SEARCH HEALTH STUDIES

Going Gluten-Free Does Not Improve Digestive Symptoms in Healthy Volunteers

If you don’t have a medically-diagnosed problem with gluten, is there any benefit to going gluten-free? New research suggests not. In this study, scientists randomly assigned 28 people without medical problems with gluten to a gluten-free diet or a gluten-containing diet for 2 weeks. The gluten-containing diet did not generate any symptoms (diarrhea, reflux, constipation, fatigue, etc.) in these healthy volunteers. They concluded that because a gluten-free diet is often less healthy than a typical diet, “there is possibly clinical justification in actively discouraging people from starting it if they have no diagnosable sensitivity.”
Gastroenterology. 2019 September;157:881-883. doi: 10.1053/j.gastro.2019.05.015. (Croall ID et al.)

AMERICANS CAN CORRECTLY CATEGORIZE MOST FOODS AS WHOLE GRAIN OR REFINED GRAIN

In this study, researchers asked 169 low-income adults to look at 11 foods in their original packaging and determine if each was a whole grain or a refined grain. The majority of participants (7 out of 10) correctly identified 4 out of 5 of the whole grain products as whole grain, and nearly as many (6 out of 10) participants correctly identified 5 out of the 6 refined grain products. Specifically, 9/10 people correctly identified whole grain bread, 8/10 correctly identified whole grain crackers & whole grain cereal, and 7/10 correctly identified oatmeal as a whole grain, while popcorn tripped most people up (with only 3/10 people correctly identifying it as a whole grain food). Similarly, 8/10 correctly identified refined crackers, 7/10 correctly identified refined macaroni and tortillas, and 6/10 correctly identified refined bread and cereal, while white rice was tricky for people (with only 4/10 correctly identifying it as a refined grain). Based on interviews with a subset of 60 of the participants, the researchers found that helping people more clearly identify whole grains on the package, and reducing the cost (or perceived cost) of whole grain foods may help increase whole grain consumption in low-income adults.
Current Developments in Nutrition. 2019 May 16;3(7):nzz064. doi: 10.1093/cdn/nzz064. (Chea M et al.)

Whole Wheat Promotes Resilience in Liver, Protects Against Higher Inflammation

Health not only implies being free of disease; health also takes into account how well we adapt to the stresses of everyday life, and the inevitable wear-and-tear on our bodies – in other words, resilience. To see how whole wheat might impact inflammation and resilience, 50 overweight and obese adults were randomly assigned to either 98 grams of whole wheat per day (from bread and cereal) or 98 grams of refined wheat per day for 12 weeks. Scientists then measured markers of inflammation and liver health and used modeling (the “health space” approach) to determine how resilient their bodies were to external stressors based on these findings. In this experiment, whole wheat was shown to protect against higher inflammation, and was also shown to promote resilience in the liver. 
Journal of Nutrition. 2019 Aug 27. pii: nxz177. doi: 10.1093/jn/nxz177. (Hoevenaars FPM et al.)

Avoiding Wheat Linked with Low Fiber, High Saturated Fat Intakes

Although wheat has been a staple crop for centuries, in recent years it has (unjustly) become a scapegoat by fad-dieters seeking a wheat-free or low-carb diet. In this study, researchers analyzed the diets of 30 people who reported avoiding wheat to see if this wheat-free diet impacted their nutrient intake. The wheat avoiders (many of whom happened to be avoiding dairy as well) consumed too little fiber and calcium, and too much saturated fat and total fat according to dietary recommendations. Interestingly, although 85% of the participants reported avoiding ALL wheat products, ⅓ of the participants reported eating a wheat-based food in their food record (mostly in the form of discretionary snacks/desserts).
Nutrition & Dietetics: The Journal of the Dietitians Association of Australia. 2019 Jul;76(3):305-312. doi: 10.1111/1747-0080.12521. (Golly S et al.)

Low-Carb Paleo Diet Linked with Unhealthy Changes to Gut Microbiome

Paleo diets tend to be high in meat and vegetables, while restricting all grains and dairy products. In this study, researchers analyzed the microbiome of 44 people who had been following a Paleo diet for at least 1 year, and 47 people who eat a healthy diet reflective of dietary guidelines. Those strictly following a Paleo Diet and those eating a standard healthy diet ate significantly more fiber than those only loosely following a Paleo diet. However, those who strictly followed the Paleo diet (eating the lowest levels of whole grains and total grains) were significantly more likely to have higher levels of TMAO (a compound generated by the gut microbiome that is associated with plaque buildup in the arteries). The authors also added that “the rationale to exclude whole grains is not supported by data presented here; being inversely associated with body weight and TMAO concentrations.”
European Journal of Nutrition. 2019 Jul 5. doi: 10.1007/s00394-019-02036-y. [Epub ahead of print] (Genoni A et al.)

Whole Grains, Moderate Alcohol Intake Linked with Lower Diabetes Risk

Numerous studies have been published on diet and diabetes risk, but the quality of these studies varies widely, making it hard to compare the risks and benefits of different food choices. In this analysis, researchers reviewed 53 studies on diet and type 2 diabetes risk, and evaluated their strength and validity. There was high evidence that 30g per day of whole grains was linked with a 13% lower risk of developing type 2 diabetes and that 10g per day of fiber from grains was linked with a 25% lower risk of developing type 2 diabetes. There was also moderate evidence that 0.5-1 ounce of alcohol per day was linked with a 25% lower risk of type 2 diabetes than not drinking at all. On the other hand, eating 3.5 ounces of red meat daily, 2 ounces of processed meat daily, 2 slices of bacon daily, or one serving of sugar sweetened beverages were all strongly linked with a higher risk of type 2 diabetes.
BMJ. 2019 Jul 3;366:l2368. doi: 10.1136/bmj.l2368. (Neuenschwander M et al.)

