Is a multivitamin supplement good for my health?

Nearly half the adult population in the United States takes a multivitamin supplement. Does it boost your general health? Does it reduce your risk of cardiovascular disease and cancer?

You will be surprised to learn that certain vitamins when taken in excess may increase your risk of developing cancer.

Multivitamins provide little protection for cardiovascular disease, the number 1 cause of death globally.

Some special groups of people like pregnant women, elderly and young children need specific supplements.

But for most of us, before popping the pill in your mouth, ask yourself – Do I really need it? Is this going to harm rather than benefit?

You could use the money you spend on pills on good nutritious food, that will provide you the same nutrients.

“The benefits of nutrient intake from foods may reflect synergistic interactions among multiple nutrients and other bioactive substances in foods.” writes Fang et al in BMJ 2020.

Role of vitamins and minerals

Our body needs vitamins and minerals to function properly.

There is a minimum requirement. If this is not met, you develop deficiencies and certain diseases.

On the other hand, taking too much of it can be toxic to your body.

For those interested, the Public Health England has a recommendation of the need of different vitamins and minerals in various age groups. You can read it here.

There are 2 main types of vitamins:

  1. Water soluble – Generally speaking if you eat a little more than needed it is flushed out in the urine.
  2. Fat soluble – If you consume in excess, it can build up stores in the liver and may cause toxicity.
Water soluble vitamins

Water soluble vitamins | Source | Uses
Thiamine (Vitamin B1) | Whole grains, meat, fish   | Helps convert nutrients into energy  
Riboflavin (Vitamin B2)   | Organ meats, eggs, milk | Energy production, cell function and fat metabolism  
Niacin (Vitamin B3)   | Salmon, meat, leafy greens, beans   | Production of energy from food  
Pantothenic acid (Vitamin B5)   | Mushrooms, tuna, avocado   | Fatty acid synthesis   
 Pyridoxine (Vitamin B6)  | Fish, milk, carrots, potatoes   | Releases sugar from stored carbohydrates for energy and also has a role in production of red blood cells    
Biotin (Vitamin B7)   | Eggs, almonds, spinach   | Metabolism of fatty acids, amino acids and glucose  
Folate (Vitamin B9)   | Beef, spinach, asparagus   | Important for proper cell division   
Cobalamin (Vitamin B12)   | Fish, meat   | Red blood cell formation and proper nervous system and brain function    
Ascorbic acid (Vitamin C)   | Citrus fruits, bell peppers, Brussels sprouts   | Formation of neurotransmitters and also collagen, the main protein in your skin  
Water soluble vitamins

Fat soluble vitamins

Fat soluble vitamins | Source | Uses
Vitamin A | Liver, dairy, fish, sweet potatoes, carrots, spinach   | Good vision
Vitamin D | Sunlight, fish oil, milk   | Immune function, helps absorption of calcium and bone growth
Vitamin E | Wheat germ, almonds   | Immune function, prevents cell damage
Vitamin K | Leafy greens, soyabeans, pumpkin   | Blood clotting, bone development
Fat soluble vitamins


Some minerals like Calcium and Magnesium are needed in large quantities.

Others like Iron and others are needed in small quantities.

Minerals | Source | Uses
Calcium | Milk products, leafy greens, broccoli   | Bone and teeth formation, helps muscle contraction
Magnesium | Almonds, cashews, black beans   | Regulates blood pressure, helps in many enzyme reactions in cells
Iron | White beans, spinach, meat   | Part of Haemoglobin which carries oxygen in blood
Zinc | Meat, shellfish | Growth, immunity, wound healing
Iodine | Cod, tuna, shellfish, dairy products | Thyroid function
Fluoride | Spinach, grapes, black tea | Bone and teeth formation

This list is by no means exhaustive.

There are many other good food sources and uses of vitamins and minerals that I have not mentioned.

The purpose of this table is to highlight that vitamins and minerals are extremely important in the normal functioning of the body.

Why do people take supplements?

The rationale behind taking MVM (Mutivitamin Mineral) supplements for most people is :

  1. The expectation that it boosts general health, energy levels and so forth.
  2. Prevention of cardiovascular disease (mainly heart attacks and stroke) and cancer.
  3. Prevention of vitamin and mineral deficiency and diseases that arise from deficiencies like anaemia and under-functioning thyroid.
Deficiency diseases in normal healthy adults in the developed world is negligible, if you eat a wholesome diet.

