Nutritional Deficiencies

Nutrition Food Rainbow

Nutritional deficiencies occur when the body lacks certain micronutrients i.e. vitamins and/or minerals. 

Micronutrients are vital to life in many ways e.g.:

  • Optimal growth and development
  • Maintenance of bodily processes such as functioning of major organs like the heart, lungs and brain
  • Supporting the immune system in warding off infections
  • Psychological well-being

Causes of nutritional deficiencies may be multifactorial and can include:

  • Malabsorption that is:
    • Drug-induced (e.g. prolonged use of antibiotics, corticosteroids) 
    • Resulting from a disorder (e.g. celiac disease, Crohn’s disease, colon cancer) 
    • Post bariatric surgery (reducing stomach size to achieve weight loss)
  • Inadequate dietary intake e.g.
    • People on restrictive diets (such as vegans or vegetarians)
    • Elderly with poor dentition or appetite
  • Increased nutritional requirements
    • Pregnancy and lactation
  • Increased depletion
    • Drug-induced (e.g. diuretics cause increased excretion of calcium, potassium, magnesium, zinc)

Nutritional deficiencies may thus lead to developmental abnormalities and diseases. This can usually be prevented or remedied by eating a balanced diet, or with additional supplementation. 

Read on to learn more about common nutritional deficiencies and how to avoid them.

Common Nutritional Deficiencies 

Micronutrient & Recommended Daily Allowance (RDA)

Role Sources (%DV*)

Complications arising from deficiency

  • Required for the synthesis of thyroid hormones which are involved primarily in regulating heart rate, the rate of digestion, weight, and energy levels
  • Abundant in iodised salt,  seafood (85g of baked cod provide 66% of the DV), seaweed (1g of kelp packs 460–1,000% of the DV) 
  • Goitre, which is the enlargement of the thyroid gland, usually manifesting as a swelling in the neck, rapid heart rate, shortness of breath, difficulty swallowing etc. 
  • Congenital iodine deficiency syndrome causes cretinism (physical deformities – short stature, bone deformities, and intellectual disabilities.)

Adults: 150mcg/day

Pregnant women: 220mcg/day

Vitamin D 
  • Helps absorb calcium and phosphorous from food; also regulates calcium homeostasis in the kidney. This affects bone health, blood pressure, cardiovascular health, and neurodevelopment
  • Involved in immune function
  • Helps to regulate cell growth and differentiation 
  • Weak/brittle bones lead to rickets in children, predisposes to osteoporosis and fractures 
  • Dysregulation of calcium homeostasis can lead to heart disease, stroke

Adults: 15mcg (600IU)/day

>70yo: 20mcg (800IU)/day

Vitamin A 
  • Involved in the production of certain cells e.g. B- and T-cells, which play central roles in immune responses against disease.
  • Maintaining good vision
  • Essential for reproduction – plays a role in sperm and egg development.
  • Also critical for placental health, foetal growth.
  • Foods of animal origin – cod liver oil (one tablespoon contains ~500% of the DV), liver (one 60g slice of beef liver contains ~800% of the DV)
  • Beta-Carotenes (converted into Vitamin A):  carrots (one large carrot provides 75% of the DV), sweet potato (one medium 170g boiled sweet potato contains 150% of the DV), spinach (one 28g serving of fresh spinach provides 18% of the DV)
  • Increased susceptibility to infection 
  • Eye (ocular) problems such as blindness in children, night blindness in pregnant women and corneal ulceration
  • Pregnancy complications

Men: 900 mcg/day

Women: 700 mcg/day

  • Required to form healthy red blood cells
  • For foetal development – brain and nervous system functioning
    • Beans (one 177g cup of cooked kidney beans contains 33% of the DV) and lentils 
    • Dark leafy greens e.g. kale, spinach (One 30g serving of raw spinach provides 15% of the DV)
  • Fortified grains (One 140g cup of cooked spaghetti contains ~26% of the DV)
    • Meat (poultry, pork)
  • Folic acid tablets
  • Folate deficiency anaemia; symptoms include extreme tiredness, weakness
  • Foetal abnormality – neural tube defect (such as spina bifida)

