Advice regarding healthy diets has focused on the notion that a high intake of fats is bad and cause an array of medical problems. Nutrition scientists reviewed the evidence to arrive at a consensus of opinion with regards to macronutrients and disease.
For many years, advice regarding healthy diets has focused on the notion that a high intake of fats is bad for you and cause a whole array of medical problems. Evidence that surfaced recently demonstrated the negative effects of processed carbohydrates and this has led to the comeback of low-carbohydrate diets and ketogenic diets. However, there is much controversy that still remains around this topic.
In 1977, the U.S Senate Committee on Nutrition and Human Needs published a report advising Americans to decrease their intake of total and saturated fat, increase carbohydrate intake, and to decrease their calorie intake. In response to the ever-growing diet-related diseases, the elected members of Congress who had little or no scientific knowledge wrote this report, which was prompted by President Eisenhower’s heart attack in 1955.
Going beyond the quantity of macronutrients
The nutritional scientists of a recent review published in Science highlight the need to go beyond macronutrient quantity when assessing a diet’s impact on health. It is an important need to consider factors such as the quantity and combinations of foods that can influence hormonal response, gene expression, and metabolic pathways. In addition to this, biological differences between people, particularly with regards to glucose homeostasis, can affect responses to specific diets.
The national nutrition research agenda has also failed to acknowledge important areas of dispute. In addition to this, scientific results within this area are often unreliable due to studies being too short or too small or lacking intensity. There has even been a lack of major studies on the ketogenic diet for the treatment of diabetes, which is a shame as the preliminary results were exciting.
The authors outlined three different points on dietary guidelines for the consumption of fats and carbohydrates:
- Increased intake of fat leads to obesity, diabetes, heart disease, and possibly cancer. Low-fat diets are thus ideal.
- Carbohydrates that have been processed have unfavourable effects on metabolism, meaning that low-carbohydrate diets such as the ketogenic diet are better for health.
- The amount of dietary fat and carbohydrate has minimal impact, what is imperative is the type of fat and carbohydrate source.
Diet quality is more important
The authors concur that concentrating on diet quality – by increasing unsaturated fats and decreasing saturated fats together while substituting refined carbohydrates with whole grains and non-starchy vegetables – can help all individuals to sustain good health. This includes people with a fast spectrum of fat-to-carbohydrate ratios.
The authors also outlined three questions which require further investigation and research:
- Do diets with differing carbohydrate-to-fat ratios affect body composition (ratio of fat-to-lean tissue) irrespective of calorie intake?
- Can ketogenic diets give metabolic benefits, especially for diabetes?
- What are the best amounts of different types of fat in a very-low-carbohydrate diet?
More research is needed to answer these questions.
Written by Jade Marie Evans, MPharm, Medical Writer
References:
- Ludwig , D.S et al. 2018. Dietary fat: From foe to friend?. [Online]. [21 December 2018]. Available from: http://science.sciencemag.org/content/362/6416/764
- Eurekalert . 2018. Dietary fat is good? Dietary fat is bad? Coming to consensus. [Online]. [21 December 2018]. Available from: https://www.eurekalert.org/pub_releases/2018-11/htcs-dfi111318.php
