Nutritional numerology

The latest study in the news, said to “confirm the health benefits of whole grains,” gives us another look at meta-analyses and chance to see just how shaky the science is behind many of our popular beliefs about “healthy” eating.

One of the most popular beliefs is in the special health-promoting properties of whole grains and dietary fiber. Refined foods are supposed to be “bad” for us and if we listen to today’s popular diet doctors and government spokespeople, white foods are nothing short of deadly and should be eliminated from our diet!

These beliefs are nothing new and date back hundreds of years, popularized by religious and social reformers of each era. One of the first health books published in America was a “discourse of temperance” by Thomas Tryon entitled, The way to health, long life and happiness, in 1683. It advocated a vegetarian diet devoid of any stimulants and said wholemeal bread is the most important way to a long, happy life. The Enlightenment philosophers of the time believed: “Better individuals made better citizens, better citizens made for a more civil democratic society.”

An especially entertaining thesis was written by Alex Whitely in 1894, Health and Strength: Practical athletics for busy people, which preached a Life Force which was said to impart vitality. Although this life energy couldn’t be seen, he compared it to steam, saying:

Given proper habits, people of vital temperament or strong constitution would never be sick. They are the favored type...Only by persistent and careful husbanding of vitality and a systematic building-up of all the bodily functions, can weak constitutions expect to keep well, or look for permanent improvement.

Foods with the greatest life-energy were believed to be natural and whole, uncooked, vegetarian, and unflavored by salt or sugars. Sound familiar? Unnatural foods “make strong people too fat, and weak ones bilious an costive,” he wrote. “All inflammatory diseases, rheumatism, gout, catarrh, cold, fever, etc. are benefitted by a natural diet...Skin eruptions will disappear in four to six weeks.” Cooking with fats was the fastest path to harm. His natural diet was coupled with vigorous exercise. He promised that following his prescriptions would: “add many years to your life and make you as able to struggle at fifty as you are at thirty.”

Yankee preacher Reverend Sylvester Graham is one of the most-known of the early proponents of wholemeal, high-fiber natural foods. He believed an austere, pure diet would save the souls of dietary heathens and preached that it would cure premature aging, violence, sexual perversion, cholera, the alcohol demon, and digestive problems. Suffering from tuberculosis, he’s believed to have created his regimen fearing his own ill health. His brown bread became the fad among the upper class during the early 1800s, even capturing Queen Victoria’s fancy.

Dietary beliefs of various denominations continue, despite the lack of credible evidence that any reasonable dietary practice or foods are appreciably better than any others or magically ensure better health and longevity. Dietary practices regularly reflect social standing and support and in studies, when those socioeconomic and stress factors are equalized, the presumed benefits disappear. You’ll also see higher rates of heart disease and diabetes among discriminated groups, for instance, even when they’re eating exactly the same as whites of higher standing.

With the better availability of safe food, sanitation and infectious disease control, populations in developed countries continue to be healthier and live longer. While dietary fashions have come and gone, most people continue to eat the foods of their heritage and things they love. So before we ditch French baguettes, Italian pasta, Japanese sushi or Grandma’s delicate white cake from our diets and make brown our favorite food color, let’s take a look at this latest study. It is typical of modern nutritional epidemiology being used to try and convince us of some perfect diet we should all be eating. As UPI reported:

Whole grains linked to better heart health

A diet high in whole grains is associated with a lower risk of cardiovascular disease, including heart disease and stroke, says a U.S. study. Consuming an average of 2.5 servings of whole grains each day is associated with a 21-percent lower risk of cardiovascular disease compared with consuming only 0.2 servings, according to the study published online in Nutrition, Metabolism & Cardiovascular Diseases.

“These findings suggest that we should redouble our efforts to encourage patients to include more of these foods in their diets,” lead author Dr. Philip Mellen of Wake Forest University School of Medicine said [in the press release].

The findings are based on an analysis of seven studies involving more than 285,000 people. By combining the data from the seven studies, researchers were able to detect effects that may not have shown up in each individual study, according to Mellen.

These three passages alone, give you everything you need to recognize this isn’t useful science: it is reporting “associations” and even coming up with untenable numbers; the importance of its findings are elevated to promote a political or marketing agenda; and it was a meta-analysis.

