There are 13 vitamins and 14 major and trace minerals. Vitamins and minerals are required for hundreds of diverse bodily functions including metabolic reactions, growth, immunity, and tissue repair. Individuals who are healthy and regularly consume a well-balanced diet do not normally need vitamin and mineral supplements, but there are situations where supplements are beneficial or essential. Multiple vitamins or minerals may be lacking, and multivitamin and mineral supplements may prove beneficial. There are examples where there is a recognisable deficiency caused by the lack of a single vitamin or mineral, and a specific supplement is needed. Some individuals misuse supplements, consuming higher quantities than recommended, and consequently risk toxic side effects.
Dietary deficiencies of multiple vitamins and minerals
Blood and urine tests together with tell-tale symptoms of deficiency and physical examination can often reveal which vitamins or minerals might be lacking. There is evidence that our nutrient requirements change as we age. For example, older people over 60 may require greater amounts of potassium, calcium, folate, and vitamin D than younger adults, and may benefit from one or more supplements.
Vegan plant-based diets do not allow meat, fish, eggs, and dairy products, and consequently, probably lack some essential nutrients. The four vitamins and minerals most likely to be scarce in a vegan diet are vitamin B12, vitamin D, iron, and iodine, which are usually found in multivitamin formulations. Vegans should also look out for the many foods that are fortified with one or more supplements; for example, B12 and iron in wholegrain cereals; vitamin D in plant-based margarines; and iodine in table salt.
Western diets increasingly contain high levels of tasty ultra-processed foods that are high in sugar and fats and low in fibre, vitamins, and minerals. These foods are often cheaper than fresh fruits and vegetables. It is, therefore, unsurprising that people on low incomes choose these unhealthy diets despite the adverse effects on their health. Multivitamin supplements or foods fortified with vitamins and minerals may go some way to mitigating the consequences of unhealthy diets. Nevertheless, people on poor diets should be encouraged to eat a more balanced diet containing fresh fruits and vegetables before resorting to supplements.
Patients with advanced chronic kidney disease (CKD) or kidney failure have a disrupted metabolism and abnormal vitamin levels. Intake of vitamins B2, B5, B6, B7, and C is typically lower in people with advanced CKD or kidney failure; in contrast, plasma vitamin A levels are usually elevated in CKD. It has been proposed that CKD patients will benefit from carefully selected combinations of vitamin supplements or even multivitamins to prevent vitamin deficiencies. Because even moderately increased levels of vitamin A can be toxic, care must be exercised in the use of multivitamins that include vitamin A in the treatment of CKD.
Deficiencies in iron, vitamin B12 and magnesium
There are deficiencies in iron, vitamin B12 or magnesium which can be resolved with supplements. Iron- deficiency anaemia is caused by lack of iron which results in a loss of haemoglobin, and consequently insufficient red blood cells. Multiple symptoms including fatigue, shortness of breath, and sore tongue are among the many hallmarks of anaemia. A ferrous iron supplement can increase iron levels in those whose diets may lack sufficient absorbable iron; but before taking a supplement, increasing the amounts of iron-rich and iron-fortified foods in the diet should be tried. An iron supplement can also restore iron levels in pregnancy and following heavy periods.
Pernicious anaemia is a type of anaemia in which a shortage of red blood cells is caused by autoimmune gastritis that restricts the absorption of dietary vitamin B12 from the digestive system. B12 is required for many bodily functions, which include the synthesis of red blood cells, maintaining a healthy nervous system, utilising energy from food, and assisting in the functioning of folate. Poor absorption of B12 in pernicious anaemia is normally treated with long-term B12 injections that bypass the digestive system.
Magnesium (Mg) has several critical roles: controlling nerve and muscle function, supporting the immune system, and regulating blood pressure. Despite its important roles, Mg deficiency often goes unrecognised in the general population but is far more prevalent in hospital wards and ICU units, where it is more likely to be diagnosed in patients with certain serious illnesses. People with diabetes, chronic diarrhoea, alcohol use disorder, and coeliac disease are at an increased risk of Mg deficiency. There are at least seven symptoms of Mg deficiency including heart arrhythmia which is often not diagnosed until Mg levels are dangerously low. A Mg supplement may help to restore Mg levels in the treatment of heart arrhythmia and other medical conditions resulting from Mg deficiency.
Other single deficiencies – folate, vitamins D and C
There are also deficiencies in folate and vitamins D and C which can be overcome with supplements. Folate plays a crucial role in DNA biosynthesis and neurodevelopment in the early embryo. Folic acid is the synthetic version of folate that is abundant in many foods, and a large majority of adults do not need to take folic acid. But there are exceptions: women should start taking a folic acid supplement while trying to conceive and continue taking it throughout pregnancy as it substantially reduces the risk of birth defects. Children and adults who take metformin (a drug for type 2 diabetes) and people with liver failure or coeliac disease may experience a folate deficiency, and this group can benefit from a folic acid supplement.
Vitamin D has a prominent role in enhancing the efficiency of calcium and phosphate absorption from the intestines, thereby maintaining strong bones in health and disease. Vitamin D also influences immune cell function and helps to maintain a healthy nervous system. Sunlight stimulates the production of vitamin D in the skin, which is an important source of this vitamin as insufficient amounts of vitamin D are present in normal diets. Therefore, people who live indoors or in climates with low sunlight are advised to take a vitamin D supplement.
Vitamin C fulfils a crucial function in maintaining healthy tissues and preventing cell damage. Severe deficiency of vitamin C leads to scurvy, the hallmarks of which are swollen, bleeding gums and bruised skin with red or blue spots. Scurvy is rare in individuals who consume a varied diet but can arise in several medical conditions where food intake is severely compromised. Eating disorders, chemotherapy, and long-term alcohol or drug dependency fall into this category. Vitamin C supplementation can correct the deficiency in these cases.
Adverse effects of excessive vitamin intake
Some people misuse supplements by consuming large excesses, claiming “more is better.” Excess amounts of certain vitamins consumed for a long time can be toxic leading to serious illness, which in rare cases can be life-threatening. High intake of vitamin A increases the risk of birth defects, hip fractures, and prostate cancer. High intake of vitamin E also increases the risk of prostate cancer and is associated with heart failure and higher death rates. Excessive consumption of vitamin D can result in serious heart problems, abnormally high concentrations of blood calcium, and an increased risk of bone fractures and kidney stones.
Together these findings illustrate the importance of consulting a medical professional before considering taking supplements, especially those which are in excess of their recommended daily doses. Patients who are taking prescription medication should make their GP aware that they are consuming supplements as potentially serious drug interactions can arise with some combinations of vitamins, minerals, and prescription medicines. In conclusion, supplements should be used with care where there is a known deficiency and not be regarded as a substitute for a healthy diet.
