Bioavailability of a mineral, which is defined as the proportion that can be utilized, depends on many factors, including the amount of “enhancers” and “inhibitors” present, such as phytates, other minerals, and vitamins, as well as the acidity of the digestive environment. Most minerals are absorbed in the duodenum, the first part of the small intestine, assisted by the presence of stomach acid.
In supplements, minerals are bound, or chelated, to different compounds to help their absorption. Amino acid–chelated minerals are bound to amino acids, examples of which are chromium picolinate and selenocysteine or zinc amino acid chelate. These are well absorbed, as are other “organic” compounds including citrates, gluconates, and aspartates. Inorganic compounds such as carbonates, sulfates, and oxides are less well absorbed.
For some minerals, the extra cost of amino acid–chelated minerals outweighs the advantage. For example, magnesium amino acid chelate is only twice as well absorbed as magnesium carbonate, an inexpensive source of magnesium. Iron amino acid chelate, on the other hand, is four times better absorbed, making the price differential worth it. Generally speaking, the following forms are most readily available to the body, listed in decreasing order of their bioavailability (that is, the very best first).
Calcium: Amino acid chelate, ascorbate, citrate, gluconate, carbonate
Magnesium: Amino acid chelate, ascorbate, citrate, gluconate, carbonate
Iron: Amino acid chelate, ascorbate, citrate, gluconate, sulfate, oxide
Zinc: Picolinate, amino acid chelate, ascorbate, citrate, gluconate, sulfate
Manganese: Amino acid chelate, ascorbate, citrate, gluconate
Selenium: Selenocysteine or selenomethionine, sodium selenite
Chromium: Picolinate, polynicotinate, ascorbate, gluconate
What about sustained release?
Some vitamins are called prolonged, sustained, or time released, implying that the ingredients are not all made available for absorption in one go. This can be useful when taking large amounts of water-soluble vitamins such as B complex or vitamin C. However, absorption depends also on the person and the dosage. Some people are able to absorb and use 1,000 mg of vitamin C taken in one dose; taking it in sustained-release form would provide little benefit. However, if you take three 1,000 mg tablets a day, sustained release would allow you to take them all in one go. Since sustained-release vitamins are more expensive, you have to weigh up the pros and cons. And there is no point in having a sustained-release fat-soluble vitamin, such as A, D, or E, as these can be stored in the body.
The best sustained-release products are capsules containing tiny “beads,” each containing the desired nutrients, which dissolve at different rates and so release the nutrients over time. This method, however, consumes a lot of space, so the dose is not usually very high, making the necessity for sustained release less relevant.
What about food form?
A critical question is, Do vitamins and minerals in food work better than those in supplements? Some companies sell “food-form” vitamins and minerals and claim they absorb better into the body. These food-form supplements are made by feeding nutrients to yeast, having the yeast ferment and incorporate the nutrient into its food matrix, then killing off the yeast by a combination of heat and enzymes from pineapple and papaya. This ensures there are no yeast cells left and hence no adverse effects for those sensitive to yeast.
While the research to date, which has looked at the ability of supplements to raise body levels of nutrients, appears to be positive, there is still much to be done to find out what exactly makes food-form nutrients more bioavailable and also to prove the extent to which they work better in promoting health. The answer is bound to be as complex as nature herself.
In nature, nutrients are bound in a complex way to peptides, proteins, glycoproteins, and so on. When we eat, the high acid content of the stomach, plus enzymes, breaks down these bonds to liberate the nutrients. The nutrients then have to be reassembled into forms that can be transported and used by the body. It looks as if the complex way food incorporates nutrients, which is what the food-form process mimics, allows the nutrients to be more easily released, transported, and used.
Given that we have evolved over millions of years to use the nutrients available to us in foods, it certainly makes good sense to provide nutrients in supplements in a form a close as possible to that found in nature. That said, a nutrient in the form found in food may not in all cases be better for you than that in a supplement. Taking folic acid supplements, for example, has been well proven to be twice as effective in raising blood levels of folic acid and lowering homocysteine as eating the equivalent amount of folate in food.
Good and bad combinations
The general rule is to take supplements with food. This is primarily because the presence of stomach acid helps many minerals to be absorbed and because the fat-soluble vitamins are carried by the fats or oils present in most meals. Nutrients do, however, compete for absorption. For example, if you want to absorb a large amount of a specific amino acid such as lysine (good for the arteries and for preventing herpes), more will be absorbed if you take it on an empty stomach or with nonprotein foods such as a piece of fruit. Similarly, a tiny mineral like selenium will be absorbed better on its own than as part of a multimineral.
However, no one wants to end up taking each supplement separately. So unless you have a specific need or deficiency and want to maximize absorption by taking the nutrient on its own, spread your nutrients out through the day and take them with meals as nature intended.
There is, however, always one exception. If you want to take the alkaline-forming “ascorbate” type of vitamin C in quite large doses (3 grams or more a day), take it away from meals to avoid neutralizing the acidity in your stomach. If you ever experience a burning sensation after taking vitamin C as ascorbic acid (a weak acid), you may have some gastrointestinal irritation or even an ulcer. See your doctor and have this possibility checked out. While vitamin C helps heal wounds, the acid form can aggravate an existing problem and should be avoided.