The study’s conclusions said: “In light of this evidence, policy-makers, scientists, and clinicians should redouble efforts to incorporate clear messages on the beneficial effects of whole grains into public health and clinical practice endeavors.” But, epidemiological studies looking at associations among groups of people can never demonstrate that the associations are causally related and something we should change our diet for, let alone invest public policy; they only provide clues for further study. Randomized controlled clinical trials have repeatedly shown earlier dietary hypotheses based on observational studies to be wrong.

Researchers from the University of Bristol, for instance, recently examined the inconsistencies of nutritional epidemiology surrounding dietary fiber in the International Journal of Epidemiology. Observational studies frequently contradict each other and “it is difficult to make sense of the findings,” they wrote. “High fibre cereals may not be all that good for you after all:”

To date there have been five randomized trials of dietary fibre in high-risk patients... none of these trials has found fibre to be effective at reducing the recurrence of polyps or the occurrence of colorectal cancer....[I]f fibre really is protective against heart disease and cancers (the two biggest killers in the Western world) then one would expect it to have an important impact on all-cause mortality. To date randomized trials have found no evidence that dietary fibre confers any short-term benefit on all-cause mortality. Indeed, a large study on British men post myocardial infarction suggested, if anything, that mortality was higher among those allocated to dietary advice aimed at increasing fibre consumption.

It is important not to be taken in by meta-analyses and their impressive sizes or claims. They lump together data from a bunch of studies, and the worst examples of meta-analyses pool weak studies, hoping to create a statistically significant effect that wasn’t there any other way. A previous post reviewed the caveats of meta-analyses, so I won’t repeat them here, except for the favorite definition among critics:

Meta Analysis is making a strong chain by combining weak links. — John Brignell, Ph.D., The Epidemiologists: Have they got scares for you!

This study was led by Dr. Philip Mellen, M.D., in the Department of Internal Medicine at Wake Forest University Health Sciences in Winston-Salem, NC. They identified eight publications from seven population studies after doing “a MEDLINE search for the words ‘whole grain’ and ‘cardiovascular disease’ from 1966 to April 2006. Additional studies were drawn from reference lists of relevant manuscripts.” As they noted, the studies used self-reported quantitative measures of whole grain intake, which they pooled together, taking the average high intakes in each study and compared them with the low-intakes in each study. Among the studies, wholegrain intakes were measured and scored differently, some noting whole grain bread, others cereals, some servings per day or week, others by grams of fiber. No matter.

This meta-analysis illustrates the problems with these studies. They tallied studies that all had major weaknesses and differed wildly in all sorts of ways. The studies were done on differing age groups, ranging from 35 to 98; the follow-up periods varied from 6 to 15 years; only three included men; none of the studies except one considered aspirin usage or statin medications; none but one considered people’s history of congestive heart failure, only two even bothered with family health history; none of the studies accounted for socioeconomic status, only two considered marital status or race, only three considered education; and only three of the studies looked at actual cardiovascular deaths! Death is really the most clinical meaningful endpoint, after all. And not one was a randomized, clinical trial.

The observational study they used that included the most confounding factors and looked at mortality data was the Iowa Women’s Health Study published in the Journal of the American College of Nutrition, which looked for associations among over 11,000 post menopausal women. Using their computer modeling, those researchers had reported a mere 17% lower risk for death among the women eating the most compared to the least whole grain fiber. The women didn’t differ in prevalence of chronic diseases such as hypertension, cancer, diabetes or heart disease, however, and this study didn’t account for race/ethnicity, family histories of heart disease or aspirin use. Was it really the dietary fiber to account for the 17% mortality risk, or might it have been the fact that the low fiber cohort was also less likely to be college-educated (a marker for economic status) and more likely to be single, to smoke and not engage in physical activity? Good heavens, you can't conclude anything from this association, and this was the strongest study.

Anyway, these researchers dumped all of these self-reported dietary fiber intakes for 149,000 people from the seven studies together, stirred them up in their computer and out popped their conclusion: “that consumption of at least 2.5 grams of whole grains every day was associated with a 21 percent reduction in the risk of cardiovascular events than consumption of 0.2 grams per day.” Junkfood Science readers well understand that anything less than a 200% relative risk derived from these types of data dredge studies isn’t considered tenable by scientists, and could just as likely be due to statistical error, random error, let alone overlook a billion other confounding factors that could point to the real cause(s). In other words, this was actually a nonfinding and they weren’t able to show that dietary fiber mattered for poo.

