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Recent research: American Journal of Clinical Nutrition on weight, sugared drinks, vitamin D, vegetarianism & climate change

I like the American Journal of Clinical Nutrition (AJCN).  It comes out monthly and nearly always has an article or two that I find interesting and helpful.  The AJCN May edition produced a bumper crop.  Interesting articles included a report by Chen and colleagues (see below for all abstracts) on the effects of encouraging people to reduce their consumption of sugar-sweetened beverages (SSB).  In the 810 US adults they studied, 19% of total daily energy intake came from drinks.  They found "A reduction in liquid calorie intake had a stronger effect than did a reduction in solid calorie intake on weight loss. Of the individual beverages, only intake of sugar-sweetened beverages (SSBs) was significantly associated with weight change. A reduction in SSB intake of 1 serving/d was associated with a weight loss of 0.49 kg ... at 6 mo and of 0.65 kg ... at 18 mo."  Cashman and colleagues studied vitamin D, a pet subject of mine.  They found that in an older population "The intakes required to maintain serum 25(OH)D concentrations of >37.5, >50, and >80 nmol/L in 97.5% of the sample were 17.2, 24.7, and 38.7 {micro}g/d, respectively."   Remembering that 10 micrograms of vitamin D is equivalent to 400 I.U., this means that these people, aged 64 and above, would have needed about 1,600 I.U. daily to ensure that nearly all of them had something like an optimal serum 25(OH)D level.

The May AJCN included nearly 30 papers from the Fifth International Congress on Vegetarian Nutrition.  Examples include the review by Fraser on the effects of vegetarianism on a series of chronic diseases.  He concluded that "There is convincing evidence that vegetarians have lower rates of coronary heart disease, largely explained by low LDL cholesterol, probable lower rates of hypertension and diabetes mellitus, and lower prevalence of obesity. Overall, their cancer rates appear to be moderately lower than others living in the same communities, and life expectancy appears to be greater."  He also cautioned that "It is probable that using the label "vegetarian" as a dietary category is too broad and that our understanding will be served well by dividing vegetarians into more descriptive subtypes. Although vegetarian diets are healthful and are associated with lower risk of several chronic diseases, different types of vegetarians may not experience the same effects on health."  There's also a paper by Craig looking at benefits associated with vegan diets, but also the risks of nutritional deficiencies too.  Finally I've included a couple of papers on the environmental effects of different patterns of food consumption.  Carlsson-Kanyama & Gonzalez compared the kg of carbon dioxide emissions per kg of edible product for 20 or so types of food in Sweden.  They found "For protein-rich food, such as legumes, meat, fish, cheese, and eggs, the difference is a factor of 30 with the lowest emissions per kilogram for legumes, poultry, and eggs and the highest for beef, cheese, and pork."  Similarly Marlow and colleagues, in a US study, report " ... nonvegetarian diet required 2.9 times more water, 2.5 times more primary energy, 13 times more fertilizer, and 1.4 times more pesticides than did the vegetarian diet."  

Chen, L., L. J. Appel, et al. (2009). "Reduction in consumption of sugar-sweetened beverages is associated with weight loss: the PREMIER trial." Am J Clin Nutr 89(5): 1299-1306.  [Abstract/Full Text
Background: Consumption of liquid calories from beverages has increased in parallel with the obesity epidemic in the US population, but their causal relation remains unclear. Objective: The objective of this study was to examine how changes in beverage consumption affect weight change among adults. Design: This was a prospective study of 810 adults participating in the PREMIER trial, an 18-mo randomized, controlled, behavioral intervention trial. Measurements (weight, height, and 24-h dietary recall) were made at baseline, 6 mo, and 18 mo. Results: Baseline mean intake of liquid calories was 356 kcal/d (19% of total energy intake). After potential confounders and intervention assignment were controlled for, a reduction in liquid calorie intake of 100 kcal/d was associated with a weight loss of 0.25 kg (95% CI: 0.11, 0.39; P < 0.001) at 6 mo and of 0.24 kg (95% CI: 0.06, 0.41; P = 0.008) at 18 mo. A reduction in liquid calorie intake had a stronger effect than did a reduction in solid calorie intake on weight loss. Of the individual beverages, only intake of sugar-sweetened beverages (SSBs) was significantly associated with weight change. A reduction in SSB intake of 1 serving/d was associated with a weight loss of 0.49 kg (95% CI: 0.11, 0.82; P = 0.006) at 6 mo and of 0.65 kg (95% CI: 0.22, 1.09; P = 0.003) at 18 mo. Conclusions: These data support recommendations to limit liquid calorie intake among adults and to reduce SSB consumption as a means to accomplish weight loss or avoid excess weight gain. This trial was registered at clinicaltrials.gov as NCT00000616.

