Vitamin Absorption Percentages

The B Vitamins

The current reasoning is that since B vitamins are soluble in water, any excess taken would just be quickly flushed out of the body so you can safely take any amount, even mega-dosages. Researchers have now discovered that this is not entirely true, but many health advisors apparently are not yet aware of these facts. And Vitamin companies that are increasing the vitamin dosages in formulas also appear to be unaware of this new information. Folic acid and vitamin D are two nutrients dramatically increased in supplements by 100% to 500% recently.  Without knowing the true facts, these changes might put certain subsets of the consuming public in jeopardy. 

Nutrient absorption, utilization, and effectiveness have now become paramount for health maintenance and proper dosage recommendations. 

You might think this is a well studied area, but in reality very little research existed prior to 1995. The last ten years finally brought some insightful information, but for some reason, it hasn't filtered down to the public in a meaningful presentation. Media News and product marketing have repeated clichés which do little justice to reveal these truths. Strange, especially since these aspects are some of the most telling statistics for supplement validity. Maybe it is because if you knew this information, you would not buy into the mega dose mania without supervision. Some products have scientific support while some stretch a glimmer of truth beyond recognition. Here is a chart that shows the absorption pathways for each vitamin, but not the absorption percentages. This chart shows nutrient absorption percentages from different foods. 

Liquid multiple vitamin companies try to gain an advantage by claiming greater absorption over tablets or capsules. While it sounds logical, there is very little actual proof, unless of course, the tablet does not breakdown according to USP 30 minute requirements, or the digestive system is compromised, often a factor for Seniors. No vitamins are 100% absorbed from any source as claimed by liquid vitamin marketing, especially for the fat soluble vitamins A, D, E & K which would be jeopardized by a liquid water rather than a fat emulsified delivery system. Yes, some liquid vitamins might get absorbed faster, but properly prepared capsule or tablet vitamins catch up soon enough. The actual differences for some nutrients between liquid and capsules may be less than 5% in healthy people, with the liquids not even always on top. Some Vitamins in a liquid medium are very unstable. Nasal sprayers and sublingual dissolving tablets have slight advantages for some nutrients, but not as much as promoted when scientific research tests absorption.

How Absorption Rates are Determined?

There are about 4 factors Scientists consider:

1. Blood cell and blood plasma content and saturation points,
2. Percentage that spills into urine and the first point spillage starts.
3. Elimination rate from blood plasma and amount of metabolites formed. Metabolites are formed as the vitamin begins to get processed. Metabolites can be co-enzymes which do most of the work attributed to vitamins or the forms created when these co-enzymes breakdown.
4. Tissue content and saturation point. Very difficult to measure and determine for some nutrients.

Generally, blood plasma reaches a saturation point first, then spillage into urine, next blood cell saturation, and last tissue saturation. All the while fecal elimination is progressively increasing, and at mega-dosages can reach very high percentages. A test measuring just plasma levels would not necessarily give blood cell levels or tissues levels. Measuring the metabolites formed is often influenced by other nutrients needed for their generation. The time it takes to reach these different saturation points is governed by time, body size, and dosage amount factors. It is possible that lower intake levels could actually reach and maintain saturation points before mega-dosages since the body develops defensive processes to quickly eliminate higher amounts, often by drastically turning off absorption mechanisms.

Vitamin B1 Thiamine

Absorption of thiamine at dietary levels is by an active transport protein carrier, while at higher mega dosages, absorption is be passive assimilation.

UPDATE: The next study is from a now very old work. It appears the Scientists used plasma levels to measure increase in absorption. It is now known that plasma levels remain low while absorption levels can be very high. Thiamine is rapidly eliminated if already sufficient. Current absorption levels now are at 95%. Rather high, but even in these new studies, the plasma levels did not increase very much.

