Current Recommended Dietary Allowance Research Articles

The effects of whey, pea, and collagen protein supplementation beyond the recommended dietary allowance on integrated myofibrillar protein synthetic rates in older males: a randomized controlled trial

BackgroundSkeletal muscle mass is determined predominantly by feeding-induced and activity-induced fluctuations in muscle protein synthesis (MPS). Older individuals display a diminished MPS response to protein ingestion, referred to as age-related anabolic resistance, which contributes to the progression of age-related muscle loss known as sarcopenia. ObjectivesWe aimed to determine the impact of consuming higher-quality compared with lower-quality protein supplements above the recommended dietary allowance (RDA) on integrated MPS rates. We hypothesized that increasing total protein intake above the RDA, regardless of the source, would support higher integrated rates of myofibrillar protein synthesis. MethodsThirty-one healthy older males (72 ± 4 y) consumed a controlled diet with protein intake set at the RDA: control phase (days 1–7). In a double-blind, randomized controlled fashion, participants were assigned to consume an additional 50 g (2 × 25g) of whey (n = 10), pea (n = 11), or collagen (n = 10) protein each day (25 g at breakfast and lunch) during the supplemental phase (days 8–15). Deuterated water ingestion and muscle biopsies assessed integrated MPS and acute anabolic signaling. Postprandial blood samples were collected to determine feeding-induced aminoacidemia. ResultsIntegrated MPS was increased during supplemental with whey (1.59 ± 0.11 %/d; P < 0.001) and pea (1.59 ± 0.14 %/d; P < 0.001) when compared with RDA (1.46 ± 0.09 %/d for the whey group; 1.46 ± 0.10 %/d for the pea group); however, it remained unchanged with collagen. Supplemental protein was sufficient to overcome anabolic signaling deficits (mTORC1 and rpS6), corroborating the greater postprandial aminoacidemia. ConclusionsOur findings demonstrate that supplemental protein provided at breakfast and lunch over the current RDA enhanced anabolic signaling and integrated MPS in older males; however, the source of additional protein may be an important consideration in overcoming age-related anabolic resistance.This trial was registered clinicaltrials.gov as NCT04026607.

Protein intake and physical function in older adults: A systematic review and meta-analysis.

The present study explored cross-sectional and longitudinal associations between protein intake and physical function in older adults. We conducted a systematic review and meta-analysis of cross-sectional and longitudinal studies that investigated the association between protein intake and measures of physical function in older adults. Cross-sectional, case-control, and longitudinal cohort studies that investigated the association between protein intake and physical function as a primary or secondary outcome in people aged 60+years were included. Studies published in languages other than English, Italian, Portuguese, or Spanish were excluded. Studies were retrieved from MEDLINE, SCOPUS, EMBASE, CINAHL, AgeLine, and Food Science Source databases through January 31, 2022. A pooled effect size was calculated based on standard mean differences (SMD), MD, log odds ratio (OR) and Z-score.. Twenty-two cross-sectional studies examined a total of 11,332 community-dwellers, hospitalized older adults, and elite senior athletes with a mean age of approximately 75 years. The pooled analysis indicated that a protein intake higher than the recommended dietary allowance (RDA) was significantly associated with higher Short Physical Performance Battery (SPPB) scores (SMD: 0.63, 95% CI: 0.27, 0.99, P-value: 0.0006), faster walking speed, greater lower-limb (SMD: 0.22, 95% CI: 0.04, 0.40, P-value: 0.02) and isometric handgrip strength (Z-score: 0.087, 95% CI: 0.046-0.128, P-value: 0.0001), and better balance (SMD: 0.33, 95% CI: 0.05, 0.62, P-value: 0.02). Nine longitudinal studies investigated 12,424 community-dwelling and native older adults with a mean age of approximately 85 years. A protein intake higher than the current RDA was not associated with lower decline in either isometric handgrip strength (logOR: 0.99, 95% CI: 0.97-1.02, P-value= 0.67) or walking speed (logOR: 0.92, 95% CI: 0.77-1.10, P-value= 0.35). A protein intake higher than the RDA is cross-sectionally associated with better physical performance and greater muscle strength in older adults. However, a high consumption of proteins does not seem to prevent physical function decline over time.