In fact, they said just that in their Results:

There was no evidence of decreased risk for cardiovascular events when comparing groups with high versus low refined grain intake components.

Yet the Wake Forest researchers ignored their own findings and went on to say that refined foods were unhealthy and whole grains offer special cardiovascular benefits because they “consist of bran, germ, and endosperm components. When refined, the carbohydrate-rich endosperm component is retained, while many biologically active agents, such as fiber, vitamins, minerals, antioxidants, and other plant compounds (lignans, phytosterols, etc.) are removed with the bran and germ.” Refined carbohydrates, they wrote, is why “Western lifestyle patterns” have also been linked to obesity and type two diabetes, while “whole grains appear protective.” They considered whole grain foods and flours to be: amaranth, barley, buckwheat, corn, millet, oats, quinoa, brown rice, rye, sorghum, teff, triticale, wild rice and wheat.

Popular beliefs about the benefits of soluble and insoluble dietary fibers may sound good, but they aren’t especially logical or evidence based.

For those interested, here are some fun facts we don’t often hear. Soluble fiber fibers are found inside plant cells and include pectin, dextrin and gum. Fibers in the cell walls of plants that are water insoluble include cellulose, hemicellulose and lignin. Like these researchers, when we think of “healthy” sources of fiber most of us think of foods like those listed on this government website (grains, legumes, vegetables and fruits).

You can bet that coffee, for example, isn’t included in most dietary fiber or wholegrain studies, even though a medium cup of coffee has 3 grams of soluble fiber — as much as an apple! Nor is beer, which has significant amounts of dietary soluble fiber and would make just as much sense. And while these beverages aren’t seen as “healthy,” we are quick to pay dearly to guzzle down “healthy” functional drinks containing the very same soluble fibers. Jellies are never included, even though they’re thickened with natural pectins. And what about guar gum, which is commonly used to thicken and keep our favorite puddings and ice creams creamy? Without soluble fiber ingredients, like locust bean gum, carageenan and guar gum, these foods would separate and become grainy messes. But the fiber in “bad” foods doesn’t “count” — even though it’s the same thing! :)

Fears surrounding enriched flours and popular beliefs about wholegrain flours get food scientists rolling their eyes by their simplistic understandings of grains and how they are processed.

Grains provide about three-fourths of the energy and protein for the world’s population, according to food scientists and nutritional researchers at Oxford Brookes University, UK, in a 2001 Issue Paper, “Micro-nutrient changes during food processing and storage,” for the Crop Post-Harvest Research Programme. Grains and starchy foods are invaluable and have long sustained the human species. We needn't fear carbs. There's good reason bread is called the staff of life.

But different types of fibers have different effects in the gastrointestinal system (i.e. regularity) and on the bioavailability of nutrients. With today’s beliefs in the special properties of dietary fiber and focus on increasing fiber at all costs, many forget what we’ve come to understand about fiber and why too much of a good thing isn’t desirable, either.

Insoluble fibers are most associated with reduced absorption of nutrients because the cellulose and bran in soy, corn, wheat and rice bind with minerals, they explain. That’s why the diets of poor peoples in developing countries, based on all-natural foods high in dietary fiber and plant products, may be filling but they also contribute to lower absorption of already scarce macro- and micro-nutrients. We often forget these peoples don't live as long as we do, either.

“The bioavailability of micro-nutrients also appears to be influenced by the interaction between fibre and other food components such as tannins, phytates, oxalates and citrates,” according to the Issue Paper. It’s complicated and lots of things in foods can interact with fiber and other things, such as ascorbic acid and certain amino acids can enhance the absorption of iron, while tannins and phytate inhibit the absorption, etc. That’s why the most varied diets typically prove better.

According to the Food and Agriculture Organization of the United Nations, in their scientific review, “Preventing Micronutrient Deficiencies: A Guide to Food-based Approaches,” among the world’s people, the three deficiencies of “greatest public health significance are those of vitamin A, iron and iodine:”

Vitamin A deficiency is most common in young children. Untreated, it can lead to blindness and death. Iron deficiency is the most common dietary deficiency globally, affecting mostly children and women of childbearing age. It leads to anaemia, which contributes significantly to maternal and neonatal deaths. Iodine deficiency disorder occurs in mountainous and flood plain areas of the world where iodine has been washed away from soils. It is the most common cause of preventable mental retardation, including low IQ (intelligence quotient). Severe iodine deficiency can lead to cretinism, stillbirth and birth defects.