One of the best studies on Vitamin B1 assimilation reports that intake of 2.5 mg is the amount for the top percentage absorption rate at about 30%. Over 5 mg, percentages rapidly decline until at about 20 mg there is little if any further increases found in blood plasma or urine metabolites. This is because vitamin B1 has an active absorption process and needs a carrier element, usually a protein, to transport it across the intestinal wall barrier. At higher intake dosages, there could be a small amount of passive absorption taking place as well.  ref

Update: new research on Vitamin B1 shows that at mega amounts, 100 mg - 1500 mg, the passive transport overrides the controlled active process and follows nonlinear increasing blood levels. This is far beyond any nutritional application since foods do not naturally have such large amounts.  Plus, there could of course be increased absorption interference of other nutrients which is why these mega-doses should be monitored by a health professional. This new study did not access the biological aspects of these higher dosages. ref 

Vitamin B2  Riboflavin

Vitamin B2 is absorbed by a passive osmotic gradient method and exhibits a generally straight line linear increase up to at least 20 mg. Measuring the amount excreted reveals at least 60% of the ingested dose is absorbed. Over 2.5 mg it begins to be eliminated in urine, thus the yellow color. 

Vitamin B6  Pyridoxine

Vitamin B6 absorption was extensively reported in 2008 from the over 6000 participant National Health and Nutrition Examination Survey of 2003-2004. One interesting fact that emerged was that blood levels of the co-enzyme form of B6, pyridoxal 5' phosphate (PLP) decreased as men aged unless they took supplements. Young Women have lower levels due to such situations as child-birth and oral contraceptive use. The recommended amount for vitamin B6 established by the Government Nutrition Council is 2 mg. This amount falls about 50% short of protecting the last 10% of the population.  At 3 to 4.9 mg, most people would be covered and only a few would still need higher intakes. Vitamin B6 at 3 to 4.9 milligrams was enough to keep Seniors protected from hyperhomocysteinemia, a possible factor in artery disease. This is why the Vitamin Workshop's new vitamin criteria set it's standards for Vitamin B6 between 5 to 20 mg. About 4 mg twice a day would be ample for blood cell saturation and ample tissue content. B6 also has a role to play in water balance within the body. 

Vitamin B5  Pantothenic Acid, Pantethine,

Vitamin B5, pantothenic acid, can be utilized at slightly higher amounts, maybe up to 10-15 mg. The need is established at 7 mg. for adults. Since B5 is widely distributed in foods, it is rare that a deficiency would be found. Stress increases need.

Niacin, and Niacinamide

The recommended amount for Niacin is 30 mg. 50 milligrams will give a flushing sensation to the skin surfaces since Niacin opens up blood capillaries. The skin becomes red. As soon as the liver processes or buffers it, the flushing stops. Niacinamide is the buffered form of Niacin and does not cause a flush. Niacin is not a true vitamin in the strict definition for a vitamin. The body can build niacinamide from the amino acid tryptophan in 9 steps. Thus, the FDA adjusted the requirement for niacin or niacinamide or nicotinic acid, or nicotinamide, which are all the small thing with the amides representing a buffered form, to reflect this conversion from tryptophan to list as 1 niacin NE. The NE stands for Niacin Equivalant. Both 60 mg of tryptophan and 1 mg of niacin = 1 NE niacin. 

CAUTION: Mega-dosages of NIACIN are being used to lower cholesterol. It is very effective when added with statins.  BUT, you have to be monitored by a health Professional since the action of niacin OVER TIME can damage eye capillaries and liver functions. Do NOT take on your own.

This is the B vitamins reality. They are vitally critical to health, but only needed and utilized in very small amounts. More is not always better. Tissue levels would be the only area where extra might initially help, but offer no further benefit once tissue saturation is achieved and maintained. Once blood cells are saturated, or blood plasma, most extra spills rapidly out in urine. With B1, excess consumed over 5 mg is most likely not absorbed by the turning off active transport and is eliminated out the colon. At very large dosages, over 100 mg, passive absorption appears to have a linear increase through 1500 mg. This is not a normal nutritional application since foods rarely have over 2 mg.   

Other B vitamins like Biotin and B12 don't seem to have problems at higher amounts, Biotin is set at 30 mg. With B12, large amounts can be utilized at one time and stored for later use, unlike the other water soluble B vitamins. As people age, B12 absorption is usually reduced and intakes have to increase to compensate. A similar situation exists for vitamin D. Fat soluble vitamins need a separate discussion.

