Is vitamin A consumption a risk factor for osteoporotic fracture?

Severe vitamin A toxicity is known to have adverse effects on skeletal health. Studies involving animal models and case reports have documented that hypervitaminosis A is associated with bone resorption, hypercalcaemia and bone abnormalities. More recently, some epidemiological studies have suggested that high habitual intake of vitamin A could contribute to low bone mineral content and fracture risk. The evidence relating to the possible deleterious role of vitamin A in bone health is of variable quality and is potentially confounded by collinearity of nutrient intake and difficulties in assessing vitamin A exposure. Furthermore, because intake of vitamin A varies between studies it is not possible to define an intake threshold associated with harm.     

Mild dehydration: a risk factor for dental disease?

A review of the published international literature was undertaken to investigate whether dehydration is a risk factor for dental disease. Published evidence of associations between saliva and dental disease and between saliva and dehydration was observed, but the precise nature of these associations is unclear and no evidence of a direct link between dehydration and dental disease was found. It is concluded that no direct link between dehydration and dental disease has been proven, although there is considerable circumstantial evidence to indicate that such a link exists.     

Vitamin A: is it a risk factor for osteoporosis and bone fracture?

Results from observational studies of the association between vitamin A intake or serum concentration and bone mineral density or fracture are mixed. The inconsistencies may be due, in part, to difficulties in obtaining an accurate assessment of vitamin A intake or status. Serum retinol is a poor measure of vitamin A status because it is subject to homeostatic control. Stable-isotope-dilution methodology gives a validated assessment of the total-body and liver vitamin A stores and is recommended in future studies on vitamin A status and osteoporosis. The potential for exacerbating an already serious public health problem with intakes of vitamin A currently considered safe indicates further research into this matter is warranted.     

Recreational drug use: a major risk factor for gastroschisis?

The authors tested the hypothesis that the birth prevalence of gastroschisis is positively associated with use of recreational drugs in early pregnancy. A matched case-control study was carried out in three regions of the United Kingdom over the period January 2001 through August 2003. For each case, three liveborn controls were matched by initial intended place of delivery, region, and maternal age. Maternal hair analysis provided independent verification of recreational drug use. Conditional logistic regression was used to estimate mutually adjusted odds ratios. Estimates were revised using data from hair analysis. Statistically significant adjusted odds ratios for gastroschisis were associated with first-trimester use of 1) any recreational drug (odds ratio (OR) = 2.2, 95% confidence interval (CI): 1.2, 4.3) and 2) vasoconstrictive recreational drugs (defined as cocaine, amphetamines, and ecstasy) (OR = 3.3, 95% CI: 1.0, 10.5). Other significant exposures included aspirin use (OR = 20.4, 95% CI: 2.2, 191.5), cigarette smoking (OR = 1.7, 95% CI: 1.1, 2.6), and prior history of gynecologic infection/disease (OR = 2.6, 95% CI: 1.2, 5.6). Recreational drug use is a significant risk factor for gastroschisis and is one of a constellation of potentially preventable exposures which include cigarette smoking, aspirin use, and history of gynecologic infection/disease. Maternal hair analysis proved an acceptable and valuable method of independently verifying recreational drug use.     

Is zinc deficiency a risk factor for atherosclerosis?

The development of atherosclerosis is influenced by genetic, lifestyle and nutritional risk factors. Zn and metallothionein deficiency can enhance oxidative-stress-related signalling processes in endothelial cells, and since changes in available plasma Zn may affect the Zn status of the endothelium, Zn deficiency could be a risk factor for IHD. Although the association of Zn with many proteins is essential for their function, three key signalling processes are highlighted as being principal targets for the effect of Zn deficiency: the activation of NF-kappaB, the activation of caspase enzymes and the signalling of NO. The need to develop a reliable indicator of Zn status is critical to any epidemiological approach for studying the relationship between Zn status and disease incidence. Studies using appropriate animal models and investigating how the plasma Zn pool influences endothelial intracellular labile Zn would be helpful in appreciating the importance of Zn deficiency in atherogenesis.     

High-dose vitamin C: a risk for persons with high iron stores?

