America's Phytonutrient Report: Immune Health by Color - Nutrilite

AMERICA’S PHYTONUTRIENT REPORT: IMMUNE HEALTH BY COLORThe following sections outline the select antioxidant vitamins and trace minerals included in this report.Each section identifies the top food sources in the diet of American adults based on a published analysisof dietary intake data collected in 1994-1996, 11 as well as an overview of the existing peer-reviewedliterature on the effects of these vitamins and trace minerals on immune health.T H E A N T I OX I D A N T V I TA M I N SVitamin AResearch: The “anti-infective” properties of vitamin A play a vital rolein the maintenance and functioning of both the innate and adaptiveimmune systems. 12 And while vitamin A is not generally associatedwith cold and flu season directly, like vitamin C for example, researchsuggests vitamin A deficiency interferes with normal regeneration ofmucosal barriers damaged by infection, and is associated with recurrentinfections. 13 Further, vitamin A plays a role in the developmentof both T-helper (Th) cells and B cells; a deficiency of which couldlead to diminished antibody-mediated responses. 14 Previous studiesof both humans and animals have shown that vitamin A deficiencyresults in increased severe infection incidence and mortality,particularly among children in lesser developed countries. 15,16Food Sources: Based on a published analysis of key nutrientsources in the diets of American adults, 11 carrots were the primarysource of vitamin A (measured in IUs/day) in the diet, contributing38.6% of total intake of the nutrient from food sources. Other topvegetable sources of vitamin A included tomatoes (6.1%), spinachand salad greens (5.1%), sweet potatoes (4.6%), and tomato andvegetable juices (2.2%).The plant-based food sources which contribute vitamin A in thediet also contribute phytonutrients from multiple color categories.For example, carrots contain beta-carotene (yellow/orange group),tomatoes contain lycopene (red group), and spinach contains lutein(green group). Essentially then, within the context of the “phytonutrientgap” color paradigm, three of the five color categories are ofimportance when seen in the context of vitamin A-containing foods.Vitamin CResearch: Vitamin C has been shown to stimulate white blood cellfunctions, and may play a significant role in the regulation of theinflammatory response. Such mechanisms may include the inhibitionof proinflammatory cytokines or the inhibition of T-cell apoptosissignalingpathways. 6Since the 1940s, numerous studies have examined the use of vitaminC both as a prophylaxis and as a treatment for the common cold;results have been mixed. For example, a meta-analysis of 55 trials(15 statistical comparisons) looked at the severity of cold symptomsand showed that those taking vitamin C had fewer days confined tothe home or off from work or school. 17 Another meta-analysis of 21studies showed a 23% reduction in duration of episodes and severityof symptoms in patients taking at least 1g per day of vitamin C. 18In contrast, a five year randomized controlled trial among mid to olderaged Japanese adults supplementing their diets with 5 to 500 mgper day of vitamin C showed no effect on duration or severity ofcolds; however the 500 mg per day group had significantly reducedcold frequency. 19Food Sources: Based on a published analysis of key nutrientsources in the diets of American adults, 11 the primary food sourceof vitamin C was orange/grapefruit juice, with these juices providing23.8% of total vitamin C intake (measured in mg/day). Other topfruit sources included fruit drinks (10.0%), oranges/tangerines(4.1%), other non-citrus juice sources (2.5%), and cantaloupe(2.4%). Key vegetables sources of vitamin C included tomatoes(9.9%), peppers (6.7%), white potatoes (5.8%), and broccoli (5.7%).The plant-based food sources which contribute vitamin C in the dietalso contribute phytonutrients from multiple color categories. Forexample, oranges also contain hesperitin (yellow/orange group),tomatoes contain lycopene (red group), and broccoli containsisothiocyanates (green group). Similar to vitamin A, three of thefive color categories are of importance when seen in the contextof vitamin C-containing foods.5