Folic Acid in Prenatal Supplements: Labeled Amounts Compared to Recommendations (P11-024-19)

ObjectivesMost prenatal supplements available in the US contain synthetic folic acid. We compared the labeled amounts of folic acid in prenatal supplements with: 1) the Recommended Dietary Allowance (RDA) of 360 mcg and Tolerable Upper Intake Level (UL) of 1000 mcg for pregnant women established by National Academies of Science, Engineering and Medicine’s Food and Nutrition Board (FNB) and expressed as synthetic folic acid from supplements and fortified foods; 2) current population-based Daily Values (DV) used for labeling dietary supplements and established by the US Food and Drug Administration (FDA); 3) FDA criteria for making a neural tube defects health claim on prenatal supplement labels; and 4) 2009/2016 recommendations for the prevention of neural tube defects by the US Preventive Services Task Force (USPSTF). In 2016, the FDA revised its DV to 600 mcg DFE folate (360 mcg folic acid) to reflect amounts consistent with the RDAs. This new DV is lower than the pre-2016 DV of 800 mcg from food and supplement sources and the 800 mcg level to make a health claim. MethodsWe reviewed the synthetic folic acid content as declared on prenatal supplement labels sold with and without a prescription, using data in the Dietary Supplements Label Database (DSLD) (website: https://dsld.nlm.nih.gov/dsld/) and DailyMed (website: https://dailymed.nlm.nih.gov/dailymed/index.cfm). ResultsThe many recommendations for folate versus folic acid are often unclear (e.g., Dietary Folate Equivalents vs. mcg folic acid). Amounts ≥ 800 mcg folic acid per serving, the prior DV, were present on 99% of 79 prescription and 91% of 121 nonprescription labels reviewed. 94% of the prescription and 16% of nonprescription prenatal supplements were labeled at 1000 mcg per serving, and none (0%) of the prescription and 74% of the nonprescription were labeled at 800 mcg. These labeled amounts (from supplements alone) were higher than the USPSTF recommended daily intake of 400 to 800 mcg and the current DV and RDA values. ConclusionsThe DV, UL, the criterion for making a health claim on prenatal supplement labels, the USPSTF recommendations, and the units used for expressing folate and folic acid recommendations need to be harmonized and clarified. Funding SourcesOffice of Dietary Supplements, NIH.

Current Concepts and Unresolved Questions in Dietary Protein Requirements and Supplements in Adults.

Protein needs for otherwise healthy individuals older than 19 years are defined by the recommended dietary allowance (RDA) at 0.80 g protein/kg/day. There is no recommendation in the current RDA for subpopulations of older adults or people in various pathological situations. Despite the lack of a separate recommendation, there exists a growing body of evidence that is strongly suggestive of an increased need and/or benefit for protein in older persons. That is, intakes beyond the RDA are, in older persons, associated with benefits. In addition, a number of catabolic states including critical illness also result in a sharp elevation in the needs for protein and amino acids. An underappreciated issue in protein nutrition is the impact of protein quality on clinically relevant outcomes. The introduction of a new protein scoring system—the digestible indispensable amino acid score (DIAAS)—for protein quality has raised a forgotten awareness of protein quality. The DIAAS, which replaces the protein digestibility-corrected amino acid score (PDCAAS), is based on ileal digestibility of protein and a different test protein than PDCAAS and has values greater than 1.0. The aim of this article is a brief review and summary recommendations for protein nutrition and protein requirements in populations who would benefit from more protein than the RDA. The emphasis of the review is on muscle protein turnover, and there is a discussion of the impact of protein quality, particularly as it applies to commercially available protein sources. The evidence for more optimal protein intakes is considered in light of the potential health risks of consumption of protein at levels greater than the RDA.

