Classifieds powered by Gulf News

Risks of vitamin overdose

Eat healthy from all food groups

Image Credit: Getty Images/Stockbyte Platinum
Capsules spilling out of jar, close up
Gulf News

Worried about your hair loss, you drop into a pharmacy and pick up a bottle of zinc supplements. You have read somewhere that zinc is essential for hair health and you are wondering if a lack of the mineral could be the cause of your hair loss. Happy with your purchase, you get home and pop a pill with your lunch.

Have you wondered for a second if you are doing the right thing? No. Did you consult a doctor before heading for the pharmacy? No. Did you spare a thought for the fact that taking regular zinc supplements minus expert supervision may lead to problems of overdosing? No.

“ ”Tweet this

Clearly, you are being silly. But you are not the only one. Hundreds of people all over the world self-prescribe vitamin and mineral supplements without any idea of whether it truly benefits them or worse, causes problems.

Do you really need vitamin and mineral supplementation and what are the risks of overdosing on them?

The main thing you need to be aware of is that there are two groups of Vitamins: fat-soluble and water-soluble, says Lena Nasih, registered dietician, Mediclinic City Hospital, Dubai.

The fat-soluble vitamins such as A, D, E and K, are absorbed through the intestines with the help of fats. As a result, they are more likely to accumulate in the body, and therefore more likely to lead to hypervitaminosis (a condition of high storage levels of vitamins, which can lead to toxic symptoms) when taken in excessive amounts.

Vitamin D supplements are commonly prescribed as it can be very hard to get enough Vitamin D from food sources or the sun. A doctor would be careful to prescribe it for only a short period of time, says Nasih. Excessive intake of Vitamin D over a long period of time can make the intestines absorb too much calcium, which can in turn lead to high levels of calcium in the blood. High levels of calcium in the blood can result in: calcium deposits in soft tissues such as the heart and lungs; confusion and disorientation; damage to the kidneys ; kidney stones; nausea, vomiting, constipation, poor appetite, weakness, and weight loss.

Water-soluble vitamins, which include the B-complex group and Vitamin C, says Nasih, dissolve easily in water and, in general, are readily excreted from the body. As they are not as readily stored, a more consistent intake is important, and the risk of hypervitaminosis is very low.

“The only time you may need vitamin and mineral supplementation is when you are deficient in them due to a certain disease state where they are not being as well absorbed. Deficiencies can also happen if you are not eating from the five food groups every day,” she says. (The five food groups being grains, fruits, vegetables, dairy, and meat/meat alternatives) “For a well-balanced meal, we should be having at least three out of the five at every meal,” she recommends.

Still, there are certain illnesses and conditions that affect our vitamin and mineral intake and requirements. Chronic kidney disease, for instance, changes the body’s need for certain vitamins and minerals. This is mainly due to the kidney diet limiting some food groups (fruits, vegetables, dairy), therefore the possible need to take certain vitamin supplements (as per your doctor’s advice).

The dietician warns that higher than recommended intake of certain minerals (such as phosphorus and potassium for example) when you are suffering from kidney disease can cause toxic levels due to the inability of the kidneys to excrete the excess.

Those who suffer from Irritable Bowel Syndrome (e.g. Crohn’s Disease) may also need vitamin/mineral supplementation (Calcium, Iron, Vitamin D) due to certain deficiencies that may happen as a result of malabsorption, inadequate intake and side effects of certain medications.

Pregnant women also need certain vitamin and mineral supplementation to ensure they are getting all the vitamins and minerals they need (Folic Acid, Iron, Calcium).

Nasih lists the main vitamins and minerals, their recommend intake, the risks and effects of toxicity and the natural sources from where you can get them.



Vitamins and minerals Checklist:


ug/d (micrograms/day)

UL (Tolerable Upper Intake Level)



NOTE: How much of each vitamin one need depends on age and gender. Other factors, such as pregnancy and ones health, are also important. The recommended intakes as well as UL (tolerable upper intake levels) listed below are for healthy adults from 19 years of age and older.


Vitamins and minerals checklist:


Vitamins and minerals Checklist:


ug/d (micrograms/day)

UL (Tolerable Upper Intake Level)



Vitamin A


Function: Growth and development, normal vision; Immune function.

Recommended intake: 600-900 ug/d (micrograms/day).

Effects of deficiency: Xeropthalmia (irreversible drying of the eyes).

Risks and effects of toxicity: Moderate risk of toxicity, liver disease, skin rash.

UL (Tolerable Upper Intake Level): 3000 ug/day.

Natural sources: Fruits, vegetables (carrots, broccoli, spinach, cantaloupe, liver, fish).


Vitamin D

Function: Aids in absorption of calcium and hosphorus (bone health).

Recommended intake: 15 UG/D.

Effects of Deficiency: Osteomalacia (adults); Rickets (children); Risks and Effects of Toxicity: High risk of toxicity, calcification (hardening of

blood vessels).

UL: 100 ug/d.

Natural sources: Flesh of fatty fish, some fish-liver oils, milk.


Vitamin E


Function: works as an antioxidant.

Recommended intake: 11-15 mgs/d.

Effects of deficiency: Hemolytic anaemia (in children); Peripheral neuropathy.

Risks and effects of toxicity: Low risk of toxicity; no known effects.

UL:1000 mgs/d.

Natural sources: Nuts, fruits, vegetables, and meat (the fatty portions).


Vitamin K


Function: Helps in blood coagulation (clotting)and bone metabolism.

Recommended Intake: 60-120 ug/d.

Effects of Deficiency: Bleeding disorders.

Risks and Effects of Toxicity:Low risk of toxicity with natural Vitamin K. Increased coagulation in people on Warfarin (a blood thinner).