Gluten-Free Diet Not Appropriate without Medical Diagnosis

Gluten is a compound found naturally in wheat, barley, and rye that helps dough stretch and bread rise. Many misguided dieters today choose to go gluten-free, even though only about 1% of the population has celiac disease (an autoimmune disorder where gluten must be avoided). In this review, researchers analyzed studies on the nutritional adequacy of gluten-free diets. They found that gluten-free diets tend to have less fiber, calcium, magnesium, zinc, vitamin B12, folate, and vitamin D, and tend to have more saturated fat and exposure to arsenic. The researchers note that “the majority of persons adopting a [gluten-free diet] have no medical basis for doing so,” and that “only persons with [celiac disease], [wheat allergy], or [non celiac gluten-sensitivity] should follow a [gluten-free diet], and they should do so under medical supervision.”
Journal of Nutrition and Metabolism. 2019 Jul 1;2019:2438934. doi: 10.1155/2019/2438934. [Diez-Sampedro A et al.]

Whole Grains Linked with Healthy Aging

Longevity is fascinating to study, but what is perhaps more important than the years in your life is the life in your years – the ability to age successfully from a medical, social, and lifestyle point of view. In this study, researchers evaluated whole grain intake and measured “successful aging” (using social, lifestyle, and medical indicators) in a group of 3,349 adults ages 50+. Those eating the most whole grains (about 7 servings per day) were significantly more likely to score higher on the “successful aging index” than those eating the least whole grains (about 1.5 servings per day). Those eating the most whole grains were also less likely to have high blood pressure, diabetes, and high cholesterol.
Nutrients. 2019 May 29;11(6). pii: E1221. doi: 10.3390/nu11061221. (Foscolou A et al.)

Poor Diet Linked with 1/3 of All New Colorectal Cancer Cases

Eating a healthy diet can help protect our health from a number of conditions and complications, so researchers wonder how diet might relate to cancer risk. In this study, researchers used models and dietary data to analyze the cancer cases from 2015. They found that 5.2% of all new cancer cases in 2015 could be attributed to poor diet, with 1.8% attributable to low whole grain consumption, 1.2% attributable to low dairy consumption, and 1% attributable to processed meats. The link with colorectal cancer shows the strongest relationship with diet, as poor diet is linked with 38.3% of all new colorectal cancer cases.
JNCI Cancer Spectrum. 2019 May 22;3(2):pkz034. doi: 10.1093/jncics/pkz034. (Zhang FF et al.)

Minimally Processed & Unprocessed Foods Linked with Weight Loss

Many ultra-processed convenience foods are designed to keep us coming back for more. In this study, researchers randomly assigned 20 adults to a diet of ultra-processed foods (packaged pastries, chicken nuggets, American cheese, deli meats, flavored fruit drinks, etc.) or unprocessed foods (spinach, nuts, fruit, chicken breast, plain Greek yogurt, avocado, sweet potato, bulgur, farro, etc.) for 2 weeks, immediately followed by the other diet for the next 2 weeks. The meals on both diets had the same number of calories, carbohydrates, fat, protein, sugar, sodium, and fiber, but participants could choose to eat as much or as little of the food that they wanted. People tended to eat 500 more calories on the ultra-processed diet, and gained about 2 pounds, while people tended to lose 2 pounds on the unprocessed diet. The categorization of ultra-processed vs unprocessed/minimally-processed is based on the NOVA system of food classification. While there are some concerns about the classifications used in the NOVA system (such as white rice and white flour being included in the “minimally processed” category alongside intact whole grains), helping direct consumers towards more wholesome, minimally-processed foods may be one strategy to address overeating and associated weight gain.
Cell Metabolism. 2019 May 16. pii: S1550-4131(19)30248-7. doi: 10.1016/j.cmet.2019.05.008. (Hall KD et al.)

Diets High in Red/Processed Meat and Low in Grain Fiber Linked with Colorectal Cancer

In a recent study, researchers enrolled over 400,000 participants and followed them for 5 years, analyzing their diet and health outcomes. The researchers found that the participants who ate the most red or processed meat had the highest risk of developing colorectal cancer. There was also an increased risk of colorectal cancer in participants who drank the most alcohol. Interestingly, the group that ate the most red and/or processed meat also tended to have a higher intake of alcohol, a lower intake of fruits and vegetables, and were more likely to smoke tobacco. The group with the highest intake of fiber from grains had the lowest risk of colorectal cancer. This study indicates that diets high in red or processed meats and lower in whole grains may be associated with an increased risk of colorectal cancer.
International Journal of Epidemiology. 2019 Apr 17. pii: dyz064. doi: 10.1093/ije/dyz064. (Bradbury KE, et al)

Switching to Whole Grains May Help Improve Insulin/Blood Sugar Management

Insulin is a hormone that helps your body manage your blood sugar, by keeping it from getting too high or too low. In this study, 13 adults with “pre-diabetes” were given a diet with either whole grains or refined grains for 8 weeks, then given a glucose test to assess how well their blood sugar was being managed. They then had a washout period of their normal diet for 8-10 weeks, before switching to the other diet for 8 weeks and taking the glucose test again, thus serving as their own controls. The whole grain diet improved the function of beta cells (the cells that secrete insulin) compared with the refined grain diet, and this effect was found to be independent of gut hormones (such as grehlin, the “hunger hormone”).
Molecular Nutrition and Food Research. 2019 Apr;63(7):e1800967. doi: 10.1002/mnfr.201800967. (Malin SK et al.)

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