Variable Intensity Exercise Increases Protein Requirements in Active Male and Female Adolescents as Determined by the Indicator Amino Acid Oxidation (IAAO) Technique

Adolescence is characterized by the greatest increase in linear growth and accrual of fat‐free mass (FFM) during the life cycle. This growth spurt is optimized by adequate energy and protein intake. Active adolescents also display a greater FFM than their sedentary peers with the sexual dimorphism of puberty leading to a greater total gain in males than females. Given current evidence which suggest that protein requirement is higher in active adults than their sedentary counterparts, we aimed to determine the protein requirements of active, growing adolescents by utilizing the minimally invasive Indicator Amino Acid Oxidation (IAAO) technique. Fourteen active male (n=7; 13±0.6 years; 171±2.8 cm; 57.3±4.2 kg; 48.4±5.0 kg FFM; 0.3±0.2 years from peak height velocity (PHV); means±95% CI) and female (n=7; 11±0.4 years; 159±3.3 cm; 51.6±8.1 kg; 41.5±6.7 kg FFM; 0.5±0.4 years from PHV; means±95% CI) participants each underwent 6 metabolic trials that included an acute bout of a variable intensity exercise (modified Loughborough Intermittent Shuttle Test) followed by the ingestion of 8 hourly meals providing a variable amount of protein (0.2 – 2.67 g·kg−1·d−1), 6 g·kg−1 of carbohydrate, and sufficient energy to match habitual intake. Protein was provided as crystalline amino acid mixtures modeled on the basis of egg protein, with the exception of tyrosine (40 mg·kg−1·d−1) and phenylalanine (30.5 mg·kg−1·d−1 of which 5.46 mg·kg−1 was L‐[13C] phenylalanine over the final 4 drinks). After the determination of breath 13CO2 enrichment by continuous‐flow isotope ratio mass spectrometry and CO2 production by indirect calorimetry, the estimated average requirement (EAR) was determined from the breakpoint of the 13CO2 excretion (F13CO2) after application of a bi‐phase linear regression. Preliminary analysis of F13CO2 revealed breakpoints of 1.53 g·kg−1·d−1 (r2 = 0.57) and 1.34 g·kg−1·d−1 (r2 = 0.69) for males and females respectively. When normalized to FFM, the breakpoints were 1.97 ± 0.33 g·kg FFM−1·d−1 (r2 = 0.68) and 1.45 ± 0.22 g·kg FFM−1·d−1 (r2 = 0.63) for males and females, respectively. The breakpoints derived herein exceed current estimated breakpoint values using the IAAO method for sedentary adults and children (0.93 g·kg−1·d−1, and 1.3 g·kg−1·d−1 respectively). Adjusting for the upper 95% CI, a recommended dietary allowance (RDA) was determined to be 1.83 g·kg−1·d−1 and 1.54 g·kg−1·d−1 for males and females respectively. Our estimate of the RDA in active adolescents exceeds the current protein RDA based on the factorial estimate of nitrogen balance for adolescents (0.9 g·kg−1·d−1), suggesting that variable intensity exercise increases daily protein requirements in active adolescents (and especially males) to potentially support greater FFM development and/or the replenishment of exercise‐induced oxidative losses.Support or Funding InformationSupported by the Ajinomoto Innovation Alliance Program.

The Link between Dietary Protein Intake, Skeletal Muscle Function and Health in Older Adults.

Skeletal muscle mass and function are progressively lost with age, a condition referred to as sarcopenia. By the age of 60, many older adults begin to be affected by muscle loss. There is a link between decreased muscle mass and strength and adverse health outcomes such as obesity, diabetes and cardiovascular disease. Data suggest that increasing dietary protein intake at meals may counterbalance muscle loss in older individuals due to the increased availability of amino acids, which stimulate muscle protein synthesis by activating the mammalian target of rapamycin (mTORC1). Increased muscle protein synthesis can lead to increased muscle mass, strength and function over time. This review aims to address the current recommended dietary allowance (RDA) for protein and whether or not this value meets the needs for older adults based upon current scientific evidence. The current RDA for protein is 0.8 g/kg body weight/day. However, literature suggests that consuming protein in amounts greater than the RDA can improve muscle mass, strength and function in older adults.

