Monday, February 23, 2015

Nutrients, Food and Eating Patterns

Nutrients vs. Food

A response to the meta-analysis by Harcombe, et al is that we should focus on foods rather than nutrients, sometimes implying that modern conventional dietary advice successfully does this.  This type of response is couched as a sort of acceptance of the paper (in so far as not directly arguing against the results), but serves to shift the topic elsewhere.

I agree that research and recommendations should be based on food rather than nutrients.  It’s difficult to translate the effects of nutrients to foods, and it’s very reductionist and illogical to generalise the proposed effect of a nutrient on disease to foods high in that nutrient, as doing so ignores the other nutrients in food or other factors of the disease, yet alone any nutrient interactions.

The recommendation to reduce intake of dietary cholesterol is a good example of the issues of making dietary recommendations based on nutrients rather than food.  Eggs, offal and certain seafoods are among the most nutrient dense foods*, but also happen to be rich sources of dietary cholesterol, resulting in previous dietary recommendations to limit their consumption.  So it’s good news that the USDA dietary guidelines are planning to catch up to the rest of the world** by no longer considering dietary cholesterol ‘a nutrient of concern’.  Hopefully it doesn’t take too long before this information becomes widespread.

The problem is that most conventional dietary advice is still largely about single nutrients such as SFA and salt*** (both of which has poor evidence against them), rather than food.  The advice to reduce SFA is perhaps the single most influential recommendation in conventional dietary advice.  It provides the basis to recommend low fat dairy and lean meats over full fat dairy and fattier cuts of meat; to recommend margarine and vegetable oils instead of butter and animal fats; and to emphasise plant foods over animal foods.  So it should hardly be surprising that meta-analyses continue to be written that focus on single nutrients, especially SFA.

* These foods also comprise most of the very short list of foods that are rich in choline, a nutrient only ~6% of adult Americans exceed the recommendation for [1].  It could easily be argued that the advice to reduce dietary cholesterol is largely responsible for widespread insufficient intakes of choline

** For example, this seems to be all the Australian Dietary Guidelines (2013) has to say on dietary cholesterol is this: “Eating cholesterol does not necessarily increase cholesterol in human blood plasma because when it is absorbed the liver tends to reduce its own endogenous cholesterol synthesis” and “There do not appear to be any increased health risks associated with consumption of eggs. There is recent evidence to suggest that consumption of eggs every day is not associated with increased risk of coronary heart disease” [2]

*** Not to mention widespread assumptions based on the lipid hypothesis.  Sometimes it seems like half the Australian Dietary Guidelines is about whether a food or some component in food influences some measure of blood lipids.

Eating Patterns

Unfortunately this type of response really just moves on to discuss ‘eating patterns’, such as the Mediterranean diet, which isn’t the answer either

When discussing eating patterns, many people simply recite a list of foods, which are no doubt healthier than the SAD/SWD, but with very little discussion of why certain foods are on or off the list, except for being a part of, or not a part of, the diet of a healthy population.  As such, eating patterns can often be quite susceptible to dogma and be poorly defined, varying from person to person based on each their individual biases, and may not even be a completely accurate representation of the population’s diet they are trying to convey (e.g. the politically correct ‘Mediterranean diet’)

Eating patterns are also quite susceptible to confounding variables, such as lifestyle, environmental and genetic factors.  Due to many dietary differences, research on various eating patterns makes it difficult to determine what foods in a specific eating pattern are good, bad and ok, and therefore how they can be improved.

* The eating pattern approach is one of the basic arguments for Paleo: HGs ate A,B,C, didn’t eat X,Y,Z and had near population wide freedom of disease.  This Paleo argument also suffers from the same issues associated with other eating patterns and vice versa (so no double standards), but has the advantage over other eating patterns as we are more likely to be better adapted to eat a Paleo diet than a Mediterranean/Asian/etc diet (the evolutionary argument).

Brazil’s Dietary Guidelines

This is as good a place as any to mention Brazil’s Dietary Guidelines (2014).  Unlike other national dietary guidelines, Brazil’s dietary guidelines are refreshingly almost free of proposed effects of nutrient/food on disease/blood lipids, although fat, SFA and red meat, are mentioned a little.  The guidelines are written for the average person and are mainly a collection of common sense approaches to eat well, which are outlined in its ‘ten steps to healthy diets’:

1.      Make natural or minimally processed foods the basis of your diet
2.      Use oils, fats, salt, and sugar in small amounts when seasoning and cooking natural or minimally processed foods and to create culinary preparations
3.      Limit consumption of processed foods
4.      Avoid consumption of ultra-processed foods
5.      Eat regularly and carefully in appropriate environments and, whenever possible, in company
6.      Shop in places that offer a variety of natural or minimally processed foods
7.      Develop, exercise and share cooking skills
8.      Plan your time to make food and eating important in your life
9.      Out of home, prefer places that serve freshly made meals
10.  Be wary of food advertising and marketing 

Forget about all the low fat/low carb/gluten free/sugar free/Paleo/etc cupcake binges in your 80:20 rule.  Following these guidelines will most likely get you at least 80% of the benefit of any diet/way of eating/healthy eating pattern.  Brazil’s dietary guidelines are really needed in other countries to simplify food for the average consumer and get them to focus on the things that matter most

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