Dietary Deficiencies and Diseases

Vitamins and minerals are only needed in small amounts for human health, but a lack of any of these micronutrients can cause ill-health, either directly, or by reducing resistance to disease. Modern nutritional science has its origins in the repeated demonstration that disease can be the result of chronic nutrient shortages, and that these diseases can be treated with appropriate vitamins and minerals.

In developing nations, an inadequate intake of protein and calories – due to lack of food or a very poor diet – is the major nutritional problem; it results in starvation syndromes, with hundreds of millions of people suffering from nutritional deficiencies. The effects of starvation and even semi-starvation are profound, resulting in anaemia, infections, chronic diarrhoea, stunted growth and failure to thrive.

In developed nations, although diet has improved considerably in terms of nutrition over the last few decades, deficiencies in certain minerals, such as iron and calcium, are still relatively common, resulting in conditions such as iron-deficiency anaemia and osteoporosis. In the developed world, any nutrient shortages are usually due to modern food processing techniques and poor choice of food -such as not eating enough fresh fruit and vegetables, and eating too many sugary and fatty foods. Even if an individual is marginally malnourished (a condition known as subclinical deficiency), he can experience a weak immune system and decreased resistance to viral and bacterial infections, as well as a variety of symptoms ranging from fatigue to depression. Malnourishment can eventually lead to degenerative diseases, including cancer, heart disease, osteoporosis, and arthritis.

Deficiencies can also result from an inability to digest or absorb nutrients properly – even if the diet is balanced and healthy. These conditions are known as maldigestion and malabsorption.


Foods vary greatly in nutrient content, so it is important to eat a balanced and varied diet. If the early signs of a deficiency are not treated, a deficiency-related disease may develop. The main deficiency-related diseases include anaemia, beri-beri, goitre, night blindness and xerophthalmia, osteoporosis, rickets and scurvy. A person displaying any of the symptoms of a deficiency-related disease should seek medical advice. Treatment and prevention include the redressing of the vitamin or mineral imbalance by adding to the diet foods that are rich in the deficient nutrient.


The term ‘anaemia’ describes a range of illnesses that involve a lack of the oxygen-carrying substance haemoglobin in the blood, resulting in tiredness and general weakness. Anaemia is often caused by a lack of iron, vitamin B12 or folate. Once any form of anaemia has been identified, medically supervised supplementation is the most effective form of treatment. Thereafter, eating a well-balanced diet should help to prevent any recurrence.

Iron-deficiency anaemia Iron deficiency is the most common cause of anaemia – either from high blood loss (for example, during menstruation) – or from a low intake of iron in the diet. People at risk from iron-deficiency anaemia include vegans (who eat no animal products, people who eat a lot of junk food, and children with inadequate diets.

Iron makes it possible for the blood cells to deliver life-giving oxygen from the lungs to the rest of the body; it also helps the body to fight infections. Iron-deficiency anaemia leaves a person feeling tired, listless, and prone to infection. Symptoms include pallor and shortness of breath.

To avoid iron-deficiency anaemia, it is advisable to include iron-rich foods in your diet. These include red meat, offal, poultry and fish. The richest source of iron is liver, but this should be avoided during pregnancy because of the risk of excess vitamin A intake, which can result in birth defects. Some health experts also recommend general avoidance of offal (particularly liver and kidneys) because of the high level of toxins stored in these organs.

Other good sources of iron in the diet include beans, lentils, nuts, dark-green leafy vegetables, iron-fortified breakfast cereals, prunes and tofu. A combination of plant proteins, such as rice with lentils, aids iron absorption. In order to help the body absorb iron from plant sources, such meals are best accompanied by a source of vitamin C, such as a tomato salad or a glass of orange juice. For meat-eaters, a small amount of animal protein, in the form of a little red meat, can also facilitate the absorption of iron contained in vegetables.

Vitamin B12-deficiency anaemia

Anaemia can also result from a lack of vitamin B12 in the diet. Vegans are particularly susceptible to vitamin B12 deficiency, because this vitamin can only be found in significant quantities in animal foods such as liver, sardines, eggs, and cheese or bacteria-fermented food such as yoghurt. A form known as pernicious anaemia is caused by the inability of the body to absorb vitamin B12.

The symptoms of vitamin B12 deficiency include memory loss, weakness, personality and mood swings and numbness and tingling in the hands and feet. Anaemia may develop at a later stage.

To prevent vitamin B12-deficiency, vegans are often advised to take vitamin B12 supplements. People with pernicious anaemia require vitamin injections.

Folate-deficiency anaemia

Anaemia can also result from a lack of folate (also known as folic acid) in the diet; pregnant women and alcoholics are at risk. The symptoms are similar to those experienced in iron-deficiency anaemia.

