Highlights of the Annual Food and Nutrition Conference (Online Exclusive)

Held October 3–6, 2015, in Nashville, Tenn., the Food and Nutrition Conference and Expo included more than 300 exhibitors and featured more than 130 educational presentations and culinary demonstrations. The principal theme of the conference was improving health through food and nutrition, and several educational sessions focused on the best means to that end, investigating sensory perception and weight management, the benefits of plant foods and their bioactive compounds, and dietary trends.

Sensory Receptors and Weight

Taste is a chemical sense perceived by specialized receptor cells on the tongue, and smell is a chemical sense detected by specialized receptors in the nose; both sets of receptors transmit information to the brain. The combination of taste and smell determines flavor, but not all flavors affect people in the same manner. During the session “Bitter-Sweet: How Our Senses Impact Chronic Disease and Weight,” two speakers discussed why and how people’s perception of taste and flavor varies and how such variation affects food choices and weight management.

Danielle Reed of Monell Chemical Senses Center explained that there are five tastes (sweetness, saltiness, sourness, bitterness, and umami), but different genotypes determine how individuals taste foods and perceive flavor. Plants create bitter-tasting compounds to protect themselves from insects, pathogens, and other antagonists, so they release a bitter taste when they are chewed. The genotypes of humans’ taste receptors means that some people don’t mind the bitter taste of vegetables while others find vegetables extremely distasteful. In particular, cruciferous vegetables are quite bitter to some people, so they may avoid consuming cruciferous vegetables as well as other vegetables, making for a lower quality diet and perhaps poor weight management.

John Hayes of Pennsylvania State University said that although genetics influence perception and thus food choices, consumers can learn to override their innate taste aversions and preferences. As a consequence, people do not always eat what they like, but can develop a tolerance for what they dislike. For example, many people eat vegetables not because they think vegetables taste good but because they know that vegetables are good for them. Moreover, if people can learn to like coffee or beer (and many do), they can learn to like vegetables. Hayes also pointed out that not all vegetables are bitter: Yellow, red, and orange vegetables are either less bitter or not bitter at all, Hayes said, and bitterness can be masked by both salt and sugar.

Why would a speaker at a nutrition conference recommended sugar to mask bitterness? Whereas many so-called experts blame sugar for the increased incidence of overweight and obesity, Hayes questions that logic. Many foods that are sweetened with sugar such as ice cream, cakes, pies, pastries, and chocolate are also high-fat energy-dense foods. Even though there may be an association between intakes of caloric sweeteners and body weight, Hayes said there is no scientific evidence independent of energy intake that indicates a direct causative effect between increased consumption of caloric sweeteners and increased incidence of obesity. He therefore suggests that the supposed link between sugar intake and obesity may actually be due to the energy density of sweet foods, for which the bulk of calories is from fats, not sugar.

The Power of Plant Foods

Cardiovascular disease is the leading cause of morbidity and mortality in industrialized societies; cancer is the second highest. Although both diseases are consequences of increasing age, people who eat a vegetarian or predominantly plant-based diet significantly reduce their risk of both diseases. During the session “Hypertension and Vascular Function: A Role for Functional Foods and Bioactive Components in Medical Nutrition Therapy,” Douglas Seals of the University of Colorado-Boulder explained that as humans age, arterial dysfunction develops. Two major manifestations of arterial dysfunction are progressive stiffening of arterial walls and endothelial dysfunction. Stiffening of the arteries primarily occurs in the large elastic arteries: the aorta and the carotid arteries, which are full of elastic fibers that expand to accept blood and recoil to drive that blood to cells and tissues. And the vascular endothelium—a single-cell layer within the arteries that forms an interface between the flow of blood in the arteries and the arterial walls— produces a wide array of important molecules that determine the health of arteries. The most important of these molecules is nitric oxide, and as humans age, endothelial dysfunction reduces the production of nitric oxide. Arterial stiffening and endothelial dysfunction can each lead to hypertension, stroke, coronary heart disease, and other cardiovascular problems. In addition, chronic low-grade inflammation and oxidative stress both increase endothelial dysfunction and arterial stiffening.

Seals said that one of the primary lifestyle factors that can prevent or minimize arterial dysfunction is diet. Altering dietary composition to a healthy diet (e.g., a vegetarian or plant-based diet, the DASH diet, or the Mediterranean diet) seems to improve vascular function in middle-aged and older adults. Nutraceuticals—foods or food supplements with naturally occurring ingredients that have health benefits—may also be an effective prevention strategy. For example, nitrate/nitrite supplementation has been shown to reverse vascular endothelial dysfunction in animal studies, specifically with respect to the production of nitric oxide. Nitrates and nitrates can be found in almost all plant foods because they absorb nitrates from soil, nitrogen-based fertilizers, water, and the atmosphere, but celery, leafy greens, beets, leeks, endive, cabbage, fennel, and parsley are the most potent sources. And compounds in mushrooms, grapefruit, honey, and hard cheeses have been found to be effective against arterial dysfunction.