AMERICA’S PHYTONUTRIENT REPORT: IMMUNE HEALTH BY COLORVitamin EResearch: It is hypothesized that vitamin E may stimulate the productionof NK cells and enhance the production of B cells, though some studies20, 21have failed to show an association between vitamin E and immunity.Other research suggests supplementation with vitamin E improvesseveral markers of immune response. For example, two studies testingsupplementation between 200 mg – 800 mg per day of vitamin Eyielded improvements in interleukin 1 (IL-1), interleukin 2 (IL-2) anddelayed-type hypersensitivity (DTH), suggesting supplementationmay improve immune responsiveness in some populations. 22,23 Relatedresults have also shown a protective benefit against upper respiratorytract infections. Supplementation of 200 IU per day of vitamin E yieldeda 20% reduced risk for acquiring a cold among nursing home residentsover the course of one year. 24Food Sources: Based on a published analysis of key nutrient sourcesin the diets of American adults, 11 fruits and vegetables accounted fora relatively small percentage of total intakes of vitamin E (measuredin mg vitamin E/day). Tomatoes accounted for 7.0% of total vitamin Eintake and broccoli accounted for 1– 2% of intake. Additionally, nutsand seeds accounted for 4.2% of total vitamin E intake.T H E T R A C E M I N E R A L SZincResearch: Zinc has been shown to increase the production of whiteblood cells such as macrophages and neutrophils, and to help thesecells release more antibodies to better fight infection. Thus, loweredzinc status has been associated with impairment in both white bloodcell function and NK cell activity. The observation that rhinovirus (thevirus causing the common cold) replication is inhibited by zinc furtherestablishes the therapeutic role for zinc against the common cold. 25In a large cross-over study, adults were given a placebo for threemonths, followed by 30 mg per day of zinc for six months. Resultsshowed that supplementation improved both DTH and IL-1 production.26 In addition, a small randomized, controlled trial found thattreatment with zinc acetate in the form of lozenges was associatedwith a decrease in the duration and severity of cold symptoms,especially coughing. 27 Supplementation studies using zinc gluconate(instead of zinc acetate) did not yield significant findings. 28,29Food Sources: While zinc can be found in shitake mushrooms,most fruits and vegetables are relatively poor dietary sources of zinc.However, some plant-based foods do contribute zinc to the diet.Based on a published analysis of key nutrient sources in the dietsof American adults, 11 dried beans and lentils accounted for 2.5%of total zinc intake and nuts and seeds provided 1– 2% of totalintake (measured in mg/day).SeleniumResearch: Selenium contributes to membrane integrity and plays animportant role in balancing the redox state. 6 Selenium supplementationamong adults with a “functional deficit” resulted in more rapidclearance of viruses and fewer virus mutations compared to theun-supplemented group, with amounts of at least 100 mcg per daywarranted to optimize immune function. 30 Selenium supplementationalso appears to stimulate immune function in those with adequateselenium stores. In one study, 11 men were fed diets either highor low in selenium for 120 days, during which time both influenzaand diphtheria tetanus vaccines were administered. Results showedthat antibody titers against diphtheria vaccines were 2.5 times higheron the high selenium diet. Further, cytotoxic T lymphocytes andactivated T cells were also significantly increased. 31Food Sources: While selenium can be found in spinach, mostfruits and vegetables are a relatively poor dietary source of selenium.Based on a published analysis of key nutrient sources in the dietsof American adults, 11 however, nuts and seeds accounted for1 – 2% of total selenium intake (measured in mcg/day).6

AMERICA’S PHYTONUTRIENT REPORT: IMMUNE HEALTH BY COLORClosing the “Phytonutrient Gap”Overall, consuming a wide variety of the most phytonutrient-rich whole fruits and vegetablesis the primary dietary goal, with an emphasis on quality of foods not just quantity. For immunehealth in particular, choosing phytonutrient-rich fruits and vegetables across all five colorcategories is particularly important because many contain phytonutrients as well as nutrientsassociated with immunity including the antioxidant vitamins, zinc and/or selenium. Of all thenutrients examined, the greatest difference in intakes between “meeters” and “non-meeters”was found for vitamins A and C, two nutrients particularly concentrated in fruits and vegetables.A simple, actionable goal is to eat two servings from each of the five phytonutrient colorcategories every day, for a total of 10 servings of fruits and vegetables daily. Beyond this,a natural plant-based dietary supplement is an option for those wishing to fill their“phytonutrient gap” year round, including during cold and flu season.7