How Vitamins A, D, E, and K Interact – Part 1: The Players
Last week, we discussed some of the various diseases that can result from vitamin D deficiency. Today, I want to look at the other three fat-soluble vitamins – A, E, and K – and see how these four vitamins function within the body.
What Are The Four Fat Soluble Vitamins?
Vitamin A – The Vision Vitamin
Vitamin A is probably most well-known from your mother’s admonitions to “eat your carrots, so you can see well.” One of the many roles of vitamin A is eyesight, but this vitamin is also key for proper gene transcription, immune function, embryonic development, bone metabolism, and (Teenagers take note!) skin health and acne prevention. Vitamin A also affects the production of growth hormone and testosterone.
Vitamin A comes in two main forms: retinol and beta-carotene. Animal foods provide retinyl palmitate, which is changed in the small intestine to retinol, known as “true” vitamin A as it is nearly ready for the body to use (retinoic acid is the active form of A). Beta-carotene, on the other hand, must be converted to retinol or vitamin A, and comes from plant foods. Because retinyl palmitate is pre-formed vitamin A, it is theoretically possible to overdose (though exceedingly rare). With beta-carotene on the other hand, it’s highly unlikely that one will exceed the body’s requirements as the conversion factor of beta-carotene to retinol is about 12-to-1.
Vitamin D – The Sun Vitamin
I won’t go too much into what vitamin D is here or how it’s made in the body since it was covered last Thursday. But I will get a bit more in-depth. There are two major forms of vitamin D (along with three other forms): D2 and D3. D2 comes from plant and fungal sources, while D3 comes from animal sources, most notably your own skin when exposed to sunlight.
To sum up last week’s article, this vitamin is responsible for maintaining blood levels of calcium and phosphorus, growing bone, and shoring up the immune system. Studies have shown that deficiency can play a role in myriad diseases, from rickets to Alzheimer’s, Parkinson’s, Rheumatoid Arthritis, and skin cancer, and that sufficient levels are protective against some skin infections and radiation.
Vitamin E – Tocoph-a-what?
Vitamin E is actually a set of eight related substances known as tocopherols and tocotrienols. The four tocopherols are alpha, beta, gamma, and delta (creative, I know), with alpha-tocopherol being the form preferentially absorbed and used by humans. The tocotrienols are similarly named. Vitamin E is largely used within the body as an anti-oxidant. Each of the eight forms of vitamin E has about the same antioxidant potential, though some research suggests that the tocotrienols are more potent in their anti-oxidant and anti-cancer effects than are the tocopherols.
However, new research suggests that vitamin E may serve most importantly as a signaling molecule, not as an anti-oxidant. Vitamin E also appears to have a function in heart disease prevention through regulation of phosphorylation cascades. Further, a metabolite of delta-tocopherol has a regulatory effect on sodium in the blood, possibly contributing to a blood pressure lowering effect. Finally, vitamin E has proven in rats to reduce infertility, improving sperm production in males and the ability of females to carry to term.
Unfortunately, most multi-vitamin manufacturers ignore the other seven forms of vitamin E and provide predominantly alpha-tocopherol. While alpha-tocopherol is the most readily absorbed of the eight forms, I’m sure I don’t need to say that the other seven forms obviously serve important roles in the body. Studies on vitamin E typically supplement solely with alpha-tocopherol which leads to reduced concentrations of gamma- and delta-tocopherols.
Vitamin K – Activator X
The final fat-soluble vitamin is vitamin K. It was identified by Dr. Weston A. Price as a compound he called “Activator X”. As with vitamins A and D, there are two main forms of vitamin K, known as K1 and K2. K1 is the predominant form of vitamin K in the diet, coming from plant foods. K2 consists of MK-4 and MK-7 forms, which are found in animal foods and natto.
Vitamin K deficiency can result in calcification of soft-tissue, atherosclerosis, and uncontrolled bleeding owing to K’s role in blood clotting. Further, deficiency is associated with malformed bones and prostate cancer.
Once again, we see that the MK-4 form of the vitamin, the form that comes pre-formed from animal foods, is much more highly usable than the K1 form (and also more so than the MK-7 form produced by bacterial fermentation). Humans are very inefficient at converting K1 to K2.
Stephan at Whole Health Source has done an entire series on vitamin K and its role in disease prevention (which is where I got much of the above information). It’s good reading and goes far more in-depth than the skim I just gave the issue.
Next Time
Today, we looked at the four fat-soluble vitamins in isolation. In the next installment of this series, I’m going to discuss the far more important interplay between these vitamins once they are in the body.
About Scott
Scott Kustes loves to cook and loves to eat. He started Real Food University to help you get maximum enjoyment out of the meals that you eat. To find out more about how he has rebelled against the fast food culture and counting calories or carbs, join the Real Food Revolution.
