The article by Dietrich in this issue of Nutrition Today recognizes that the obesity epidemic is a serious health problem owing to a combination of overconsumption of calories and lack of adequate exercise.1 All nutritionists can certainly agree on that. However, the approach to rectify this problem can take various directions, with the dietary aspect focusing narrowly on certain foods or food groups, or by taking a broader, more inclusive perspective of the total diet. Many foods, including beef and pork (and probably veggie burgers), can fit in most diets. However, one may start to encounter nutritional adequacy problems when specific foods, or food groups, are excluded at the expense of others.
If diet variety and balance is combined with overall moderation in terms of caloric needs based on age, sex, and activity levels, it is quite likely that the risk of many, or most, chronic diseases would decrease. In fact the update to the Dietary Guidelines rightly says, "Americans should increase the variety of their foods and nutrients, reduce caloric intake, and increase their physical activity."
Whenever I see diet recommendations that completely replace one food or diet component with another, I immediately become a bit skeptical as to the motives of those making the recommendations. There may be potential health-promoting benefits, or there may be corporate marketing motives, or perhaps some of both. One does not want to be creating new dietary problems while appearing to solve other diet problems with an overly simplistic recommendation.
There is probably no end to the many dietary substitutions that could be examined. Within the spectrum of dietary protein sources, one could compare, as in the Dietrich article, substituting plant protein for beef or pork. One might also substitute plant protein for chicken or fish. One might substitute red meat products with vegetarian diets of various nutrient levels or types. Each of these substitutions would no doubt result in some increases and some decreases for various nutrients. The importance of these changes may well depend on the individual.
In the Dietrich article, the authors do note that the proposed substitution might not be the only modification in the diet and that it might not be made every day. They even acknowledge that meats of all sorts have a place in a healthful diet and that issues of dietary habits and consumer acceptability should be taken into account. Unfortunately, these points are somewhat buried in the article and may be lost on the more casual reader.
Reference is made to the "benefit" that might be achieved by the proposed substitution, whereas a more appropriate term might be the "change" that occurs. The authors do note that, among the micronutrients that could be compared, zinc intake was significantly lower after the substitution with the plant protein source. Furthermore, with the plant protein product, one is dealing with a "fortified" product. This may or may not cover all the micronutrients found in a "natural" protein source.
Rather than cast doubt on naturally nutrient-rich foods such as lean beef or pork, one should keep in mind the total diet. Consider where excess calories and fat are actually coming from in most diets. If one examines trends regarding nutrient intakes over the past 20+ years, people are basically eating too many calories and the increases have not been occurring in terms of red meat (beef and pork) intake.2 Between the early 1970s and 2000, red meat intake went down ~12% (beef going down ~20%), whereas poultry intake increased 90% and fish increased 22%. Intake of flour and cereal products increased ~44%. Furthermore, if one looks at these intakes in terms of the existing Food Guide Pyramid (FGP) recommendations, intake of foods in the "Meat Group" is about the only part of the FGP that is in line with the recommendations (6.0 oz recommended and 6.2 oz meat equivalent being consumed). Of this meat equivalent, only ~1.8 oz is beef and ~1.2 oz is pork. This same report notes that vegetables, fruit, and dairy products are underconsumed, while added fats and sugars are greatly overconsumed. This would be in line with the discussion leading to the newly proposed Dietary Guidelines. These facts and trends alone should indicate that red meat, especially beef and pork, is not the major problem.
Other reports look at changes in the total diet from the early to the late 20th century and find that total fat available in the food supply has increased by 33% (from 120 to 159 g per capita per day).3 Also the type of fat has changed dramatically, going from 78% animal/22% vegetable to 45% animal/55% vegetable. One needs to address the major sources of fat in the diet.
Analysis of this type may place an overemphasis on such substitutions' being necessary to reduce CVD risk factors. Several years ago, a long-term study compared the effectiveness of sources of meat protein on reducing blood lipids in hypercholesterolemic individuals.4,5 A diet with primarily red meat (beef and pork) was compared with one with primarily white meat (poultry and fish), with results being essentially equivalent and both being effective in modifying blood lipids when part of a Step I diet. The total fat levels and not necessarily the source of the fat was most important. In another study, beef as the protein source was compared with chicken in a reduced-calorie weight reduction diet.6 Both protein sources were equally effective in improving the blood lipid profile. Once again the total level of calories was a key factor.
The study authors note a modest change in caloric intake with the substitution proposed and suggest how going from a beef/pork to a plant protein source will be so beneficial. Granted that every bit helps, but it is really the caloric intake of the total diet, combined with activity and exercise, that should be addressed. There were also modest changes in fat (type and level) and fiber intakes. However, reference is also made to significant reductions in zinc intake and modest changes in the intake of other micronutrients such as iron and vitamin B12. Also, it was recognized that a lower-quality protein was being substituted. A potential concern with substitution of plant protein sources for animal protein sources would be the issue of phytate levels and subsequent impact on micronutrient bioavailablilty. Once again, you do not want to be creating new nutrient adequacy problems while attempting to solve other ones. The response to these changes (not all beneficial) was that they were "insignificant" or other dietary sources could make up the difference. Suddenly, the total diet starts to make sense and comes into consideration.
Rather than encourage the exclusion of any one food or food group, a more beneficial approach would be to encourage individuals to consume naturally nutrient-rich foods, so that one obtains the most nutrients per 100 calories in a given food, while keeping total caloric intake in line. Keep in mind where different nutrients "naturally" come from in the diet. For instance, red meat such as beef and pork are excellent sources of protein and many of the B vitamins and micronutrients. Iron, especially the highly bioavailable heme iron, zinc, and B12 are just three examples of critical micronutrients. Whole grains can contribute fiber along with key micronutrients. Vegetables are necessary for vitamins and minerals. Fish products can contribute unique essential fatty acids. And, even fortified veggie burgers would no doubt contribute many nutrients. Furthermore, one should not lose sight of the importance of consuming a wide variety of natural foods. While food fortification may be able to supply the known nutrient needs, there still may be unique nutrient interactions that are only optimal when provided by the natural food sources.
Variety in the diet not only increases one's likelihood of achieving nutritional adequacy, but also contributes to food acceptability and palatability. Food should be enjoyed, and variety encourages long-term adherence to any diet. I might even have a veggie burger once in a while, depending on the rest of my diet, and if the real thing was unavailable. Meanwhile, I would continue to encourage consumption of a variety of naturally nutrient-rich foods in moderation and consistent with exercise and activity levels.
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