Are the Recommended Dietary Allowances for Vitamins Appropriate for Elderly People?

BackgroundAn adequate vitamin intake is essential for a good nutritional status, especially in older women, who are more sensitive to nutritional deficiencies. The American, European and Italian Recommended Dietary Allowances (RDAs) derive mainly from studies on adults, and it is not clear whether they also apply to elderly people. Comparing the RDAs with the actual vitamin intake of a group of healthy older women could help to clarify the real needs of elderly people. ObjectiveOur aim was to compare the American, European, and Italian RDAs with the actual vitamin intake of a group of healthy older women. DesignThis was a cross-sectional study. ParticipantsThe study included 286 healthy women aged older than 65 years. Main outcome measuresFor each micronutrient, the 50th percentile of the distribution of its intake was considered as the average requirement, and the corresponding calculated RDA for our sample was the average requirement×1.2, as recommended by the US Food and Nutrition Board. This calculated RDA was then compared with the American, European, and Italian RDAs. Statistical analyses performedStudent’s t test or the Mann-Whitney test (after checking the normal distribution of the micronutrient) for continuous variables; the χ2 test for categorical variables. ResultsThe calculated RDA were 2,230 μg retinol equivalents for vitamin A, 2.8 μg for vitamin B-12, 0.9 mg for thiamin, 1.4 mg for riboflavin, 3.6 mg for pantothenic acid, 1.4 mg for vitamin B-6, 320 μg for folic acid, and 115 mg for vitamin C. ConclusionsOur findings suggest that the current RDAs are adequate for older women’s intake of riboflavin, vitamin B-6, and folic acid, but should be raised for vitamin B-12 and for vitamin C.

Assessment of protein requirement in octogenarian women with use of the indicator amino acid oxidation technique

Data on the protein requirements of elderly adults are limited, because it is impractical to conduct repeated nitrogen balance protocols in these vulnerable humans. This study was designed to determine the dietary protein requirement of elderly women by using the recently developed minimally invasive indicator amino acid oxidation (IAAO) technique. Six white women aged 80-87 y [mean ± SEM: 82 ± 1 y and body mass index (in kg/m²) 26 ± 2] completed a 3-d protocol 7 times. Each woman consumed an adaptation diet for 2 d and on day 3 consumed a complete test diet with a crystalline amino acid mixture containing 1 of 7 protein intakes (0.1, 0.3, 0.6, 0.9, 1.2, 1.5, or 1.8 g · kg⁻¹ · d⁻¹) tested randomly. A group-based protein requirement was assessed by using a nonlinear mixed model of protein intake and L-[1-¹³C]phenylalanine oxidation. The breakpoint, at which there was no further decline in the rate of appearance of ¹³C in the breath, was used as an index of the mean protein requirement. The mean protein requirement (95% CI) was 0.85 (0.60, 1.09) g · kg⁻¹ · d⁻¹. This requirement is 29% higher than the current Estimated Average Requirement (EAR) for adults of 0.66 g · kg⁻¹ · d⁻¹ based on the nitrogen balance technique, although the 95% CI includes the current EAR. The corresponding adequate protein allowance of 1.15 (0.77, 1.54) g · kg⁻¹ · d⁻¹ is 44% higher, although the 95% CI includes the Recommended Dietary Allowance (RDA) of 0.80 g · kg⁻¹ · d⁻¹. Notwithstanding uncertainty about the validity of the use of the IAAO technique to assess protein requirements, the results of this study with octogenarian women suggest that the current EAR and RDA for elderly women may be underestimated. The limitations of this short-term, noninvasive method underscore the need for new research that uses alternative experimental designs and measuring physiologic, morphologic, and health-related outcomes.