Drug-nutrient interactions: difficulties and dangers
There are very few dangerous drug-nutrient interactions. However, there are many drugs that interfere with the action of nutrients, increasing your need.
Aspirin increases the need for vitamin C.
Birth control pills and HRT increase the need for B6, B12, folic acid, and zinc.
Antibiotics increase the need for B vitamins and beneficial bacteria.
Acetaminophen increases the need for antioxidants.
Here are details of some potentially dangerous combinations that must be avoided:
Coumadin (a blood-thinning drug), aspirin, vitamin E, and high-EPA/DHA fish oils all thin the blood, and the combined effect would be too much. It is better to reduce the drugs and increase the nutrients, but first check with your doctor.
When taking MAOI antidepressants (such as Nardil or Parnate) you must avoid yeast (including supplements), alcohol, and certain specific foods.
Some anticonvulsants are antifolate, creating an increased need for folic acid, yet supplementation can impair the action of the drug. Specialist advice from your doctor and nutrition consultant is recommended. Epileptics should be careful about supplementing the brain nutrient DMAE.
In cases of vitamin B12 deficiency, supplementing folic acid can reduce the symptoms while the underlying deficiency gets worse. Therefore, it is best to supplement both nutrients, preferably as part of a B complex.
Do’s and don’ts of supplement-taking
Very few problems occur with vitamin supplements, but it is sensible to be aware of the following:
Vitamin A (retinol) in doses in excess of 8,250 IU should not be taken by pregnant women or women trying to conceive. Check that the total provided by all your supplements (for example, a multivitamin or antioxidant complex) does not exceed this level.
Beta-carotene in excess makes your skin go very yellow. If you
have excessively yellowing skin, check your beta-carotene intake from food and supplements. This is quite different from jaundice or hepatitis, in which the whites of your eyes go yellow. Also, don’t supplement beta-carotene on its own if you are a smoker. Take it as part of an all-round antioxidant complex.
vitamin B2 (riboflavin) makes your urine bright yellow. This is normal.
vitamin B3 in the form of niacin, usually in doses of 100 mg or more, can make you flush and go red, hot, and itchy for up to thirty minutes. This is normal and is not an allergy. While the nutrient is beneficial, if you do not like this side effect, take less or else take half the dose twice a day. Your flushing potential will reduce with regular supplementation. (Alternatively, buy the “no-flush” type of niacin.)
Vitamin C has a laxative effect in very high doses, normally above 5 grams a day. A small number of people are very sensitive even at 1 gram a day, while others can tolerate 10 grams a day. The ideal level is the “bowel-tolerance” level, so adjust your intake accordingly.
Copper is an essential mineral but it is toxic. Do not take supplements containing copper unless they contain at least ten to fifteen times as much zinc. So, for example, if there is 1 mg of copper, make sure there is 10 to 15 mg of zinc. This will prevent copper accumulation. Conversely, zinc is an antagonist of copper, so don’t take large amounts of zinc without adding a little copper.
Value for money
For a supplement to be good value, it must be well made, well formulated, and well priced. The quality of manufacture is hard to assess unless you have an advanced chemistry laboratory in your back room! However, there are four simple tests you can do:
Is the stated number of tablets actually in the bottle? (When we tested one manufacturer’s product at ION, we found an average of ninety-five tablets instead of a hundred.)
Is the tablet coated all around and therefore easy to swallow? (Uncoated or badly coated tablets can break up or taste unpleasant.)
Does the label tell you everything you need to know? (The better the company, the more information it will want to give you.)
Does the company emphasize its quality control and, if asked, can it supply you with independent analyses of its products?
If you are buying fish oil supplements, make sure the company emphasizes the purity of its fish oils. Good products are free from residues of mercury or PCBs and other undesirable pollutants found in fish. Less expensive supplements often come out badly on independent analysis.
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Vitamins and Minerals— How Much Is Safe?
Just how safe are supplements? What happens if you take more vitamins or minerals than you need? How much is too much? These are common concerns, fueled by media reports linking vitamin C with kidney stones and warnings against vitamin A in pregnancy. How much is fact and how much is fiction?
The optimal intake of a nutrient varies considerably for each individual, depending on age, sex, health, and numerous other factors. It is therefore to be expected that the level that would induce signs of toxicity also varies considerably. When certain illnesses are present, a person’s need for a vitamin can increase dramatically: vitamin C is the prime example, when you are fighting an infection. In this chapter, I have erred on the side of caution by listing the levels of nutrients that may induce toxicity in a small percentage of people, if taken both over a short period (up to one month) and over a long period (three months to three years), indicating which symptoms persist and which go away once the high level is reduced.
It is important to realize that just about everything is toxic if the dose is high enough. In 1990, a man died as a result of drinking 10 quarts of water in two hours. So the critical question is, How much more of the substance than is normally consumed do you need to consume to reach toxic levels? In other words, what is the safety margin?
