Diet Soda: Providing Insight into a Rare Metabolic Disorder

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Diet Coke is advertised as a sugar free alternative to regular Coke Cola, using aspartame as a sweeteners

Have you ever read the Nutrition Facts on a diet soda or sugar-free gum? If so, you might have noticed a bolded sentence that reads: PHENYLKETONURICS: CONTAINS PHENYLALANINE. In the U.S., this sentence is present on every commercially available medicine, food, or beverage that contains the artificial sweetener aspartame. Often, this warning goes unnoticed, partly because it is nestled quietly at the foot of the list of ingredients and partly because it only applies to 1 in every 10,000 individuals in the United States. Nevertheless, this subtle message is essential for this subset of consumers.

 

Typical nutrition facts label for a product that contains phenylanaline

Phenylketonuria  (Phe·nyl·ke·ton·uria)

Those people are “Phenylketonurics,” or people with a rare metabolic disorder called Phenylketonuria (PKU). PKU is a genetic disorder that results in the inability to convert the amino acid phenylalanine (Phe) into the amino acid tyrosine (Tyr), both essential amino acids that are found in most protein. Phe’s most important biological function is its role as a precursor to Tyr, which is involved in many processes such as the synthesis of neurotransmitters. Without the ability to convert Phe to Tyr, there is less Tyr available for the synthesis of dopamine, norepinephrine, and epinephrine (all important neurotransmitters) and Phe can accumulate in the brain, resulting in local metabolic dysfunction. PKU can result in severe developmental complications and mental retardation if left untreated. Fortunately, PKU can be successfully managed by abiding by a strict low-protein diet, avoiding foods that contain sources of phenylalanine such as meats, fish, dairy, and nuts.

Now, you might ask, “How does PKU have anything to do with the Nutrition Facts on my Diet Coke?” Good question. The answer lies in the chemical structure of the aforementioned artificial sweetener, aspartame.

Image Credit: Blaide Woodburn

Aspartame, an artifical sweetener in Diet Colas, is broken down into phenylalanine, methanol, and aspartate

Aspartame, sold under the brand name NutraSweet, is a dipeptide that contains the amino acids aspartic acid and phenylalanine. Aspartame is rapidly hydrolyzed (i.e. split in two by water) into its respective amino acids in the small intestine, serving as a source of aspartic acid and phenylalanine. Thus, it is important to communicate the presence of aspartame in all artificially sweetened products, especially since the products that usually contain aspartame (soft drinks, candies, etc.) are not typical sources of phenylalanine.

Yet, nutrition labels aren’t just important for Phenylketonurics. With the increased incidence of heart disease, it’s more important now than ever to understand the nutritional value of the foods you’re eating. But, do not fear! Stay up to date on some of my upcoming articles for The Pipettepen and Nutrition at UNC and Translational Science where I’ll outline the basics for healthy eating and overall wellness!

Peer edited by Amanda Tapia.

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No Fermentable Foods? Yes Please!

Created by Kaylee Helfrich

Many foods aren’t allowed on the low-FODMAP diet.

No bread. No sugar. No rice, potatoes, corn, soy, milk, onions, garlic, chocolate, processed meats, or alcohol. Is this a starvation diet or a method of torture? Actually, this is a diet with a 7086% success rate in relieving the symptoms of a disorder that is notoriously difficult to treat. This diet is called the “low-FODMAP” diet, which is short for “restriction of Fermentable Oligosaccharide, Disaccharide, Monosaccharide, and Polyols in the diet”. Thank goodness for the FODMAP acronym to prevent that mouthful of words!

The low-FODMAP diet treats a disorder called Irritable Bowel Syndrome (IBS), which is characterized by stomach pain, bloating, diarrhea or constipation, and general gastrointestinal discomfort. According to Dr. Miranda van Tilburg, an associate professor in medicine from UNC-Chapel Hill who studies IBS, people with IBS often have a very low quality of life. “Those with IBS frequently miss days of work and school, and anxiety and depression are very common as people worry about future symptoms and how those symptoms will impact their life,” she says.

IBS is a common disorder with a global prevalence of 10-20%. It is clinically diagnosed based on certain symptoms. Unfortunately, the exact cause of IBS is unknown, but it is thought to be triggered by multiple issues including changes in gut motility, increased sensitivity of intestinal nerves, bacterial growth in the small intestine, intestinal inflammation, and psychological factors. Although medicines exist to treat IBS, they do not always provide adequate relief and often cause unwanted side effects. Instead, a combination of diet, exercise, and even hypnotherapy often provide more relief with fewer side effects.