Authors' Perspective: What is the Optimum Intake of Vitamin C in Humans?

The recommended dietary allowance (RDA) of vitamin C has traditionally been based on the prevention of the vitamin C deficiency disease, scurvy. While higher intakes of vitamin C may exert additional health benefits, the limited Phase III randomized placebo-controlled trials (RCTs) of vitamin C supplementation have not found consistent benefit with respect to chronic disease prevention. To date, this has precluded upward adjustments of the current RDA. Here we argue that Phase III RCTs—designed principally to test the safety and efficacy of pharmaceutical drugs—are ill suited to assess the health benefits of essential nutrients; and the currently available scientific evidence is sufficient to determine the optimum intake of vitamin C in humans. This evidence establishes biological plausibility and mechanisms of action for vitamin C in the primary prevention of coronary heart disease, stroke, and cancer; and is buttressed by consistent data from prospective cohort studies based on blood analysis or dietary intake and well-designed Phase II RCTs. These RCTs show that vitamin C supplementation lowers hypertension, endothelial dysfunction, chronic inflammation, and Helicobacter pylori infection, which are independent risk factors of cardiovascular diseases and certain cancers. Furthermore, vitamin C acts as a biological antioxidant that can lower elevated levels of oxidative stress, which also may contribute to chronic disease prevention. Based on the combined evidence from human metabolic, pharmacokinetic, and observational studies and Phase II RCTs, we conclude that 200 mg per day is the optimum dietary intake of vitamin C for the majority of the adult population to maximize the vitamin's potential health benefits with the least risk of inadequacy or adverse health effects.

Daily intake of 4 to 7 μg dietary vitamin B-12 is associated with steady concentrations of vitamin B-12–related biomarkers in a healthy young population

Studies have questioned whether the current Recommended Dietary Allowance (RDA) of 2.4 microg vitamin B-12/d is adequate. We examined the association between dietary vitamin B-12 intake and biomarkers of vitamin B-12 status. Dietary vitamin B-12 intake was estimated, and biomarkers of vitamin B-12 status were measured, in healthy men and women (n = 299; age range: 18-50 y) who were recruited from a Florida community. The National Cancer Institute Diet History Questionnaire was used. Plasma cobalamin, total transcobalamin, holo-transcobalamin, methylmalonic acid (MMA), total homocysteine (tHcy), and autoantibodies against intrinsic factor (IF) and Helicobacter pylori were analyzed in blood samples. Antibodies to H. pylori were detected in 12% of subjects (35/299), and negative results for IF antibodies were obtained for all subjects. The intake of vitamin B-12 correlated significantly with cobalamin, holo-transcobalamin, MMA, and tHcy. Subjects were divided into quintiles on the basis of their dietary vitamin B-12 intake (range: 0.42-22.7 microg/d), and biomarkers of vitamin B-12 status were plotted against estimated dietary vitamin B-12 intake. All biomarkers appeared to level off at a daily dietary vitamin B-12 intake between 4.2 and 7.0 microg. In persons with normal absorption, our data indicate that an intake of 4-7 microg vitamin B-12/d is associated with an adequate vitamin B-12 status, which suggests that the current RDA of 2.4 microg vitamin B-12/d might be inadequate for optimal biomarker status even in a healthy population between 18 and 50 y of age.

Increasing Dietary Protein Requirements in Elderly People for Optimal Muscle and Bone Health