Boosting Plant-Based Diets

While vegetarians are less likely to have cardiovascular disease and cancer than health-conscious non-vegetarians, many vegetarians and vegans may have inadequate intakes of certain essential nutrients. During the session “Vegetarian Nutrition for a Healthy Body and Healthy Planet,” Brenda Davis, a registered dietitian in private practice, pointed out that vegetarians and vegans may not get enough protein, iron, calcium, vitamin B12, and omega-3 fatty acids because these nutrients are naturally more abundant in non-vegetarian foods.

Meat, poultry, seafood, eggs, and other animal products are excellent sources of protein and vitamin B12, so when such foods are excluded from the diet, the body’s levels of these nutrients can dip. In addition, inadequate vitamin B12 intakes in vegetarians and vegans causes raised homocysteine levels, which is a risk factor for cardiovascular problems. Even though some plants can be good sources of protein, plant proteins (beans, peas, etc.) have reduced protein digestibility, Davis said. To increase the digestibility of plant proteins, plant foods must be soaked, cooked, blended, or chewed. Vitamin B12 is generally not a natural component of plant foods, but Davis advises vegetarians and vegans to consume vegetarian foods that are fortified with vitamin B12, such as cereals.

Heme iron is derived from hemoglobin and is naturally present in foods from animals that utilize hemoglobin: beef, chicken, fish, pork, liver and other organ meats, and oysters and other seafood. Non-heme iron is naturally present in some animal foods and certain plant foods: beans, peas, nuts and seeds, dark green leafy vegetables, and whole grains. Usually vegetarian diets contain as much or more iron content as non-vegetarian diets, Davis said, but some compounds in vegetarian foods (e.g., phytates in wheat and soy; tannins and other polyphenols in tea; oxalates in spinach, kale, nuts, chocolate, herbs, etc.) inhibit the body’s absorption of iron. In addition, the body naturally absorbs heme iron better than non-heme iron.

Davis emphasized the importance of finding ways to ensure adequate intakes of calcium while consuming a vegetarian diet. Calcium, an essential nutrient, is required for proper contraction and dilation of vascular vessels, muscle function, and structure and function of bones and teeth. The best sources of calcium are non-vegetarian foods (milk, yogurt, cheese, sardines, etc.), and many vegetarian foods contain compounds that inhibit calcium absorption (e.g., oxalates in spinach, kale, nuts, chocolate, herbs, etc.).

Research indicates that omega-3 fatty acids—alpha linolenic acid (ALA), docosahexaenoic acid (DHA), and eicosapentaenoic acid (EPA)—reduce mortality from all causes of cardiovascular diseases, ensure normal heart rate and blood flow, lower triglyceride levels, and play important roles in the brain’s anatomy and function. In particular, DHA makes up a significant proportion of nerve-cell membranes and synapses in the central nervous system. Both plant and animal foods are natural sources of ALA, but the only natural sources of DHA and EPA are seafood and microalgae (fish and other marine animals obtain DHA and EPA by consuming microalgae). Although the human body can convert ALA to EPA and DHA (ALA → EPA → DHA), the conversion rate is poor. Davis suggested that vegetarians and vegans consider consuming microalgae directly and/or taking fish oil supplements to boost their intake of DHA and EPA.

No Halo for Paleo

It therefore seems that a modern diet based predominantly on vegetables, fruits, and whole grains may be the key to optimal health and nutrition, but a popular diet suggests otherwise, limiting food choices to foods in their most natural state that can be hunted, fished, or gathered. The creators of the Paleo diet say that the current agriculturally based diet is mismatched to our genes, which they claim have not changed much since the Paleolithic era. However, many nutritionists disagree. During the session “The Paleo Diet: Stone Age Nutrition for Today’s Athlete,” Steve Hertzler of EAS Sports Nutrition highlighted many problems with the paleo diet.

The paleo diet permits consumption of lean grass-fed meats, eggs, organ meats, fish and shellfish, nuts, fruits, and vegetables. Dairy foods, cereal grains, legumes, starchy vegetables, sweets and sweetened beverages, and salty foods are not allowed on the paleo diet. Many paleo dieters experience weight loss because the diet eliminates several food groups, which translates to the consumption of fewer calories and weight loss. Hertzler said that while most nutritionists and dietitians appreciate the diet’s emphasis on eating lean meats, vegetables, and fruits and limiting sweets, they disapprove of the diet because of its inadequate levels of calcium, iron, dietary fiber, and carbohydrates. The research on which the diet is based is either taken out of proper context or based on rodent models, and none of the foods available today are representative of the types of meats and vegetables that Paleolithic beings ate, he declared. Moreover, populations in regions with the longest lifespans (Ikaria, Greece; Okinawa, Japan; Ogliastra region, Sardinia; Loma Linda, Calif.; and Nicoya Peninsula, Costa Rica) eat diets that are predominantly plant-based: Vegetables and cereal grains constitute a large part of their diets, and meat is consumed in small amounts or not at all. Instead of the paleo diet, Hertzler suggested following a healthy sensible diet based on moderation and sound dietary guidelines.

Overall, the conference illustrates that diet trends may come and go, but the principles of good nutrition and a healthy diet remain unchanged: to protect against chronic diseases and maintain good health, consume diets high in vegetables, fruits, whole grains, and modest amounts of seafood and lean meats.

 

Toni Tarver is senior writer/editor of Food Technology magazine ([email protected]).