Scientific Report of the 2020 Dietary Guidelines Advisory Committee: Evidence on Diet and Health Part Two

Have you read the scientific report of the 2020 Dietary Guidelines Advisory Committee? You can find it in its entirety here. This report is now open for public comment, and there will be an online meeting on August 11 to discuss thoughts on the report.

We've been steadily working our way through overviews of each section. Here's what we've done so far...

  1. Executive Summary
  2. Setting the Stage and Integrating the Evidence
  3. Methodology
  4. Evidence on Diet and Health Part One

Today we're tackling evidence on diet and health part two! Here's what we're going to cover...

  • Diet and Health Relationships: Pregnancy and Lactation
    • Food, Beverage, and Nutrient Consumption During Pregnancy
    • Food, Beverage, and Nutrient Consumption During Lactation

Let's get started!

Diet and Health Relationships: Pregnancy and Lactation begins with a closer look at pregnancy. Though pregnancy is a distinct 40-week period that has its own needs and requirements, it is both heavily influenced by various factors before pregnancy and also plays a role in affecting dietary patterns and health status after pregnancy. The report maintains "a mother’s health and nutritional status during the first 1,000 days of an infant and child’s life, beginning at conception and continuing through the second year of life, are crucial for ensuring optimal physical, social, and psychomotor growth and development and lifelong health."

In this section, the committee poses

and then addresses the following questions...

  1. What is the relationship between dietary patterns consumed during pregnancy and risk of gestational diabetes mellitus?
  2. What is the relationship between dietary patterns consumed during pregnancy and risk of hypertensive disorders during pregnancy?
  3. What is the relationship between dietary patterns consumed during pregnancy and gestational weight gain?
  4. What is the relationship between frequency of eating during pregnancy and gestational weight gain?
  5. What is the relationship between dietary patterns during pregnancy and gestational age at birth?
  6. What is the relationship between dietary patterns consumed during pregnancy and birth weight standardized for gestational age and sex?
  7. What is the relationship between beverage consumption during pregnancy and birth weight standardized for gestational age and sex?
  8. What is the relationship between maternal diet during pregnancy and risk of child food allergies and atopic allergic diseases, including atopic dermatitis, allergic rhinitis, and asthma?
  9. What is the relationship between seafood consumption during pregnancy and neurocognitive development of the infant?
  10. What is the relationship between omega-3 fatty acids from supplements consumed before and during pregnancy and developmental milestones, including neurocognitive development in the child?
  11. What is the relationship between folic acid from supplements and/or fortified foods consumed before and during pregnancy and 1) maternal micronutrient status, 2) gestational diabetes, 3) hypertensive disorders, 4) human milk composition, and 5) neurocognitive development in the child?

For the sake of brevity, we are not going to dive into each question individually in this blog post, but you can find them asked and addressed in order in the pregnancy section of the report.

This section of the report concludes "The evidence reviewed by the Committee reinforces the importance of nutrition for women of reproductive age and women who are pregnant for optimal maternal and fetal outcomes." While many pregnant women follow the same patterns observed in most of the US population in terms of nutrients that are underconsumed (vitamin D, calcium, fiber, and potassium) and food elements that are overconsumed (added sugars, saturated fat, sodium), they also generally appear to not be getting enough iron. Folate and folic acid consumption should also be emphasized for women who are considering becoming pregnant and until after the first trimester of pregnancy. And finally, "Choline and magnesium are also underconsumed in the diets of women who are pregnant and should be considered for further evaluation, given limited availability of biomarker, clinical, or health outcome data [...] Low iodine intake is potentially of public health concern among women who are pregnant, based on biomarker data that suggest low nutrient status."

But why focus on healthy eating patterns during pregnancy? "The evidence reviewed relating to healthy dietary patterns before and/or during pregnancy suggests a modest reduction in the risk of GDM, hypertensive disorders, excessive GWG, and preterm birth [... adherence to healthy dietary patterns] has the potential to ameliorate the risk of the predominant complications of pregnancy, which result in adverse maternal and infant outcomes."

Luckily, these healthy patterns are largely the same as the ones proposed to reduce the risk of chronic disease in the general population. In addition to following the proposed patterns -- Healthy US, Healthy Vegetarian, and Healthy Mediterranean -- pregnant women should also supplement with sources of folic acid, iron, choline, vitamin D and vitamin E. The committee outlines several possible strategies for women of reproductive age for making the healthiest choices on pages 65-66 of this section of the report.

