Tuesday, November 13, 2018

Carbohydrate Consumption And Mortality


Carbohydrate consumption has been a hot button issue in the field of nutrition for decades. The type and amount of carbohydrate we should be including in our diets is the subject of intense debate in both the research and weight loss communities. This is a subject that is near and dear to my own heart since carbohydrate metabolism was the subject of my own doctoral research. A new study has been published on this topic that is well done and very important.

The Article
This investigation actually consists of two separate studies (Reference 1). The first is a prospective cohort study using the ARIC cohort (The Atherosclerosis Risk in Communities). The second is a meta-analysis including 7 separate studies.

Results
Prospective Cohort Study in the ARIC Cohort
Over 15,000 adults aged 45-64 years in 4 U.S. communities had their diet assessed by means of a food frequency questionnaire and were followed for 25 years. Subjects who consumed 50-55% of their calories as carbohydrate had the lowest mortality rate. Subjects who ate more or less carbohydrate had an increased mortality risk.

-A 50 year old subject consuming less than 30% of calories as carbohydrate would have a projected life expectancy of 29.1 years.

- A 50 year old subject consuming 50-55% of calories as carbohydrate would have a projected life expectancy of 33.1 years.

A 50 year old subject consuming greater than 65% of calories as carbohydrate would have a projected life expectancy of 32 years.

Meta-analysis
The meta-analysis consisted of 8 separate studies with a total of 432,179 subjects and showed a similar result. There was an increased risk of mortality with both a low and high carbohydrate intake when compared to a moderate carbohydrate intake.

Subjects consuming less than 40% of calories as carbohydrate had a statistically significant 20% higher risk of mortality.

Subjects consuming greater than 70% of calories as carbohydrate had a statistically significant 23% higher risk of mortality.

Substituting animal fat and protein for carbohydrate resulted in an increased risk of mortality.

Substituting vegetable fat and protein for carbohydrate resulted in a decreased risk of mortality.

Conclusions And Recommendations
Many people manipulate their carbohydrate consumption in an effort to lose weight. It is really important to examine what effect these weight loss diets may have on long term health. My professional goal has always been to provide a strategy that helps my client lose weight effectively, while improving overall health and decreasing risk of chronic disease. 

This study sheds some light on the long-term health effects of diets that severely manipulate carbohydrate consumption. The mechanisms are pretty straight forward. A low carb diet will generally include less healthy foods such as fruits, vegetables and whole grains and higher amounts of red meat and saturated fat. This results in fewer vitamins, minerals, fiber and cancer fighting phytochemicals. This eating pattern likely results in higher levels of oxidative stress, inflammation and biological aging.

On the other hand, diets very high in carbohydrates tend to include too many refined carbohydrates and not enough healthy vegetable fat. This results in a much higher dietary glycemic load, which has been associated with many negative health outcomes.

Here is what we learn from this important study:
1) Going very low carb is probably not a great idea.

2) Going very high carb is probably not a great idea.

3) Stay in the mid carb range, which is around 50-55% of calories.

4) The quality of carbohydrates consumed is of the utmost importance. Focus on low glycemic carbs such as fruits, vegetables, legumes and whole grains.

5) The majority of your fat should be vegetable fats such as nuts, avocado, nut butters, seeds and healthy vegetable oils such as olive oil and canola oil.

6) Minimize sources of protein that are high in saturated fat, especially red meat and processed meats like bacon, sausage, pepperoni, hot dogs, etc. 

References
1) Seidelmann SB, et al. Dietary carbohydrate intake and mortality; a prospective cohort study and meta-analysis. Lancet Public Health 2018; 9:pe419-e428.

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