Many people stuff themselves with over-the-counter dietary supplements, either as an insurance against not-so-perfect diets or as a shortcut to improve immunity and overall health. During the pandemic, we saw many people consume vitamin D to boost their immunity. Sales of nutrition supplements skyrocketed last year and, according to Businesswire , their global market size is expected to grow from $136.2 billion in 2020 to $272.4 billion by 2028. The Indian market too is predicted to grow around 18 per cent till 2026.

But the big question is: Do supplements work? Are they safe?

Scientific evidence varies widely — we have tons of information for some of the supplements, while others lack interventional studies showing clear benefits. Supplement, as the name suggests, should only be added to your diet to reverse your body’s nutrition deficiencies. To do that we must first identify and quantify these nutritional shortcomings.

Nutritional deficiency occurs when our body does not absorb or get enough nutrients from diet. Altered absorption could result from subtle genetic defects in the enzymes processing micronutrients, gut microbiome imbalance, unidentified food allergies, leaky gut lining, pancreatic insufficiency or an autoimmune condition.

Also, poor nutritional status is not confined to only undernutrition. Obesity and diabetes — conditions often associated with over-nutrition, can also lead to vitamin and mineral imbalance in the body. India is the capital of both under- and over-nutrition. Varied diets, ethnicity and climate, on top of our unique habits and lifestyle make us more vulnerable to nutritional deficiencies.

About 30 per cent Indian are vegetarians. Plant-based food does not naturally contain vitamin B12, therefore vegetarians and vegans can develop a deficiency if they do not supplement their diet with either dairy products, eggs or fortified cereals and foods. Vitamin B12 deficiency can lead to precocious anemia and other serious health consequences. In such cases supplements can help.

As for vitamin D, normal levels may help the immune system fend off infections, but taking it as supplement does not prevent or treat Covid-19.

Several clinical studies demonstrated that vitamin D deficiency increases the severity of Covid-19 infection but there is not enough evidence that higher levels will prevent the disease. Since it is a fat-soluble vitamin, body fat composition and toxicity levels should be considered before recommending dosage. It is important to know such subtle differences before taking any supplements.

Most manufacturers of food supplements market them as an elixir for preventing and curing all ailments, which is not only misleading but also potentially dangerous. Another popular trend is to rebrand them as customised supplements, based merely on biometric data or online questionnaires.

The truth is, we all react differently to the same supplements. Also, supplements can interact with other medications or other supplements, which can decrease their efficacy. Therefore, it is wise to check with a doctor before starting a new supplement or to use genetic testing to understand how you metabolise and absorb various food items. Only guided and personalised supplements work.

We need a personalised approach to identify the shortcomings in our diet, lifestyle, health and genes that may lead to nutritional deficiencies, and then, wherever possible, quantify the deficiencies before supplementation.

The writer is founder and chief scientist of wellOwise, a health start-up