A large component of treatment for IBS is diet management. Tilburg points out a few well-known triggers of IBS symptoms, including spicy and fatty foods, along with incompletely absorbed carbohydrates. The low-FODMAP diet specifically addresses the latter dietary component.

What are FODMAPs, and how can a diet low in FODMAPs treat IBS symptoms? FODMAPs are carbohydrates, such as lactose, fructose, and sugar alcohols, that are difficult to absorb in the small intestine. When the FODMAPs are not absorbed, they produce intestinal water and gas. For various reasons, those with IBS often have more difficulty when consuming FODMAPs than other people.

Created by Kaylee Helfrich

FODMAPs can cause gastrointestinal discomfort via 2 methods.

The mechanism behind FODMAP-induced discomfort is twofold. First, when FODMAPs are not fully absorbed, they remain in the small intestine and attract water, which enters the small intestine in a process called osmosis. This leads to bloating as well as increased water delivery to the large intestine, which can cause diarrhea. Second, incompletely absorbed FODMAPs can be fermented by intestinal microbiota, leading to gas, which causes pain, bloating, and general discomfort.

Consequently, for some people with IBS, a diet low in these offending carbohydrates can be beneficial. In fact, six randomized controlled trials have shown benefits for IBS patients who consume a low-FODMAP diet. However, this diet is very restrictive concerning which foods can be eaten, so people can have trouble adhering to the diet if they are not properly supported by clinical guidance.

One question that many people ask is: how can someone follow a diet that cuts out virtually all of the delicious foods that are normally eaten? Although this diet is restrictive, it offers a good chance at relief for people who have usually lived with pain for years. And this diet is not meant to be followed forever. Tilburg explains that “every person’s case of IBS is unique, and every person will have different foods to which they are sensitive.” So after following the low-FODMAP diet for 2-6 weeks to reduce the food-induced symptoms, the excluded foods are slowly added back, and the patient is monitored by a dietician for adverse symptoms. If a certain food increases symptoms, then it is removed from the diet and other foods are tried instead.

Although it may seem impossible to go without your favorite chocolate cake or garlic bread, people with IBS often welcome the chance to reduce their symptoms, even if it requires a sacrifice of ice cream and deli sandwiches.

Peer edited by Alexandria Mullins.

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Should Coconut Oil be in Your Pantry?

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Coconut oil is actually not a healthy alternative to butter in cooking. Feel free to use it as a moisturizer though!

Maybe it reminds us of a warm beach vacation. Or sipping a pina colada. But whatever the reason, many Americans are making coconut oil a part of their diet.

But be warned– coconut oil is extremely high in saturated fat. In fact, 92% of the fat in coconut oil is saturated. To put this in context, the fat content of butter is 63% saturated fat.

As a nutrition researcher, I’ve spoken with many Americans about their diets, and lots of people are excited about coconut oil. I’ve heard every claim– it promotes brain health, it helps you lose weight…I could go on. The truth is, the evidence isn’t strong for any of these claims.

It’s time to set the facts straight. Let’s discuss two common “myths” around coconut oil.

Myth 1: Saturated fats from plants are less harmful than animal saturated fats. Many foods contain saturated fat, such as steak, butter, and–you guessed it–coconut oil. Some people claim that plant-based saturated fats are less harmful than saturated fats from animal sources. While differences do exist between plant-based and animal saturated fats, this claim is false. Saturated fats from red meat, butter, and coconut oil all contain carbon, hydrogen and oxygen atoms, but they contain different numbers of each of these atoms, which makes them chemically different. But that’s where the differences end.

Let’s compare butter with coconut oil. The saturated fat in coconut oil is comprised mainly of a saturated fatty acid called lauric acid (which has 12 carbon atoms, 24 hydrogen atoms, and 2 oxygen atoms). Butter consists mostly of a saturated fatty acid called palmitic acid (which contains 16 carbon atoms, 32 hydrogen atoms, and 2 oxygen atoms). So yes–the saturated fats in coconut oil and butter are different, but they actually have very similar effects on our bodies. Feeding studies show that both lauric and palmitic saturated fatty acids raise our body’s cholesterol levels, which can lead to all kinds of health conditions, including heart attacks and strokes. Additionally, scientists recently combined data from 21 studies on coconut oil and found no evidence that coconut oil should be viewed differently from other sources of saturated fat. Thus, despite the chemical differences, saturated fats have similar effects on our health.

