Interview with Prof. Vineeta Bal


What is immunity?

It is the accumulation of responses the defense system of an individual mounts against infectious diseases, allergens etc.. The infectious diseases can be by viruses or bacteria.

If there is an attack by a virus for instance, there will be virus-specific immunity. Otherwise immunity is a steady state of the body ready to defend.

Are there different types of immune responses?

There are two major types of immunity: Innate and adaptive immunity. Both types have cells and secreted components involved.

Innate immunity is extremely important in very early days of any infection. And it becomes much more important in the case of diseases that the individual has not encountered such as Covid-19.

Adaptive immunity is infection specific but slow to develop, it does not even come into the picture in the first 48 hours or so. It will be apparent only after day seven or day 8 of an infection.

There are several articles in the media about specific foods that claim to “boost” immunity. Do they mean that the foods boost innate immunity?

It is difficult to say what the articles are talking about. But in general terms when people say that a particular food is “boosting” immunity or “improving immunity” none of this has any meaning because they claim a general improvement in the immune status which is hard to document as useful.

However, specific boosting of immunity is possible. When, for example, a vaccine is developed for Covid-19 and given to people they will develop a response and the response will prevent the occurrence of Covid-19 in them. That boost can be given by the vaccine, and not by vegetables or meat or any other food that you consume. These foods are not going to boost or undermine the immune system. Of course if we are speaking of people who are malnourished or elderly, that will be a different issue and question.

Some articles say that some specific foods have vitamins, and other foods have minerals, and that will boost your immunity. Are these articles correct in the context of immunology?

Yes and no, of course for the proper function of the immune system you need minerals, vitamins, micronutrients, everything. But in the case of people who eat and live reasonably, any supplementation of any particular food has not been scientifically proven to be effective.

We are saying this because in immunology as well as for robust medical practice we look for evidence in scientific literature from clinical trials, proper comparison studies, etc.

Once again we must mention we are speaking about the majority of healthy human beings and not immunodeficient people.

We often hear people say that children playing outdoors, say in mud, will have better immunity. Is there any truth to that?

This is a difficult question to answer, but we can compare a baby born in a clean environment such as a middle class indian house to a baby born in a less hygienic environment such as a slum. We see that the children in less clean environments get exposed to several different types of microorganisms (microbes) in the first few months of life. Whereas children who live in very clean environments don't but a higher proportion of them tend to develop signs of allergy. This is not better or worse but it shows what types of assaults are there on the body. But both sets of children are immunocompetent.

What about a child born in a village that is relatively clean as compared to a slum?

The rural poor are still exposed to several types of bacteria through gobar, sewage etc. and hence they may get exposed to a somewhat different type of microbes as opposed to children in urban slum areas. But this does not produce any difference in immunocompetency of the children.

But there are people, including teachers, who say that if you eat soil, you develop immunity?

It does help in stimulating adaptive immunity towards some organisms from soil because you have been exposed to it, but it doesn’t mean that there is a significant advantage.

Let us speak about the role of diet in immunity, how does food turn into the cells and components of the immune system?

All cells in our body go through a process of ageing where they develop and are eventually replaced. For this they need carbohydrates, fats, proteins, minerals and other nutrients. These components are available from food and delivered to all systems of the body, including the immune system, through the same mechanism.

Which is why when this mechanism malfunctions during severe malnutrition it affects all systems of the body including the immune system. Assigning a particular benefit to a single food item which will affect immunity is thus difficult.

But in chronically undernourished people who do heavy physical work the immune compromises can manifest. However it is unlikely that middle class, well fed people will not get immunocompromised even if they fast for a few days.

Does obesity or being very overweight affect the immune system?

Yes, in obesity some of the fat cells secrete a component of the immune system called cytokines which causes inflammation in the body. Cytokines are usually associated with with infection, but very obese people have a continuous low level of inflammation which is detrimental.

Does physical activity do anything to help the immune system?

A person who is moving around is likely to be healthy, but if you are bedridden or are moving very little, there will obviously be problems and that will affect your whole body and also the immune system.

Does pollution have an impact on immunity?

Let us speak about the urban poor where children are exposed to high levels of pollution. There are evident consequences of this on the immune system but unfortunately these associations are not studied extensively so far.

Since experimenting cannot be done on humans, these studies need to be done on animals. These are early days to say anything concrete about which pollutants, at what level, will increase the risk of which disease.

Does work stress have an effect on immunity?

Yes, if we are stressed then levels of corticosteroid hormone go up. Chronic stress or sudden high level of stress both can suppress your immune system via corticosteroid. This also negatively affects the bone marrow and thymus which make cells of the immune system which again affects the immune system negatively.

Does ayurvedic medicine or Chyawanprash help the immune system?

In the field of evidence based medicine, there have not been enough appropriately conducted clinical trials on ayurvedic medicine, or the clinical trials comparing the effects of consuming Chyawanprash of different companies with people who do not eat Chyawanprash. There is no solid evidence to convince the scientific community that this is useful.

A word of precaution, there are also no studies done on the toxicity of these compounds given the fact that quite often there are heavy metals in these preparations.

Does a Vegetarian/Non-vegetarian diet affect the immune system?

There is no evidence that a vegetarian or non-vegetarian diet consumed in moderation has any adverse effect on immunity except for allergies in susceptible individuals.

Bear in mind though that some traditional ayurvedic preparations are reported to have animal bone and other animal based components, so they are not always pure vegetarian.

Does one have to keep oneself absolutely clean to stay healthy?

One should take extra care in the present circumstances, and that is good. But what should be minimum is different for different people. If there is a question of getting no food versus somewhat unhygienic food, different people will make different choices. I will eat the less hygienic food, personally. Trusting your immune system can help ensure that you may not have problems of a larger scale later.

So to summarise, what can be done to improve your immunity?

Live with less stress, which is admittedly easier said than done. Eat well, veg, non-veg food is not a problem. Ensure that you take hygiene into account if you are eating raw foods, wash your food before eating.

Most importantly, taking basic care which we normally tend to do goes a long way in making sure you are healthy.

But when we say we, it means we are the privileged who are able to maintain hygienic conditions and not the several hundred million poor who do not have the same benefits as we do.