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Recently, this magazine ran a series of articles on vitamin and mineral supplements addressing the seemingly simple question, “Who needs them?” This seemed like a good jumping off point. Whenever you look at a supplement, you ask yourself what benefits its various ingredients will deliver. One formula promises to provide insurance against a multitude of vitamin and mineral deficiencies, another to supply protection against stress, and a third claims to protect against, say, bone loss. Athletes, in particular, constantly push their bodies “to the edge,” and they rightly expect ergogenic aids to be just that—substances that improve the body’s capacity to engage in physical activities. Moreover, serious athletes and body builders often cross the line between training and over-training. Dietary supplements are expected to a variety of needs, both minor and major. However, is choosing a supplement merely a matter of finding one with ingredients that match perceived needs?

If only it were that simple! All supplements work through the metabolism of the body. This is the reason that good formulators try to take the body’s metabolism into account when designing products. At stake is the bioavailability of nutrients. The absorption of nutrients involves at least three steps: any supplement must first be digested, then assimilated, and, finally, utilized. Increasing bioavailability may require the manipulation of one or more of these factors.

Fortunately, there are steps that can be taken to improve the bioavailability of nutrients. For convenience, these steps can be described as aspects of digestion, assimilation and utilization, although some aids to nutrient absorption actually will be active in all three areas.

Let’s start with that can of expensive protein powder you are consuming or the specialty minerals you take. Without adequate production of hydrochloric acid and pepsin in the stomach, neither the proteins nor the minerals will be well assimilated. Probably 40 percent of all adults suffer from too little stomach acid (hypochlorhydria).1 It is likely that the majority of those who have frequent indigestion think they are secreting too much stomach acid and reach for antacids for relief when, in reality, their stomach’s secrete too little stomach acid. Even individuals in apparent good health can bring on digestive difficulties through food choices. Athletes who have increased their protein intake dramatically or those who drink large amounts of milk with meals have increased the demands made upon their stomach’s digestive capacities. (Milk’s calcium content tends to neutralize stomach acid and thus reduces the stomach’s ability to digest protein.) If you suffer from bloating or discomfort immediately after eating or feel nauseous after taking supplements, you should explore the possibility that you are not producing adequate hydrochloric acid.

Digestion starts in the mouth, continues in the stomach and finishes in the intestines. Malabsorption syndromes are usually problems that originate in the stomach and small intestine and lead to a variety of nutrient deficiencies. Aside from inadequate hydrochloric acid, chiefly involved in these syndromes is the pancreas, the organ which secretes almost one half gallon of pancreatic juice into the small intestine in a 24-hour period. This fluid includes amylases to break down starch into sugars, lipases to aid in the digestion of fats, and proteases to finish the digestion of proteins. Finally, bile, which is produced by the liver and released by the gallbladder, aids in the assimilation of fat-soluble vitamins and other nutrients and helps to soften the stool to prevent constipation. A less recognized fact is that, along with stomach acid, bile and the proteases are the primary barriers to the infestation of the gastro-intestinal tract by parasites and yeasts.

Quite a number of supplements can be used to improve the digestive functions of the stomach. These include betaine hydrochloride, pepsin, pancreatic enzymes, bromelain (from the stem of the pineapple), papain (from green papaya fruit), ginger, niacin, cayenne pepper, black pepper and its extracts, etc. The most direct approach is to use hydrochloric acid bound to betaine and mixed with pepsin in a ratio of 600 mg betaine hydrochloride to 150 mg pepsin. Jonathan Wright, MD suggests a regimen that starts with one tablet per meal. The dosage is increased by one tablet at each subsequent large meal until there is a feeling of slight warmth in the stomach and then reduced by one tablet. No more than seven tablets are taken at any given meal and the dosage is reduced if there is discomfort. Once digestion improves, the dosage may need to be reduced,2 as well. Various commercial preparations of amylases, lipases, proteases, and other enzymatic digestive aids are available and should be used according to package directions. Plant sources of the enzymes include members of the fungal family of Aspergillus. Other formulas contain pancreatic enzymes derived from ox or porcine sources and should have a United States Pharmacopoeia (USP) number of 1 × pancreatin or greater. Better sources run from 4 × to 10 × USP. Some authorities suggest that the USP value should be as high as 10× and that 500 –1,000 mg should be taken before each meal for best results.3