Myth 2: Coconut oil helps you lose weight. The myth that coconut oil helps people lose weight probably comes from a study in 2008 on how the human body processes different types of stored fat. All living things store fat in two types of molecules known as triglycerides: medium-chain triglycerides (MCTs) and long-chain triglycerides (LCTs). When a human, animal, or plant needs energy, these fats are broken down. The 2008 study by Dr. Marie-Pierre St.-Onge showed that eating oil rich in MCTs can increase a person’s ability to break down fat more than oils rich in LCTs, leading to faster weight loss. Coconut oil contains MCTs, so this is seemingly great news for coconut oil supporters. But dig a little deeper, and you’ll find out that the science is much more complicated.

First off, St-Onge’s study used an oil that contained 100% MCTs. But coconut oil contains only 4% MCTs. Therefore, St.-Onge’s study cannot be generalized to coconut oil. And what’s more– St.-Onge published another study in 2017 that showed that small doses of MCTs do not help with weight loss in overweight adolescents.

Additionally, MCTs containing lauric acid (remember, this is the main fatty acid in coconut oil) are heavier than other MCTs. To give you some numbers, the average weight of a triglyceride in coconut oil is 638 grams per mole (g/mol), versus 512 g/mol in other medium-chain triglyceride oils. The heavier weight of the triglycerides in coconut oil means they are broken down by the body differently than other MCTs. (If you’d like a more detailed explanation of this process, click here.) This is another reason as to why many studies on MCTs, such as the 2008 St.-Onge study, cannot be generalized to coconut oil.

Unless you’re using coconut oil to moisturize your skin, it should not be in your pantry. The science shows that unsaturated fats—like olive oil and avocados— remain the healthiest types of fat. So you can indulge in that pina colada periodically, but my everyday advice– let’s ease up on the coconuts!

Peer Edited by JoEllen McBride

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Whole Milk, how about that?

Many of us can still remember seeing our favorite pop singers with the perfect milk mustache on commercials for “Got milk?”. Later, in the school cafeteria, we would try to recreate this perfect milk mustache with milk provided by the cafeteria for lunch. Since those seemingly blissful times, much controversy has arisen surrounding milk and its supposed benefits.

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Enjoy a glass of milk and cookies! Whole milk may not be an unhealthy option after all.

Milk has always been promoted as a great source of calcium and vitamin D– essential vitamins and minerals for maintaining health. However, the emphasis on these nutrients disregards the high fat, saturated fat, and lactose content of milk. To address these less desirable components of milk, the milk industry has promoted low-fat milk and fat-free milk. Furthermore, governmental nutritional guidelines, like MyPlate, also recommend three daily servings of lower fat options over whole milk. This begs the question: is reduced-fat milk healthier than whole milk? To bolster these low-fat and fat-free options, the sugar industry has biased the answer to this question by promoting research that minimizes the hazards of sugar, and casts fats as the dietary enemy. These influences have contributed to a negative public perception of fats, ideal for promoting reduced-fat milk—reduced-fat milk still has the beneficial nutrients, but no longer with dietary enemy number one: fat.

In 2013, a provocative scientific review, questioned whether the three daily servings of reduced-fat milk was an evidence-based recommendation. Turns out there is a lack evidence to support replacing whole milk with reduced-fat milk based on weight management or cardiovascular disease prevention. Rather, the authors suggest, that consumption of reduced-fat milk might cause harm if sugar or simple carbohydrates are substituted for the fat. The suggestion to replace whole milk with reduced-fat milk relies on the presupposition that consumption of reduced-fat milk will lead to a total reduction in caloric intake. However, reduced-fat foods tend to be less satiating which may lead to additional caloric consumption.  For example, because a snack that includes reduced-fat milk may be less filling than a snack with whole milk, a child eating the reduced-fat snack might compensate for the reduced feeling of satiety by eating more. If these compensatory calories are more than the difference in calories between reduced-fat and whole milk or if they come in the form of refined starches and sugars, the net result of consumption of reduced-fat milk may be increased calorie consumption and increased risk for cardiovascular disease. A low-fat diet, rich in low-fat dairy products, may not only increase hunger but also negatively impact weight loss and cardiovascular health when compared to a higher fat diet.

When considering the benefits of whole milk versus its reduced-fat counterparts, I consider how milk consumption fits into my entire diet. You cannot assess food items as singular entities since they are a part of whole diet; it is important to approach dietary recommendations holistically. This makes generalized nutrition recommendations incredibly difficult to make and easily influenced by entities with vested interests in having their products promoted over others. So, maybe let’s enjoy whole milk in moderation, how about that?

