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Nutrients with Cautions and Interactions

General | November 6, 2017 | Author: Naturopath

Alternative Therapies

Nutrients with Cautions and Interactions

Many people believe that just because vitamins are natural there will be no side-effects. Even though the potential for harm is very rare, in some instances there are specific warnings. If you have a medical condition and are taking medications in conjunction with vitamin supplements it is good to double check with a naturopath or doctor first.

Vitamins with warnings and adverse reactions include:

Vitamin A

An essential nutrient for eye health, skin and to support healthy immunity. Although this isn’t a common supplement that people take it is often misunderstood because of the warnings for pregnant women. Care should be taken when dosing this fat-soluble nutrient as it stores in the body. This is only likely to occur in people who are exceeding well above the recommended dose.  

Unsafe during pregnancy

Vitamin A is an essential nutrient for during pregnancy but when taken in excess of 3,000 micrograms per day it may cause birth defects. It is therefore recommended that women who are pregnant or planning to conceive speak to their doctor or pharmacist before taking vitamin A supplements. Beta-carotene which converts to vitamin A in the body is considered a safer nutrient to take as there is no association with birth defects.

If you are taking tetracyclines use with caution or avoid as it increases the risk of side-effects such as headache and pressure inside the skull.

Vitamin C

A popular supplement taken for a variety of reasons including heart health, immune support, wound healing and allergies. Vitamin C is a water-soluble vitamin which our body is unable to produce itself and store. Vitamin C is considered a very safe supplement to take but it does have the following precautions.

Vitamin CReaching bowel tolerance

Excess intake of this supplement can cause loose bowels or diarrhoea. To avoid this from happening naturopaths sometimes advise to take vitamin C to bowel tolerance. Which means that you take the amount of vitamin C which is just short of the doses which produce diarrhoea. Otherwise low doses for general wellbeing and kids is the best way to go.

Other precautions

Vitamin C supplements can increase the amount of iron absorbed. For the average person this can be very beneficial but in haemochromatosis (excess iron storage) this can be dangerous. In these instances, vitamin C intake should only be taken under medical supervision. Vitamin C is safe to take during pregnancy as long as therapeutic doses are not exceeded. It is also recommended to not cease supplementation abruptly. Large doses of vitamin C taken long-term does not increase your risk of kidney stones.

B vitamins

The B complex is a group of vitamins that work in synergy. Although they are grouped together they can provide very different actions in the body and each have their own precautions.

When to take

B vitamins often cause nausea if they are taken on an empty stomach. The best time to take them, particularly if they are part of a multivitamin is immediately after breakfast.

Common reactions

Some of the most common interactions and adverse reactions are as follows. Taking high doses of vitamin B6 is not recommended long-term as it can cause toxicity. Niacin can cause flushing as it dilates blood vessels and creates a sensation of warmth, called a “niacin flush”. This is an immediate side effect but is harmless.


IronA deficiency in iron is common—especially in vegans and vegetarians. It can also be due to heavy menstruation, poor absorption and gastrointestinal bleeding. Because of this iron is a popular supplement that people take. However, supplementation without any demonstrated need isn’t advised because of potential risks.

Adverse reactions

Constipation is the common side-effect of iron supplements which can be additionally associated with nausea, vomiting, stomach pain, diarrhoea, headache or dark-coloured stools. Ferrous sulphate is more likely to cause these side-effects as it is poorly absorbed and prescribed in high doses. Other forms such as iron disglycinate, iron polymaltose and amino acid chelate are less likely to cause these problems.


Iron should be taken 2 hours away from calcium supplements, antacids and from certain kinds of medications. They are contraindicated in people with hemochromatosis, thalassaemia and sideroblastic anaemia.


Iron toxicity, with subsequent organ damage can develop from long-term excessive use. Acute poisoning can occur if very high doses are taken.
This is why it is important to keep iron supplements out of reach from children!


Most people who have osteoporosis or don’t have dairy in their diet are usually advised by their practitioner to take calcium supplements. Calcium is important for bone, muscle and nerve health as well as blood coagulation and maintenance of immune function.

CalciumAre there any safety issues?

In very high doses calcium supplements can clog up the bowels—leading to constipation. Gastrointestinal discomfort, nausea and flatulence may also be experienced.

High-doses should not be consumed by people taking certain medications. Caution should be exercised with high doses in individuals with pre-existing cardiovascular disease. But generally speaking, calcium is considered safe and has a wide therapeutic range.


Legs cramps, fatigue, migraines and PMS can all be relieved by taking magnesium supplements. Magnesium helps to regulate muscle activity, is involved in nerve conduction and the production of energy. In high doses some magnesium doses will cause diarrhoea due to having an osmotic effect in the bowel. This is more likely to happen in supplements that contain magnesium oxide. High dose supplements should not be used by people with severe kidney disease or heart block.


Zinc is important for healthy immunity, wound healing, mental health and digestion. It can be taken as a supplement individually but is often found in multivitamins and in antioxidant and immune formulas.


Unfortunately, high doses can cause nausea, vomiting and gastrointestinal discomfort. This can be counteracted by taking after a meal or reducing the dose. Long-term use can reduce copper levels. Zinc interacts with many other foods, minerals and medicines—usually by contributing to its increased excretion. The main exception to this is the medication amiloride which reduces zinc excretion and can lead to excess amounts in the body. This combination should therefore be used with caution.

As you can see there are there are many precautions and adverse reactions that can be experienced with taking certain nutrients. It is best to check with a healthcare professional before supplementing to avoid any side-effects and interactions with medications. Australia’s best online discount chemist


Braun L, Cohen M. Herbs and natural supplements: An evidence based guide vol. 2. Churchill Livingstone, Australia

Hechtman L (2014). Clinical Naturopathic Medicine. Churchill Livingstone, Australia

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