Cashman, K. D., J. M. W. Wallace, et al. (2009). "Estimation of the dietary requirement for vitamin D in free-living adults >=64 y of age." Am J Clin Nutr 89(5): 1366-1374.  [Abstract/Full Text
Background: Older adults may be more prone to developing vitamin D deficiency than younger adults. Dietary requirements for vitamin D in older adults are based on limited evidence. Objective: The objective was to establish the dietary intake of vitamin D required to maintain serum 25-hydroxyvitamin D [25(OH)D] concentrations above various cutoffs between 25 and 80 nmol/L during wintertime, which accounted for the effect of summer sunshine exposure and diet. Design: A randomized, placebo-controlled, double-blind, 22-wk intervention was conducted in men and women aged > or = 64 y (n = 225) at supplemental levels of 0, 5, 10, and 15 {micro}g vitamin D3/d from October 2007 to March 2008. Results: Clear dose-related increments (P < 0.0001) in serum 25(OH)D were observed with increasing supplemental vitamin D3 intakes. The slope of the relation between total vitamin D intake and serum 25(OH)D was 1.97 nmol · L-1 · µg intake-1. The vitamin D intake that maintained serum 25(OH)D concentrations >25 nmol/L in 97.5% of the sample was 8.6 {micro}g/d. Intakes were 7.9 and 11.4 {micro}g/d in those who reported a minimum of 15 min daily summer sunshine exposure or less, respectively. The intakes required to maintain serum 25(OH)D concentrations of >37.5, >50, and >80 nmol/L in 97.5% of the sample were 17.2, 24.7, and 38.7 {micro}g/d, respectively. Conclusion: To ensure that the vitamin D requirement is met by the vast majority (>97.5%) of adults aged < or = 64 y during winter, between 7.9 and 42.8 {micro}g vitamin D/d is required, depending on summer sun exposure and the threshold of adequacy of 25(OH)D.

Fraser, G. E. (2009). "Vegetarian diets: what do we know of their effects on common chronic diseases?" Am J Clin Nutr 89(5): 1607S-1612.  [Abstract/Full Text]
A number of studies have evaluated the health of vegetarians. Others have studied the health effects of foods that are preferred or avoided by vegetarians. The purpose of this review is to look critically at the evidence on the health effects of vegetarian diets and to seek possible explanations where results appear to conflict. There is convincing evidence that vegetarians have lower rates of coronary heart disease, largely explained by low LDL cholesterol, probable lower rates of hypertension and diabetes mellitus, and lower prevalence of obesity. Overall, their cancer rates appear to be moderately lower than others living in the same communities, and life expectancy appears to be greater. However, results for specific cancers are much less convincing and require more study. There is evidence that risk of colorectal cancer is lower in vegetarians and in those who eat less meat; however, results from British vegetarians presently disagree, and this needs explanation. It is probable that using the label "vegetarian" as a dietary category is too broad and that our understanding will be served well by dividing vegetarians into more descriptive subtypes. Although vegetarian diets are healthful and are associated with lower risk of several chronic diseases, different types of vegetarians may not experience the same effects on health.

