Thursday, January 02, 2014

If You Care About Nutrition You Must Read This!

For the next few weeks I'm going to take some time off from blogging - but don't you fret, I've curated a collection of some of my favourite posts from 2010. Today's post highlights the brilliance of two of my favourite researchers - Drs. Dariush Mozaffarian and David Ludwig.
I've long argued that we live in the nutritional dark ages where belief seems to trump science and evidence in the creation of nutritional public health policy and recommendations.

Moreover even in cases where science is purported to be a cornerstone (for instance Canada's Food Guide), I believe the wrong science is given too much sway.

Putting aside my concerns regarding the hijacking of Canada's Food Guide by the food industry and political interests, the Guide was built explicitly to ensure Canadians met their recommended dietary allowances of various nutrients and micronutrients and as I've noted before, the bulk of the science on the interaction of diet on chronic disease prevention centres on the consumption of different patterns of foods, not nutrients.

In an editorial that clearly nails my confirmation biases square on their heads, Drs. Dariush Mozaffarian and David Ludwig take on this madness, and they do such an amazing job discussing the issue that I'm going to reprint a pile of it for those without institutional journal access to read,
"Nutritional science has advanced rapidly, and the evidence now demonstrates the major limitations of nutrient based metrics for prevention of chronic disease. The proportion of total energy from fat appears largely unrelated to risk of cardiovascular disease, cancer, diabetes, or obesity. Saturated fat—targeted by nearly all nutrition-related professional organizations and governmental agencies—has little relation to heart disease within most prevailing dietary patterns. Typical recommendations to consume at least half of total energy as carbohydrate, a nutrient for which humans have no absolute requirement, conflate foods with widely divergent physiologic effects (eg, brown rice, white bread, apples). Foods are grouped based on protein content (chicken, fish, beans, nuts) despite demonstrably different health effects. With few exceptions (eg, omega-3 fats, trans fat, salt), individual compounds in isolation have small effects on chronic diseases. Thus, little of the information found on food labels’ “nutrition facts” panels provides useful guidance for selecting healthier foods to prevent chronic disease.

In contrast with discrete nutrients, specific foods and dietary patterns substantially affect chronic disease risk, as shown by controlled trials of risk factors and prospective cohorts of disease end points. Fruits, vegetables, whole grains, and nuts are consistently associated with lower risk of disease. Fish consumption reduces risk of cardiac mortality, belying categorization with other protein sources. Conversely, processed meats, packaged and fast foods, and sugar sweetened beverages increase chronic disease risk. The effects of foods likely reflect complex, synergistic contributions from and interactions among food structure, preparation methods, fatty acid profile, carbohydrate quality (eg, glycemic index, fiber content), protein type, micronutrients, and phytochemicals. Healthy eating patterns share many characteristics, emphasizing whole or minimally processed foods and vegetable oils, with few highly processed foods or sugary beverages. Such diets are also naturally lower in salt, trans fat, saturated fat, refined carbohydrates, and added sugars; are higher in unsaturated fats, fiber, antioxidants, minerals, and phytochemicals; and are more satiating. Thus, a focus on foods increases the likelihood of consuming more healthy nutrients and fewer calories and decreasing chronic disease risk, whereas the opposite has arguably occurred through decades of nutrient-focused guidelines.

The nutrient-based approach may foster dietary practices that defy common sense. Countless highly processed products are now marketed in which refined carbohydrate replaces fat, providing an aura of healthiness but without actual health benefits. School nutrition guidelines specify a minimum number of total calories but a maximum proportion of fat calories, and foods like gelatin desserts and sugar-sweetened low-fat milk have been used to achieve these nutrient targets. Based primarily on consideration of a few nutrients, a national obesity prevention program categorizes whole-milk yogurt and cheese with donuts and french fries as foods to eat occasionally; sauteed vegetables and tuna canned in vegetable oil with processed cheese spread and pretzels as foods to eat sometimes; and fresh fruits and vegetables with trimmed beef and fat-free mayonnaise as foods to eat almost anytime. Taking the nutrient approach to self serving extremes, the food industry “fortifies” highly processed foods, like refined cereals and sugar-sweetened beverages, with selected micronutrients and recharacterizes them as nutritious. These marketing ploys provide little public health benefit and could potentially produce harm.

The prevailing nutrient-focused approach has broad consequences, influencing food-labeling priorities, school lunch and low-income food assistance policies, industry and restaurant product formulations, and public perceptions of healthier vs unhealthy foods. This focus contributes to confusion, distracts from more effective strategies, and promotes marketing and consumption of processed products that nominally meet selected nutrient cut points but undermine overall dietary quality. The relatively recent focus on nutrients parallels an increasing discrepancy between theory and practice: the greater the focus on nutrients, the less healthful foods have become. As national and international organizations update dietary guidelines, nutrient targets should largely be replaced by food-based targets. Such change would facilitate translation to the public, correspond with scientific advances in chronic disease prevention, mitigate industry manipulation, and remedy widespread misperceptions about what constitutes healthful diets.

Although this approach may seem radical, it actually represents a return to more traditional, time-tested ways of eating. Healthier food-based dietary patterns have existed for generations among some populations. Modern nutritional science now provides substantial evidence for how foods and food-based patterns affect health, guiding the design of more effective approaches for the prevention of chronic disease."