Principles of USDA dietary guidelines
The 2020-2025 USDA dietary guidelines emphasize the following principles (among other things):
- Dietary cholesterol consumption should be as low as possible.
- Saturated fat should be limited to less than 10 percent of calories.
- At least 30 grams (varies by age) of fiber per day. (points out that more than 90% of women and 97% of men do not meet this minimum recommendation).
The "other things" mentioned above is that dietary patterns must include lots of fruits, vegetables and whole grains. I have seen the same recommendations from many doctors and organizations I respect.
Recommendations for protein sources
When it comes to recommending specific protein food, it recommends the following:
Lean meats, poultry, and eggs; seafood; beans, peas, and lentils, and nuts, seeds, and soy products.
Well, lets see how these foods stand up to their own principles. Below is a table showing some nutritional information for some of the above mentioned protein sources. I normalized according to protein content as they are cited as protein food.
The first 4 are animal based sources, and the last 3 are plant based sources. We can make the following observations.
Cholesterol
The animal based food are high in cholesterol, whereas plant based sources have zero cholesterol. Notice the ridiculously high cholesterol content in eggs!! To get a perspective of how big these numbers are, the RDA for dietary cholesterol used to be 300 mg per day for healthy people, and 200 mg a day for people with risk factors. However, as the dangers of dietary cholesterol are becoming clearer, the guidelines have now changed to "as little as possible" putting dietary cholesterol in the same category as trans fats. If they are follow their own principle on dietary cholesterol, then their specific food recommendations should be restricted to plant based sources.
Saturated fat
Animal based foods are much higher in saturated fats relative to plants. The only animal based source which is somewhat comparable is chicken breast, but all the rest are at least 10 times higher in saturated fat. The dietary guidelines committee recognizes that only 23% of individuals consume saturated fat within limits due to poor eating habits which include food sources with added saturated fats. While they do recommend strategies to reduce saturated fat intake, it seems they are losing a valuable opportunity while recommending protein sources.
Fiber
As the guidelines emphasize, there is a national crisis when it comes to fiber. Almost all Americans are deficient in fiber. As the table above shows, animal based sources have zero fiber, whereas plant based sources which are rich in protein (the legume family) also tend to be very high in fiber. In fact, they are probably the richest sources of fiber amongst all food. Once again, if the USDA dietary guidelines committee is really concerned about fiber deficiency, they should restrict their protein recommendations to plant based sources.
The above three points are summarized in the table below
The conflict of interest
In keeping with the principles of dietary patterns laid out, it seems that the USDA guidelines should stick to plant based protein sources. Then why are they not? My guess is because they have to protect the interests of the meat and egg industries as it is a part of their mandate. As is clear in this discussion, this conflict of interest is creating contradictions in their recommendations.