Folate-deficiency anaemia can be prevented by eating plenty of leafy green vegetables, fortified breakfast cereals, pulses, eggs, wholemeal cereal products, brewer’s yeast and wheat bran. Pregnant women who think that they may have a folate deficiency should see their doctor, who is likely to advise them to take supplements.


The thiamin (vitamin B1) deficiency disease called beri-beri is common in developing nations among populations subsisting on polished white rice from which most of the vitamins and minerals have been removed. Whereas four average portions of boiled brown rice meet an adult’s daily requirement for thiamin, polished white rice contains barely any thiamin.

In developed nations, thiamin deficiency has almost been eliminated. However, people who drink excess alcohol and have a poor diet may still be affected by beri-beri.

The symptoms of beri-beri include fatigue, irritability, poor memory, appetite loss, confusion, swelling of the limbs, numbness and muscle weakness.

Beri-beri can be prevented by eating a balanced diet. Particularly good sources of thiamin include pork, liver, heart, kidneys, Brazil nuts, seeds, beans, brown rice and fortified cereals.


A swelling of the thyroid gland in the front of the neck is known as goitre; this condition can sometimes be caused by insufficient iodine in the diet. Iodine is a mineral found in kelp, seaweed, seafood, milk and iodized table salt. In some parts of the world, people still suffer from iodine deficiency. Goitre is most likely to affect people living inland – where the availability of sea-food is limited – and in areas where the top-soil contains little or no iodine, such as the plains of Africa, Asia and South America.

Night blindness and xerophthalmia

Because vitamin A has a specific function in the retina of the eye, this nutrient is also known as retinol. Deficiency can result in an inability to see in poor light, a condition known as night blindness, and also dryness of the cornea and conjunctiva.

The formation of ‘visual purple’ (the pigment required for vision in dim light) requires vitamin A. In vitamin A-deficient people, inadequate pigment causes an abnormally slow adaptation in vision when the person moves from strong to dim light.

Vitamin A-deficient individuals can develop a condition called xerophthalmia, in which areas of the eye called the conjunctiva and cornea can become abnormally dry; the eye then compensates with excessive watering. If left untreated, severe damage to the cornea may result.

Vitamin A is found in foods of animal origin, such as full-fat dairy produce, eggs and liver. The vitamin is also available indirectly from plant foods, in which it occurs as a carotenoid called beta-carotene, which the body converts into vitamin A.


The term ‘osteoporosis’ means ‘porous bones’. As the human body ages, the bones become progressively thinner and weaker – due in part to a loss of calcium – which is vital for strong bones. The most common form of the disease, post-menopausal osteoporosis (type one), affects postmenopausal women; type two osteoporosis occurs with ageing and affects both men and women.

The symptoms of osteoporosis (in both men and women) include a curved spine, loss of height, and brittle bones.

Regular exercise and a healthy diet play an important role in both preventing and treating this degenerative disease. Milk and dairy products have long been considered to be an excellent source of calcium. However, it is also known that an excess intake of animal protein can interfere with calcium absorption. It is possible, therefore, that the protein in dairy products may cancel out the benefits of the calcium. Research shows that the incidence of osteoporosis is highest in countries where protein intake is high. Calcium intake should come from a range of foods, including green leafy vegetables, nuts, seeds and beans.

Calcium works alongside other nutrients for healthy bones, including vitamin D, and the minerals phosphorus and magnesium, so it is important to also eat foods that are rich in these nutrients.


The deficiency disease called rickets is a childhood disease in which the growing bones soften and bend, becoming malformed. Rickets is caused by a deficiency of vitamin D, which results in not enough calcium salts being deposited in the bones to make them rigid. The condition is prevalent in some developing countries.

Vitamin D is often referred to as the ‘sun-shine’ vitamin because it is produced when the skin is exposed to the sun. In developed countries, the people most at risk of deficiency are those who are compelled to stay indoors, such as babies, the sick and the elderly, or women who traditionally wear clothes that completely cover their bodies.

The symptoms of rickets include pain in the affected bones, a prominent forehead, bow legs and knock knees, swelling and deformity of bones at the wrists, knees and ankles, a hunchback and distorted pelvic bones. Vitamin D deficiency also causes a bone disease in adults called osteomalacia – a softening of the bones which causes pain and increases the likelihood of fractures. Osteomalacia is still relatively common in elderly people.

Good food sources of vitamin D include fortified foods such as margarine and breakfast cereals, as well as eggs and oily fish.


In severe cases, vitamin C-deficiency can lead to scurvy. For centuries the disease was the bane of sailors with no access to fresh fruit or vegetables on voyages. Even today, elderly people on a low income are prone to scurvy if they do not have vitamin C.

The symptoms of scurvy include loss of teeth due to diseased gums, poor wound healing, weakened bones, weight loss, painful muscles, swollen joints and confusion.

Scurvy can be prevented by increasing the vitamin C content in the diet; good sources include citrus fruits, blackcurrants, peppers and tomatoes.