Climate and Digestion: Summer Diarrhea, Winter-Weight and More

In what ways does climate impact our digestion? Experts share ways to avoid food-related seasonal sickness.

Picture this. The sun is glaring outside and drops of sweat are sliding down the back of your neck one after the other. You can’t wait to rush into an air-conditioned room and have a glass of chilled water. But what you would not want, perhaps, is a plate of heavy food (freshly fried bhature with choley, maybe?) or a hot cup of tea.

There is this connection between the temperature outside and our food choices that comes almost naturally to us. But what explains our instinct? In what ways does climate impact our digestion- or does it at all?

Summer Diarrhea: Is There Such a Thing?

Base this purely on observation- and then I’ll present to you some facts.

Isn’t it common for our washroom visits to increase during times of extreme heat- thanks to the constant churning and aches in the stomach?

An article in JAMA Network discusses the reason why mortality rate from diarrhea among infants and young children during summer may be higher than in other seasons. The explanation could be two-fold: unclean food and hot weather. “Bacteria of various sorts, whether introduced from the food, or already present in the intestine, are undoubtedly the exciting causes, but they seem unable to act deleteriously until the vital resistance of the child has first been decidedly weakened by protracted heat or humidity.”

Speaking with FIT, Dr Ashwini Setya, a Gastroenterologist and Programme Director in Delhi’s Max Super Speciality Hospital, explains that the link between temperature and digestion is indirect.

The heat does not impact the functioning of the digestive enzymes, but makes the food more prone to bacteria and infections.

“Humans are warm blooded. The enzymes in their bodies are programmed to maintain the average body temperature at 37’C- no matter where they are,” he adds.

But What Happens During a Heat Stroke?

A study by Swiss researchers found that during a heat wave, “there's an increased risk for inflammatory bowel disease flare-ups, and a greater risk of infectious gastroenteritis”.

Study author Dr Christine Manser explains the several mechanisms that might be at play, including the rise in mercury levels outside or chances of dehydration due to extreme sweating.

One possibility is that heat waves induce physical stress, which has been shown to cause flares of inflammatory bowel disease.

Dr Christine Manser

A heat stroke, however, is an altogether different matter. A person suffering from the condition has a compromised temperature-regulating mechanism, especially because of the obstructed activity of sweat glands. Since sweating is the body’s response to extreme heat, once it is disrupted, the body temperature rises to 40’C or higher, resulting in fever, unconsciousness, and in extreme cases- death.

Dr Setya says,

During a heat stroke, the person stops sweating and has a running fever. All metabolic activities, including digestion, are affected adversely. That might be the reason why people hardly feel like eating anything at such a time.

Winter-Weight: How, Why and Ways to Avoid

While gaining weight during winters may seem customary to a lot of us, there exists some scientific reasoning behind it.

A research by the University of Exeter found that people face ‘subconscious urges to over-eat during winter because being underweight has posed a serious threat to our survival as species in the past’.

Storing fat is an insurance against the risk of failing to find food, which for pre-industrial humans, was most likely in winter.

Lead author Dr Andrew Higginson from the College of Life and Environmental Sciences at the University said, “You would expect evolution to have given us the ability to realize when we have eaten enough, but instead we show little control when faced with artificial food. Because modern food today has so much sugar and flavour the urge humans have to eat it is greater than any weak evolutionary mechanism which would tell us not to.”

The model also predicts animals should gain weight when food is harder to find. All animals, including humans, should show seasonal effects on the urge to gain weight. 

Several other studies agree with such an explanation. However, none of these suggest that gaining weight during the season is inevitable, or that it is caused solely due to this ‘hibernation’.

That is true especially in today’s day and age, when our surrounding is almost always artificially controlled by devices such as air-conditioners and heaters.  

Much of the weight gain may be blamed on laziness and the lack of will to get out of bed in winters (due to a possible increase in the sleep-inducing hormone melatonin). A healthy lifestyle and regular physical activity will always help avoid any excess weight gain, regardless of the season.

'Hot Foods', 'Cold Foods' and Ayurveda

There is a reason why certain foods heat you up, why you prefer not to eat heavy meals when the weather’s too hot, and why your food choices change seasonally.

‘Diet induced thermogenesis’ is the process by which heat is generated in the body after consumption and digestion of food- and it varies based on the diet consumed. Certain items such as root vegetables (like ginger), hot peppers, ghee, and others that generally contain a higher amount of fat, protein and carbohydrates, are known to add more heat to the body.

But the explanation for all these mechanisms goes beyond just the outside temperature or food composition. Dr Ashwini Setya brings up the importance of indigenous knowledge systems like Ayurveda to suggest that many other factors might be at play.

We cannot run down or denounce our indigenous systems. Just because modern medicine seems to be unaware of its basis- does not mean the science does not exist.

Dr Ashwini Setya

According to Ayurveda, while there is a distinction between ‘hot’ and ‘cold’ foods- this alone cannot explain which food items suit our bodies the best. Different foods are ideal for the three different body types, depending upon which of the three doshas (vata, pitta, kapha) is dominant in a person.

Moreover, the classification into ‘hot’ (ushna) and ‘cold’ (shita) is not based on the temperature of the food itself, but on its effect on the body or its innate potency. For instance, ice-cream, despite being cold, induces heat in the body, as per Ayurvedic principles.

How Do You Avoid Food-Related Seasonal Sickness?

While Dr Setya reaffirms that the temperature outside does not directly impact the functioning of digestive enzymes, there are multiple reasons why seasonal health problems may emerge.

This is where he recommends eating food that is naturally grown in the particular season.

We humans want to compete with nature. That’s where we go wrong. We should be aiding nature. Seasonal fruits like mangoes are available throughout the year now. But there is a reason that nature has given you these in certain temperatures- because that’s when they are most suitable for your body. 

Further, he adds that the understanding of ‘light’ and ‘heavy’ food is very subjective. For instance, in north India, the staple food-for-the-sick is ‘khichdi’, while in south, it is recommended to avoid rice in any form when suffering with an illness.

So a definite answer on ‘what to eat when’ may not be possible, but seasonality of the item, food allergies, its cooling or warming effects, and the body composition of an individual- all may be considered before making the right choices.