OTHER FACTORS

The above information regards isolated vitamins. Vitamins from foods seldom if ever get to mega-dose milligram amounts so it is not much of a concern.  But there are other concerns for vitamin supplements that influence absorption. A few nutrients have many different formats and each one could vary absorption by a few percentage points. How the tablets are made, coatings, fillers, and binders can all affect breakdown rates and thus absorption. Capsules can breakdown at different rates as well. Digestive conditions of course can dramatically affect rates and genetics also plays a role. So, science has to deal with these many specifics by using generalities to cover as many people and conditions as possible when establishing recommended guideline dosages.

CATCH 22

At the mega vitamin dosages some nutritionists recommend, such as for B vitamins at over 100 mg, saturation is achieved at much lower dosages and the extra over the saturation point often quickly generates greater elimination and even absorption interference? Surely they must have knowledge of these facts, especially since the phrase, "expensive urine" is mentioned often enough. Is there a therapeutic effect at monster potencies that overrides normal digestive principles? Can tissues supersaturate? Just because companies put out such high dosages of vitamins does not prove greater utilization or effectiveness. Research is lacking to answer all these questions concerning mega dosages. Some known facts need repeating here.

PRECAUTIONS FOR HIGHER DOSE B VITAMINS

Vitamin B6 and Folic acid have cautions for higher dosages. B6 over 100mg begins to negatively affect the nervous system in a few individuals and folic acid over about 650 mcg per day suppresses the immune system's killer cell activity. Plus it might be a factor in cancer growth rates and dementia progression. New research points out that high dose B1 might also influence cancer growth rates. While Neurologists have positively used very large dosages of some B vitamins in mental therapy, which might reflect serious genetic challenges to vitamin processing or metabolite conversions, this is beyond the nutritional scope of this website. A very real possibility exists for single vitamin mega-dosages to crowd out other vitamin absorption allowing it to achieve higher plasma levels and force greater uptake into the brain.

Satisfying nutritional needs is priority one, prime consideration for this discussion and new vitamin criteria.

Vitamin Absorption

This topic generates a lot of rhetoric for supplement marketing stories, very little of it factual. Knowing the science for absorption pathways is like seeing a magician's tricks from the back side. The Lady doesn't really disappear. For vitamins, this adds clarity to dosage interpretations. Here are some of the back side glimpses into vitamin absorption:

• No nutrients are 100% absorbed
• Time release tablets can both increase or reduce (mostly) absorption percentages depending on the type of release mechanisms used, the digestive capabilities of each person, and the digestive method for each nutrient. The general rule is not to use time release for the majority of nutrients, except maybe Alpha Lipoic Acid. 
• Calcium averages about 33%. More or less depends upon body needs and amount ingested.
• Most calcium supplements are within a 5% point difference in comparative absorption studies
• Nutrient promotions that claim 75% are usually referring to a solubility percent indicating potential absorption rather than actual absorption.
• Calcium first has an active absorption process regulated by calcium blood levels, and then further down the intestinal tract, calcium and the other minerals compete for abosprtion through osmotic gradients.
• This free competition of minerals at this point highlights why excess calcium can hinder abosprtion of other minerals when un-balanced amounts are consumed.  
• There is little proof that liquid vitamins are better absorbed than powder or capsules, except when there are major digestive limitations and /or the tablets do not quickly breakdown. 
• There are some quick release tablets that dissolve faster than capsules.
• Vitamins in a liquid form are active and need more stabilizers to prevent breakdown or interaction with other nutrients.
• There are limits to how much of a vitamin can be absorbed at one time. Mega-dosages of many nutrients are largely wasted, like calcium and vitamin B1.
• Some nutrients like vitamin B1 ( and other B vitamins) have an active carrier system to aid absorption. ref  
• This system is reduced or down-regulated when vitamin levels are normal or in excess and increased when vitamin or nutrient levels are low.
• Concentrated nutrients can crowd out other nutrients for absorption sites. Vitamin E over K, zinc over copper, calcium over magnesium, Iron and vitamin E interaction, etc
• Vitamins and minerals often compete for the same carrier proteins.
• Intestinal wall docking stations can become saturated.
• Digestive processes breakdown most if not all supplements into isolated parts. 
• Natural vitamins often enjoy increased absorption advantages over synthetic vitamins, but there are some exceptions, like folic acid.
• High fiber diets can slow absorption down and / or reduce assimilation percentages, which can be either an advantage or a detriment.
• Fat soluble nutrients in powder form have a very low absorption percent. i.e. CoQ10 @ 5%.
• Emulsified oils in base increase fat soluble vitamin absorption by up to 300% or more.
• This research shows a 5 times greater amount of vitamin D absorbed in normal subjects compared to those with diminished fat metabolism 
• Some nutrient forms do have as much as 300% better absorption percentage over other forms of the same nutrient.
• "Food Form Vitamins" may have some absorption advantages. 
• Vitamin B1 is absorbed at about 30% up to 2.5 mg. ref The percentages rapidly decrease with higher dosages. From 5 to 20 mg, the extra absorption is only about 1.3%, most is eliminated thru colon. (NOTE: this is from a very old study, and may just reflect the amounts measured in plasma at a point after ingestion. Actual absorption might be far greater. A European study puts it at 95%, that is rather high.) 
• Vitamin B2 is absorbed on a linear increase up to about 20 mg. then rapid decrease. One study showed an increase in excretion of vitamin B2 of over 90% from extra over the base requirements. ref 

