Thursday, June 6, 2019

Personalizing Vitamin E Requirements

Anyone who has ever attempted to track their micronutrient intake has likely noticed just how difficult it can sometimes seem to achieve the recommended dietary allowance (RDA) of α-tocopherol (vitamin E). Especially if we're eating certain restrictive diets such as the paleo diet or even just a calorie restricted diet. On some days it may certainly seem impossible—it's baffling! We find ourselves doing everything right, eating a diet of entirely whole foods, and hitting every micronutrient target in excess with the sole exception of vitamin E. Maybe you decide to take a supplement to make up for it. Maybe you chow down on an extra 200 calories worth of almonds. Maybe you decide to cook your eggs in red palm oil instead of coconut oil. Maybe you juice a whole kilogram of carrots. Don't panic, though. Chances are good that your vitamin E intake is actually just fine!

Did you know that everyone’s vitamin E requirement is likely different, and that vitamin E requirements probably vary drastically from day to day? It’s true. This is due to how vitamin E fulfills its role in the body. Vitamin E’s only clearly established role in the body is to protect polyunsaturated fatty acids (PUFAs) in cell membranes from an oxidative process called lipid peroxidation [1]. Lipid peroxidation is a form of oxidative damage that occurs as a consequence of normal metabolism, but is accelerated in certain disease states like type II diabetes. 
The reason they are uniquely vulnerable to lipid peroxidation is because they possess more than one double bond in their carbon chain.

In vivo human trials consistently show reductions in lipid peroxidation with vitamin E supplementation [2]. Monounsaturated fatty acids (MUFAs) are not particularly vulnerable to this process, though vitamin E intake has been shown to protect MUFAs from lipid peroxidation in animal tissues as well [3]. Saturated fatty acids (SFAs) on the other hand are completely resistant to peroxidation at body temperature. This means that vitamin E offers no special protection to SFAs in cell membranes. 

The official RDA for vitamin E is set at 15mg per day for adults, 4-11mg per day for children, and up to 19mg per day for lactating women [4]. In the dietary reference intake (DRI) report for vitamin E, we discover that the RDA for vitamin E was set to accommodate population-wide averages in PUFA intake, with the primary PUFA being linoleic acid, an omega-6 fatty acid found in plants and abundantly in nuts, seeds, and most vegetable oils. Based on a ratio of 0.4mg of vitamin E per gram PUFA (as linoleic acid) per day, they merely calculated the RDA of vitamin E based on how much vitamin E would be required to cover the average person's PUFA intake. We can surmise from this that half of the population likely needs less than the RDA of vitamin E, while the other half very likely needs more than the RDA of vitamin E. But, this actually tells us nothing about our own personal vitamin E requirements as individuals. It only tells us that we have a 50/50 chance of needing more or less than the RDA.

Because the body does not synthesize PUFAs de novo (from scratch), all of the PUFAs in our cell membranes got there because we ate them. This suggests that we have at least some control over how vulnerable our cell membranes are to oxidative damage. If vitamin E's one and only job is protecting PUFAs from damage, what might happen to our vitamin E requirements when we go out of our way to limit dietary PUFAs?

If we indeed can modulate our needs for vitamin E by adjusting our PUFA intake, how might we go about calculating our own personal vitamin E requirements? Luckily, researchers have actually answered this question in amazingly fine detail [5]. As it turns out, each individual dietary PUFA (of which there are about five relevant types) alter vitamin E requirements differently due to each PUFA’s relative degree of unsaturation. In fact, the reason such imprecise methods were used to establish the RDA of vitamin E is that it is just too damn complicated to capture all of the nuances in a single general recommendation. This is partly because our vitamin E requirements not only change depending on how much PUFA we consume, but what kinds of PUFAs as well.

This means that if we had precise knowledge of our own dietary intake of these dietary fatty acids, we could approximate a vitamin E requirement that was personalized and custom tailored to our own dietary habits. Pretty cool, eh? I thought so too.

First we have to use a nutrition tracking tool like Cronometer to log a typical day of eating. Don’t do this while on vacation or over the holidays if your eating behaviour typically wavers during those times. Once you have an accurate accounting of a typical day’s worth of food it should look something like this: 

Below, we can see that this sort of dietary pattern yields ample amounts of all of the vitamins with the exception of vitamin E. Is this really a problem? Let's find out!