UL: ND (not determined).

Natural Sources: Few green vegetables (spinach, salad greens, broccoli, brussels sprouts, cabbage), beef liver.



Thiamin (Vitamin)


Function: Helps the body convert carbohydrates into energy.

Recommended Intake: 0.9 -1.2 mgs/d.

Effects of Deficiency: Weakness, fatigue, nerve damage. Beriberi (very rare),Wernicke-Korsakov Syndrome (very rare).

Risks and Effects of Toxicity: Low risk of toxicity, no known effects.

UL: ND (not determined).

Natural Sources: Grain products (in germ of cereals), pulses.



B12 (Cobalamin)


Function: Involved in normal functioning of the brain, nervous system and for the formation of blood.

Recommended Intake: 1.8-2.4 ug/d.

Effects of Deficiency: Megaloblastic anaemia.

Risks and Effects of Toxicity: Low risk of toxicity, no known effects.

UL: ND (not determined).

Natural Sources: Animal products.


Folate (Vitamin)


Function: Synthesis and repair DNA.

Recommended Intake: 300-400 ug/d.

Effects of Deficiency: Megaloblastic anaemia. Growth retardation. Birth defect (Neural tube defects in pregnancy).

Risks and Effects of Toxicity: Low risk of toxicity. High levels can mask Vitamin B12 deficiency (can cause neurological problems).

UL: 1000 ug/d.

Natural Sources: Dark green vegetables, beans, legumes.



Biotin (Vitamin)


Function: Cell growth. Necessary for metabolism of fats and amino acids.

Recommended intake: 20-30 ug/d.

Effects of deficiency: Dermatitis. Hair loss, Conjunctivitis.

Risk and effects of toxicity: Low risk of toxicity, no known effects.

UL: ND (not determined).

Natural sources: Most foods (biotin content of foods not generally documented).



Vitamin C



Function: Antioxidant.Aids in absorption of iron.

Recommended intake: 45-90 mgs.Increased requirements for smokers (+ 35 mgs).

Effects of deficiency: Scurvy. Impaired wound healing.

Risk and effects of toxicity: Low risk of toxicity. Diarrhoea, oxalate stones.

UL: 2000 mgs/d.

Natural sources: Citrus fruits.



Sodium (Mineral)


Function: Transmit nerve impulses. Influences contraction and relaxation of muscles. Maintain fluid balance.

Recommended intake: 1.5 gms/d.

Effects of deficiency: Little evidence on any adverse effects of low dietary sodium intake.

Risk and effects of toxicity: Excessive intake (very common) results in high BP (risk factor for heart disease, stroke, kidney disease).

UL: 2.3 gms/d.

Natural sources: Milk, meat, shellfish.



Potassium (Mineral)


Function: Transmit nerve impulses. Muscle contraction.Maintain fluid balance.

Recommended intake: 4.5-4.7 gms/d.

Effects of deficiency: Uncommon in general population.Can cause irregular heartbeats, muscle weakness, glucose intolerance.

Risk and effects of toxicity: None for healthy individuals. Seen in those who cannot excrete excess potassium (people with kidney disease) when taken in high amounts.

UL: ND (not determined).

Natural sources: Fruits and vegetables (especially green leafy vegetables).


Iron (Mineral)


Function: Important component in haemoglobin (transport oxygen throughout the body).

Recommended intake: 8-18 mgs/d.

Effects of deficiency: Iron deficiency anaemia; most common nutritional deficiency (fatigue, impaired cognitive function, increased risk of infection).

Risk and effects of toxicity: Gastrointestinal distress.

UL: 1100 ug/d.

Natural sources: Meat, poultry, fish.


Calcium (Mineral)


Function: Bone health. For proper muscle function. Nerve transmission.

Recommended intake: 1000-1300 mgs/d.

Effects of deficiency: Osteopenia, osteoporosis.increased risk of fractures.

Risk and effects of toxicity: Can cause kidney stones.

UL: 2500 mgs/d.

Natural sources: Milk, yogurt, cheese, Chinese cabbage, broccoli, spinach, fish with bones.



Phosphorus (Mineral)


Function: Major component in bones and teeth.

Recommended intake: 700-1250 mgs/d.

Effects of deficiency: Muscle weakness, bone pain, rickets/osteomalacia.

Risk and effects of toxicity: Seen in those who cannot excrete excess phosphorus (people with kidney disease) when taken in high amounts.

UL: 4 gms/d.

Natural sources: Nearly all foods contain P. dairy products are a rich source.



Copper (Mineral)


Function: Stimulates immune system to fight infections, repairs injured tissues, promotes healing.

Recommended intake: 700-900 ug/d.

Effects of deficiency: Anaemia, Neutropenia (low white blood cells, therefore more risk of infections); Osteoporosis in children.

Risk and effects of toxicity: Low-risk of toxicity, no known effects.

UL: 10,000 ug/d.

Natural sources: Meats, seafood, nuts, seeds, whole grain products.



Zinc (Mineral)


Function: Growth and development, protecting the immune system.

Recommended intake: 8-11 mgs/d.

Effects of deficiency: Growth retardation, diarrhoea, skin rash, hair loss, immune deficiency.

Risks and effects of toxicity: Adverse effects usually due to chronic supplementation of zinc (suppression of the immune system, copper deficiency, nausea/vomiting).

UL: 40 mgs/d.

Natural sources: Red meat, shellfish, whole grains.




Iodine (Mineral)


Function: Used in production of hormones (example, thyroxine regulates our metabolism).

Recommended intake: 120-150 ug/d.

Effects of deficiency: Very rare, Goitre, Hypothyroidism.

Risk and effects of toxicity: Weight gain, fatigue, water retention.


Natural sources: Seafood, seaweed.