Dietary Reference Intakes should be updated to better combat nutrient deficiency in U.S., authors say

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A group of leading dietary supplement and nutrition experts are proposing that Dietary Reference Intakes (DRIs) in the United States be updated for a handful of critical nutrients that Americans are likely deficient in. In a recently published Nutrients¹ article, the authors propose either amending or creating DRIs for the nutrients vitamin K, magnesium, lutein, and omega-3 fatty acids EPA and DHA. They also state that nutritional supplementation is a means of helping the public increase their intake of these nutrients if intake is otherwise lower than recommended.

The U.S. Dietary Guidelines for Americans (DGA), first established in 1980, advise the U.S. population on nutrition recommendations to maintain overall health, meet nutrient needs, and prevent diet-related chronic diseases, and is the backbone of federal nutrition programs. The latest recommendations, the “2020-2025 Dietary Guidelines for Americans,” were published earlier this year. DGA’s dietary recommendations are based on dietary reference intakes, or DRIs, which encapsulate the following values: Recommended Dietary Allowance (RDA), Adequate Intake (AI), Tolerable Upper Intake Level (UL), and Estimated Average Requirement (EAR). Researchers and policymakers use DRIs to make recommendations to help the public meet their nutrition requirements. The 2020-2025 Dietary Guidelines for Americans also acknowledge the useful role of dietary supplements in helping Americans meet their nutrient intake needs if it’s challenging to meet those needs through diet alone.

The authors, whose recommendations were recently published in the journal Nutrients, suggest it might be time to update some DRI values especially to more accurately reflect nutrient requirements determined by modern science and the latest health information, which would in turn modernize public health recommendations for nutrient intake. They point out that many U.S. nutrient recommendations have not been updated for decades.

Lutein

The carotenoid lutein plays a crucial role in healthy vision, as it is one of the key nutrients to populate the macular pigment in the retina. It is also the predominant carotenoid in the brain, the Nutrients authors note. Lutein is important not only to visual performance but also to cognitive function such as verbal fluency, memory, and processing speed and accuracy, they write.

The authors observe that typical lutein intake in the U.S. is 1-2 mg/day, which is lower than the 10 mg/day studied in the National Eye Institute’s Age-Related Eye Disease Study 2 (AREDS 2), which found benefits of lutein supplementation for certain subgroups. In addition, lutein doses as high as 20-40 mg/day have been either studied or been shown to be safe.

Currently, there is no DRI established for lutein. The Nutrients authors write that, based on current research evidence showing the positive effects of lutein intake: “In summary, there is evidence to support the promulgation of lutein DRI to achieve [macular pigment optical density] levels that are associated with healthy visual and brain function.”

EPA + DHA

The Global Organization for EPA and DHA Omega-3s (GOED) has been part of a global charge for the past decade to establish a DRI for omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Supplementation and adequate status of these fatty acids have been linked to improved cardiovascular and cognitive function, as well as lower total mortality.

EPA and DHA omega-3s currently do not have an established DRI, although both have been nominated for a DRI. At present, the Institute of Medicine says it has not concluded that there is sufficient evidence to establish a DRI. Meanwhile, intake recommendations for these nutrients exist in other countries.

In 2019, FDA appeared to sanction a new qualified health claim for EPA and DHA linked to reduced risk of hypertension and coronary heart disease, and updated the upper limit for EPA and DHA in supplements from 3 g/day to 5 g/day. Still, no DRI exists in the U.S.. The Nutrients authors state, “[T]he growth in evidence associating higher EPA+DHA levels with beneficial health outcomes coupled with updated safety data is sufficient to justify setting EPA + DHA DRIs to achieve target blood ranges.”

Vitamin K

Growing research shows that the fat-soluble vitamin K—and, specifically the form of vitamin K2 MK-7—is linked not only to cardiovascular health but also bone health. Low vitamin K2 status is associated with low bone mineral density—and, therefore, risk of fracture—and an increased risk of cardiovascular disease and death. Meanwhile, the other form of vitamin K—vitamin K2—plays a key role in blood clotting.

Vitamin K does have an overall DRI value; however, given current scientific evidence showing the unique health benefits of each vitamin K form (notably, blood clotting for vitamin K1 and cardiovascular/bone health benefits for vitamin K2), the Nutrients authors suggest that perhaps the vitamin K DRI could be updated to distinguish between the two, “possibly dividing the DRI into vitamin K1 and K2 forms.”

Magnesium

The Nutrients researchers also observe that magnesium “has been repeatedly identified as an under-consumed nutrient,” despite its important role in functions such as vitamin D metabolism and bone health and the fact that “almost every organ system is affected by the availability of Mg.”

Magnesium currently does have a DRI established; however, the Nutrients authors note that the amount of magnesium not only consumed but also absorbed by the body can differ depending on factors such as weight, sex, and ethnicity. They advise, “Current DRIs need to be updated to consider physiological factors, i.e., body mass and obesity…” There is also a need to update food databases to better estimate the amount of magnesium and other nutrients in food, they said.

Biomarkers

Finally, the authors state, there is a need for better biomarkers to help assess nutrient deficiencies and to better target healthy dietary intake levels. “There is an opportunity to modernize vitamin and mineral intake recommendations based on biomarker or surrogate endpoint levels needed to ‘prevent deficiency’ with DRIs based on the ranges of biomarker or surrogate endpoints levels that support normal cell/organ/tissue function in healthy individuals, and to establish DRIs for bioactive compounds.”

The growing trend of personalized nutrition also requires updated nutrient targets, the authors said, adding, “We propose greater research investment in validating biomarkers and metabolic health measures and the development and use of inexpensive diagnostic devices. Data generated from such approaches will help elucidate optimal nutrient status, provide objective evaluations of an individual’s nutritional status, and serve to provide personalized nutrition guidance.”

In conclusion, the authors write, “Underconsumption of some essential nutrients and food bioactive components, especially from food alone, is still a concern in the U.S. population, even though dietary guidance recognizes the contributions from food fortification and vitamin and mineral dietary supplements. The DGA aim is to provide recommendations for healthy eating to promote health and prevent disease, and are updated periodically to incorporate current scientific evidence; yet, recommended intakes still rely on DRIs established decades ago. Moreover, U.S. DRIs define dietary intakes needed to maintain nutritional status at levels that prevent vitamin/mineral deficiency diseases; DRIs should be revised to be based on intake levels that provide cells, organs, and tissues with access to adequate amounts of micronutrients (and bioactives) to functional optimally, i.e., healthy structure/function outcomes."

Many of the authors of the Nutrients paper were speakers at the Council for Responsible Nutrition’s (CRN; Washington, DC) October 2020 “Science in Session: 2020” virtual conference, whose focus was “challenges and opportunities for public health recommendations around dietary supplements.”

Reference

1. McBurney MI et al. “Beyond nutrient deficiency—Opportunities to improve nutritional status and promote health modernizing DRIs and supplementation recommendations.” Nutrients. Published online May 28, 2021. Accessed here.