There are numerous, usually less serious and less common, contraindications to the use of nutritional supplements. Some are common and others rare and many are only of mild significance but they may be of considerable importance to particular individuals. It seems likely that other potential minor adverse reaction reports will be added to this already long list.
Many of these clinically important situations are not covered adequately by the otherwise thorough EVM 2003 of report. In many of the situations given below the advice of a doctor or experienced dietitian/nutritionist who can make an assessment of the need for and benefits and risks of supplementation should be sought. In the case situations involving prescription medication usually adequate guidance is given in the accompanying patient information leaflet or can be obtained from www.medicines.org.uk
Acute adverse reactions to a drug or food supplement can be assessed using the Naranjo algorithm which is a series of questions to which numerical scores are assigned that then allow the degree of probability to be assessed. http://en.wikipedia.org/wiki/Naranjo_algorithm
|Clinical Problem||Potentially Harmful Nutrient||Reasons for Caution|
|Obesity BMI >30kg/m2||Vitamin A – retinol*
Selenium >200 ug/day – Persistent use
|Both supplements might aggravate obesity-associated liver disease.
Persistent use of selenium 200 ug/day for several years has been associated with a 55% increase the risk of type II diabetes and those who are prone should consider a lower dose schedule
|High Cancer Risk
due to: chemical exposure, personal or family history
|Vitamin A – retinol*
|High dose supplements of these nutrients have been associated with an increased risk of cancer in clinical trials and they should be avoided or used with caution in those at increased risk.|
Vitamin C >1g/day
|Supplements could occasionally increase the risk of kidney stones.|
|Gastritis or Active Peptic Ulcer||Zinc
|All of these supplements can sometimes cause gastro-intestinal irritation. The risk is reduced if they are taken after food.|
|Vitamin C 1g/day||In a trial in physically active young men supplements of vitamin C 1g/day resulted in increased post-exertional delayed muscle soreness compared to placebo.|
|Diarrhoea||Magnesium usually >150 mg
Iron usually >17 mg/day
Vitamin C >1000 mg/day.
Chewable supplements containing sorbitol or xylitol
|Supplements of these three nutrients can cause or aggravate diarrhoea especially at high dose.
The artificial sweeteners sorbitol and xylitol can sometimes cause diarrhoea.
|Constipation||Iron usually >17 mg/day||Supplements of iron, especially high dose, can cause constipation as well as diarrhoea.|
|Vascular Disease: Stroke, TIA or Coronary Disease||Calcium > 1000 mg/day||High dose supplements have been linked to an increase in the risk of vascular events in elderly women. A daily calcium dose of 500 mg and vitamin D 10 ug with healthy diet and exercise may be better.|
|Peripheral Vascular Disease||Niacin > 100 mg/day||Niacin at 1g/day increased plasma homocysteine levels by 55% in those with arterial disease. Use of other B vitamins may prevent this.|
or similar disorder of movement
- industrial exposure
|Parkinsonism from manganese accumulation in the brain is usually resistant to levodopa treatment and can occur in association with liver disease or a portal-systemic shunt. Chronic anaemia may increase the risk.|
|Fish Odour Syndrome||Choline and lecithin granules||A few individuals may produce malodorous sweat which is worsened by taking choline.|
||Vitamin A* –retinol, including cod liver oil
Folic acid < 400 ug/day*Vitamin C >1000 mg/day
Vitamin E >400 IU/day
|Retinol has been associated with birth defects.
Supplement must provide > 400 ug folic acid.
High doses of vitamins C and E use have been associated with more low birthweight babies.
|Breast feeding||High dose supplements||Breast milk concentrates many nutrients and high dose supplements should be avoided unless indicated.|
|Riboflavin – vitamin B2*Vitamin B6*
Vitamin B3 – nicotinamideCalcium*Iron*
Vitamin C > 1g/day
|Riboflavin may alter the activity of some antimalarial drugs.
Evening Primrose Oil is not always contraindicated in epileptics
High doses of vitamin B6 and folic acid might rarely reduce drug effectiveness.
Nicotinamide may increase the blood levels of this drug; use with caution.
Minerals form an insoluble complex with Sotalol. Separate them by at least 4 hrs.
The absorption of penicillamine can be reduced by these minerals.
May increase the level of oestrogen and possibly effects/side-effects
|Vitamin B12 deficiency or anaemia||Folic acid > 1000 ug/day||Folic acid supplements treat the anaemia but not the neurological effects of vitamin B12 deficiency and may thus delay the diagnosis.|
|Unexplained or persistent anaemia
|Zinc > 25 mg/day||High zinc intakes impede copper absorption leading to deficiency and anaemia, bone marrow failure and neurological problems.|
* Relevant amounts are often found in standard strength multivitamin/multimineral supplements