Friday, May 2, 2014

Vitamin A, D, E & K - How Much and What Type of Fat Do You Need to Absorb These Fat Soluble Vitamins?

Some butter on top of the broccoli would allow for the assimilation of the absorption of the 101.6μg vitamin K
623IU vitamin A (various).
There are a handful of very basic questions in nutrition science, no one appears to have an answer to. One of these questions, which is directly related to the  well-known fact that the vitamins A, D, E & K are "lipid soluble". This means that they are "solved" and thus made absorbable by fats and oils. The general assumption is thus that the vitamins A, i.e. the retinol and carotenoids, all forms of vitamin D, the tocopherols and -trienols (vitamins E) and the two major forms of vitamin K, i.e. phylloquinone (K1) and menaquinone (K2) will only be absorbed, if you consume them with a sufficient amount of dietary fat. Now, the questions obviously are (a) is this correct and (b) how much is sufficient.
Is there a rule of thumb? Well, I guess if there was one, it would be to consume 5-10g of low PUFA fats with every meal to maximize the absorption of fat-soluble vitamins. Needless to say, that this does not imply that you'd have to start adding olive oil to your post-workout shake ;-)
In view of the fact that the answers to (a) and be are not necessarily identical for all four vitamins of interest, it appears sensible to tackle them one after the other.

Starting with vitamin A and the various forms of carotenoids, we can already confirm that (a), i.e. the assumption that we need dietary fats to optimally absorb vitamin A is correct. As Karin van het Hof and her colleagues point out, the "amount of dietary fat required to ensure carotenoid absorption [does yet] seem low (∼3–5 g per meal), although it depends on the physicochemical characteristics of the carotenoids ingested." (van het Hof. 2000) In spite of the fact that 5g of fat are not exactly much, the classic uncooked vegetarian orthorexic salad often comes with a total of only 5g of fat of which 95% remain at the bottom of the salad bowl. If that sounds like your favorite dish, you should be aware that you are risking that all the good  beta- and other carotenoids in the salad will pass right through.
Red Palm Oil is an excellent carotene source that comes with tons of fat for optimal absorption | learn more
With carotenes you should keep in mind that they have individual and "vitamin A"-related effects that occur after their conversion to retinol and the uptake of the latter through the lymphatic system in the gut. For this to take place the presence of a couple of ~5g of fat  (Jayarajan. 2013) in the intestinal lumen is paramount importance. Even more than preformed vitamin A, carotenes do thus rely on the presence of dietary fat in your meals to be optimally converted (Goodman. 1966) and absorbed.
Figure 1: Changes in hepatic vitamin A (retinol) and carotenoid stores in gerbils after 14 days on high fat (30%) vs. low fat (10%) diet (Deming. 2000)
In that, the concomitant presence of both dietary fat and carotenoids in a meal is a necessary prerequisite for the absorption of vitamin A, also because the fatty acids will trigger the conversion of of beta-carotene into vitamin A and its subsequent absorption via the lymphatic system (Ribaya‐Mercado. 2002). It is thus not surprising that animal studies by Lakshman et al. (1996) and Deming et al. (2000; see Figure 1) suggest that low fat diet can lead to a depletion of the vitamin A tissue stores even if the serum levels remain constant. The amount of fiber in the diet, on the other, has no influence the absorption of vitamin A (Mills. 2009).

Interestingly enough, the provision of the fat blocker Orlistat reduces the absorption of vitamin A only insignificantly, as a 1996 paper by Angela T. Melia, Susan G. Koss‐Twardy, and Jianguo Zhi would suggest (Melia. 1996).