Vitamin Triage Theory

This rather unique title, borrowed from the hospital emergency room concept of giving aid first to those with the most urgent need, helps clarify many seemingly controversial vitamin research study results. The body has a great innate ability for survival and directs nutrients that are under supplied by the diet to perform the most vital functions while holding off on less important processes until more nutrients arrive. While this doesn't work for all nutrients, let's look at a few examples where it does.

VITAMIN K

Vitamin K was for a long time a forgotten nutrient by scientists. They assumed that since the diet usually supplied adequate levels from green leafy vegetables, fermented cheeses, butterfats, and that the beneficial bacteria in the intestinal tract also produced vitamin K, they did not have to pay much attention to it. The major function they knew about was to stop bleeding from an injury by activating coagulating proteins in the liver to clot blood. 

It is now known that vitamin K has many other vital functions that are represented in bone structure,  prostate tissues, and cardiovascular artery health. For bone health, Doctors for many years measured the amount of activated osteocalcin in the blood as a marker for bone building. Since vitamin K is needed to activate osteocalcin, what these tests were really measuring was the level of vitamin K action. But Doctors never communicated that fact to their patients. To this day, the Osteoporosis Foundation does not mention vitamin K in their recommendations for healthy bones.

Vitamin D directs the production of the nonactive form of Osteocalcin. Vitamin K has to activate it before it helps bind calcium to bone crystals. That seems like a vital action for bone building, but only recently have some bone supplements started to include vitamin K.

People with weak and broken bones often test low for vitamin K. But studies have not always shown a benefit by increasing vitamin K intake. It turns out there are many different forms of vitamin K and they each exhibit different action levels. All the forms seem to do the coagulation part, but K2 has greater action on bone, cardiovascular, and prostate health. Even between the different K2 forms there are various different life span times. Vitamin K2 as MK7 lasts for a few days while MK4 only a few hours. This explains why much larger dosages of MK4 are needed. In some studies, the vitamin K1 form did not show an effect on some of these other functions. The body is able to convert some K1 into K2 and the degree that this happens might influence research results. Beneficial probiotic bacteria levels might have some effect on K1 conversion to K2.

Scientists now know that probably only Gorillas who consume their own feces get a significant amount of this bacteria developed vitamin K2 from the intestinal tract. Thus there may be a need to consume the pre-formed K2 from fermented food products, such as natto, a fermented soy product that is often used in supplements, listed as MK-7. 

When body production and dietary vitamin K are low, the body allocates the available vitamin K to the building of coagulation proteins first, and then to less vital but still important functions of preventing calcium from entering arteries or binding calcium to bones, and then only the amount it is able to convert from K1.  