The safety of vitamins
The general conclusion from a survey we conducted at the Institute for Optimum Nutrition of the results of over one hundred research papers in scientific journals is that for the majority of vitamins, with the exception of A and D, levels one hundred times greater than the recommended daily allowance (RDA) are likely to be safe for long-term ingestion.1 Two recent comprehensive reviews broadly support this position.2
In practical terms, this means that the chances of having a toxic reaction to even the higher-dose supplements available in health food shops is extremely unlikely unless you take considerably more tablets than recommended. This is consistent with the public health record of deaths attributed to nutritional supplements. To date, no one has been reported as dying as a result of a vitamin supplement. Very rarely there are deaths due to children’s swallowing handfuls of their mother’s sugar-coated iron supplements. Compare this with deaths attributed to prescribed drugs. These were the conclusions of a survey of hospitalized patients, published in the Journal of the American Medical Association: “We estimated that in 1994 overall 2,216,000 hospitalized patients had serious adverse drug reactions and 106,000 had fatal adverse drug reactions, making these reactions between the fourth and sixth leading cause of death.”3 Similar findings have also been reported in Britain.4
In the table on the next page, you can see that you are more than one hundred thousand times more likely to die from a highly preventable medical injury, including prescribed drugs, than you are from a dietary supplement. Death, however, is a rather severe yardstick. What about toxicity or adverse effects? These too are extremely uncommon in relation to nutritional supplements. In nearly twenty years of practice, teaching, and writing, I have yet to come across a single case of actual toxicity.
Vitamin A
Vitamin A comes in two forms: the animal form, retinol, which is stored in the body; and the vegetable form, beta-carotene, which is converted into retinol unless body levels are already high. Beta-carotene is therefore not considered toxic, with the exceptions that excessive intake can cause a reversible yellowing of the skin and that there is possibly an increased cancer risk, only for smokers, if it is supplemented on its own.
There have been a number of incidences of adverse reactions to retinol, usually from intakes of 495,000 IU or more over a considerable length of time. The symptoms include peeling and redness of the skin, disturbed hair growth, lack of appetite, and vomiting. According to Dr. John Marks, medical director at Girton College, Cambridge (England), “toxic reactions have been extremely rare below 30,000 IUs (10,000 mcg) … daily administration in adults up to about 50,000 IUs (17,000 mcg) would appear to be safe.” This is consistent with estimates of the intake of 50,000 IU of vitamin A that our ancestors would have eaten in a more tropical environment, although a large part of this would have come from beta-carotene.
Relative risk of death from dietary supplements versus medical treatment This assessment of risk, from Australia, shows that if the risk of dying from a natural or dietary supplement is 1, your risk of dying from a shark attack is 6, of being murdered 828, and of dying from a highly preventable medical injury, including an adverse drug reaction, more than 100,000 times higher!5
A number of cases of toxicity and birth defects have been reported for a synthetic relative of vitamin A, isotretinoin, sold as the drug Accutane. These effects have been wrongly extended to natural vitamin A. Five cases of birth defects have been reported in babies born to women taking large amounts of retinol (247,500 to 495,000 IU per day); however, no clear cause-and-effect relationship has ever been established in any of these cases.
One study published in 1995 found a possible association: in a group of 22,747 women, 121 gave birth to children with the kind of defect associated with, among other things, vitamin A toxicity. Of these 121, two of the cases could have been attributable to supplementing in excess of 10,890 IU of vitamin A in the form of retinol. In view of the possibility that large amounts of retinol could induce birth defects, it is wise for women of childbearing age to take no more than 10,890 IU of retinol in supplemental form. (Other studies have shown that women who supplement
their diet with multivitamins including vitamin A, usually at a level of 8,250 to 24,750 IU, have a lower incidence of defects in their babies.)
The same caution as for retinol does not apply to beta-carotene. This has, however, been shown to slightly increase the risk of lung cancer and colon cancer if given in isolation to smokers. My advice here is to stop smoking and, if you don’t stop, supplement beta-carotene only as part of a multivitamin or antioxidant complex. Beta-carotene in food reduces the risk of cancer even for smokers.
Vitamin D
Of all the vitamins, D is the most likely to cause toxic reactions. It encourages calcium absorption, and excessive intake can lead to calcification of soft tissue. However, the levels that create this effect are certainly in excess of 120,000 IU and probably more like 600,000 IU. A daily intake not exceeding 264,000 IU for adults and 13,000 IU for children is generally considered safe.
Vitamin E
Vitamin E has been well researched for toxicity. A review of 216 trials of high-dose vitamin E in ten thousand people showed that daily doses of 3,000 IU for up to eleven years and 52,500 IU for a few months had no detrimental effect. However, adverse reactions have occasionally been reported at lower levels of 1,950 IU, especially in children, possibly due to an allergic reaction to the source of the vitamin E.
Vitamin E appears to increase the anticlotting effects of the drug Coumadin, and therefore high levels are not recommended for those on Coumadin. High levels are also best avoided by people suffering from rheumatic fever. Some old reports that vitamin E should not be taken in supplement form by women with breast cancer are inaccurate: it is highly beneficial to do so. A daily intake of up to 1,500 IU is considered safe.
The New Optimum Nutrition Bible Page 44