Craig, W. J. (2009). "Health effects of vegan diets." Am J Clin Nutr 89(5): 1627S-1633.  [Abstract/Full Text]  
Recently, vegetarian diets have experienced an increase in popularity. A vegetarian diet is associated with many health benefits because of its higher content of fiber, folic acid, vitamins C and E, potassium, magnesium, and many phytochemicals and a fat content that is more unsaturated. Compared with other vegetarian diets, vegan diets tend to contain less saturated fat and cholesterol and more dietary fiber. Vegans tend to be thinner, have lower serum cholesterol, and lower blood pressure, reducing their risk of heart disease. However, eliminating all animal products from the diet increases the risk of certain nutritional deficiencies. Micronutrients of special concern for the vegan include vitamins B-12 and D, calcium, and long-chain n-3 (omega-3) fatty acids. Unless vegans regularly consume foods that are fortified with these nutrients, appropriate supplements should be consumed. In some cases, iron and zinc status of vegans may also be of concern because of the limited bioavailability of these minerals.

Carlsson-Kanyama, A. and A. D. Gonzalez (2009). "Potential contributions of food consumption patterns to climate change." Am J Clin Nutr 89(5): 1704S-1709.  [Abstract/Full Text
Anthropogenic warming is caused mainly by emissions of greenhouse gases (GHGs), such as carbon dioxide, methane, and nitrous oxide, with agriculture as a main contributor for the latter 2 gases. Other parts of the food system contribute carbon dioxide emissions that emanate from the use of fossil fuels in transportation, processing, retailing, storage, and preparation. Food items differ substantially when GHG emissions are calculated from farm to table. A recent study of {approx}20 items sold in Sweden showed a span of 0.4 to 30 kg CO2 equivalents/kg edible product. For protein-rich food, such as legumes, meat, fish, cheese, and eggs, the difference is a factor of 30 with the lowest emissions per kilogram for legumes, poultry, and eggs and the highest for beef, cheese, and pork. Large emissions for ruminants are explained mainly by methane emissions from enteric fermentation. For vegetables and fruits, emissions usually are [&le;]2.5 kg CO2 equivalents/kg product, even if there is a high degree of processing and substantial transportation. Products transported by plane are an exception because emissions may be as large as for certain meats. Emissions from foods rich in carbohydrates, such as potatoes, pasta, and wheat, are <1.1 kg/kg edible food. We suggest that changes in the diet toward more plant-based foods, toward meat from animals with little enteric fermentation, and toward foods processed in an energy-efficient manner offer an interesting and little explored area for mitigating climate change.

Marlow, H. J., W. K. Hayes, et al. (2009). "Diet and the environment: does what you eat matter?" Am J Clin Nutr 89(5): 1699S-1703.  [Abstract/Full Text
Food demand influences agricultural production. Modern agricultural practices have resulted in polluted soil, air, and water; eroded soil; dependence on imported oil; and loss of biodiversity. The goal of this research was to compare the environmental effect of a vegetarian and nonvegetarian diet in California in terms of agricultural production inputs, including pesticides and fertilizers, water, and energy used to produce commodities. The working assumption was that a greater number and amount of inputs were associated with a greater environmental effect. The literature supported this notion. To accomplish this goal, dietary preferences were quantified with the Adventist Health Study, and California state agricultural data were collected and applied to state commodity production statistics. These data were used to calculate different dietary consumption patterns and indexes to compare the environmental effect associated with dietary preference. Results show that, for the combined differential production of 11 food items for which consumption differs among vegetarians and nonvegetarians, the nonvegetarian diet required 2.9 times more water, 2.5 times more primary energy, 13 times more fertilizer, and 1.4 times more pesticides than did the vegetarian diet. The greatest contribution to the differences came from the consumption of beef in the diet. We found that a nonvegetarian diet exacts a higher cost on the environment relative to a vegetarian diet. From an environmental perspective, what a person chooses to eat makes a difference.

 

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