Scientific Update
By Reed Mangels, PhD, RD
Eat a Carrot Every Day!
Although dementia mainly affects older people, it is not a normal part of aging.
Health care providers don't have an effective treatment for dementia, and so it is
important to find ways to reduce the risk of developing dementia and to delay its
onset.
Substances called carotenoids, found in many vegetables and fruits, may help to prevent the cognitive decline that leads to dementia. Carotenoids, such as alpha- and beta-carotene and lutein, are found in especially high amounts in deep orange vegetables and fruits and in dark green vegetables. Carotenoids may reduce cognitive decline because of their antioxidant properties.
Researchers began studying close to 50,000 women in 1984 when their average age was 48 years old. They collected information about the women's diets over the next 22 years. The women's cognitive function was assessed at 28 or 30 years after the start of the study. At that point, 41% had good cognitive function, 47% had moderate function, and 12% had poor function. Women who had the highest long-term intake of total carotenoids were 33% less likely to have poor cognitive function and 14% less likely to have moderate cognitive function than those who had the lowest intake. The same results occurred when the researchers examined individual carotenoids.
Good sources of carotenoids include apricots, cantaloupe, carrots, collards, kale, peaches, spinach, sweet potatoes, tomatoes, watermelon, and winter squash. While we can't say with certainty that eating more of these fruits and vegetables will reduce risk of dementia, they have other health benefits and should be eaten liberally.
Yuan C, Fondell E, Ascherio A, et al. Long-term intake of dietary carotenoids is positively associated with late-life subjective cognitive function in a prospective study in US women. J Nutr. 2020:150:1871-1879.
Human Milk: The Ideal First Food
The ideal food for a baby is human milk. That's true whether the baby will be raised
vegetarian (including vegan) or not. Some may wonder if there is a difference
between breast milk from vegetarians and nonvegetarians. The short answer —
there are differences, but they don't affect the nutritional quality of the milk.
The main difference is that the kind of fat in breast milk tends to reflect a woman's diet. Women whose diets are high in unsaturated fat, as is the case with many vegetarians, have breast milk that is higher in unsaturated fat. Those whose diets are higher in saturated fat, as would be the case for those eating meat, have more saturated fat in their milk. Overall, however, milk of well-nourished vegan and vegetarian women is nutritionally equivalent to the breast milk of well-nourished nonvegetarian women.
For more information about vegetarian nutrition during lactation, visit The Vegetarian Resource Group website: www.vrg.org/nutrition/lactation.htm.
Karcz K, Królak-Olejnik B. Vegan or vegetarian diet and breast milk composition — a systematic review Crit Rev Food Sci Nutr. 2020;1?18. [epub ahead of print].
Vegan Motivations
Researchers in Australia wondered how well people adhere to different types of diets
including vegetarian and vegan diets. In other words, are people who choose to
follow a vegetarian or vegan diet likely to continue on this path? Are there factors
that affect dietary adherence? The researchers studied 292 people, predominantly
women, who identified as following a vegetarian, vegan, paleo, gluten-free, or
weight loss diet or were not on a specified diet. More than half had followed their
selected diet for more than two years.
Participants answered a variety of questionnaires including one that checked for dietary adherence by asking questions such as, "How often do you eat animal products?" with responses ranging from "never" to "daily." The vegan group had the highest measured adherence to their diet; the weight loss group had the lowest.
Vegans were most likely to identify ethical/moral reasons as explanations for their dietary adherence and to say that being vegan was a core part of their identity. They were least likely to identify weight loss as a motivation. One study subject said, "It's SO easy to be vegan once you have made the ethical connection. Once you see animals as living being creatures who feel pain and joy. Animal products and byproducts don't look like food to me. Eating a steak would be as absurd as eating cardboard."
Vegans were most likely to report no barriers to dietary adherence. Several groups, including vegans and vegetarians, identified "inconvenience" as the main barrier to dietary adherence.
Cruwys T, Norwood R, Chachay VS, Ntontis E, Sheffield J. "An important part of who I am": the predictors of dietary adherence among weight-loss, vegetarian, vegan, paleo, and gluten-free dietary groups. Nutrients. 2020;12(4):970.
Quality of Restaurant Meals
The most recent figures, prior to the COVID-19 pandemic, indicate that people in the
United States were spending more than half of their food dollars on food from
outside their home. More than 20% of the average person's calories came from
restaurants. While we can't say with certainty whether these figures will change
post-COVID-19, they can help us think about the quality of meals eaten in
restaurants.
Almost half (46.4%) of U.S. adults ate a fast-food meal on any given day during the study period which was 2003 to 2016. The nutritional quality of the food at fast-food restaurants was rated as low, based on a rating that considers dietary risk factors for cardiovascular disease, obesity, type 2 diabetes, and other chronic conditions. Less than 0.1% of fast-food or full-service restaurant meals consumed were rated as ideal from a nutritional quality standpoint. That's less than one out of 1,000 meals! Meals scored especially poorly at including whole grains and nuts/seeds/legumes. There was also an overall reduction in fruit and vegetable consumption from meals from full-service and fast-food restaurants between 2003 and 2016.
The study's authors suggest several ideas for improving the quality of meals, including making fruit or vegetable the default serving as a side dish in place of French fries and using marketing and pricing to influence healthier choices. Consumer demand is another way to influence the nutritional quality of available items at fast-food and full-service restaurants.
Liu J, Rehm CD, Micha R, Mozaffarian D. Quality of meals consumed by US adults at full-service and fast-food restaurants, 2003-2016: persistent low quality and widening disparities. J Nutr. 2020;150(4):873?883.
Vegetarian, and Especially Vegan Diets, Are Effective in Reducing Blood
Pressure
Hypertension, also known as high blood pressure, affects almost half of adults in
the United States. High blood pressure costs the United States about $131 billion
dollars a year and is a contributing factor in almost 1,300 deaths a
day.1
Studies suggest that vegetarians have lower blood pressure than do nonvegetarians. What would happen if nonvegetarians were placed on a vegetarian or vegan diet? A recent metaanalysis2 combined results from 15 randomized controlled studies in which people were on a lacto-ovo vegetarian or vegan diet for at least two weeks. Their results regarding blood pressure were compared to those of nonvegetarians. The greatest reduction in blood pressure was seen in those on vegan diets; the least reduction in those on nonvegetarian diets; lacto-ovo vegetarians were intermediate.
Additional research is needed before we can conclusively say that vegan diets are an effective treatment for high blood pressure. The existing studies are small and have many differences among subjects including alcohol use, cigarette smoking, and sodium intake. Despite these limitations, the study's authors conclude that "vegetarian diets, especially vegan diets...may be crucial in the primary prevention and overall management of hypertension."
1 Centers for Disease Control and Prevention. Facts about hypertension. www.cdc.gov/bloodpressure/facts.htm. Updated February 25, 2020.
2 Lee KW, Loh HC, Ching SM, Devaraj NK, Hoo FK. Effects of vegetarian diets on blood pressure lowering: a systematic review with meta-analysis and trial sequential analysis. Nutrients. 2020;12(6):E1604.