Adults: 400mcg/day

Pregnant women: 400-1000mcg/day

  • Necessary to produce red blood cells, which carry oxygen throughout the body,
  • Organ meat (One 81g slice of liver gives >50% of the DV)
  • Shellfish e.g. Clams, mussels, and oysters (85g of cooked oysters provide ~50% of the DV.)
  • Canned sardines (One 106g can offers 34% of the DV.)
  • Beans (Half a cup or 85g of cooked kidney beans provides 33% of the DV.)
  • Seeds e.g. pumpkin, sesame, and squash seeds (One 28g serving of roasted pumpkin or squash seeds contains 11% of the DV)
  • Dark, leafy greens e.g. Broccoli, spinach, kale (One 28g serving of fresh kale provides 5.5% of the DV)
  • Iron deficiency anemia i.e. decrease in red blood cells and blood’s ability to carry oxygen; symptoms usually include tiredness, weakness, shortness of breath, a weakened immune system, and impaired brain function

Adult >50yo: 8 mg/day

Adult women <50yo: 18 mg/day

  • Maintain strong bones and teeth
  • Control muscle and nerve function
  • Maintain heart function
  • Dairy products – cheese, milk, yoghurt (3 servings a day will meet RDA)
  • Fortified cereal or orange juice
  • Dark leafy greens e.g. spinach, kale (one 28g serving of fresh kale offers 5.6% of the DV)
  • Weak, brittle bones
  • Numb, tingling fingers
  • Abnormal heart rhythm


♀ > 50yo and
> 70yo: 1200mg/day

  • Helps support bone health
  • Involved in >300 biochemical reactions in the body 
  • Maintain normal nerve and muscle function
  • Keeps the heartbeat steady
  • Assists in energy production
  • Whole grains (One 170g serving of oats contains 74% of the DV)
  • Nuts (20 almonds pack 17% of the DV)
  • Dark chocolate (One 30g serving of dark chocolate offers 15% of the DV)
  • Dark green, leafy vegetables (One 30g serving of raw spinach provides 6% of the DV)
  • Loss of appetite, nausea and vomiting, fatigue, and weakness
  • In severe cases, it may lead to numbness and tingling, muscle cramps or contractions, seizures, irregular heart rhythms etc. 

Adults: 1000mg/day

♀ 320mg/day

Pregnant women: 360mg/day

Vitamin B12
  • Involved in the production of red blood cells and DNA, 
  • Ensures proper functioning of the nervous system
  • Shellfish e.g. Clams and oysters (One 85g portion of cooked clams provides 1400% of the DV)
  • Organ meat (one 60g slice of liver packs >1000% of the DV)
  • Meat (A small, 170g beef steak offers 150% the DV)
  • Eggs (one egg provides ~6% of the DV)
  • Milk products (one 240 ml cup of whole milk contains about 18% of the DV)
  • Megaloblastic anemia i.e. red blood cells produced in the bone marrow are too large to pass out of the bone marrow into your circulation; symptoms include pale, jaundiced skin, weakness and fatigue, breathlessness, dizziness
  • ↑ homocysteine levels, predisposes to arterial damage and blood clotting, thus also ↑ risk of stroke, coronary artery disease, dementia
  • Depressed mood

Adults <50yo: 2.4mcg/day#

Pregnant women: 2.6mcg/day

* The DV allows people to easily compare the nutrient contents of different foods. It is a percentage based on the recommended daily intakes of key nutrients from the Food and Drug Administration (FDA). 

#Elderly need more; with age, the body makes less stomach acid and intrinsic factor (a type of protein)— both of which can affect the absorption of vitamin B12.

Diagnosis of Nutritional Deficiencies

Whatever the nutritional deficiency is, there are usually generic tell-tale signs and symptoms like weakness, fatigue, poor concentration, light-headedness, shortness of breath, pale skin, constipation, palpitations, numbness or tingling, and hair loss. Blood tests e.g. complete blood count, along with a discussion with the physician on dietary habits will be able to confirm specific deficiencies.

Treatment of Nutritional Deficiencies

  • Dietary changes
    • The doctor may refer you to a dietitian to discuss possible dietary modifications to boost nutritional intake.
  • Supplementation
    • Doctors will prescribe oral supplements at appropriate frequencies and dosages, tailored to the individual.
    • In very severe cases, such as when a nutritional deficiency does not respond to oral medications or vitamins, it may be necessary to administer the nutrient parenterally via the veins or muscles.
    • Regular blood tests may be carried out to assess status.


Malnutrition can lead to many health issues. The best way to prevent deficiency and consequent disease is to eat a balanced diet that includes whole, nutrient-dense foods. Supplements may be necessary for those who cannot obtain enough from diet alone. This includes the elderly, pregnant or lactating women, vegans, vegetarians, and in people with malabsorptive conditions.

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