Study under review: Carbohydrate quality and human health: a series of systematic reviews and meta-analyses.
Generally made up of sugars, starches, and dietary fiber, carbohydrate-containing foods are a prominent source of dietary energy worldwide. However, there have been reports as early as 1969PMID: 0 warning about associations between refined carbohydrate and chronic disease. Now, recommendations embrace a 45%-65% range of total energy from carbohydrate, with sugar making up less than 10% of total energy in the overall diet.
Indeed, studies have demonstrated that an excessive consumption of calorically dense and micronutrient-poor foods, or “empty calories,” that are generally found at a convenience store, are associated with various cardiometabolic complications such as coronary heart disease, stroke, and type 2 diabetes. However, researchers have also started to understand how carbohydrate-containing foods may not be all that bad when whole. As you can see in Figure 1, the processing to achieve a refined grain removes several healthful components (especially dietary fiber), turning this staple into a demon—transforming the whole grain into an “empty” grain.
This has become even more relevant as the benefits of different components of carbohydrates are revealed, raising the question of whether different carbohydrate components might serve as markers of carbohydrate quality in the overall context of a diet. Dietary fiber is one component in particular that has demonstrated modest beneficial influence on satiety, appetite, and blood lipids. While dietary fiber is a kind of carbohydrate that can’t be digested by our body’s enzymes, the ‘good’ microbiota in our guts feed on them and appear to be driving some of the potential benefits attributed to dietary fiber. Beside that indigestible part of our diet, whole grains also carry phytochemicals, such as carotenoids and polyphenols, and vitamin E that exhibit antioxidant potential and have been associated with reductions in inflammation and chronic disease.
Previous studies have demonstrated positive associations between health and diets characterized by higher markers of carbohydrate quality. However, these studies only explored a single aspect of carbohydrate quality (e.g., whole grain intake) and a limited number of clinical outcomes. This makes it difficult to determine how useful markers of carbohydrate quality are for predicting their potential for chronic disease prevention. The authors of the study under review aimed to quantify the predictive potential of several markers for carbohydrate quality and determine which might be most useful to predict chronic disease mortality and risk. A particular focus was placed on dietary fiber and deriving a quantitative recommendation for its intake. For this purpose, the researchers used data from both prospective studies and randomized controlled trials (RCTs) to quantify and ideally bridge the gap between experimental and observational data.
Carbohydrates are a staple of the human diet. Types of dietary carbohydrates include sugars, starches, and dietary fiber. Excessive processing of whole sources of carbohydrates might be stripping the foods of components that might improve their quality by making them healthier. Whole grains and dietary fiber have been associated with various benefits, including associations with reduced chronic disease, but previous studies have only investigated single markers of carbohydrate quality and a limited number of clinical outcomes. The authors of the study under review aimed to quantify and compare the predictive potential of several markers of carbohydrate quality for chronic disease mortality and risk based on data from both observational and experimental data.
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Other Articles in Issue #55 (May 2019)
NERD Mini: Food groups’ association with the risk of overweight and obesity
How much do certain food groups contribute to obesity risk? A recent systematic review and meta-analysis explored this question.
NERD Mini: The state of the evidence concerning A1 beta-casein
A1 beta-casein is a type of protein found in the milk of certain breeds of cattle. There's some evidence to suggest that this protein is associated with negative health outcomes. But how good is this evidence?
Examining coenzyme Q10 for migraine relief
The exact causes of migraine headaches aren't fully known, but part of the equation may involve mitochondrial problems. Could supplementing a major player in mitochondrial energy production help mitigate migraines?
Are we saffroning our way to mitigating diabetes?
Certain herbs and spices may have a beneficial impact on diabetes. We've covered lemon balm and cinnamon in the past. In this volume, we add saffron to the list of spices we've examined in the NERD.
Pomegranate's antioxidant capacity may be one of a handful of reasons it could help with both exercise performance and recovery. This recent clinical trial put pomegranate extract to the test by exploring its effects in cyclists.
The myth of the sugar rush
Common sense and plausible mechanistic arguments suggest that carbohydrates can influence mood. But do they? And by how much?
Dietary carbohydrate for glycemic control: Does it matter in type 1 diabetes?
This randomized controlled trial adds to the scarce literature examining the medium-term effects of a lower carb diet in people with type 1 diabetes.