Why is it so important for humans to have a balanced nutrition but not for animals?



Most animals have a fairly simple diet, carnivores eat only meat their whole life, cows eat exclusively grass etc. So why are human bodies so picky and need a balance of protein, fat, carbs etc from different sources to perform well?

In: Biology

Every animal, including humans needs a balanced diet. It’s just that “balanced” for a human is different than “balanced” for, say, a dog.

In general animals are adapted to eat the “balanced” diet that they can find in the environment, humans can manipulate their environment to create whatever food they like so can easily get an unbalanced diet.

Carnivore and herbivore are very general. Cows, deer, etc. will eat meat and bone to get nutrients rare in a plant based diet. There are deer that will seek out and kill baby birds because their heads are rich in phosphorus. Only “obligate” carnivores eat/need only meat. Most can and will munch on some plants.

These animals SEEK OUT balanced diets because their main food sources don’t provide full nutrients. There are reasons captive animals live longer, and one is being well fed a balanced diet.

Humans are animals, always keep that in mind

The real reason is that animals evolve to get all their nutrients from the food that’s available to them. For example a cow’s four stomachs and long digestive track are perfect to take what they need mostly out of grass. Since we acquired a wide variety of available meals, we stopped making certain key nutrients because it was cheaper to get them through just eating, adapting our bodies to this lifestyle, making it needed for survival.


In a lamer sense than the previous comments, every animal indeed needs a balanced diet, considering balanced means getting all necessary nutrients for your body to function correctly.

When I was a kid I regularly asked, “why isn’t there a Purina People Chow?” It’d get boring after maybe a day.

Seen this BBC documentary about a black reporter seeking his African roots, he went to live with a family in the middle of nowhere with the intention of staying a month

They lived in a mud house, wake up in the morning eating some fire cooked flour and spend the whole day trying to find some grass, plants or any food they could find

The reporter left before the week was over but the lesson for me was how shocking amazingly little food they needed to get by and stay active searching, their environmental footprint was almost animal level

Granted that they were living pretty suboptimal lives in the middle of a draught area but regardless the comparison between their food consumption and ours was huge

One type of genetic anomaly that aided our ancestors’ survival and led to us evolving to *Homo sapiens sapiens* was the elimination of most vitamin manufacturing in our cells. We only need small amounts of these nutrients, and our precursor ancestors made them. As our food sources and diets diversified and we developed better digestive systems, it was advantageous to shift the body’s resources from making vitamins to other processes. By essentially moving vitamin production “off-site” to “external suppliers” (food animals & plants), our internal manufacturing process got leaner and our ancestors’ bodies were able to pursue innovations that increased the odds of survival past reproduction.

We still make our own vitamin D, but we get all of our other required vitamins from the foods we eat. Different species of plants and animals make all the different vitamins we need. The downside to this “lean manufacturing” is that we cannot compensate if essential nutrients are not available. Widespread disease caused terrible suffering until researchers (like Dr. Casimir Funk) proved that vitamin deficiencies were to blame. We’ve all heard of anemia (B12) & scurvy (C *arrrgh!*), but beriberi (B1), pellagra (B3), rickets (D), and many other ailments are caused by a lack of vitamins and affect people worldwide. WHO estimates 250,000-500,000 children go blind every year due to vitamin A deficiency, and sadly half of them die within a year of going blind. In modern food processing, synthetic vitamins are added to many foods (esp those that fill supermarkets in richer nations) due to public health initiatives in the early 20th century.

A lot of animals have processes inside them that can convert and produce some of the things they’re missing in their diet.

**Simply put, because we’ve changed our own environment the most. (Also animals care.)**

A dog is still eating meat, but *you’ll see the difference* if you feed dogs cheaper grade food full of fillers. They literally won’t live as long. If you want your dog to live a long, healthy life, you want to give them expensive vet-grade food, not cheap crap. We think of ourselves and our ‘balanced diet’ from the perspective on one who can *feel* an unbalanced diet, so we’re more strict on ourselves. And in countries where cattle can’t be grassfed year-round, they are absolutely given supplementary grain-fed while barned in winter – *and it’s still* not as healthy as being grassfed all year-round in more temperate climates. And you’re looking at animals as a collective, not the livelihood of each individual cow, deer, dog. So when they’re fine enough as a whole, we don’t think about it. We *do* think of *ourselves* in the individual.

But humans? We’ve bred our crops for size and yield. We’ve processed our food for shelf-life and flavour. Our food is now REALLY good at hitting that dopamine – fat, sugar, salt, proteins – as easily as possible, as cheaply as possible, for as much of the year as possible. Sugary foods that used to be seasonal and rare (honey, fruit) are now available all the time. We want to eat these things as much as we can because historically, sugar was valuable and hard to get. Now it’s the cheapest thing there is, it’s everywhere, it’s easy to get – but our bodies are running old software and haven’t gotten the memo. Same thing for the amount of meat we eat – it’s *good diet* to eat meat! But a lot of us eat *way too much* of it.

**Humans have to make a deliberate decision to get a balanced diet because we’ve spend generations making an *indulgent* one more attainable.**

It isn’t. Humans can and do quite easily reach breeding age and reproduce successfully without a balanced diet, provided they have enough calories. We need to eat reasonably well to have consistently good health and live to old age, but the importance of those things is largely an emergent human/social construct. Animals in the wild aren’t necessarily “healthy” as we define the term. Many are malnourished, have parasites, etc. Entire regional populations of some animals can be stunted and unhealthy.

Your question includes a few common misconceptions, one that’s been addressed already.

Humans need a balanced diet, but that doesn’t necessarily imply a vast array of food types. That simply means the nutritional value of our food has to cover our needs.

It doesn’t have to be varied. You can very well thrive by eating the same handful of things every day.

Cows and other herbivores do not eat “just grass”. A natural pasture large enough will grow hundreds or thousands of different varieties of grasses, herbs and other plants that provide most of the nutrients (carbohydrates, proteins, fatty acids, vitamins, etc) that the animals need. Animals will also straight up eat dirt in small amounts to gain minerals. Every species of animal has their own digestive system (including microbiome) specialised on a diet that provides them with what they need. “Balanced” is different for different animals.