What does “food matrix” mean?
French researchers Anthony Fardet and Edmond Rock lament the public confusion about the health value of foods. Much of the confusion arises from the focus on specific nutrients to emphasize or avoid. The nutrient-based recommendations, Fardet and Rock opine, reflect a reductionist approach to nutrition that's gone overboard, while ignoring a more holistic view. These authors note that during the last five decades, nutritional research seems to have done little to avoid or at least temper the surge in obesity and type 2 diabetes, among other chronic diseases. Or consider the fact that the public promotion of a low-fat diet in the US starting in the 1960s accompanied a sharp rise in the prevalence of obesity.
The food matrix refers to the nutrient and non-nutrient constituents of foods and their interactions. Fardet and Rock propose that the food matrix should be considered along with nutrient composition, because the former substantially affects the latter. The food matrix affects satiety, nutrient bioavailability, chewing, particle size after chewing, hormone secretions, and gastric emptying. For example, eating a whole apple induces different bodily responses than does eating the same apple that’s been ground into juice and pulp. Processing can greatly affect the food matrix usually not for the better.
Thus, a key message to improve the quality of Western diets should be to emphasize eating whole vegetables, fruits, and grains and to minimize eating ultra-processed foods. Fardet and Rock assert that a more holistic approach to eating will help increase the environmental sustainability of food production and distribution and promote more humane treatment of animals that produce food for humans. Specifically, Fardet and Rock propose three rules to eat better: 1) at least 83 percent of calories from plants, 2) no more than 15 percent of calories from ultraprocessed foods, and 3) eat diversified, preferably local, organic, seasonal non-ultra-processed foods.
Misleading Nutrition Facts
The Nutrition Facts labels on food packages can be misleading, causing people to discount the health value of certain foods. This problem arises from the fact that the same nutrient can be digested to different extents depending on the food matrix, processing methods, and meal composition. The standard approaches of calculating the number of calories of carbohydrate, protein, and fat in a particular food ignores the above factors. Happily, the actual number of calories from carbohydrate, protein, and fat absorbed by a human digestive system for can be substantially less for seeds, nuts, legumes, and whole-grain cereal products than what appears in Nutrition Facts. In addition, the presence of high amounts of dietary fiber can further lower the fraction of calories that the body actually absorbs.
The cell walls in plant foods that receive no or minimal processing (as in a whole apple) remain relatively intact and to some degree shield the contents of the plant cells from digestion, thereby reducing the number of calories available for absorption. For example, the caloric availability of whole almonds and walnuts are 30 and 21 percent lower, respectively, than those which appear in Nutrition Facts labels. Mediterranean and vegan diets typically include higher proportions of healthy plant foods, such as seeds, nuts, legumes, and whole-grain cereal products, than the standard American diet. This means that the caloric contents of Mediterranean and vegan diets calculated from Nutrition Facts data overestimate the number of calories actually absorbed by about 4-6 and 7-8 percent, respectively. A diet that features high amounts vegetables, fruits, nuts, seeds, legumes, and whole-grain products may contain fewer calories that you might think, possibly helping you maintain a healthy body weight.
Beyond food composition
The conventional wisdom surrounding food assumes that its nutritional composition is pretty much all that matters. This perspective follows the reductionist tendency of science to attempt to understand something, such as the health value of an orange, in terms of its constituent parts, such as carbohydrate, sugar, fiber, protein, and fat. Fardet and Rock urge a different approach based on the idea that the food matrix substantially affects its health value. For example, eating an orange (minus the peel) has a different health impact from drinking the juice of the orange, especially if the fiber is removed. The degree processing that foods undergo (physical grinding, adding chemicals to render the food more palatable and to lengthen shelf life) can affect their nutritional value, often negatively. Processing can make starches and sugars more readily digestible, increase a food’s glycemic index, and reduce satiety. Fardet and Rock propose the tag phrase of “Real, Vegetal, and Varied,” which translates into emphasizing a Variety of Whole, un- or minimally processed foods, largely Vegetables.
Dietary advice typically focuses on the nutrient composition of foods. However, the form, texture, and matrix of foods can substantially affect the rate of energy intake and subsequent metabolism. Form includes solid, semi-solid, or liquid. Consuming foods as liquids (such as orange juice) compared to solids (whole peeled oranges) tends to increase eating rate and energy intake and reduce satiation. Texture refers to surface attributes that can be detected by human mechanical, tactile, or visual or auditory receptors. Perceived (real or imagined) differences in texture can affect eating rate, caloric intake, and subsequent rates of nutrient uptake. Foods that require more oral processing (such as harder foods) typically take longer to chew and swallow, thereby reducing eating rate and caloric intake. People generally consume less of smaller pieces of food (such as a piece of chocolate) than larger pieces (a bar of chocolate). The food matrix can affect nutrient uptake in unanticipated ways. For example, calcium is preferentially absorbed in the human digestive system when it’s consumed in full-fat dairy products. Much of the fat and energy of whole almonds isn’t absorbed by the digestive system compared to ground almonds. Considering the effects of food form, texture, and matrix opens novel pathways to reduce caloric intake, caloric uptake, and body weight.
Processed and unprocessed fruits
The US Department of Agriculture’s Dietary Guidelines for Americans 2020-2025 recommends a daily intake of 2 cups of fruit. Health authorities generally recommend eating more fruits. French researchers conducted a systematic review and meta-analyses that included a total of 10 cohort studies and randomized, controlled trials. The included reports investigated links between processed or unprocessed fruit consumption and risk of chronic disease and metabolic regulation. The results showed that the degree of processing that the fruits underwent affected their health value. Fresh and dried fruits appeared to have neutral or protective effects; 100 percent fruit juice had intermediate effects; and high consumption of canned fruit and sweetened fruit juice predicted higher risk of mortality.
Specifically, consumption of whole, fresh fruits predicted a significant 17 percent decline in risk of adiposity (excess body fatness) and small declines in body weight and waist circumference. Consumption of canned fruit predicted a significant 13 increase in all-cause mortality. Compared to 100 percent fruit juice, sweetened fruit predicted a significant 28 percent increase in risk of type 2 diabetes. Overall, fresh fruits seemed to be more protective against chronic diseases than fruit juices. These results reinforce the idea that the food matrix affects the health value of fruit. When a fruit’s matrix is destroyed or otherwise greatly altered, the health value generally declines.
The food matrix greatly affects calcium uptake
Food researchers in the Netherlands summarized the effects of the food matrix on the absorption of calcium from natural and fortified foods. Calcium is the most abundant mineral in the human body. All of it must come from external sources, mostly the food we eat. The key message: The fraction of calcium present in different foods that is actually absorbed by the human body varies widely. Just because a food contains relatively high amounts of calcium does not mean that a high fraction of that calcium will be absorbed. In addition, the number of calories associated with adequate calcium intake, other nutrients in foods, and the greenhouse gas emissions associated with food production and distribution merit consideration when deciding which foods best provide sufficient calcium in our diets. The overall winner appears to be the vegetable, kale. It provides lots of calcium expressed as either 1) per 100 grams of kale, or 2) relative to daily caloric intake, or 3) relative to the amount of greenhouse gas emissions required for its cultivation. Cheese also gets high marks. Lettuce and other dairy products have relatively high rankings but with higher greenhouse gas emissions for dairy products. Vegans and vegetarians who avoid dairy products should find ways to eat lots of kale. The rest of us would do well to get on the kale bandwagon.