Effects of Overnutrition

What is Overnutrition ?

Definition of overnutrition :

Overnutrition is a state of nutrition in which one or more of the components of a healthy diet are consumed to excess such that adverse medical effects of that excessive intake are apparent and measureable.

As also applies to undernutrition, overnutrition can be general or specific (i.e. due to over-consumption of just one vitamin or mineral, e.g. due to a 'fad diet').

Dietary excesses can lead to various medical conditions and diseases. The actual consequences of any particular dietary intake depend on which components of the diet are being (or have been) consumed to excess, and to what extent.

Overnutrition can be either:

  • General, i.e. due to excessive amounts of food of any or all types, leading to obesity and the many life-threatening conditions associated with it (see causes of obesity and health risks of obesity).
  • Specific, i.e. excess of of a single nutrient e.g. a single vitamin or mineral. The health consequences of such excess depend on the nutrient and the severity of the excess. Different medical conditions, hence different symptoms and risks, follow from different excesses. See effects of overnutrition.

The most common consequence of overnutrition, or 'over-eating' in general is obesity.

However, even people of a healthy weight (or who are under-weight) can experience adverse effects of 'overnutrition' as a result of consuming an excessive amount of a single nutrient, e.g. a vitamin or mineral. That can happen for various reasons such as:

  1. Only having access to a limited range of foods hence consuming too much of some dietary components as well as, perhaps, not enough of others.
  2. Having a healthy diet and lifestyle and also consuming unnecessary dietary supplements such that the combination of food and supplement intake result in an overall dangerous excess of one or more nutrients. This can be a particular risk when taking several different types of supplements without studying the labels carefully to ensure that the combination is appropriate for the person.
  3. 'Fad diets', meaning extreme eating regimes which are often promoted with claims about achieving desired goals, e.g. for weight loss, in a very short time, can be unsafe if they involve consuming excessive quantities of a limited range of foods. Such regimes can place people at risk from excessive amounts of some nutrients as well as from undernutrition diseases.

List of signs of excessive intake of some common vitamins and minerals:


Signs of Excessive Intake:

A (Retinol)

Early indications of excess vitamin A can include dry skin and itching.

Vitamin A can be stored in the body in such large quantities that it can become toxic.
Symptoms can include:

  • dizziness
  • nausea
  • headaches
  • vomiting

B1 (Thiamin, Aneurine)

Excessive doses (possibly by injection) may lead to toxic symptoms such as:

  • Allergic reactions
  • Disturbance of heart beat
  • Nervousness
  • Shaking and swellings

B2 (Riboflavin)

Overdose of vitamin B2 (also known as riboflavin) is unlikely but extremely large doses are associated with numbness and itching.

B6 (Pyridoxine)

Excessive intake of vitamin B6 (also known as pyridoxine) can lead to poisoning and damage to the central and peripheral nervous systems, especially the sense of touch.

C (Ascorbic Acid)

Excessive vitamin C in the body is associated with:

  • Sudden high intake of vitamin C can cause diarrhoea.
  • Very high dosage can lead to stomach problems in some people


Excessive vitamin D is associated with:

  • Over-calcification of the bones and teeth
  • Formation of calculus stones in the kidneys and other organs
  • Hardening of arteries.
  • In cases of extreme over-dose, vitamin D may lead to poisioning.
    Symptoms may include: General discomfort, itchy eyes and skin, extreme thirst, diarrhoea.

E (Tocopherols & Tocotrienols)

Some vitamin E can be safely stored in the body, though excessive doses may result in stomach problems and diarrhoea.


Some people with liver diseases cannot tolerate supplements of vitamin K.


Signs of Excessive Intake:

Calcium (Ca)

Excessive amounts of calcium in the body may lead to to formation of 'stones' in the body, especially in the the gall bladder and the kidneys.

Iron (Fe)

Long-term excessive intake of iron can lead to:

  • haemochromatosis or haemosiderosis (involving organ damage), both of which are rare
  • insufficient calcium and magnesium in the body (because these minerals compete with each other for absorption)
  • increased susceptibility to infectious diseases

Phosphorous (P)

Excessive ammounts of phosphorous can interfere with the body's absorption of:

  • calcium (Ca)
  • iron (Fe)
  • magnesium (Mg)
  • zinc (Zn)

Potassium (K)

Excessive amounts of potassium in the body (whether due to intake or other causes) can lead to:

  • arrhythmia, and ultimately cardiac arrest ('heart attack')
  • metabolic disturbances

Sodium (Na)

Excessive amounts of sodium in the body (whether due to intake or other causes) can lead to:

  • hypernatraemia
  • de-hydration (especially in babies)
  • possible long-term effects may include hypertension

Manganese (Mn)

Excessive intake of manganese has been associated with brain conditions such as symptoms similar to those resulting from Parkinson's disease.

Selenium (Sn)

Excessive intake of selenium can lead to selenium poisoning.

Zinc (Zn)

Excessive intake of zinc is not a common problem but can occur especially if zinc supplements are taken over an extended period of time. It can reduce the absorption of copper (hence copper supplements may be appropriate in that case).

Note: This page mentions some of the consequences of excessive consumption of certain nutrients that should be included, in the correct proportions, in a healthy balanced diet. That is very different from the consequences of consumption of other substances, including some chemical elements, that are not essential as part of a healthy diet and should not be consumed at all.

See also carbohydrates, types of sugar, dietary fibre (roughage), fatty acids, fats and proteins.

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Although care has been taken when compiling this page, the information contained might not be completely up to date. Accuracy cannot be guaranteed. This material is copyright. See terms of use.

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