For many people, nutritional supplements are a regular part of their diet. In 2015, over 45% of Canadians reported taking at least one type of nutritional supplement, including but not limited to vitamins, minerals, fibres, and fish oils. In general, nutritional supplements are defined as any substance consumed in addition to normal food that is used to correct a nutritional deficit.

The popularity of such supplements stems from a large body of scientific research linking a healthy diet to proper growth and development, and reduction in the risk for developing diseases such as type 2 diabetes, cardiovascular disease, stroke, and cancer. Indeed, 85% of surveyed Canadians taking supplements indicated that they did so to improve and maintain their health.

Various dietary nutrients have been identified that, when lacking, contribute to disease. For example, severe deficiency of ascorbic acid (vitamin C) causes scurvy, a disease common in the past when access to fresh fruits and vegetables was limited. By extracting these key nutrients from our food and distilling it into a single pill, nutritional supplements promise to deliver the best advantages of a healthy diet in the most efficient package.


Neural tube defects (NTDs) are a group of congenital disorders caused by impaired neural tube development during early gestation, leading to severe defects in the brain and spinal cord. Research over the past few decades have demonstrated a strong link between maternal folic acid supplementation and decreased rates of NTD. Folic acid is metabolized into folate, which is required for many processes related to fetal growth and development, including DNA replication, amino acid synthesis, and vitamin metabolism. Folate cannot be synthesized by our bodies and must be derived from the diet or by supplementation.

Experimental and observational studies since the 1980s have shown that folic acid supplementation during pregnancy can reduce the risk of NTD occurrence by over 70%. Based on these studies, Canada began fortifying various cereal food products with folic acid in 1998, leading to a 46% reduction in the rate of NTDs over the next 10 years. Currently, Health Canada recommends a daily dose of 0.4 mg of folic acid per day to women who are or are thinking of becoming pregnant.


Calcium is best known for its role in maintaining bone health, but this mineral is also important for muscle and nerve function. Low calcium levels can lead to weakening of the bones, increasing the risk of developing osteoporosis later in life. Various factors can influence calcium levels, including low dietary intake, high calcium excretion, long-term corticosteroid usage, or diseases of the small intestine that reduce the body’s ability to absorb calcium. For individuals meeting any of the above criteria, calcium supplements may be recommended to meet their calcium needs.

However, there is growing evidence that taking too many calcium supplements may be detrimental to cardiovascular health. A 2010 meta-analysis of 11 randomized clinical trials involving calcium supplements suggested that taking these supplements could increase the risk of heart attack by up to 30%. While the underlying reasons for these observations are unknown, it is possible that high calcium levels could lead to the buildup of calcium-based plaques in blood vessels, which is associated with coronary heart disease.


Nicknamed the “sunshine vitamin”, vitamin D is a unique nutrient in that we obtain most of what we need by synthesizing it ourselves in the skin following sun exposure. Vitamin D is required for optimal calcium and phosphate absorption, and parathyroid hormone regulation. It is often used in combination with calcium supplements to treat diseases related to bone deficiency, such as nutritional rickets and osteomalacia. Various observational studies have also suggested that low vitamin D levels are associated with negative outcomes in cardiovascular, autoimmune, neurological, and infectious diseases, as well as cancer and total mortality.

Vitamin D has been identified by Health Canada as a shortfall nutrient, in which a significant proportion of Canadians do not meet the average daily intake requirement. This has been attributed to lifestyle and environmental changes that have reduced our sun exposure, such as less time spent outdoors and increased air pollution. Although vitamin D supplementation is recommended to maintain healthy vitamin D levels, it is important to emphasize that these supplements should be taken in moderation. High levels of serum vitamin D can lead to vitamin D intoxication, characterized by hypercalcemia and/or hyperphosphatemia impairing renal, cardiac, parathyroid, and brain functions.

While there is a role for supplements in correcting nutritional deficits, their importance for the general healthy population is less clear. The impact of nutritional supplements on preventing disease in healthy adults are conflicting, with some studies linking specific supplements to benefits in overall health, while others showing minimal or even negative outcomes.

Nutritional supplements are classified by Health Canada as a sub-category of drugs under the umbrella term “natural health products” (NHPs), but are subject to different regulations than other drug products. Unlike prescription and non-prescription drugs that are required by the Food and Drug Regulations to be labelled in plain language, NHPs are not required to follow a standardized labelling format. Inconsistent and inadequate access to information about NHPs can result in adverse NHP-drug interactions, unsafe dosing, or allergic reactions, especially as NHPs can be purchased without medical consultation or prescriptions. In 2011, the Canadian Institute for Health Information estimated that 12% of emergency hospitalizations were related to preventable medication errors, including improper NHP usage. Of note, one of the major reasons for hospitalization was accidental overdose.

Although there is a perception of nutritional supplements as a benign health product as they are essentially a concentrated nutrient extract, the adage “too much of a good thing” is particularly relevant to their consumption. Like any drug, exceeding the recommended dosage of nutritional supplements can lead to adverse effects. There is also evidence that our bodies handle these concentrated doses of micronutrients differently compared to when they are gradually absorbed with other nutrients from our diet. For example, a 1997 study showed that high dietary and supplemental calcium levels were associated with opposing kidney stone outcomes – women with a high dietary calcium intake had a decreased risk for kidney stones, while those taking calcium supplements had an increased risk. Such observations may be due to synergistic effects of different nutrients acting upon one another when taken together in the diet.

Despite the modest to limited benefits of nutritional supplements in the healthy population, there is still a role for nutritional supplements for those facing true nutritional deficits, whether due to a medical condition or malnutrition. According to the World Health Organization (WHO), 2.3 billion adults suffered from malnutrition in 2021, and undernutrition was the cause of 45% of deaths in children under 5 years of age, particularly in low- and middle-income countries. Vitamin A deficiency is one of the major public health problems related to micronutrient deficiency, as it leads to weakening of the immune system and increases general susceptibility to other diseases and overall mortality. Various organizations like the WHO, UNICEF, and Nutrition International have implemented vitamin A supplementation programs that deliver vitamin A supplements to children and mothers in need, which have reduced childhood mortality by up to 12%. Other food fortification, supplementation, and sustainable food development programs have also been established to address the global issue of malnutrition.  

It is easy to be tempted by the convenience of taking a pill that contains key nutrients that promises to improve our health. However, nutritional supplements are not a substitute for a healthy diet.

“Pills are not a shortcut to better health and the prevention of chronic diseases,”

Dr. Lawrence Appel, director of the Johns Hopkins Welch Center for Prevention, Epidemiology and Clinical Research

Rather than focusing on nutritional supplements, many experts agree that building better lifestyle habits – eating healthily, exercising, and sleeping well – is the key to good health.


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