Osteoporosis and sarcopenia are degenerative diseases frequently associated with aging. The loss of bone and muscle results in significant morbidity, so preventing or attenuating osteoporosis and sarcopenia is an important public health goal. Dietary protein is crucial for development of bone and muscle, and recent evidence suggests that increasing dietary protein above the current Recommended Dietary Allowance (RDA) may help maintain bone and muscle mass in older individuals. Several epidemiological and clinical studies point to a salutary effect of protein intakes above the current RDA (0.8 g/kg per day) for adults aged 19 and older. There is evidence that the anabolic response of muscle to dietary protein is attenuated in elderly people, and as a result, the amount of protein needed to achieve anabolism is greater. Dietary protein also increases circulating insulin-like growth factor, which has anabolic effects on muscle and bone. Furthermore, increasing dietary protein increases calcium absorption, which could be anabolic for bone. Available evidence supports a beneficial effect of short-term protein intakes up to 1.6 to 1.8 g/kg per day, although long-term studies are needed to show safety and efficacy. Future studies should employ functional measures indicative of protein adequacy, as well as measures of muscle protein synthesis and maintenance of muscle and bone tissue, to determine the optimal level of dietary protein. Given the available data, increasing the RDA for older individuals to 1.0 to 1.2 g/kg per day would maintain normal calcium metabolism and nitrogen balance without affecting renal function and may represent a compromise while longer-term protein supplement trials are pending.

Does the MTHFR 677C→T variant affect the Recommended Dietary Allowance for folate in the US population?

Background: The MTHFR 677C→T variant is associated with reduced enzyme activity, abnormalities of folate metabolism, and potential increase in folate requirement. The effect of this variant on the Recommended Dietary Allowance (RDA) for folate is unclear.Objective: The aim of this study was to assess the effect of the MTHFR 677C→T polymorphism on the current folate RDA for US adults aged ≥19 y (400 μg/d) by race and ethnicity.Design: We calculated the projected RDA for folate for each racial and ethnic group according to the methods of the Institute of Medicine. We modeled the projected RDA with different hypothetical effect sizes ranging from 5% to 50%. The RDA value was then weighted according to the US prevalence of the TT (or the combined CT/TT) genotype in each racial and ethnic group.Results: The projected RDA ranges were based on TT genotype frequencies and on different effect sizes (5–50%) that ranged from 400 to 421 μg/d for non-Hispanic whites, 401–436 μg/d for Mexican Americans, and 400–402 μg/d for non-Hispanic blacks.Conclusions: Our findings suggest that the current RDA for folate differs little for non-Hispanic whites, non-Hispanic blacks, and Mexican Americans irrespective of the MTHFR TT genotype, and, from a population perspective, the MTHFR 677C→T variant does not warrant modifications to the current RDA for dietary folate at this time.

Immunology: Functions to Assess Nutrient Requirements

In July 1994, the U.S.D.A. Western Human Nutrition Research Center and the University of California at Davis co-sponsored a symposium on “New Approaches to Define Nutrient Requirements.” A major objective of the symposium was to define functional parameters of human health which could be used in determining future recommended dietary allowances (RDA). This paper reviews the compelling evidence that certain vitamins and other micronutrients given in levels above the current RDA have critical, beneficial effects on human immune responses. Thus, the argument is made that immune function should be considered in the development of the next national nutrition recommendations.

The acute and chronic toxic effects of vitamin A

The acute and chronic effects of vitamin A toxicity are well documented in the literature. Emerging evidence suggests that subtoxicity without clinical signs of toxicity may be a growing concern, because intake from preformed sources of vitamin A often exceeds the recommended dietary allowances (RDA) for adults, especially in developed countries. Osteoporosis and hip fracture are associated with preformed vitamin A intakes that are only twice the current RDA. Assessing vitamin A status in persons with subtoxicity or toxicity is complicated because serum retinol concentrations are nonsensitive indicators in this range of liver vitamin A reserves. The metabolism in well-nourished persons of preformed vitamin A, provided by either liver or supplements, has been studied by several research groups. To control vitamin A deficiency, large therapeutic doses are administered in developing countries to women and children, who often are undernourished. Nevertheless, little attention has been given to the short-term kinetics (ie, after absorption but before storage) of a large dose of vitamin A or to the short- and long-term effects of such a dose given to lactating women on serum and breast-milk concentrations of retinol and its metabolites. Moreover, appropriate dosing regimens have not been systematically evaluated to ascertain the quantitative improvement in vitamin A status of the women and children who receive these supplements. The known acute and chronic effects of vitamin A toxicity have been reported previously. However, further research is needed to ascertain the areas of the world in which subclinical toxicity exists and to evaluate its effects on overall health and well-being.

