Yes, you may. And you probably could be eating more than you think you can. At least, that’s the suggestion of the latest study published in The Lancet on September 1st.
This study is actually a meta-analysis of decades of observational studies. What that means is the researchers didn’t conduct a new study. Rather, they pooled together a number of studies done world-wide over several decades for the purpose of researching a population’s mix of dietary fats, proteins and carbohydrates and determining if there is a significant correlation with mortality based on various mixes.
Here are the main points the study observed:
- Populations whose diets were composed of 60% carbohydrates or more had the highest rates of mortality.
- The higher the concentration of refined, high-glycemic carbohydrates in these populations, the greater the risk of mortality.
- Those populations with the highest percentage of dietary fats (mean of 35% total fat, 13% from saturated fats) had significantly lower rates of mortality compared to populations with high carbohydrate intake.
There are only three macronutrients that make up the human diet – carbohydrates, fats and proteins. Reducing intake of one macronutrient necessarily means an increased intake of one or both of the other two macronutrients.
Since the turn of the 20th century, there has been a push to increase carbohydrate intake while decreasing fat intake, saturated fats in particular, in order to reduce the risk for heart disease, the leading cause of death in developed countries. However, even though populations have adopted these guidelines, mortality linked to heart disease has not decreased, while instances of other lifestyle diseases (such as type 2 diabetes, metabolic syndrome, obesity) have increased.
This meta-analysis was seeking to learn if the original hypothesized culprit for rising heart disease rates over the last century, saturated fats, was an incorrect conclusion. And, if so, did instructing populations to consume less fat and more carbohydrates not lead to lower heart disease rates while having the unintended consequence of increasing the rates of other, previously uncommon, diseases?
The results do seem to support decreasing daily carbohydrate intake below 60%, with the majority of the intake coming from unrefined, low-glycemic sources. This allows for a higher intake of proteins and fats (including saturated fats), also in their least processed forms.
The bottom line is, this study suggests the healthiest diets include a balance of fruits, vegetables, legumes, nuts and seeds, whole grains, fish, eggs, dairy, and unprocessed meats (including beef, pork, poultry, lamb and game). On the restricted list is all processed/cured meats, processed dairy, and refined grains and sugars.
The important thing to remember is, these conclusions are based on mostly observational studies. Observational studies are conducted via surveys and questionnaires and, therefore, have a high degree of error due to flawed recall and response bias. The benefits of observational studies are they tend to be long-term analyses and have a large number of participants. Observational studies are helpful in identifying possible correlations so researchers can create informed hypotheses and develop clinical studies, whose results are more reliable, to test those hypotheses.
The authors of this meta-analysis noted that a few clinical studies have already been conducted that support some of the correlations this study identified. They are hoping their meta-analysis will encourage more clinical studies aimed at discovering what mix of unprocessed carbohydrates, proteins and fats is healthiest.
In the meantime, it appears everything in moderation really is the best advice. I would add just one word to that adage: unprocessed. So, go ahead, eat unprocessed meat, dairy and eggs along with unrefined plant foods, all in moderation, to be fit and happier.