Experts defend US dietary guidelines

In February 2015, a committee of 14 experts who were appointed to review the research evidence and inform government officials of the relevant science that underpins the US dietary recommendations issued a 560-page report. The report’s conclusions included a request to guide the population toward nutritional patterns, which are:

Rich in fruits, vegetables, grains, legumes, and seafood

Moderate consumption of low-fat dairy products, alcohol, and non-fat milk (among adults).

Reduced consumption of red and processed meat

Low in refined grains and sugar-sweetened beverages.

The report recommended that unhealthy foods should not be marketed to children and that food labels must be more clear. It also suggested that sustainability concerns need to receive greater attention.

The report caused a lot of anger. It was expected, as many people consider themselves experts on nutrition, and it upset many organizations with vested interests to maintain the current US diet, with its high meat and junk food intake.

The advisory committee received over 29,000 written replies to its recommendations. The Sugar Association and the National Cattlemen’s Beef Association both challenged the report.

Senators complained to Congresswere particularly upset by the suggestion that experts in health and nutrition consider sustainabilityOther experts were in favor of its inclusion.

The hearing is scheduled for October 7th.

People in Glass Houses

The recommendations were also met with displeasure by those who promoted high-fat and low-carbohydrate dieting. This week, the BMJ gave voice to a person who is guilty of this. Nina Teicholz, a US journalist and the author of Why Butter, Meat, and Cheese Are Part of a Healthy Diet, has conducted an “investigation.”

New US dietary guidelines have upset the junk food and meat industries. Paul Townsend/Flickr CC-BY

Teicholz’s criticism of the Scientific Report 2015 guidelines is in line with her arguments from her book. She says the advisory committee failed to conduct a thorough review of recent evidence or identify their conflict of interest.

After a closer look, however, I found little evidence that the members of the committee had any conflicts of interest. The members of the committee were carefully chosen to represent a variety of viewpoints and not to represent any one group. They held public meetings and invited other experts to provide data.

Teicholz is hard-pressed to explain his criticism of a report that’s so comprehensive, systematic, and practical. The panel used a thorough methodology that was clearly laid out and adhered to strict scientific guidelines.

The committee studied a large amount of data over two years in a scientifically rigorous and detailed manner. The USDA Nutrition Evidence Library published the committee’s responses to scientific research questions. The committee used systematic reviews, which pay close attention to biases and sources. They also graded the evidence using strict criteria.

Teicholz’s criticism of saturated fat is perhaps in line with her conflict of interest, which she has in promoting her ideas and those listed in the BMJ article (honoraria from the meat, dairy, and restaurant industries). In the US, saturated fat is prevalent in many foods, including pizzas, cakes, desserts, biscuits, and savory or sweet snacks. This is due to vegetable oils that have been hydrogenated and used in commercial frying. It comes partly from the high consumption of processed meats and fatty foods, such as burgers. Cheese is another major source.

Saturated fat controversy

The report of the advisory committee does not ignore recent controversy about saturated fats and heart disease. Discusses in detail major studies conducted between 2009 and 2014, including randomized controlled trials. The committee focused on studies that examined what replaced in the majority of diets. This was suggested by recent research reviews, which found that there is no relationship between total saturated fat intake and heart disease.

The best evidence shows that replacing saturated fats with polyunsaturated ones improves cholesterol levels and reduces the risk of heart disease. The key is to know where the polyunsaturated fatty acids come from. For example, if you get them from snack foods or deep-fried food, it won’t help your heart.

Some critics claim that the report of the committee advocates a high-carb or low-fat diet. This is incorrect. The report states that it is pointless to swap saturated fats for refined grains and sugar. It recommends instead foods rich in unsaturated fatty acids, echoing the World Health Organization’s recommendation that added sugars should not exceed 10% of daily calories.

The US diet contains a lot of saturated fats, and cheese is a big source. Alan Levine/FlickrCC BY

Teicholz says the committee ignored many low-carbohydrate studies. As the report points out, many of these studies were small, short, and often case-control or pilot studies, which rely on recalling information subjectively (both of those are not considered good evidence). If you compare the results of published studies that have been undertaken over six months, it’s not clear whether they are better than more balanced diets.

Teicholz acknowledges that the effects of stricter low-carb diets are not sustained over time but defends his position by referring to only one meta-analysis. The authors chose to include “grey literature,” which was not peer-reviewed and came from organizations outside academic publishing channels. The study she chose also concluded that even strict low-carb diets have little clinical impact in the long run when compared to conventional therapy.

Teicholz could have had a valid complaint if the advisory report had made recommendations based on this basis.

Food is the only thing you should eat, not nutrients.

It is important to know the sources of fats and carbohydrates. Talking in general terms about these macronutrients makes it difficult to differentiate between healthy foods and junk food. The advisory panel’s main message reports that diets need to be based on whole foods and not specific nutrients. This makes sense.

Take into consideration that bacon, lard, and olive oil all contain some saturated fat. The health benefits of a diet that is high in these two fats are well documented. If anyone tries to convince you that the first two are the key to weight loss and good health, then back away slowly from the bookstore. The report notes that there is evidence to support a diet pattern that favors olive oil and almonds.

Teicholz’s complaint is not the first. This is not a new thing. Other countries, such as Australia, also produce dietary guidelines that are criticized. This confuses the public, and some people abandon advice due to “experts always changing their mind.”

It’s therefore not surprising that, as well as lobbyists from the meat and sugar industries as also companies selling junk food, have expressed their in response to the US report. It is a shame that the BMJ, a respected journal, published an article written by a journalist instead of an expert scientific assessment.

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