Protein Needs of Older Adults Engaged in Resistance Training: A Review

Protein recommendations by some professional organizations for young adults engaged in resistance training (RT) are higher than the recommended dietary allowance (RDA), but recommendations for resistance-training older adults (>50 years old) are not well characterized. Some argue that the current RDA is adequate, but others indicate increased protein needs. Although concerns have been raised about the consequences of high protein intake, protein intake above the RDA in older adults is associated with increased bone-mineral density when calcium intake is adequate and does not appear to compromise renal health in older individuals with normal renal function. Individual protein needs for older adults in RT are likely highly variable according to health and training regimen, but an intake of 1.0-1.3 g x kg(-1) x day(-1) should adequately and safely meet the needs of older adults engaged in RT, provided that their energy needs are met.

Supplements and Tuning Up Metabolism

Americans’ intake of the 40 essential micronutrients (vitamins, minerals, and other biochemicals that humans require) is commonly thought to be adequate. Classic deficiency diseases, such as scurvy, beriberi, pernicious anemia, and rickets, are rare. The evidence suggests, however, that much chronic metabolic damage occurs at levels between the level that causes acute micronutrient deficiency disease and the recommended dietary allowances (RDAs). 5 In addition, the prevention of more subtle metabolic damage may not be addressed by current RDAs. When one input in the metabolic network is inadequate, repercussions are felt on a large number of systems and can lead to degenerative disease. This may, for example, result in an increase in DNA damage (and cancer), neuron decay (and cognitive dysfunction) or mitochondrial decay (and accelerated aging and degenerative diseases). The optimum amount of folic acid or zinc that truly is ‘‘required” is the amount that minimizes DNA damage and maximizes a healthy life span, which is higher than the amount needed to prevent acute deficiency disease. The requirements of the elderly for vitamins and metabolites are likely to differ from those of the young, but this issue has not been examined seriously. An optimal intake of micronutrients and metabolites also varies with genetic constitution. A tune-up of micronutrient metabolism should give a marked increase in health at little cost. It is a distortion of priorities for much of the world’s population to have an inadequate intake of a vitamin or mineral, at great cost to health, when a year’s supply of a daily multivitaminmineral pill as insurance against deficiencies costs less than a few packs of cigarettes. The poor, in general, eat the worst diets and have the most to gain from multivitamin-mineral supplementation and improvement in diet.

Vitamin A in dietary supplements and fortified foods: Too much of a good thing?

Vitamin A consumption by many Americans is quite high, in part because of the consumption of fortified foods and the use of vitamin supplements. Most multivitamin supplements provide two or more times the recommended dietary allowance (RDA) for vitamin A because the daily value (DV) is based on 1968 and not current RDAs. Consumption of just one multivitamin often provides excessive vitamin A, the majority of it as preformed vitamin A esters. Given recent epidemiologic evidence that suggests a link between chronic intakes of vitamin A that exceed the RDA and hip fractures, it may be time to reexamine food and supplement fortification policies and to discontinue the clinical practice of prescribing two multivitamins to the elderly and other patients whose needs for certain micronutrients are high.

Dietary antioxidant intake in patients at risk for second primary cancer.

