During my college days at Faculty of Food Technology and Biotechnology, I had my lunch and dinner in the student canteen. I was warned almost instantly that canteen food was horrible, unhealthy, toxic, cancerogenic, other-currently-popular-words. Even though I supported this viewpoint in the beginning, as I educated myself more I started to question it.
How can food have a negative effect on our health? Why is canteen food unhealthy? Can I as a student eat healthy, with my limited financial abilities, if I prepare my own meals?
Healthy and unhealthy food
Food is essential. It ensures energy and nutrients necessary to sustain a life. If we don't eat, we die. And that's extremely unhealthy. We can conclude that any food is healthIER than no food. However, some foods can be a better choice than some others, but only in the context of the entire diet.
There is no healthy or unhealthy food, but there is a healthy or unhealthy diet.
Healthy diet (I prefer the term balanced, but due to the parallel I'd drawn above, I'll keep using the term healthy) would be the one where we consume necessary amounts of energy, water, essential macronutrients, micronutrients, phyto- and zoochemicals. (1) Intake higher of that which our body needs won't have a beneficial effect on health, and an excessive intake could have a negative effect. Healthy diet allows for popularly called unhealthy foods. I cannot emphasize enough the fact that this does not mean that food is unhealthy.
Is there a food or a nutrient that in itself has a bad effect on health? The answer is a vague „yes“. The nutrient in this question are trans-unsaturated fatty acids present in the process of partial hydrogenation of plant oils and excessive thermal processing of plant oils, and are found in products which have one of these names in them: partially hydrogenated plant oil, plant fats, solidified plant oil, and many combinations of these. (2)
However, another important thing to keep in mind is that „the dose makes the poison“ – it's relevant whether we ingest a single molecule of asbestos or enough of it to cause consequences. Same goes for trans-fatty acids. Did you know that drinking over 10 liters of water in a short time period can cause death?
If you read the above part, you'll see that the question Why is canteen food unhealthy? makes no sense. The question we can, and should, ask is: Could the quality of food and its preparation be better? The answer is a stern „yes“. But you have to take into account that this leads to more expenses. There are less expensive and more expensive interventions, and the price does not always follow the quality, but let's leave that for a different article.
The food choices in canteens, as (financially) limited as they are, are acceptable from nutritionist point of view. Choose roast chicken instead of fried chicken. Choose baked potato instead of fries. Eat vegetables, the more colorful the better. Have some fruits instead of a dessert. You can eat healthy in a canteen. Your choice makes a difference. You are responsible for the quality of your diet.
If you wish to prepare your own meals, and make healthy choices, relax. You don't need to spend thrice the value of your scholarship. Buy discount food (the fact that its expiration date is close by doesn't make it any „less healthy“) and pick foods that are in season. Bear in mind that famous brands do not guarantee nutritive quality. Make sure your plate has a source of protein (meat, fish, eggs, dairy), carbohydrates (potato, whole wheat grain), vegetables, and pay attention to food preparation (minimal but adequate thermal processing, avoid frying and broiling, use olive oil). Don't forget to add colorful fruits and nuts.
(1.) There are scientifically based recommendations for macro- and micronutrient intake (DRI), but there aren't any just yet for phyto- and zoochemicals so I can't discuss exact quantities.
(2,) Trans-unsaturated fatty acids are present naturally in animal meat as well. Some authors claim that as such they do not have a negative effect on health, but no consensus is reached.