After digestion comes assimilation. This takes place primarily in the small intestine. Just as with digestion, many factors can adversely affect assimilation. Some nutrients can only be assimilated within the first foot or so of this intestine, whereas others can pass into the blood stream along almost the entire length of both intestines. Some nutrients interact badly or compete for absorption. Others require that your body secrete special proteins as carriers before they can be absorbed. Vitamin B-12 requires a substance secreted by the stomach in order to be absorbed, whereas folic acid requires a substance secreted by the small intestine. Fat soluble vitamins, including A, D, E and K, all are best absorbed when taken with meals which contain some fat or oil. Sometimes strictly digestive enzymes are included in formulas to improve absorption as well as digestion, but the verdict on these is mixed. Bromelain is probably the best known of the enzymes used for this purpose. The claim made for it, i.e., that it improves the uptake of nutrients, is based on a limited number of studies which seemed to show that some antibiotics were better assimilated when taken along with this protein-digesting enzyme. Whether bromelain gives similar benefits in the cases of nutrients has never been studied.

Nevertheless, quite a number of items do increase assimilation substantially. These include glucosamine, piperine, and forms of lecithin, especially lyso-lecithin. Perhaps the biggest surprise here is the first item. Glucosamine today is particularly noted for helping in the repair of arthritic joints. However, United States Patent 2,907,697 was granted back in 1959 and covered the employment of glucosamine (in various forms) to enhance the absorption of vitamin B-12. The way in which glucosamine works to enhance absorption has not been fully understood, but we know now that glucosamine, especially in the form of N-acetyl-glucosamine (NAG) greatly improves the health of the mucosal membranes of the intestines.4 Inasmuch as glucosamine likely works by a general mechanism, taking 1–2 grams along with your most important nutritional compounds may be worthwhile. NAG, also available in a special form called Poly-NAG, is beneficial to the gastro-intestinal tract under all circumstances. Glucosamine hydrochloride similarly may be used for this purpose.

Piperine is an active principle extracted from black pepper. Approximately 5 mg of almost pure piperine administered at the same time as other nutrients (selenium, beta-carotene and vitamin B-6) resulted in increased absorption ranging from 30 to 250 percent in trials.5 Although there is some controversy on this point, capsaicin, the “hot” compound found in cayenne and related peppers, while improving the digestion of some foods, may not improve nutrient bioavailability in the same way as piperine.6 Piperine must be taken at the same time as the nutrients to be assimilated if there is to be any benefit.

Now for the champ in the category of assimilation: Lecithin, phosphatidylcholine, polyenylphosphatidylcholine (PPC) and related compounds, all grouped broadly under the heading “phospholipids,” typically help to improve liver function and to increase the solubility of bile. This means these compounds aid in the absorption of fat-soluble nutrients. However, this is not the most interesting aspect of lecithin. When we eat lecithin, small amounts are changed into lysolecithin (technically, lysophosphatidylcholine) in the small intestine. How much depends upon the type of lecithin consumed. For instance, eggs, which contain substantial amounts of lecithin in their yolks, traditionally have been considered to greatly improve the absorption of nutrients. Lysolecithin alters the permeability of membranes and thereby increases the uptake of nutrients. To put this differently, lysolecithin “changes the size of the holes” in membranes.7 Subject to a United Kingdom Patent, lysolecithin was first found to increase food efficiency in animals. Improvements in nutrient assimilation were about 30 percent for a broad range of minerals and amino acids. Lysolecithin has been further developed as a human weight gain supplement and even has been used to help lactating mothers produce more milk for their infants.

