Human Nutrition: The Settled Science

"A decrease in fat intake automatically led to an increase in carbohydrate consumption and our findings may explain why certain populations such as South Asians, who do not consume much fat but consume a lot of carbohydrates, have higher mortality rates."
Mahshid Dehgha, Population Health Research Institute, McMaster University

"Our study found the lowest risk of death in those who consumed three to four servings or the equivalent to 375 to 500 grams of fruits, vegetables and legumes per day, with little additional benefit for intake beyond that range. Additionally, fruit intake was more strongly associated with benefit than vegetables."
"The PURE study includes populations from geographic regions which have not been studied before, and the diversity of populations adds considerable strength that these foods reduce disease risk."
"Raw vegetable intake was more strongly associated with a lower risk of death compared to cooked vegetable intake, but raw vegetables are rarely eaten in South Asia, Africa and Southeast Asia."  "Dietary guidelines do not differentiate between the benefits of raw versus cooked vegetables -- our results indicate that recommendations should emphasize raw vegetable intake over cooked."
Victoria Miller, McMaster doctoral student

HealthDay News

This major study out of McMaster University, comparing various diets around the world represented a major nutritional-longevity study where lead author Mahshid Dehgha maintained that people reserving at least 30 percent of food intake in fats, saturated or unsaturated, had succeeded in lowering their mortality risk. The results of the study have been heralded as a breakthrough in understanding the effects of the composition of the human diet, pro and con mortality, yet on the other hand, there are those in the scientific community involved in human nutrition that remain skeptical.

Medical journals are rife with the results of a multitude of food/health studies. Medical studies can fall into two categories; the randomized controlled clinical trials recognized as the gold standard of medical research and the observational type of studies. The first type is severely limited when dealing directly with human subjects since people who take part in these studies cannot be subjected to the same type of treatment as would be apportioned to laboratory-test animals.

In other words, the study cannot be crafted to ensure that one-half of the study participants are given a diet that might be inimical to their health, while the other half are apportioned a healthy diet known to lead to good outcomes. Most nutrition studies as a result represent observational types, relying on food diaries where the participants make note of their food intake, also called "food frequency questionnaires". Since this type of study relies on truthfulness and careful listing of all foods consumed, they are seen to be less useful to a reliable outcome.

CTV News Channel: ‘Big piece of evidence

In one recent study published in the International Journal of Obesity, the authors concluded that the data they relied upon obtained through self-reported food studies proved to be of such poor quality they realized they were incompatible with scientific research. The researchers involved in the McMaster study concluded that a correlation between a higher-fat diet and fewer deaths existed, as they interpreted the results.

But then there is the issue of other factors, like family history, exercise, income levels, lifestyle, etcetera to be considered. Apart from which studies tend to contradict one another, some rallying against conventional wisdom; as an illustration that diets high in fat and low in carbohydrates tend to help people lose weight, while other studies claim the reverse to reflect reality. Yet researchers at the University of Pennsylvania in 2003 concluded that whether someone was on high-fat, low-carbohydrate, or a high-carbohydrate and low-fat diet was immaterial.

A follow-up study replicated the original study's results, taken seven years on. With the added observation that irrespective of which diet was used, once the diets ended so did the weight loss; weight soon returned. The human body metabolizes foods differently from individual to individual. Up to the present, cheese, milk, butter, eggs and beef have been identified in the past few decades as representing the intake of harmful foods. And then other research proceeds to reverse those results.

The public is sternly informed that excess weight leads to pressure on internal organs, and to diabetes which in turn deleteriously affects the heart, eyesight, the likelihood of stroke, kidney disease and other related ailments such as neurological problems. Yet newer studies conclude that carrying around some extra weight as we age may in fact help us get over illnesses better and live longer lives.
One thing, however, is indisputable; it is moderation in all things, including dietary intake, that exemplifies the best of all possible diets.

Moderate amounts of saturated fat, found in butter and cheese, may actually help protect against heart disease and stroke. (Madlen/shutterstock.com)