The contribution of vitamin C (ascorbic acid) to the prevention of iron deficiency anemia by promoting the absorption of dietary non-heme iron-especially in persons with low iron stores--is well established. But the question has been raised whether high-dose intakes of vitamin C might unduly enhance the absorption of dietary iron in persons with high iron stores or in patients with iron overload, possibly increasing the potential risk of iron toxicity. Extensive studies have shown that overall the uptake and storage of iron in humans is efficiently controlled by a network of regulatory mechanisms. Even high vitamin C intakes do not cause iron imbalance in healthy persons and probably in persons who are heterozygous for hemochromatosis. The uptake, renal tubular reabsorption and storage of vitamin C itself are also strictly limited after high-dose intake so that no excessive plasma and tissue concentrations of vitamin C are produced. The effect of high-dose vitamin C on iron absorption in patients with iron overload due to homozygous hemochromatosis has not been studied. Of special importance is the early identification of hemochromatosis patients, which is assisted by the newly developed PCR test for hereditary hemochromatosis. Specific treatment consists of regular phlebotomy and possibly iron-chelating therapy. These patients should moreover avoid any possibility of facilitated absorption of iron and need to limit their intake of iron. Patients with beta-thalassemia major and sickle cell anemia who suffer from iron overload due to regular blood transfusions or excessive destruction of red blood cells need specialized medical treatment with iron chelators and should also control their intake of iron. The serum of patients with pathological iron overload can contain non-transferrin-bound iron inducing lipid peroxidation with subsequent consumption of antioxidants such as vitamin E and vitamin C. The role of iron in coronary heart disease and cancer is controversial. Early suggestions that moderately elevated iron stores are associated with an increased risk of CHD have not been confirmed by later studies. In vitro, ascorbic acid can act as a prooxidant in the presence of transition metals such as iron or copper, but in the living organism its major functions are as an antioxidant. High intakes of vitamin C have thus not been found to increase oxidative damage in humans. Accordingly, the risk of CHD or cancer is not elevated. On the contrary, most studies have shown that diets rich in vitamin C are inversely related to the incidence of these diseases.     

Is a low blood level of vitamin B12 a cardiovascular and diabetes risk factor? A systematic review of cohort studies

Purpose  

To assess the prior hypothesis that low blood vitamin B12, partly through hyperhomocysteinemia and partly through direct effects, increases the risk of cardiovascular diseases and diabetes. As background, we also extracted all-cause mortality from the studies that met our criteria.     

Is early enteral nutrition a risk factor for gastric intolerance and pneumonia?

BACKGROUND: Early enteral nutrition (EN) after injury reduces septic complications, but upper digestive intolerance (UDI) occurring immediately post-trauma is a risk factor for pneumonia. Our study aimed to determine whether early intragastric feeding may lead to gastric intolerance and subsequent pneumonia in ventilated multiply injured patients. METHODS: This prospective study involved two groups of patients randomized either to immediate intragastric EN, or to delayed intragastric EN started later than 24 h after admission. UDI was diagnosed when gastric residual volume, measured with a 50-ml syringe after stopping the feeding for 2 h, exceeded 200 ml at least at two consecutive measurements, and/or when vomiting occurred. RESULTS: Out of 52 patients, 27 were included in the early EN group, and 25 in the delayed-EN group. On day 4, the early EN group received a greater amount of feeding because of intolerance problems occurring in the delayed-EN group (1175 +/- 485 ml vs. 803 +/- 545 ml). Twenty-five subjects--33% of the early EN patients and 64% of the delayed-EN patients--met the criteria for pneumonia (P = 0.050). On average, patients with pneumonia were older, more severely injured, and therefore required more ventilator days and a longer stay in the intensive care unit than patients without pneumonia. CONCLUSIONS: If properly administered, early enteral nutrition can decrease the incidence of upper intestinal intolerance and nosocomial pneumonia in patients with multiple injuries.     

Intakes of vitamin C, vegetables and fruits: which schoolchildren are at risk?

