Here's looking at you...
The teaser for this article reads Why I don’t consider myself clever enough for a vegan diet, and before that goes down the wrong way, I had better start with an explanation:
The DGE on animal foods and vegan diets
A vegan diet - sometimes called “plant based” - feels like it is being touted ever more often as the way of eating to aim for. Even the DGE reluctantly recommends the <sarcasm>seemingly massive</sarcasm> upper limit of at most 300 g of meat per week, would like the share of animal foods capped at 25%, and yet, at every mention of meat, highlights its merits (nutrient content and availability):
Meat is a source of readily available protein, numerous vitamins and minerals. Iron, selenium and zinc are particularly well available from meat. Only animal foods contain available vitamin B12 in appreciable amounts. Anyone who eats little or no animal food must take care to supplement vitamin B12.
(From the DGE recommendations on meat and sausage; my translation)
The DGE also offers guidance for vegan diets, pointing out clearly that support from the pharmaceutical industry (my words), or rather supplementation of vitamin B12, is strictly necessary. Interestingly, the general guidelines make no specific statement about the other nutrients mentioned, “readily available protein, numerous vitamins and minerals. Iron, selenium and zinc”, which then simply have to come from other sources. We’re also left in the dark with regard to the nature and composition of the numerous vitamins and minerals mentioned, and whether we’d need to pay special attention to them as well.
Pinning down what “little animal food” means is left as an exercise for the population. I, for one, consider 42 g per day (300 g per week) a distinctly small amount, even with another 8.5 g of egg per day on top (1 egg, 60 g per week). We have already learned what all counts as a dairy product - I don’t expect too much of my requirements to be covered from there.
In other words: we know about B12 - that we can handle. As for whatever else is missing: good luck…
A visit to the ophthalmologist
I am short-sighted - at my last visit, my ophthalmologist examined my retina and took a close look at the macula. It had improved slightly since the previous examination. When she remarked on this, I said: “I put that down to my diet”, to which she replied, alarmed: “Not vegan, I hope?”
In the conversation that followed, I learned what lay behind her question:
She looks deep into a lot of people’s eyes, she said - and occasionally sees the retina of 20-year-old patients (mostly women) in a state she would have expected in a 60-year-old. Without exception, those patients reported that they had been eating vegan for a long time, out of conviction and for health reasons.
I don’t know the individual stories, don’t know exactly what they supplement. But when even an ophthalmologist sees a connection(1) between the state of someone’s eyes and their diet, I am more than alarmed myself.
I don’t run experiments with my eyes - least of all when I risk being told, as my eyesight fades, that I supplemented B12 exemplarily, but that another vitamin, a mineral or some other as yet unknown building block, one that you get automatically from animal foods, was unfortunately missing.
Another problem for the retina
A fitting parallel insight - though independent of animal- or plant-based eating: the most common cause of blindness among people of working age in industrialised countries is diabetes - a permanently high blood glucose level. It is not only glycated haemoglobin , measured as HbA1c in the blood, that reacts with glucose(2) and is eventually renewed: all cells do this, including those in the eyes. And there, cells cannot simply be renewed the way freely circulating cells in the blood are.
That, too, is another strong motivation for me to stick with a ketogenic diet.
As always, blood glucose can be followed in the simulator. The projection of a day plan over a longer period also gives an estimate of how HbA1c develops. It follows mathematically from the average level of blood glucose and the time it spent elevated, plus the lifespan of the red blood cells that carry the haemoglobin. As a general rule: a few short elevated periods are considerably less concerning than permanently elevated values.
Conclusion
While a ketogenic diet - technically speaking - also works vegan, I have come to the conclusion that I cannot foresee which exact nutrients (apart from B12) I would have to supplement, and in what form. Animal fats contain vital (and bioavailable) fat-soluble micronutrients that are absent from plant fats(3) - quite apart from the fact that plants usually bring carbohydrates as their energy carrier, which would either severely restrict the choice of plants or prevent ketosis. And finally: I don’t know the behaviour of the necessary plants and their antinutrients, which might block the required nutrients from being absorbed.
With the eyes, both aspects come together: I can measure what’s too much - but not what’s missing. Blood sugar is under my control; a lack of nutrients I only notice when it’s too late.
On top of that, there is my own distinct problem with dietary fibre.
That is two fundamentally different parts of the body already, which through different mechanisms can produce very unpleasant problems with different aspects of my diet - and for even one of them alone I consider it worth deviating massively from the usual dietary guidelines. Once because I avoid certain plant substances (that is what the linked article is about). And once because I have to fear not taking in enough of the nutrients I need (this article).
In other words: I don’t consider myself clever enough for a vegan diet. When I look at my own eyes and gut, it is simply too risky for me.