“The immense beneficial effects of vitamins in preventing pellagra, rickets, and scurvy at a period when overt nutritional deficiencies were common, gave the halo of a magical effect to these drugs.” remark Kamangar et al in an article in International Journal of Preventive Medicine.

Kamangar et al also observe “Before the 1990s, some eminent scientists strongly advocated the use of vitamins and supplements. Most notably, Linus Pauling, a two-time Nobel Laureate and a towering figure in chemistry, believed that vitamin C could prevent cancer and increase the life expectancy of cancer patients.”

This was not found to be so in many other subsequent studies. But the belief that vitamin C can prevent cancer persists.

Deficiencies of vitamins and minerals

Nutritional deficiencies still occur in developing countries where there is poverty and food shortage:

  • Iron deficiency – This occurs because of dietary deficiency and parasite infections of the gut like hookworms. Pregnant women with anaemia develop complications, especially during childbirth with large amount of blood loss.
  • Iodine deficiency – Under-functioning thyroid and growth problems in children.
  • Vitamin A deficiency – Night blindness and low immunity.
  • Zinc deficiency – Immune deficiency, childhood illnesses.
In the developed countries, these deficiencies are rare because of a balanced diet, awareness and fortified food like iodised salt.

What problems can supplements cause?

The main problem is that you may exceed the required dose of a vitamin or mineral.

A balanced diet contains sufficient amount of most essential nutrients.

In most cases nutritional supplements do not undergo strict scrutiny like medications.

You can have supplements with all kinds of mixtures of vitamins, minerals, not to forget omega 3&6 oils, probiotics and more.

It is unregulated, with doses of various nutrients variable in different preparations.

If you are already eating a balanced diet, this may increase recommended amounts causing harm.

Studies showing multivitamins to be of benefit

Physicians’ Health Study II in 2011 studied the effect of supplements on men. It showed 8% reduced risk in development of cancer, 18% reduction in men aged 70 and over.

An ongoing study called the COSMOS trial is studying the effects of supplements on both men and women. Results are due end of 2021. That should throw more light on this debate.

Studies showing supplements to be harmful.

This is where we should really focus our attention.

At the end of the day you can get your nutritional needs from your diet.

If you are going to spend your money on a supplement that you think will improve your health, you need to be sure it won’t harm.

Here goes:

  • A 2011 study of around 39000 women who took MVM concluded that “several commonly used dietary vitamin and mineral supplements may be associated with increased total mortality risk; this association is strongest with supplemental iron.”
  • Physicians’ Health Study II looked at different supplements. High doses of Vitamin A increased risk of lung cancer in men who smoked.
  • Physicians’ Health Study II showed that high levels of Vitamin E increased risk of stroke due to bleed in the brain.
  • SELECT trial showed an increased risk of prostate cancer in men with high doses of vitamin E.
This certainly does not mean that supplements are a no no.

All it means is that healthy adults probably don’t need them and may be better off without them.

So who needs supplements?

Specific supplements are recommended for:

  • Pregnant women – prepregnancy to first 3 months of pregnancy. Folic acid reduces chances of some brain birth defects of the baby. Vitamin D supplement is recommended in pregnancy.
  • Breast fed babies – American Academy of Paediatrics recommends supplementation with vitamin D and iron.
  • Osteoporosis – Older adults with osteoporosis should take calcium and vitamin D.
  • Pernicious anaemia – This is relatively rare. Pernicious anaemia is more common after age of 70. Individuals with this condition may not be able to absorb Vitamin B12 well and need supplements of Vitamin B12.
  • Malabsorption – Some people are unable to absorb sufficient nutrients because of a defect in the gut. Crohn’s disease and coeliac disease sufferers are prone to it. Also people who have a surgery called gastric bypass can have malabsorption. Supplements are essential for them.
Take home message

“Overall, however, the recommendation is for the generally healthy population to try to get these vitamins and minerals from a healthful and balanced diet. That is how they are best absorbed in the most appropriate proportions.”

This is the message from Dr JoAnn Manson, professor of medicine at Harvard Medical School and Brigham and Women’s Hospital in a commentary on Medscape published on June 2nd 2021.