VITAMIN D

Vitamin D has two forms that circulate in the blood. One is a low activity form that has a longer life and serves as the material for the body to build the 1000x higher activity hormone form produced by the kidneys. The size of the pool of the low activity form is influenced by the amounts from supplements, fortified foods, and sun exposure time.

It is only at very low and deficient levels that this vitamin D form has any influence on the production levels of the hormone form. This hormone form is used to balance the calcium level of the blood, and thus has an influence on calcium absorption, elimination, and bone health. The blood calcium balance is one of the most critical processes in the body. Without the calcium balance, nerves would not fire and muscles would not contract. 

But, this is not the only function for the low active vitamin D pool. It is now known that when the pool levels are at an optimal amount, this low active D enters into the cells in the prostate, breast, and colon and at least 9 other tissues where an enzyme converts it into the active hormone form to direct the building of proteins needed to protect these cells. If the low active D pool is too low, this protection process is incomplete. More damaged cells could be formed. The same process probably occurs in breast tissues, but science is still researching. BUT, it is only at very low levels of the vitamin D pool that it's conversion into the hormone form is hindered. The body obviously knows it needs to prioritize protecting blood levels of calcium first.

CoQ10 

Coenzyme Q10 is vitally needed by most organs, tissues, and cells to maintain energy production. CoQ10 is made in the Liver in adequate amounts when young, but with ageing, less and less CoQ10 is produced each year. Many organs exhibit a gradual reduction in CoQ10 levels, but the lungs stay up until after age 60 when CoQ10 levels simply drop off the cliff. This explains why the lungs are often the weak link at this stage. The Liver is the last organ to show any redcution of CoQ10 levels due to it's critical funcitons for survival.

MINERALS

The body has very specific needs where minerals are concerned. First, some minerals compete with each other for absorption space. Zinc to Copper, Calcium to Magnesium, Calcium to Phosphorus, Sodium to Potassium. Plus, if not enough of a mineral such as calcium is supplied, the body will take it from storage areas such as in bones to help balance the blood level. If not enough potassium is present, calcium and magnesium will be used instead to buffer acid conditions the body creates. If too much sodium is present, calcium is eliminated by the kidneys. Over time, the body has developed mechanisms to quickly eliminate excess minerals that are typically supplied by the diet in large amounts and different mechanisms to conserve scarce minerals.**

**These mechanisms explain why sodium, a usually rare mineral in the natural diet but plentiful in prepared foods, presents health problems for some people. It could also by a factor in the potassium to sodium ratio. Nature puts 10 to 100 times more potassium in natural foods than sodium, but this ratio is often reversed in recipes for modern day foods. The body is still operating as if sodium was a scarce mineral and conserves it.

The Most Obvious Triage Example

In a pregnant woman who does not consume enough nutrients to nourish both her body and the growing fetus, nature satisfies the growing fetus requirments first by robbing the mother's nutrient reserves, even to the point of taking them out of vital structures.

Thus the triage theory can explain some of the more controversial research results. Often it is really not controversial, but simply how the body functions to survive. The best example may be that the body tries to find positive uses for potentially negative body generated free radicals. One recent study looking into the possible protection of the prostate by taking vitamin E and selenium (SELECT) was stopped when the mid study results showed slightly higher cancer rates in the vitamin E group and a little more diabetes in the selenium group. There are sound body function process mechanisms to explain both of these findings. Of course they were not the ones the Media talked about, or that the vitamin industry challenged, but a few scientists and past study results predicted these findings before they were announced.

Vitamin E is another radical action example. Test tube studies is the Lab reveal that both Flax oil and Evening Primrose oil have cancer cell killing properties. When vitamin E is added to the test tube, this killing action stops. Evidently, the antioxidant activity of vitamin E (alpha tocopherol) works so well that it stops the lipid peroxidation created cancer killing radicals that the flax oil and EPO set in motion. Of course, this is just a test tube study and needs verification that this process could also happen inside the body.

The Vitamin Workshop simply finds this information and incorporates it into the parameters of the vitamin criteria. Not many other websites or nutritionists are even talking about some of these concepts yet. Amazing!