Which takes us right to vitamin E, the absoprtion which is - in spite of being "blocked" by the fat blocker orlistat (Melia. 1996) - less susceptible to the absence of dietary fat than you may think. Annet JC Roodenburg, Rianne Leenen, Karin H van het Hof,  Jan A Weststrate, and Lilian BM Tijburg do in fact argue that the optimal intake of vitamin E requires only "a limited amount" of dietary fat (Roodenburg. 2000).
Figure 2: Vitamin E serum levels after 7 days on control (low fat, 3g) or high(er) fat (36g) diet with and without supplemental vitamin E (Roodenburg. 2000)
As you can see in Figure 2. A minimum intake of only 3g per day was sufficient to keep the vitamin E levels stable. The short study period of 7-days (each) and the absence of measures of tissue concentration of vitamin E do yet reduce the practical relevance of the data, Roodenburg et al. present in their Y2k paper in the American Journal of Clinical Nutrition.
The PUFA advantage: Aside from the issue of serum vs. tissue levels, there is yet another experimentally verified fat vitamin E and fat carotenoid interactions we should take into consideration, when we are talking about "optimizing" our dietary vitamin E supply; and that's the type of fat we consume: Dietary fats with increased ratio of unsaturated to saturated fatty acids enhance absorption of carotenoid and vitamin E by increasing both efficiency of micellarization and lipoprotein secretion (Chitchumroonchokchai. 2010).
If you take a look at the high prevalence of vitamin E dieficiency among the fat (and PUFA) "loving", or at least eating, majority of Americans, it does yet become obvious that a lack of dietary fat is not just theoretically, but also practically not exactly the #1 reason you may become deficient in tocopherols and -trienols. That the latter is an increased demand due to chronic inflammation and the (over-)consumption of exactly those PUFAs that come with a shitload of vitamin E in nature, for a reason would yet be a topic for another SuppVersity article and thus something we will skip to fast forward to ...

...Vitamin K, obviously. Vitamin K is a relative newcomer to the public's understanding of the alphabet soup. Aside from being it a good tool to rip customers vitamin K, or rather K1 (plant sources) and K2 (animal sources) are thus also the only fat soluble vitamins not everyone knows. The fact that the amount of phylloquinone (K1) that makes it into your blood stream is ~70% reduced if you eat your spinach without fat (Gijsbers. 1996).

And if we take the results researchers from the Gifu University School of Medicine present in a 1996 paper in the Journal of Pharmacological Sciences, as a reference, the amount of fat you need to optimally absorb your K2 (menaquinones), is not exactly low.
Figure 3: For optimal absorption of K2, there has got to be a huge amount of fat in the meal - but who wonders. K2 comes with a high amount of fat (Uematsu. 1996)
Uematsu et al. had to supply their subjects, who consumed otherwise identical test meals with 8.8, 20.0 and 34.9g of fat in them with the maximal (i.e. 35g) of fat before the K2 absorption maxed out. In that the total area under the curve did not really differ between those subjects who consumed the K2 before and those who took it immediately after the test meal.

That's a pity, 'cause a high intake of vitamin K (menaquinone from animal sources) has been associated with a 27% reduced risk of developing heart disease (Geleijnse. 2004), an ailment of which many still believe that it was brought about by the fat they need to optimally absorb their vitamin K.

For vitamin D, our last "V" on the list, things look differently. For one, everybody knows about this miracle vitamin and for two, it may be "fat soluble", but the amount of fat that's required to optimally absorb it turned out to be much lower than previously thought (see "A Fat D-Ficiency! Do You Really Need More Vitamin D or Simply More Fatty Foods? Study Shows, Even 50.000 IU of Vitamin D3 Useless, When You Ingest It Without Fat. " | read more).
Actually you could argue that it's not fat, but cholesterol that should be essential for optimal D levels. It's not necessary to absorb supplements you should not be taking, but rather as a raw material that's used to produce vitamin D in the skin, once the latter is exposed to the sun. The allegedly logical assumption that statins which lower the production of endogenous (=your body's own) cholesterol would lower vitamin D levels, however, has been refuted in study investigating the effects of fluvastatin and rosuvastatin, of which the latter actually increased the 25-OHD levels (probably due to anti-inflammatory effects and a reduced use of vitamin D as an acute phase reactant | learn more)
In fact, Niramitmahapanya et al. found in 2011 that it's not necessarily a high amount, but rather the right type of fat that determines if and how much of the vitamin D you take in capsule form or find in comparably low amounts in your foods that determines how much of the vitamin D actually makes it into your bloodstream:
"The change in plasma 25OHD (nanograms per milliliter) during vitamin D supplementation was positively associated with MUFA, (β = 0.94; P = 0.016), negatively associated with PUFA, (β = −0.93; P = 0.038), and positively associated with the MUFA/PUFA ratio (β = 6.46; P = 0.014)."
In plain English this means, that the "good" seed and vegetable oils with their high PUFA content will effectively inhibit the absorption of vitamin D - an observation that adds to the many reasons the modern sedentary, sun-avoiding, sun-screen using, soybean oil (MUFA:PUFA = 0.4) guzzling American is low in or  quasi devoid of vitamin D.

