Evaluating Nutritional Scientific Studies

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I know there is so much confusion over scientific studies that proclaim to be the “holy grail” of healthy eating. One moment you hear “eating fat leads to cancer” and the next moment you hear opposition to the first report. It really comes down to some specific questions to consider when evaluating the truth and helpfulness of a study.

  • When reviewing a study ask, who funded it. Funding and supporters have a lot of  influence on a study and its results.
  • In nutritional studies, it’s important to know, were all aspects of a person’s diet considered? By not looking at the totality of a person’s diet, we limit the ability to learn which diets might be more focused on promoting good health and which might contrarily promote bad health.
  • Was the study aiming to prove a particular nutrient is to blame at the risk of excluding exploring total dietary patterns and differences?

In other words, reducing a single nutrient without exploring what the group is increasing in that nutrient’s absence is an example of not exploring the totality. So in the Nurses’ Study (described later) the goal was to reduce fat intake and see the effects on cancer. However, those nurses then increased their protein intake, in the absence of fat, and most of that protein came from animal-based foods as opposed to plant-based food.

This is the case for the well-known Nurses’ Health Study at the Harvard School of Public Health which concluded, among many things, that fat and dietary fiber have no effect on cancer. The studies on humans in the last 20-30 years were conducted on Americans eating a rich, mostly animal-based diet using 120,000 nurses. The diet was altered by merely reducing the fat intake but continuing on with the same style animal-based diet that is associated with diseases (as shown in The China Study). The Nurses study did not compare different diets such as animal-based vs. plant-based eating. Instead it was focused on a particular nutrient: fat.

“We get hints, of course, from these studies … [of] the relationships between diet and disease, but we do not see the kind of impressive results that we otherwise could see if, in fact, in these studies we had subjects that were consuming the diets most likely to protect against the disease, and compare those subjects with people who were obviously consuming diets that are most likely to promote the disease,” says T. Colin Campbell, Ph.D.

Were the people in the study from the same area consuming the same diet? I.e.: Western women or Western men eating a Western diet (mostly animal-foods diet).

Again, comparing X to X, simply reducing the amount of X is not the same as comparing X to Y or an animal-based diet to a plant-based diet. Understanding calorie intake and where those calories are coming from, such as: the amount from protein, carbohydrate, and fat, as well as which sources (animal or plant) is vital to determine how the food consumption will result in good or poor health.

The China Study is an example of this. It is an extensive study that explores animal-based diet vs. plant-based diet and the results are clear. They show that a whole-food, plant-based diet can halt cancer and other diseases while providing nutrients and vitality for a long, healthy life. The comprehensive study looks at how animal-based foods and plant-based foods are metabolized and how these foods respond in our body. It looks at 6,500 adults from 130 villages in 65 counties of China. The study produces remarkable scientific information that is worth exploring to learn how to protect and regain your health.


Phoebe Chongchua is a multimedia brand journalist who consults and writes on wellness, all things plant-based, fitness, lifestyle, and travel. She is yoga certified and earned her certificate in Whole Food Plant-Based Eating in 2010 through eCornell and the T. Colin Campbell Foundation. She's also a top podcaster for her marketing/storytelling podcast, The Brand Journalism Advantage at

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