At this point, the next task is to separate these foods into animal foods and plant foods. This is because the PUFA that are found in animals are different than the PUFA found in plants. For example, the PUFA found in plant foods like walnuts are alpha-linolenic acid (ALA) and linoleic acid (LA), whereas the PUFA found in animal foods like salmon are eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and arachadonic acid (AA). Each of these fatty acids have different degrees of unsaturation and thus alter our vitamin E requirements differently.

In Cronometer, we can shift-click to highlight certain foods together. Doing this we can highlight animal foods and plant foods separately:

Once we have our foods stratified by animal foods and plant foods, we want to scroll down to see the omega-3 and omega-6 content of both groups. 

Record the numbers for both groups separately. Once we have those numbers recorded, the last thing we need to jot down is the MUFA content of all of our foods combined, as shown above.

The next step is to use this handy dandy vitamin E calculator designed by my brother, and input the fatty acid composition of our food selection. Input your plant omega-3 (alpha-linolenic acid), plant omega-6 (linoleic acid), animal omega-3s (EPA and DHA), animal omega-6 (arachadonic acid), and then the total oleic acid (MUFA) for all foods together. For the animal omega-3s, I tend to just divide the total animal omega-3 between the EPA and DHA boxes, as there isn't really a practical way to calculate this precisely. 

Once all your data has been inputted into the calculator, your personalized vitamin E requirement for that day will be displayed in the total vitamin E box!

As you can see, our vitamin E requirement for this particular day (7.5mg) was well below the RDA (15mg), and well below what we consumed (11mg). This means that despite not actually achieving the RDA of vitamin E on this day, we actually overshot our vitamin E requirement for this particular day by 47 percent!

If you want more granular detail, repeat this process for two weeks worth of typical eating. Take every calculated vitamin E requirement for each day, and use them to calculate an average. The more days you add, the more refined the result! Now that you know your own vitamin E requirements, you’ll probably be surprised by how little you need if you structure your diet appropriately. Personally, I’ve calculated my own requirement as being around 6mg of vitamin E per day. Well below the RDA! But I also regularly consume well above the RDA for vitamin E.

Alternatively, we can do a quick and dirty calculation based on a simple ratio proposed in the DRI report for vitamin E. This calculation is much, much less precise. As such, I'm skeptical as to how accurately it will represent our vitamin E requirements. But if we wanted to give it a shot, we would start by taking our average daily PUFA intake in grams and multiplying that number by 0.4mg of vitamin E.

For example, if our average daily PUFA intake over two weeks is 15g per day, our vitamin E requirement is 6mg per day based on this ratio. However, I share the skepticism expressed by the authors of the DRI report. I don't personally believe that this ratio is likely to capture all of our vitamin E requirements, as it fails to factor in a number of variables. It doesn't account for the modest effect of dietary MUFA, and is also based solely on linoleic acid as the primary dietary PUFA. We want to determine our requirements based on the entire breadth of dietary unsaturated fatty acids, not just one variety. 

In my opinion, if we wanted to be extra safe, we could likely capture all of our vitamin E requirements in excess by maintaining a 1g to 0.84mg ratio of PUFA to vitamin E. I arrive at this by averaging the vitamin E required per gram of each of the six relevant dietary fatty acids listed above. The average ends up being 0.84mg of vitamin E per gram of PUFA. This has a greater chance of capturing requirements for both PUFA and MUFA, in addition to considering more than just linoleic acid as the primary dietary PUFA. It is also unlikely to generate a vitamin E requirement as drastic as the official RDA. But at the end of the day, using the handy dandy vitamin E calculator that I have provided above is probably the best bet.

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1. Valk EE, Hornstra G. Relationship between vitamin E requirement and polyunsaturated fatty acid intake in man: a review. Int J Vitam Nutr Res. March 2000.

2. Kun Liu, Suyun Ge, Hailing Luo, Dubing Yue, and Leyan Yan. Effects of dietary vitamin E on muscle vitamin E and fatty acid content in Aohan fine-wool sheep. J Anim Sci Biotechnol. June 2013.

3. Huang HY, Appel LJ, Croft KD, Miller ER 3rd, Mori TA, Puddey IB. Effects of vitamin C and vitamin E on in vivo lipid peroxidation: results of a randomized controlled trial. Am J Clin Nutr. September 2002.

4. Institute of Medicine (US) Panel on Dietary Antioxidants and Related Compounds. Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids. 2000.

5. Daniel Raederstorff, Adrian Wyss, Philip C. Calder, Peter Weber, and Manfred Eggersdorfer. Vitamin E function and requirements in relation to PUFA. Br J Nutr. October 2015.