Veganism & vegetarianism

[Aractus]

I've heard that vitamin D can be found in a multitude of vegetables and vegan products actually, and that a bigger risk is the vitamin B12 deficiency which has to be supplemented since it's found exclusively in meat.

Well you've heard wrong. Vitamin D can only be found in animal foods. If you ever see vitamin d listed as being contained in a plant food it means that faecal matter is on the food. Vitamin D, like all human/animal steroids, is synthesised from cholesterol - the "parent" steroid. Plants don't contain cholesterol, thus cannot synthesise any animal steroids. Plant steroids thus have nothing to do with animal steroids and have no use (besides their ability to lower LDL levels) in the human body.

It is wrong to generalise and say "we can get enough vitamin d from the sun". For one thing, a cholesterol deficiency in the body will lead to steroid deficiencies of some description (as well as mental health problems). For another, some people cannot synthesise enough vitamin d to solely rely on biosynthesis. In a normal, healthy diet food provides around 20% of a person's vitamin d requirements. Now I'll back that up with data, in the winter months in Australia the "average" light-skinned Australian needs to spend up to 40 minutes in the sun daily with no sun-block on, no hat on, in the middle of the day, and "as much skin as possible" exposed (and that's in addition to the vitamin d from foods). See ABS, Cancer Council, and MJA. I did see a better article on this recently, but I can't locate it right now. Now bare in mind that it really is "the middle of the day" that you need to get that 20-40 minutes (depending on location); and at other times in the day (morning or afternoon) you'll require longer sun exposure. Dark skinned people require longer sun exposure: for a light-skinned person here in Canberra needing 40 minutes of direct sun exposure, a dark skinned person would need four hours! Granted if they live in the Gold Coast, it may not be a problem, but they live here in Canberra, or in Melbourne, Adelaide, Hobart, or anywhere else in our latitude they will require three to four hours a day of direct sunlight exposure, in the middle of the day, with as much skin as possible exposed in order to get their vitamin d.

So, clearly those dark skinned people need more vitamin d from their diet than a light skinned person. The only natural dietary source providing Vitamin D in a significant quantity is fatty fish and eggs, however you'd need to eat five eggs a day to reach the AI for Vitamin D. Hence why eating 2-3 serves of fatty fish is recommended in AGTHE & DASH; and for dark skinned people it wouldn't hurt to eat more than that in the winter months.

Vitamin D is the bigger risk. The effects of B12 deficiency can be reversed, however vitamin d directly affects the body's ability to use calcium; and bone demineralisation/osteoporosis is irreversible.

Malnutrition? You mean deficiencies or just too low a calorie intake? Are you saying that is necessary in any vegan or vegetarian diet? Because if you balance it out and provide substitutes, it shouldn't be a problem. Some vegetable products for example have a higher protein content than meats.

Who says it "shouldn't be a problem" Vic? The amount of a nutrient in foods is actually irrelevant, what is relevant is the bioavailability of the nutrient. Plant proteins have low bioavailability, in other words much more protein gets excreted without being absorbed when compared to animal foods. And that's also true of calcium, and many other essential nutrients. And it's because all plant foods contain lectins, and lectins bind to nutrients and prevent them from being absorbed. You would need to eat around 1.36 kg (3.00 lbs) of spinach to get the same amount of calcium in a 200ml glass of milk, because of the lower bioavailability ().

What mental health problems specifically at vegans and vegetarians at risk of?

Cholesterol deficiency is known to cause depression, aggression, anger, anxiety, other mood disorders, and suicidal thoughts. Low levels of vitamin d are also known to be positively associated with (and thus likely cause) depression, seasonal affective disorder, and schizophrenia (); no to mention other chronic disorders: "There is evidence that the vast majority of hospitalized patients have vitamin D deficiency" (). Vitamin B12 deficiency is also a known risk factor for certain mental illnesses.

And I should end by noting that vitamin supplementation is highly advised against (unless under the direction of a dietician or physician); and Vitamin D is one of the most toxic when consumed in excess from supplementation.