To analyze dietary antioxidant intake for head and neck cancer patients at risk for development of second primary cancers. Prospective observational study. Twenty-four patients underwent three random, unscheduled, 24-hour dietary recalls over a 15-day period within 6 to 60 months after successful treatment for stage I or II oral cavity squamous cell carcinoma. The study sample had a lower mean daily dietary intake of fruits and vegetables and antioxidant nutrients, including vitamins A, C, E, and total carotenes than age- and sex-matched historic control subjects (all P <.05 except vitamin A). A positive linear correlation was noted between daily servings of F&V and dietary intake of vitamins A, C, E, and total carotenoids (all P <.05 except vitamin A). Compared to current recommendations, the study sample had lower mean daily dietary intake of vitamins A, C, and E (P =.81,.06, and <.01) and servings of fruits and vegetables (P <.01). When vitamin supplements were included in the analysis, mean daily intake exceeded recommended dietary allowance (RDA) for vitamins A, C, and E (all P <.05). This study suggests that patients treated for early-stage oral cavity carcinoma, at risk for second primary cancers, have a statistically significant deficiency in dietary (food) sources of antioxidant nutrients when compared with both historic control subjects and current recommendations. Vitamin supplementation significantly exceeded current RDAs. Because increased fruit and vegetable intake, but not vitamin supplementation exceeding RDA, is associated with reduced cancer risk, physicians may consider recommending at least five daily servings of fruits and vegetables as an alternative to vitamin supplementation.

Micronutrients and genomic stability: a new paradigm for recommended dietary allowances (RDAs)

Diet as a key factor in determining genomic stability is more important than previously imagined because we now know that it impacts on all relevant pathways, namely exposure to dietary carcinogens, activation/detoxification of carcinogens, DNA repair, DNA synthesis and apoptosis. Current recommended dietary allowances for vitamins and minerals are based largely on the prevention of diseases of deficiency such as scurvy in the case of vitamin C. Because diseases of development, degenerative disease and aging itself are partly caused by damage to DNA it seems logical that we should focus better our attention on defining optimal requirements of key minerals and vitamins for preventing damage to both nuclear and mitochondrial DNA. To date, our knowledge on optimal micronutrient levels for genomic stability is scanty and disorganised. However, there is already sufficient evidence to suggest that marginal deficiencies in folate, vitamin B12, niacin and zinc impact significantly on spontaneous chromosome damage rate. The recent data for folate and vitamin B12 in humans with respect to micronucleus formation in blood and epithelial cells provide compelling evidence of the important role of these micronutrients in maintenance of genome integrity and the need to revise current RDAs for these micronutrients based on minimisation of DNA damage. Appropriately designed in vitro studies and in vivo placebo controlled trials with dose responses using a complementary array of DNA damage biomarkers are required to define recommended dietary allowances for genomic stability. Furthermore these studies would have to be targeted to individuals with common genetic polymorphisms that alter the bioavailability of specific micronutrients and the affinity of specific key enzymes involved in DNA metabolism for their micronutrient co-factor. That there is a need for an international collaborative effort to establish RDAs for genomic stability is self-evident.

Equations for predicting the energy requirements of healthy adults aged 18–81 y

Recent studies have questioned the accuracy of using the current recommended dietary allowances (RDAs) to predict usual energy requirements in adults. We developed equations to predict adult energy requirements from simple anthropometric and laboratory measures by using the doubly labeled water method to determine each subject's total energy expenditure (TEE), which is equal to usual energy requirements in weight-stable individuals. This was a cross-sectional study conducted with 93 healthy, free-living adults [44 men and 49 women; body mass index range (in kg/m2): 18.4-31.8] aged 18-81 y. Body fat and fat-free mass were measured by underwater weighing, physical activity was estimated by using activity monitors, and resting energy expenditure was determined by indirect calorimetry. Information on anthropometric variables and reported strenuous activity was also collected. Three regression equations were developed and verified for accuracy by using bootstrap analysis and doubly labeled water data published by other research groups. The first equation used information on only age, weight, height, and sex and had an SEE for prediction of TEE of 1.80 MJ/d. The second and third equations used different combinations of basic and laboratory data and had SEEs of 1.55 and 1.65 MJ/d, respectively. With use of the same analytic approaches, the RDAs for energy were shown to significantly underestimate usual energy needs by approximately 10%; the extent of underestimation was significantly greater for subjects with high TEEs than for subjects with low TEEs. Regression equations based on doubly labeled water measurements of TEE appear to be more accurate than the current RDAs for predicting energy requirements in healthy, nonobese adults living in affluent countries.