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First off thank you very much for providing a wonderful resource.
Second, I have a question for you this morning. I am generally annoyed with the BBC’s coverage of nutrition topics as the main writer still subscribes to a low fat high carb outlook, so most of the coverage is heavily I fluenced by preconcieved assumptions based on scant evidence.
But this morning they posted a review of a new study sAying that high fat diets during pregnancy can lead to increases in both birth weight, fat levels, and the hormones that control hunger giving you not only a fat child but one that is prone to becoming more prone to weight gain. The question I have is they said that the rats were fed a high fat diet and then stated that it was high levels of triglycerides associated with a high fat diet that they hypothesize is responsible for the observed results. They then jumped to the conclusion that this could be a reason that we are having the obesity epidemic.
Just to make sure I am not completely off base here, the liver also converts carbohydrates to triglycerides during carbohydrate metabolism. Also, aren’t there multiple studies out there that show high fat diets as effective at decreasing triglyceride levels? And if one is eating Paleo, and our main sources of fat are animal fats, olives, and nuts there really shouldn’t be a dangerous increase in triglyceride levels, correct?
And one final follow up question – if I am IF’ing and I am trying to take in enough calories to support training during my window, I have been focusing on getting the
majority of my calories from meat and fat with very little carb intake. But other than this poor review there isn’t anything contraindicative to doing this is there? ((I think the study just threw me for a loop).
(sorry I couldn’t post a link to the article, I am on my iPhone but if you go to news.BBC.co.uk it is on the front page).
Hey Scott,
Thanks for the post! Why do you think that the multi-vitamin manufacturers ignore the other forms of Vitamin E? Are they just being lazy or is it just that Alpha-Tocopheral is the easiest to harvest?
All the Best,
Andrew R
Andrew, the other seven forms of vit E are left out of most formulations because the public is mostly ignorant to their importance, AND these other forms are more expensive, especially the tocotrienols.
It’s important to note that MOST studies regarding vit E use the first discovered alpha tocopherol form, which IS NOT the most common form found within plants and foods, and thus doesn’t match our evolutionary needs. The form most people should focus on is gamma tocopherol. But, getting at least all four of the tocopherols is the best approach.
Note that all studies I’ve seen only use the alpha tocopherol form (and worse, often the synthetic version), and it’s no wonder why such a high percentage of these studies fail to show meaningful results.
Found this really quick, a little more on the gamma form:
http://www.lef.org/magazine/mag2006/apr2006_report_gamma_01.htm
Cool, thanks Scott!
All the Best,
Andrew R
Your information about vitamin K is not entirely accurate.
Vitamin K2 comes in several flavors, not just MK-7, but also MK-8, MK-9, etc. Also, these are much MORE bioavailable than K1, and are therefore MORE useful than K1. The long-chain K2s (particularly MK-9) are found in Swiss-style cheeses, which are fermented using propriono bacteria. The cheeses with the highest amounts are Jarlsberg and Emmenthaler. Dutch studies have shown that those who ate the most vitamin K2 (which mostly came from cheeses) had the lowest rates of calcified arteries and heart disease. This relationship did NOT occur with intake of vitamin K1.
Vit K2 is definitely a top 10 supplement. I’ve been taking Mk-4 and other varieties of K2 for several years. At 47 yrs old, I just very recently had by my arteries imaged, and they came up extremely clean–basically no sign of calcification (the doctor considered them astounding). And this is after my first 40 years of an abusive, processed foods heavy diet, which I’m certain left my coronary condition in a very worrisome state. All totally reversed now (I take some 80 supps daily, and eat a low carb, mostly natural diet, and I’m now supremely fit).
This is such a timely post – for me! I have been thinking about writing a series of posts on the different vitamins and you beat me to it! I actually had it on my list for next week and was just trawling a few of my favorite blogs when I came across your article. Nice work
Mind you, I had a slightly different approach in mind and was also going to write on which foods for which vitamins etc, so I may still do that and include a link back to your blog to fill in the gaps! Thanks for a great resource – while opinion based posts are often very interesting, it’s great to see a research based post.
Walter, thanks for pointing that out. I just skimmed the surface and pointed out the most common forms of these vitamins. Vitamin D also comes in D1, D4, and D5, but those aren’t very common in the body.
Kat, you better get to it quick. The food one goes up tomorrow.
Cheers
Scott
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Great summary of the fat soluble vitamins Scott. I covered all the vitamins on my blog this month but you have covered a lot of points that I missed.
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[...] How Vitamins A, D, E, and K Interact – Part 1 … – Real Food UniversityLast week, we discussed some of the various diseases that can result from vitamin D deficiency. Today, I want to look at the other three fat-soluble vitamins – A, … [...]