • Calcium citrate does not require an acidic environment and therefore can be taken on an empty stomach, but is still better taken with food. It is the preferred calcium product for people who need to take anti-reflux medications
  • Bones are in a constant state of maintenance and remodelling. Even as an adult your skeleton is constantly being reshaped; your skeleton is replaced, bit by bit, about once a decade. This process, known as ‘bone turnover’, takes place mainly at night-time. This is why it is best to take calcium supplements at night
  • Taking calcium with a meal minimises side effects such as constipation

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. Medicine 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.


  • Omega-3 fatty acids can be found in fish, some plants and animal products
  • It is best to avoid fish known to be high in mercury, such as shark (flake), broadbill, marlin, swordfish, orange roughy (sea perch) and catfish
  • Eating one or more serves of fish a day during pregnancy helps the baby’s nervous system develop. However this is not the case when taking similar amounts of omega-3 supplements.

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
  • seaweed
  • 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.

Omega-3 Supplements

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 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 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

  • Vegetarians are at particular risk of vitamin B12 deficiency because B12 is mostly found in animal-based products
  • Also at risk of vitamin B12 deficiency are elderly people whose diet is poor, and people with gastro-intestinal conditions such as coeliac or Crohn’s disease
  • Because the body can normally absorb and use B12 quite efficiently, a person can go for months or years without enough B12 before noticing any symptoms
  • The recommended daily dose of B12 for adults is 2.4µg per day. Supplement doses can vary between different kinds of tablets
  • The body can only absorb small amounts of B12 at a time, so small doses more often is recommended.

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.

B12 Deficiency

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.

B12 Supplements

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.

You can take supplements if you think you’re not getting what you need with just your diet.