Now let's move on to Part D Chapter 3: Food, Beverage and Nutrient Consumption During Lactation. The report asserts "Maternal nutrition is a key factor influencing the health of both the lactating woman and her child. For many nutrients, the requirements during lactation differ from those during pregnancy, so women who are lactating should adapt their dietary choices and supplement use to meet those needs."

Why? Well, the benefits of lactation are both short and long term. In terms of chronic disease risk, "Long- term benefits of lactation for women’s health include reduction in risk of breast,6 ovarian, and endometrial cancers; hypertension and cardiovascular disease; non-alcoholic fatty liver disease; and type 2 diabetes mellitus later in life."

Are women breastfeeding? The answers vary. "75 percent of U.S. infants are not exclusively breastfed for 6 months, as recommended by the American Academy of Pediatrics (AAP)13 and the World Health Organization (WHO).14 Moreover, only 36 percent of infants in the United States are breastfed for at least 12 months, 11 as recommended by the AAP and WHO."

That's where we stand now.

The rest of this section is largely guided by questions, just like in the previous section. I'm listing them below, and you can find the answers in order in the lactation section of this report...

  1. What is the relationship between dietary patterns consumed during lactation and postpartum weight loss?
  2. What is the relationship between frequency of eating during lactation and postpartum weight loss?
  3. What is the relationship between dietary patterns consumed during lactation and human milk composition and quantity?
  4. What is the relationship between maternal diet during lactation and risk of child food allergies and atopic allergic diseases, including atopic dermatitis, allergic rhinitis, and asthma?
  5. What is the relationship between dietary patterns consumed during lactation and developmental milestones, including neurocognitive development, in the child?
  6. What is the relationship between seafood consumption during lactation and neurocognitive development in the child?
  7. What is the relationship between omega-3 fatty acids from supplements consumed during lactation and developmental milestones, including neurocognitive development, in the child?
  8. What is the relationship between folic acid from supplements and/or fortified foods consumed during lactation and 1) maternal micronutrient status, 2) human milk composition, and 3) developmental milestones, including neurocognitive development, in the child?

So, what happened while the committee evaluated those questions? Here's the short answer...

"The 2020 Committee evaluated maternal dietary patterns during lactation, including frequency of eating, and their relationship to maternal PPWL. The Committee also examined the relationship between maternal folic acid supplementation and maternal micronutrient status. Maternal dietary patterns and folic acid supplementation also were considered in relation to human milk composition and quantity. In addition, maternal dietary patterns were examined in relation to child outcomes, including the risk of child food allergy and atopic allergic disease, and developmental milestones, such as neurocognitive development. The Committee also examined the relationship of maternal seafood consumption, omega-3 fatty acid supplementation, and folic acid supplementation during lactation with developmental milestones in the child."

Of note is that the committee found "Women who are lactating have a higher average Healthy Eating Index (HEI) Score (i.e., 62 out of 100) than do women of a similar age who are not pregnant or lactating (i.e., 54)." On the flip side, "Women who are lactating have lower component scores than their peers (women who are pregnant and those who are neither pregnant nor lactating) for Total Vegetables, Dairy, and Sodium. Additionally, nearly 1 in 6 women who are lactating consume Total Protein Foods in amounts less than those recommended in the USDA Food Patterns."

The report also reveals, "Food components of public health concern among women who are lactating include those for the entire population older than 1 year, including vitamin D, calcium, dietary fiber and potassium, which are underconsumed and sodium, saturated fat and added sugars, which are overconsumed (Table D3.1). In addition, diet analysis results showed that 5 percent or more of women who are lactating have intakes below the EAR for folate, magnesium, copper, thiamin, vitamin A, and zinc. Vitamin D, folate/folic acid and zinc are unique in that >5 percent of women are not meeting the EAR from foods alone, but the use of dietary supplements by women who are lactating can lead to some wormen exceeding the UL [...] Iron may be overconsumed by women who are lactating, with 29 percent of those taking supplements exceeding the UL compared to <3 percent of women who are lactating who are not taking supplements (Table D3.1). Lastly, choline and magnesium are underconsumed in the diets of women who are lactating and should be considered for further evaluation." In other words, though lactating women are on the right track in terms of healthful eating, there's still lots of room for improvement.

This section ends with strategies for women who are lactating, support for federal programs, need for future research, and extensive references.

And that brings us to the end of today's overview! We are slowly but surely working our way through section D! Next up, we have diet and health relationships from birth to 24 months, so stay tuned...

 

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