Zinc is an essential micronutrient that is needed for numerous critical health functions in the body. It is estimated that 17 to 20% of the global population is at risk for zinc deficiency, with certain groups at higher risk. The provision of supplemental zinc is a convenient and effective option for treating zinc deficiency and maintaining healthy levels of zinc. Several zinc salts are available for use in supplements. However, little information is available comparing the absorption and bioavailability of these different chemical forms of zinc. In this narrative review, we provide an overview of zinc absorption and bioavailability, discuss indicators of zinc status and risk factors for zinc deficiency, and review clinical studies comparing the absorption and bioavailability of different chemical forms of zinc in humans. This review of the clinical evidence suggests that zinc glycinate and zinc gluconate are better absorbed than other forms of zinc.

Adequate consumption of nutrients that support infant neurodevelopment is critical among pregnant women and women of childbearing age. Understanding the potential effects of socioeconomic inequalities on nutrient gaps in these life stages is thus important for informing strategies to mitigate negative health consequences. Usual intake (foods and dietary supplements) of neurodevelopment-related nutrients was determined from 24 h recalls among women of childbearing age and pregnant women (20–44 years) using data from 2007–2018 NHANES. Usual intake was compared across household food security, poverty-to-income ratio (PIR), and household participation in federal food and nutrition assistance programs. Intake of EPA + DHA was universally low with >95% of all women (pregnant and non-pregnant) below the DGA recommendation from foods alone. Women in households that participated in the Supplemental Nutrition Assistance Program had a significantly lower intake of multiple nutrients relative to those who did not participate. For example, 50% had intakes below the estimated average requirement (EAR) for vitamin A (versus 32%), 42% were below the EAR for calcium (versus 33%) and 65% were below the EAR for magnesium (versus 42%). Similar gradients were observed by PIR and household food security, and among pregnant women whereby gaps were more evident in those experiencing socioeconomic inequalities. The use of dietary supplements attenuated shortfalls for most nutrients. These findings highlight a critical need to support the nutritional requirements for women of childbearing age and pregnant women.

Women of childbearing age (WCBA) and women of menopausal age (WMENO) have distinct nutritional needs. Understanding nutrient intake and status in these life stages is critical for tailoring dietary recommendations. The objectives of this study were to evaluate total estimated usual nutrient intakes from food and food plus supplements and to compare these to established recommendations for WCBA and WMENO life stages and examine associations between self-reported estimated usual intakes and nutrient status biomarkers. Twenty-four-hour dietary recall data from 2011–2016 NHANES were used to estimate usual intake of nutrients from food and food plus supplements for WCBA (aged 15–44 y, n = 4,134) and WMENO (aged 40–65 y, n = 3,438). Estimates of mean usual intake were derived and compared across clinically defined nutrient biomarker categories. Both young (aged 15–30 y) and older (aged 31–44 y) WCBA had intakes from food below the Estimated Average Requirement (EAR) for calcium (49% and 44%, respectively), magnesium (62%, 44%), and vitamins A (50%, 44%), C (47%, 46%), D (>97%, >97%), and E (92%, 88%). Similarly, perimenopausal (aged 40–50 y) and menopausal (aged 51–65 y) women had intakes from food below the EAR for calcium (48% and 74%, respectively), magnesium (50%, 49%), and vitamins A (44%, 37%), C (44%, 41%), D (>97%, >97%), and E (88%, 86%). Nutrient gaps decreased with supplement usage. For folate, vitamins D and B-12, and DHA, women in the lowest biomarker category (indicating increased risk of deficiency) had significantly lower intake from food (315.2 ± 25.9 compared with 463.8 ± 5.2 µg dietary folate equivalents, 3.5 ± 0.1 compared with 4.2 ± 0.1 µg, 3.6 ± 0.2 compared with 4.3 ± 0.1 µg, and 0.037 ± 0.005 compared with 0.070 ± 0.006 g, respectively; P < 0.01) of the corresponding nutrient compared with the highest biomarker category. Substantial percentages of WCBA and WMENO are not meeting recommendations for multiple nutrients, whereas supplement usage partially fills nutrient gaps. Dietary intake was positively associated with most nutrient status biomarkers. Specific guidance is needed to ensure adequate nutrient intakes and nutrient status during these critical life stages.

A limited amount of research has demonstrated beneficial effects of caffeine and theanine supplementation for enhancement of mental performance. The purpose of this investigation was to determine whether the acute ingestion of a supplement containing caffeine, theanine and tyrosine improves mental and physical performance in athletes. Twenty current or former male collegiate athletes (age: 20.5 ± 1.4 y; height: 1.82 ± 0.08 m; weight: 83.9 ± 12.6 kg; body fat: 13.8 ± 5.6%) completed this randomized, double-blind, placebo-controlled crossover trial. After familiarization, each participant completed two identical testing sessions with provision of a proprietary dietary supplement (SUP) containing caffeine theanine and tyrosine or a placebo (PL). Within each testing session, participants completed assessments of mental and physical performance before and after provision of SUP or PL, as well as after two rounds of exercise. Assessments were performed using a performance testing device (Makoto Arena) that evaluated multiple aspects of mental and physical performance in response to auditory and visual stimuli. Testing was performed both with the body in a static position and during dynamic movement. General linear models were used to evaluate the effects of SUP and PL on performance. Changes in movement accuracy during performance assessment were greater following SUP ingestion as compared to PL for both static and dynamic testing (SUP: + 0.4 to 7.5%; PL: − 1.4 to 1.4% on average; p < 0.05). For dynamic testing, the change in number of targets hit was higher and the change in average hit time was lower with SUP as compared to PL (p < 0.05). However, there were no differences between conditions for the changes in number of targets hit or average hit time during static testing. There were no differences in changes of subjective variables during either condition, and performance measures during the two rounds of exercise did not differ between conditions (p > 0.05). The present results indicate that a combination of a low-dose of caffeine with theanine and tyrosine may improve athletes’ movement accuracy surrounding bouts of exhaustive exercise without altering subjective variables. Based on this finding, supplementation with caffeine, theanine and tyrosine could potentially hold ergogenic value for athletes in sports requiring rapid and accurate movements. NCT03019523. Registered 24 January 2017.

The US Dietary Guidelines for Americans (DGA) provide dietary recommendations to meet nutrient needs, promote health, and prevent disease. Despite 40 years of DGA, the prevalence of under-consumed nutrients continues in the US and globally, although dietary supplement use can help to fill shortfalls. Nutrient recommendations are based on Dietary Reference Intakes (DRIs) to meet the nutrient requirements for nearly all (97 to 98 percent) healthy individuals in a particular life stage and gender group and many need to be updated using current evidence. 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 ranges of biomarker or surrogate endpoints levels that support normal cell/organ/tissue function in healthy individuals, and to establish DRIs for bioactive compounds. We recommend vitamin K and Mg DRIs be updated and DRIs be established for lutein and eicosapentaenoic and docosahexaenoic acid (EPA + DHA). With increasing interest in personalized (or precision) nutrition, 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.