Dosage in the case of lysolecithin is important because, unlike other forms of lecithin, one can ingest too much lysolecithin. The standard recommendation of pure lysolecithin is 1 to 100 mg per kilogram (2.2 pounds) of total food intake. Commercial preparations vary dramatically in purity, so it is an excellent idea to follow directions closely.

Very interesting is the impact of probiotics on the availability of nutrients, particularly the minerals magnesium, iron and zinc, from grains. This is true of the bread-making process, sourdough preparations improving nutrient bioavailability over normal processes, but also perhaps for the use of probiotic supplements.8 There is the additional benefit of inhibiting the growth and adhesion of enteric and foodborne pathogens.9

After assimilation comes utilization. This is a complex issue that can only be touched upon here. It is known that many nutrients facilitate the actions of other nutrients. A deficiency of zinc, for instance, makes the use of vitamin A in the body more difficult. The consumption of a small amount of alcohol greatly improves the assimilation of many substances, but in large amounts alcohol not only is toxic itself, but it also prevents the body from using nutrients, such as beta-carotene, or causes the loss of nutrients, such as magnesium. Again, there appears to be a synergism between nutrients such as selenium and vitamin E or many of the bioflavonoids and vitamin C. Flax seed oil and other sources of essential fatty acids may be more effective if eaten with proteins. Therefore, be aware that balance and synergism are necessary for the proper use of nutrients by the body.

Piperine, already discussed for its ability to increase nutrient uptake, inhibits the breakdown of many compounds in the body, yet also protects against the production of certain classes of toxic compounds in the body by cytochromes P-450. The same mechanism which prevents the rapid destruction of many compounds that we would consider to be beneficial prevents drug metabolizing enzymes from activating toxins, such as aflatoxin B.10

An alternate approach to getting more from your nutrients is to look to the health of your liver. If the liver is not working up to par, eating extra protein, for instance, may lead to increased levels of ammonia in the body, and this will damage your ability to recover from workouts. Moreover, many nutrients must be transformed into coenzymatic forms in the liver before the body can use them. Classic liver supporting nutrients and herbs can be very helpful. These include choline (1 gram/day), polyenylphosphatidylcholine (PPC), L-carnitine (1,000 mg twice per day), and the extracts of dandelion, milk thistle and artichoke.


  1. Gastroenterology May 1946: 348–352; British Journal of Medicine 1930; i: 1–14.
  2. Wright JV. Dr. Wright’s Guide to Healing with Nutrition. Keats Publishing, New Canaan, CT, 1990: 30–50.
  3. Whitaker J. Dr. Whitaker’s Guide to Natural Healing. Prima Publishing 1995: 69–72.
  4. American Journal of Gastroenterology 1983; 78: 19–22.
  5. Nutrition Science News March 1996; 1, 1: 36–8.
  6. Critical Reviews in Food Science and Nutrition 1991; 29: 435–74.
  7. The Genetic Engineer and Biotechnologist 1993; 13, 2: 95 –104.
  8. J Anim Sci. 2010 Oct;88(10):3320–6.
  9. J Food Sci. 2010 Nov-Dec;75(9):M546-51. doi: 10.1111/j.1750-3841.2010.01818.x. Epub 2010 Oct 7.
  10. The Journal of Pharmacology and Experimental Therapeutics 1985; 232, 1: 258–62; Cancer Letters 1994; 86:195–200.

Dallas Clouatre, PhD

Dallas Clouatre, Ph.D. earned his A.B. from Stanford and his Ph.D. from the University of California at Berkeley. A Fellow of the American College of Nutrition, he is a prominent industry consultant in the US, Europe, and Asia, and is a sought-after speaker and spokesperson. He is the author of numerous books. Recent publications include "Tocotrienols in Vitamin E: Hype or Science?" and "Vitamin E – Natural vs. Synthetic" in Tocotrienols: Vitamin E Beyond Tocopherols (2008), "Grape Seed Extract" in the Encyclopedia Of Dietary Supplements (2005), "Kava Kava: Examining New Reports of Toxicity" in Toxicology Letters (2004) and Anti-Fat Nutrients (4th edition).