OBJECTIVE: The purpose of this study was to determine vitamin C intakes among American schoolchildren. We investigated the leading sources of vitamin C in children's diets, the leading vegetables and fruits consumed by children and differences in dietary intake associated with vitamin C consumption. METHODS: Data from 1,350 7- to 12-year-old and 908 13- to 18-year-old schoolchildren were obtained from the 1994-1996 Continuing Survey of Food Intakes by Individuals (CSFII). The children were stratified by age and gender and then split into three vitamin C consumption groups based upon two 24-hour recalls: low (0 to 30.0 mg), marginal (30.1 to 59.9 mg), and desirable (>60.0 mg). Data were analyzed by tabulation and by ANOVA followed by post hoc Scheffe's test. Outcome measures included food groups and energy-adjusted intakes of micro- and macronutrients. RESULTS: Among the 7- to 12-year-olds, 12% of boys and 13% of girls had mean vitamin C intakes that were less than 30 mg/day, and, among 13- to 18-year-olds, 14% of boys and 20% of girls had low vitamin C intakes. In addition to consuming significantly more vitamin C, children with desirable vitamin C intakes also consumed significantly more (p <0.001) energy-adjusted folate and vitamin B6; children with low vitamin C intakes tended to have significantly greater (p <0.001) energy-adjusted intakes of fat and saturated fat. Children with desirable vitamin C intakes consumed significantly more (p <0.006) high-vitamin C fruit juice, low-vitamin C vegetables and whole milk. Children with low vitamin C intakes on average consumed two daily servings of vegetables and fruits, of which less than 1/5 of a serving was citrus, while children with desirable vitamin C intakes consumed an average of one daily serving of citrus. CONCLUSIONS: A considerable number of children drastically under-consumed vitamin C and total vegetables and fruits. Overall, children with desirable vitamin C intakes had healthier diets, including more milk and vegetables, than did their peers with low vitamin C intakes. Health care professionals should continue to promote at least five daily servings of vegetables and fruits and should advise parents that at least one of these should be rich in vitamin C.     

Is diabetes mellitus a risk factor for HCV infection?

The aim of this study was to investigate whether or not the diabetes mellitus may be considered a risk factor for the HCV infection. The HCV seroprevalence was evaluated in 254 diabetic subjects, whose anamnestic data and risk factors are known, in comparison to 223 first-time blood donors, carefully age- and gender-matched. The statistical analysis showed that the studied groups belonged to the same population (Mann-Whitney U test) and that there were no significant differences between cases and controls as regards HCV prevalence (Yates corrected chi 2 test). The obtained data underline the importance of the control group selection, especially in the studies considering age-related pathologies. The authors disprove type 2 diabetes as a risk factor for the HCV infection and consider that this is a valid hypothesis only when the hepatitis C was unknown and not adequate prevention was used.     

Is radiographic vertebral fracture a risk factor for mortality?

Clinical fractures predict increased mortality risk, but few studies report mortality based on prevalent radiographically defined vertebral fracture. This study examined whether radiographically defined vertebral fracture is a risk factor for mortality in older adults. The 1,580 participants in California (631 men, 949 women) were aged > or =50 years in 1992-1996. Lateral spine radiographs, and information about medical history and behaviors, were obtained. Overall, 55 (8.7%) men and 123 (13%) women had at least one prevalent fracture at baseline; of these, 48 women and 14 men had two or more. Over 7.6 years, 460 participants died, 27.6% without and 41.0% with prevalent fractures (p < 0.001). Prevalent vertebral fracture was not associated with all-cause mortality in both sexes combined (adjusted hazard ratio = 1.09, 95% confidence interval: 0.84, 1.42) or sex-specific analyses (women: adjusted hazard ratio = 1.15, 95% confidence interval: 0.83, 1.59; men: adjusted hazard ratio = 0.89, 95% confidence interval: 0.55, 1.46). However, women with two or more prevalent fractures had increased risk of all-cause mortality (adjusted hazard ratio = 1.56, 95% confidence interval: 1.01, 2.40; p = 0.04). Women with any prevalent vertebral fractures also had increased mortality risk from "other" causes (adjusted hazard ratio = 1.59, 95% confidence interval: 1.03, 2.45; p = 0.04) but not cardiovascular disease or cancer. A single radiographic vertebral fracture is not a risk for mortality in older women; larger, longer studies of men and those with two or more radiographic vertebral fractures are needed.