During the transition from babyhood to toddlerhood, the most daunting task for you as a parent, apart from making your child eat right, is to protect her from infections. According to the World Health Organisation (WHO), climate change has a major influence on the increased occurrence of infectious diseases. The article, 'Impact of climate change on human infectious diseases: Empirical evidence and human adaptation”, by X.Wu et al., 2016, states that infections occur 3 components are essential for an infection to occur: pathogen, host and the living environment. Each of these requires favourable climatic conditions for survival, reproduction, distribution and transmission, which is very well provided by changes in weather conditions.
It is quite heartening to know that nature has provided a solution to this problem. According to the Academy of nutrition and dietetics, the nutrients that build the immune system include vitamins A, C, E, protein and zinc among others. Recent investigations have proved that vitamin D has a very important role in immune function.
How vitamin D helps prevent cold and flu
Initially, vitamin D was known only to maintain healthy bones, teeth and muscles. But today, research has shown the multifaceted role of this vitamin in the body. Although in its teething stage, there is some evidence of the role of vitamin D in preventing cold and flu. Martineau et al in their recent study entitled, “Vitamin D supplementation to prevent acute respiratory tract infections,” observed that individuals who had daily or weekly supplementation of vitamin D had a lower chance of contracting respiratory infections. They also analysed that in cases of bacterial and viral attack, vitamin D supports the release of antimicrobial agents which could prevent the entry of disease causing organisms in the respiratory system.
Daily dosage guidelines based on age (2-3 years, 3 and above)
Several studies have stated serum levels of 25-hydroxyl vitamin D (25(OH)D to be the most reliable indicator of vitamin D deficiency. To keep the serum levels of 25(OH)D >30ng/dL which is considered to be the optimal level, the US Endocrine committee has suggested the intake of 400-1000 IU/day under 1 year of age and 600-1000IU/day from 1 to 18 years of age.
Sources of vitamin D
• Sunlight: Most of the circulating vitamin D in the body is synthesised from skin exposure to the ultraviolet B (UVB) rays while <10% is obtained from dietary sources. Vitamin D3 is present under the skin in an inactive form and it undergoes two steps of activation, the first of which occurs with the help of the UVB rays of the sun.
As per the evaluation by Harinarayan et al in their study, “Vitamin D and sun exposure in India”, maximal formation of vitamin D3 from its inactive form happens between 11 am to 2 pm during the day. Thus, this is considered to be the ideal time for sunlight exposure.
• Dietary sources: Vitamin D2 and D3 are the two forms of vitamin D, the latter being more well absorbed than the former. According to the recently revised Indian Food Composition Table- 2017, mushrooms are very good sources of vitamin D2. Limited amounts of vitamin D3 is available in eggs, fish and meat.
Due to limited availability of vitamin D from dietary sources and inadequate exposure of skin to sunlight, vitamin D fortified foods are being recognised as an important source.
Supplements are good in moderation
The prevalence of vitamin D deficiency across toddlers is alarming. Since it is essential that the daily requirement is adequately met and dietary sources are not sufficient, most people resort to the use of vitamin D3 supplements. Though this is not a bad option, it is important to remember that vitamin D is fat soluble, excess amounts of which leads to toxicity.
The upper limit of vitamin D intake must not exceed:
1000 IU/ day for infants from 6 months-1 year
1500 IU/day for 1-3 years
2500 IU/day for 4-8 years
3000 IU/day for >8 years
Here’s a comprehensive list of nutrients that can help build immunity in your child as suggested by the Academy of Nutrition and Dietetics:
1. Protein is an essential component of the body’s defence system. It is available in eggs, sea food, meat, milk, soyabean, pulses and nuts.
2. Vitamin C aids the formation of antibodies thus helping in preventing infections. Include citrus fruits like sweet lime, oranges, amla, grapes, lemon juice, papaya and melons in your child’s diet to ensure the requirement for vitamin C is met.
3. Vitamin A keeps the skin and underlying tissues in the mouth, respiratory tract, intestine, stomach healthy. Papaya, mango, pink guava carrot, green leafy vegetables and sweet potato are rich sources.
4. Vitamin E is found in nuts like almond and pistachio. Vegetable oils are a good source of vitamin E. Include these foods in your child’s diet to ensure he gets his daily quota of antioxidant to boost his immunity by neutralizing the free radicals in the body.
5. Zinc ensures smooth functioning of the immune system and wound healing. Legumes like Bengal gram dhal, black gram dhal, peas, black rajmah and cereals like ragi and whole wheat flour are good sources.
6. Other nutrients like vitamin B6, folate, selenium, iron, prebiotics and probiotics also influence immune response.
The author is a nutritionist based in Chennai.