Underestimated Vitamin D Sources: Especially Eggs, But Also Chicken, Pork, Fish & Dairy Contain an Overlooked, Physiologically Relevant Amount of Ready-Made 25OHD
|What do you need for a high 25OHD picnic at the beach? Eggs!|
Among all this mess, you can still find a handful of interesting papers. You just have to look close enough to spot gems such as a review by Ovesen, Brot, and Jakobsen (2013).
Are Eggs the Best Dietary Vitamin D Source We Have?
"Eggs? The best vitamin D source?" I don't have the hubris to say that eggs are the absolute #1, but considering the fact that eggs are the #1 source of "actual", preformed 25OHD, aka 25-hydroxyvitamin D*, in our diets, you are probably going to agree that eggs may well be the most underrated source of vitamin D in our diet (25OHD is what doctors and scientists will measure in your blood stream; most essays measure total 25OHD so I will not differentiate the different forms here).
Preformed vitamin D? Isn't that dangerous? No, quite the opposite: Pharmacologic doses of 25OHD do not change or may even decrease plasma levels of 1,25(OH)D, aka calcitriol, which can potential cause calcification (Trummel. 1669; Heaney. 1997). When you are D-deficient, though, your body will retain the 25OH. This is particularly interesting for people with intestinal malabsorption, for whom 'regular' vitamin D supplements, i.e. vitamin D3, aka cholecalciferol, or vitamin D2, aka ergocalciferol, don't work (Francis. 1983)When it comes to vitamin D, eggs, fish, dairy, meat, and offal are quite unique. All of them contain "vitamin D" in the still-to-be-converted D3 form you all know. What only a few people know is that they also contain the celebrated vitamin D metabolite 25-hydroxyvitamin D (25OHD). This is not only the form your doctor will measure when you ask for a "vitamin D test", it's also the "vitamin D" that has been linked to all sorts of health benefits in the aforementioned epidemiological studies.
If you want to increase or maintain your 25OHD levels, it is obviously an advantage if you don't have to rely on your body to transform the dietary D2 + D3 into 25OHD. It is even better though, if the efficacy of this "supplement" (as of now I have not seen 25OHD in caps, so you better stick to eggs) has a higher bioavailability than its non-polar precursor, vitamin D3, which is absorbed mainly into the lymph (Thompson. 1966; Blomstrand. 1967).
"[T]he more polar metabolite 25OHD at physiological concentrations is also absorbed directly, and more rapidly and efficiently, from the proximal jejunum into the portal vein independent of fat absorption. These findings are consistent with results from clinical studies, which have found better absorption of 25OHD versus vitamin D in patients with fat malabsorption. Also, in healthy subjects and in patients with bone disease 25OHD is absorbed better and faster than vitamin D." (Ovesen. 2013)I would hope that you are by now at least considering to eat an egg instead of popping dozens of vitamin pills. For those who still need actual data before they subscribe to the egg-o-logical approach to vitamin D 'supplementation', I have compiled a couple of figures in Table 1:
|Table 1. 25OHD content (µg/100g) of chicken & egg, pork, beef, fish, dairy (various sources; cf. Oveson. 2013)|
|The sentence "You Eat What You Feed" is not new to SuppVersity regulars - it's also the title of an older article discussing how you can use food additives to increase the Omega-3 content of your steaks, milk and other animal products | read more|
If you ate the bacon of the pigs in the Thompson study from the late 1960s, for example, you would get a whoppy dose of 0.7–2.0µg 25OHD per 100g and thus max. 10x more than from regular bacon. Why? Easy: The sows were on a(n extremly) high vitamin D diets (total D-intake was 2–3mg/day for 2-3 weeks; Thompson. 1966).
- Blomstrand R, Forsgren L: Intestinal adsorption and esterification of vitamin D31,2-3H in man. Acta Chem Scand 1967;21:1662–1663.
- Francis RM, Peacock M, Storer JH, Davies AEJ, Brown WB, Nordin BEC: Calcium malabsorption in the elderly: The effect of treatment with oral 25-hydroxyvitamin D3. Eur J Clin Invest 1983;13:391–396.
- Heaney RP, Barger-Lux MJ, Dowell MS, Chen TC, Holick MF: Calcium absorptive effects of vitamin D and its major metabolites. J Clin Endocrinol Metab 1997;82:4111–4116.
- Ovesen L, Brot C, Jakobsen J. Food contents and biological activity of 25-hydroxyvitamin D: a vitamin D metabolite to be reckoned with? Ann Nutr Metab. 2003;47(3-4):107-13. Review.
- Thompson GR, Lewis B, Booth CC: Absorption of vitamin D3-3H in control subjects and patients with intestinal malabsorption. J Clin Invest 1966;45:94–102.
- Trummel CL, Raisz LG, Blunt JW, DeLuca HF: 25-Hydroxycholecalciferol: Stimulation of bone resorption in tissue culture. Science 1969; 163:1450–1451.