Peer edited by Tamara Vital

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When 2+2 Does NOT Equal 4: Dangers in Reducing Nutrition to the Sum of Its Parts

Modified from Wikipedia images and https://pixabay.com/en/dishes-plate-fork-spoon-food-295282/

Is dinner becoming a subset of chemicals instead of real food?

A researcher is looking at preliminary data from the CARET study when he does a double-take.  He thinks: that can’t be right- people who supplemented with vitamin A have higher frequency of lung cancer and death than people not supplementing with vitamin A. But the data were correct! People taking vitamin A were getting lung cancer more frequently. How could this happen when previous studies had suggested that vitamin A would reduce the risk of lung cancer?

The Carotene and Retinol Efficacy Trial (CARET) and a similar trial (the Alpha-Tocopherol, Beta-Carotene Cancer Prevention (ATBC) Study) were conducted because observational studies had suggested that people who consumed more food containing vitamin A had lower rates of lung cancer and death. The CARET and ATBC research groups designed rigorous, double-blind, placebo-controlled trials to investigate if supplementation of one’s diet with vitamin A would reduce the risk of lung cancer in high risk groups such as smokers. However, both trials ended early when it became clear that vitamin A supplementation did not reduce the risk of lung cancer, but in fact may have increased the risk.

The CARET and ATBC studies raised awareness in the nutrition community that individual food components do not necessarily have the same health benefits as whole foods. These trials exemplify the concept of nutrition reductionism, which is the idea that a complicated system of food is simply the sum of its nutrient parts. Unfortunately, we still have not learned from the reductionist studies from the 1990s, and reductionist thinking is still quite common. For example, any person who relies heavily on supplements while consuming a limited diet is using reductionism instead of considering food as a whole entity.  Even when people do not consciously restrict their diet or use large amounts of supplements, they still try to meet guidelines for “good” nutrients such as omega-3 fatty acids, vitamin C, dietary fiber, and others, while trying to minimize “unhealthy” nutrients such as cholesterol, salt, and saturated fats.

Modified from: https://en.wikipedia.org/wiki/Strawberry

If we take these individual components and mix them together, do we have a strawberry? Can we condense a strawberry into a pill, and will that pill have the same health benefits as a strawberry?

Is thinking about food as simple individual nutrients actually a problem? If we get all the required nutrients, does it matter in what form we consume them? Many food scientists and some nutritionists would say that the nutrients’ sources do not matter as long as they are consumed in appropriate amounts. However, there are issues with this pattern of thought. One problem is that science has not yet identified each component of all foods. For example, scientists agree that there are between 800 and 1000 different compounds in red wine.   Not all of these compounds have been precisely identified, and the compounds in each wine vary, which creates taste differences and diverse nutrient profiles. Some research studies investigate only one compound from red wine, such as resveratrol, and this reduction from hundreds of components into one component results in conflicting research outcomes. While some research shows that resveratrol benefits health by improving metabolic processes associated with aging in mice, other research finds that resveratrol has no impact on human health. And this theme is repeated many times in research, with some studies showing that individual nutrients affect health, and other studies demonstrating that the same nutrients have no health effect. Much of the resulting confusion in the nutrition sciences may result from neglecting to consider the impact of an entire food on human health.  After all, rarely are nutrients consumed in isolation, so perhaps they should not be studied solely as individual components.

In order to escape from nutrition reductionism, two things need to change- how we do nutrition science and how we view nutrition science.

Within nutrition science research, the first issue to address is research design. Research should consider turning from reductionist to “holism,” which considers the whole as a dynamic interaction of its parts and acknowledges that the system has features not contained in the individual parts. Expanding nutrition research from a nutrient-only focus to a broader view of food will require an interdisciplinary approach with integration of fields from computing to food science to public health to epidemiology and many others.

So how can we change our individual view of nutrition while still taking advantage of nutrition research? First, we can recognize that the food industry rarely produces “food,” and instead creates “food products” that are combinations of carbohydrates, fats, vitamins, antioxidants, and other components. Second, we can avoid these food products and instead choose to eat “real food” that naturally contains these components. Third, we should view nutrition research as imperfect and often too focused and understand that research frequently uses individual nutrients to declare a food “good” or “bad” without considering its properties as a whole. And finally, we can decide what to eat from this motto by popular food journalist and activist Michael Pollan, “Eat food. Not too much. Mostly plants.”  While this sounds like an overly simplified solution, it at least begins to answer the question of “What should I eat for dinner?”  The answer: not isolated nutrients, but whole foods such as carrots, broccoli, peas, brown rice, and chicken that will provide both a delicious stir fry and many essential nutrients.

Peer edited by Laurel Kartchner and Mikayla Armstrong.

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