It's so easy to forget how good we have things. To overcome deficiency-related health problems seen around the world, they advocate food fortification and encouraging a varied diet, practically the opposite of what many popular diets among developed countries advocate today, with their focus on returning to idealized, traditional natural diets and limiting food choices to encourage eating fewer calories.

The term “food processing” has some believing in a dark, evil industry, but humans have processed (ground, peeled, cooked, dried, fermented, stored) foods forever in order to make them edible and digestible. Centuries of women have cooked, dried, canned and preserved foods, thereby ensuring the survival of their families. And modern food processing can actually improve the nutritional quality of foods.

Rice is an example of a food that cannot be eaten raw and has to be processed to make it edible. Parboiling rice, for instance, where rice is soaked in water and partially steamed prior to drying and milling, improves the retention of protein, vitamins and minerals when it’s later cooked. Some B vitamins migrate deeper into the grain, reducing their loss during milling. “Parboiled rice may contain up to 2g/g of thiamine compared to only 0.7g/g for the untreated grain,” said the Oxford Bookes University scientists. Parboiling improves the grains keeping qualities by making them less susceptible to damage as the grains become partially gelatinized, and also improves the protein quality.

The endosperm is where most of the carbohydrates and protein that make up a grain are, but to make whole grains easier to cook, digest and chew, humans have always treated them, such as broken them down by crushing.

During milling of flours as practiced since the 1800s, the bran and germ of wheat are totally removed from the endosperm, then for wholewheat flour the bran is added back, but not the germ because the flour would quickly grow rancid. (So, all of these dietary studies that have been based on whole wheat bread products most people consume don’t actually contain the believed beneficial germ!!)

Refined grains and flours aren’t demons, nor is fiber magically healthful. There are practical reasons for refining grains. Bran and germ reduce the bread-making qualities of flour and don't make for light, delicate cakes and pastries, as any baker knows. Wholegrain baked goods are delicious, denser and earthier tasting, but wholegrain flours are not always best for every purpose, ideal or optimally digestible for every person, and not everyone likes their flavor. There's nothing wrong with that.

There are nutritional reasons for refining flours and grains, too, that we often forget. “Fiber can actually reduce the nutritional value of foods by complexing with proteins, and wheat bran contains a substance, phytic acid, that similarly makes calcium unavailable to the body,” wrote Dr. Harold McGee in On Food and Cooking: The Science and lore of the kitchen. Phytic acid forms insoluble complexes with calcium and iron, reducing the bioavailability of both minerals. Many Americans don’t remember that during World War II, when Dublin went to 100% whole grain bread, it resulted in an epidemic of rickets, with half of the children suffering from it. It’s why you’ll see commercial wholegrain breads supplemented with calcium carbonate today. “Food additives” aren’t there to poison you, but to offer some benefit.

Since 1943, white flours in the United States have been fortified, enriched with five nutrients added back at higher levels than naturally occur in whole grains. Before that, in the 1930s, beri-beri, pellagra, riboflavin deficiency and iron deficiency anemia were widespread in the United States. Pellagra and beri-beri were virtually eliminated within the first five year of enriched flours. We’ve also seen how the folic acid added to enriched grain products was followed by marked decline in babies born with birth defects, such as spina bifida and anencephaly. Enriched white flour is nothing to fear amd can be part of a perfectly healthful diet.

The most important reason for refining flours and grains is that the high lipid concentration in the germ and aleurone layer significantly shortens the shelf life of flour and whole grains, causing them to become rancid in just weeks. “It should be clear that [refining flours] is not simply a matter of industrial arrogance,” said Dr. McGee. “People have been given what they want and have wanted for a long time: a pure product that won’t spoil quickly.” The bottom line is that whole grains and refined grains an all be part of a perfectly healthful diet and there's nothing to fear or overly eulogize about either.

There is always going to be some potential loss of nutrients with processing or cooking of any food, but it’s easy to forget the overall positive benefits. When it comes to food, there’s no evidence we have to live in fear. Enjoying a variety of everything has never been shown to be harmful. Nor is there good evidence for an ideal, “healthy” diet that will prevent diseases (beyond deficiencies) or keep us from growing old. Again and again, it appears ‘enjoy everything’ is the best and soundest nutritional advice. And it’s sure a lot more fun and tasty.

Please pass the bread!

© 2007 Sandy Szwarc