Figure 4: 25(OH)D levels of 30 healthy men and women after ingestion of 50.000IU vitamin D3 supplement in conjunction with a normal or low fat breakfast (Raimundo. 2011)
Against that background it's not surprising that you will not find a conclusive answer to the question how much fat you actually need. In a study that used a fatty meal with soybean oil in it, the effect would be totally different from one in which the subjects consumed meals that were made with sunflower oil, an oil with a MUFA:PUFA ratio >1. In view of the results Gnadinger et al present in a recent appear it does still seem appropriate to consume at least some fat alongside your vitamin D supplements. As far as the food-borne vitamin D is concerned, you don't have to worry, anyways. Foods that are high in D3 usually come with all the fat you need to absorb it.

How much fat, exactly you would need to make the most of dietary and supplemental vitamin D, on the other hand, is still not known. The previously mentioned data from the study by Raimondo et al. (see Figure 4, to the right) I wrote about in "A Fat D-Ficiency" is obviously still valid. The extremely high amount of vitamin D (50,000IU!) could yet require a correspondingly high amount of fat to be optimally absorbed and the fact that the fat in the study came from a "vegetable margarine" with an undisclosed ratio of MUFA:PUFA does not make the real-world effects any more predictable.
So what do I need to optimally absorb my "fat soluble" vitamins?
Vitamin A & carotenes require relatively high amounts of fat for optimal absorption.
Vitamin D absorption benefits from additional fat in the diet. While we don't know the optimal amount, we do know the optimal type: A high MUFA, low PUFA fat (the effects of saturated fat are unknown, but I gather they will be positive, as well).
Vitamin E requires only minimal amounts of fat (~3g) for optima absorption.
Vitamin K appears to be most fat hungry. The more fat you have in a meal, the better it is absorbed. If you supplement, always take the pills with your highest fat meal in the day.
Bottom line: If you take a look at the natural sources, it should be obvious. The fat soluble vitamins are meant to be consumed with fat... well, not really. Carotenes (pre-vitamin A), one of those vitamins for which the presence of dietary fat in a meal is most important do not necessarily come with their own "absorb me better"-portion of fat. Your carrots, pepper, and other high carotene veggies and fruits do thus require a butter, olive oil or cream topic not just to be absorbed, but - more importantly - to get converted to retinol aka "active vitamin A".

Vitamin E, on the other hand, requires much lower amounts of fat to be absorbed than many of you may have thought. In fact, you could argue that good vitamin E sources are not high in fat to facilitate the absorption of vitamin A, but rather the other way around: Soybean oil (my absolute favorite poison ;-) is high in vitamin E to make sure that whoever consumes it does not die immediately from the pro-inflammatory omega-6 load it contains.

Which takes us right to the 18-20g and 12-15g of PUFAs the average US man and woman consume on a daily basis (Kris-Etherton. 2000) and their negative impact on the absorption of the already low amounts of dietary vitamin D in a diet that rarely contains the optimal amount of 35g of fat in meal that actually has a significant amount of vitamin K the absorption of which would be improved by the presence of this allegedly unhealthy and fattening macronutrient.
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  • Geleijnse, Johanna M., et al. "Dietary intake of menaquinone is associated with a reduced risk of coronary heart disease: the Rotterdam Study." The Journal of nutrition 134.11 (2004): 3100-3105.
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  • Melia, Angela T., Susan G. Koss‐Twardy, and Jianguo Zhi. "The effect of orlistat, an inhibitor of dietary fat absorption, on the absorption of vitamins A and E in healthy volunteers." The Journal of Clinical Pharmacology 36.7 (1996): 647-653.
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  • Raimundo, Fabiana Viegas, et al. "Effect of high-versus low-fat meal on serum 25-hydroxyvitamin D levels after a single oral dose of vitamin D: a single-blind, parallel, randomized trial." International journal of endocrinology 2011 (2011).
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  • Uematsu, Toshihiko, et al. "Effect of dietary fat content on oral bioavailability of menatetrenone in humans." Journal of pharmaceutical sciences 85.9 (1996): 1012-1016.