From Medical Nutrition from Marzby Russel Marz, N.D.

Problems with RDAs

Recommended Dietary Allowances (RDAs) basically have been established as recommended nutrient levels for healthy populations.  Special additional requirements may be needed for problems such as premature birth, inherited metabolic disorders, infections, chronic diseases, digestive problems (especially malabsorption syndromes), and the use of medications, both prescription and nonprescription.

In addition, environmental pollutants, anti-metabolites, excessive stress, and excessive dietary constituents, such as certain fats, proteins, carbohydrates, food additives, and naturally occurring food toxins, can also increase the requirements for many nutrients.

RDAs assume that nutrient requirements in normal healthy people are distributed according to the mathematical Gaussian (so-called “normal”) distribution.  Alternative distributions may more accurately represent the reality due to biochemical individuality and to some of the previously mentioned factors.

RDAs assume that standard deviations for nutrient requirements are generally about 15 percent of the mean (thus 2 standard deviations higher than the mean would cover about 97 percent of the healthy population).  This 15 percent standard deviation is based largely on an assumed biological measurement and of a finding for nitrogen losses in male college students deprived of protein.

The study below was done with animal and human requirements of a number of selected amino acids, calcium, and vitamin B- I (thiamin).  From examining just this small sampling, we can plainly see that there is a tremendous variation in the requirements for these nutrients.

If we were to examine all of the current existing essential nutrients, it stands to reason that we would also find a tremendous variation in the requirement for many of these nutrients as well.  The average range in the following study was about a 4-fold variation.  This is twice what the Food and Nutrition Board has assumed based on protein requirements.

How do we assess nutritional requirements for the general population?

RDAs represent the known nutritional needs of 97.5 percent of the “healthy” population. They are calculated by taking the mean requirement of a nutrient and then increasing the amount by two standard deviations.  This figure also includes a margin of safety to account for nutrient losses that might occur in the cooking and storage of food, the range of requirements in the population, and to provide a buffer under stress conditions.

Other factors considered were the stability of the nutrient, the body’s ability to store the nutrient, the range of observed requirements, the availability of the nutrient in the North American diet, the possible hazards from an excessive intake, and the difficulties involved in establishing precise requirements.

Nutrient Amt Required Ratio of Differences No. of Subjects

Tryptophan 82-250 mg 3.0 fold difference 50 Valine 375-800 mg 2.1 fold difference 48 Phenylanine 420-1,000 mg 2.6 fold difference 38 Leucine 170- 1,100 mg 6.4 fold difference 31 Lysine 400-2,800 mg 7.0 fold difference 55 Isoleucine 250-700 mg 2.8 fold difference 24 Methionine 800-3,000 mg 3.7 fold difference 29 Threonine 103-500 mg 4.8 fold difference 50 Calcium 222-1,018 mg 4.6 fold difference 19 Thiamin 0.4-1.59 mg 3.9 fold difference 15

The only conclusion that we can make from this study is that there are probably a number of nutrients that have higher than a 7.0 fold range of variation in their requirement among the population, and a number of nutrients that have a lower than 2.1 fold requirement range.

In addition, if we very conservatively estimate that about 3 percent of the healthy population is not covered by the RDA for a particular nutrient, is it acceptable to run a 3 percent deficiency risk for each of 19 different nutrients for which there are RDAS?

Optimal Daily Intake (ODI)

This is a term I would like to employ to describe a level of intake that takes into consideration a person’s genetic background, their environment — both in their home and their place of employment (or where they spend the majority of the day) — as well as their daily habits such as smoking, drinking, stress levels, prescription medications, and other factors unique to them.

In considering all of these factors, the ODI would reveal an optimal level of intake for the individual.  Each person has individual optimal requirements which depend on his or her unique biological makeup and living situation.  Because of the large divergence in requirements among people, establishing an average intake level can be very difficult.  It thus becomes a more useful term for individuals rather than for the general population.

In addition, the minimal toxic dose needs to be taken into consideration with each nutrient.  The Optimal Daily Intake usually falls between the RDA and the toxic dose.

We have seen a definite trend in “conventional nutritional” practices to embrace some of the “alternative nutritional” perspectives.  Although conventional nutritional teachings have been very slow, for fear of being labeled “unscientific,” to adapt many of the recent alternative approaches, we have seen medical schools teach classes in the alternative healing arts, including alternative nutrition.

While conventional nutrition is very conservative in its approach to the use of nutritional supplements to treat disease, the recommendations for folic acid supplements for prospective moms to prevent neural tube defects in newborns are now widely endorsed.  It took close to ten years to adapt such a basic recommendation because of the resistance to prescribing vitamin supplements.

With the wide use of vitamin, mineral, amino acid, herbal and enzyme supplements, it is really essential that today’s health care practitioner have a good knowledge of the claims that have been made, as well as the studies that are being cited, in support of such claims.

It is important to remember that the so-called scientific approach and statistical analysis do not always give a fair and complete evaluation of a particular treatment.  Statistics, in their analytical approach, exclude the subset of the population that may respond very well to a particular treatment because the results may not show statistical significance for a wider population.

If we could somehow isolate this subset of the participants who responded well in the study, we might reach quite different conclusions.  The problem is, of course, how to isolate this subset of the population that might respond particularly well.

Thus, what we see is that today’s practitioner must be acutely aware that there may be ways to determine biochemical individuality in regard to who will respond to a particular therapy versus who will not.  It is our goal  to shed some light on the variety of evaluations that could be made of a single patient by looking at a number of diagnostic criteria, both conventional and nonconventional.

Toxic Daily Dose (TDD)

This is the dosage at which, over a period of time, someone will likely develop toxicity symptoms.  This dose varies from person to person and is dependent on the biochemical individuality, level of health, and toxic environmental exposure level of the individual.  For example, an alcoholic might have a much lower TDD to vitamin A (vitamin A toxicity can affect the liver) compared to a healthy individual who is not challenging an otherwise healthy liver.  It is a dose that is designed to cover the vast majority of individuals.

It should be noted, as in the previous example of the alcoholic, that there may be some individuals who may exhibit toxicity from a daily dose below the TDD.  It is assumed that the many factors involved are also taken into consideration when evaluating this dose.  The toxic daily dose is meant to describe toxicity that will usually manifest over a period of months rather than over a few days.

What the RDAs do not cover:

1. Disease states (including malabsorption states, digestive problems, and chronic infections).

2. Environmental pollutants.

3. Genetic metabolic defects.

4. Increased requirements due to the use of both prescription and non-prescription medications.

Summary

Considering how widespread chronic fatigue, depression, hyperactivity, allergies, arthritis, cancer, cardiovascular disease, diabetes, and gastrointestinal problems are, it seems likely that the RDAs are not applicable to the majority of Americans and should not be used as a general guideline.