維他命D增強年長女性的減重效果


  【24drs.com】根據一篇新研究,對於與癌症及慢性疾病有關的全身發炎,維他命D補充品可以增強減重效果。
  
  在一篇為期一年、有關年長、過重、維他命D值不足的婦女研究中,相較於單純減重者,減重同時補充維他命D對於降低發炎前細胞激素介白質素-6([IL-6])的效果更大。
  
  第一研究者、西雅圖Fred Hutchinson癌症研究中心的Catherine Duggan博士表示,證據認為,過重者的維他命D值比較低,這是因為被隔離囤積在脂肪層,而導致生體可用率降低。
  
  她表示,這可能是體重減輕導致脂肪減少,釋出儲藏的維他命D,對於維他命D3補充品(這些補充品並未被隔離在脂肪層)產生加成效果,我們已經知道減重可降低發炎程度,所以這個效果也增強了維他命D3補充品的好處,提高了維他命D3的生體可用率,顯著降低了IL-6的數值。
  
  這篇研究線上發表於4月23日的癌症預防研究期刊。
  
  Duggan博士表示,醫師們應鼓勵人們維持健康體重,以降低慢性發炎及其相關影響,應測試過重者的維他命D缺乏/不足程度,必要時建議使用補充品。
  
  不過,一名研究維他命D對於發炎生物標記之影響的研究者並未被本研究說服。波士頓哈佛醫學院、布萊根婦女醫院、未參與本次研究的Paulette D. Chandler醫師表示,這個效果可能是因為體重。
  
  Chandler醫師解釋,觀察型研究強調了維他命D值充足時與肥胖相關疾病風險降低有關,這些疾病如:心血管疾病、糖尿病與某些癌症。鈣與維他命D的抗肥胖可能機轉,包括控制脂肪細胞死亡、脂肪生成和脂質代謝。
  
  她指出,雖然有合理的機轉以及體外證據支持維他命D在減重的角色,仍然難以確認這些效果是否是因為維他命D本身,或者是與減重計劃中的飲食改變情況有關。
  
  維他命D補充品對於肥胖或發炎可能並沒有生物效果,觀察發現的發炎前生物標記降低,可能是因為減重與連帶的飲食改變而導致。
  
  在之前一篇維他命D補充品用於黑人患者的臨床試驗中,Chandler醫師等人並沒有觀察到維他命D對於發炎生物標記有所影響(發表於Cancer Prev Res [Phila]. 2014;7:218-225),不過,她指出,這篇試驗並未被標示為減重試驗。
  
  慢性發炎被視為「前致腫瘤性狀態(protumorigenic state)」,之前的研究顯示,減重可以減少發炎,有一些證據認為,服用維他命D補充品對無營養不足的人有類似的影響。Duggan醫師等人報告指出,她們的研究是第一篇評估補充維他命D是否可增強減重對發炎標記之影響的研究。
  
  研究對象是218名停經後、過重或肥胖婦女(平均年齡59.6歲),她們的身體質量指數(BMI)大於25 kg/m2 (平均BMI值為32.4 kg/m2),血清25-hydroxyvitamin D3不足、介於10-32 ng/mL。
  
  這些婦女都參加一個為期12個月的飲食與運動計畫,每週有5天各45分鐘中等強度到費力強度的運動,隨機指定半數婦女每天服用2000 IU的維他命D3,其他半數婦女使用外觀相似的安慰劑。
  
  研究者測量了血清中的脂聯素、瘦體素、腫瘤壞死因子(TNF)-alpha、IL-6、IL-1b、IL-8、以及IL-10等標記之數值,並計算出一個綜合發炎生物標記分數。
  
  12個月時, 兩組的分析變化差異並不顯著。不過,在維他命D3組婦女的分層分析中,體重減少5%-10%者的IL-6值降低程度,顯著大於沒有減重或體重增加的婦女(37.3% vs 17.2%;P = .004)。
  
  在維他命D3組、體重減少10%以上的婦女,她們的IL-6減少程度相似但略為減弱(17.3% vs 13.6%;P = .02)。
  
  當根據體重減少情況分組時,維他命D3補充品這組的IL-1b值,對於TNF-alpha、IL-10、IL-8、綜合發炎生物標記分數、脂聯素或瘦體素沒有介入效果。
  
  資料來源:http://www.24drs.com/
  
  Native link:Vitamin D Augments Effect of Weight Loss in Older Women

Vitamin D Augments Effect of Weight Loss in Older Women

By Megan Brooks
Medscape Medical News

Vitamin D supplementation augments the benefits of weight loss on systemic inflammation linked to cancer and chronic disease, according to new research.

In the year-long study of older overweight women with insufficient vitamin D levels, weight loss coupled with vitamin D supplementation had a greater effect on reducing levels of the proinflammatory cytokine interleukin (IL)-6 than weight loss alone.

"Evidence suggests that overweight individuals have lower levels of vitamin D because it's sequestered in fat depots, leading to lower bioavailability," said lead author Catherine Duggan, PhD, from Fred Hutchinson Cancer Research Center in Seattle.

It is possible that "weight loss leading to fat loss, releasing stores of vitamin D, would have an additive effect on the vitamin D? supplements (which themselves aren't being sequestered)," she told Medscape Medical News. "We already know that weight loss reduces levels of inflammation, so this effect, plus the added benefit of vitamin D? supplements and the increased bioavailability of vitamin D?, reduces IL-6 levels by a measurable level."

The study was published online April 23 in Cancer Prevention Research.

"Clinicians should encourage maintenance of a healthy weight to reduce chronic inflammation and its associated effects. Overweight individuals should be tested for vitamin D deficiency/insufficiency and supplementation advised as necessary," Dr Duggan suggested.

However, a researcher who has studied the effects of vitamin D on inflammatory biomarkers is not convinced. The effect seen may be due to weight, said Paulette D. Chandler, MD, MPH, from Brigham and Women's Hospital and Harvard Medical School in Boston, who was not involved with the study.

"Observational studies highlight vitamin D sufficiency associated with a reduced risk of diseases that cluster with obesity, such as cardiovascular disease, diabetes, and certain cancers. Possible antiobesity mechanisms of calcium and vitamin D include the control of adipocyte death, adipogenesis, and lipid metabolism," Dr Chandler explained.

"Despite plausible mechanisms and in vitro evidence supporting a role for vitamin D in weight reduction, it remains difficult to determine whether the effects are due to vitamin D itself or are related to dietary changes that occur as part of participating in a weight-loss program," she noted.

"It is possible that there is no biologic effect of supplementation with vitamin D on adiposity or inflammation. The observed reduction in proinflammatory biomarkers may be driven by the weight loss and the dietary changes that contributed to the weight loss," she added.

In a previous clinical trial of vitamin D supplementation in black patients, Dr Chandler and her colleagues observed no effect of vitamin D on inflammatory biomarkers (Cancer Prev Res [Phila]. 2014;7:218-225). However, she added, "this trial was not imbedded in a weight loss trial."

Chronic Inflammation as a Protumorigenic State

Chronic inflammation is thought to represent a protumorigenic state. Previous studies have shown that losing weight can reduce inflammation, and there is some evidence that taking vitamin D supplements can have a similar effect in people with insufficient levels of the nutrient. Dr Duggan and her colleagues report that their study is the first to assess whether adding vitamin D can boost the effect of weight loss on inflammatory biomarkers.

The study participants were 218 postmenopausal women (mean age, 59.6 years) who were overweight or obese, defined as a body mass index (BMI) above 25 kg/m2 (mean BMI, 32.4 kg/m2), with insufficient levels of serum 25-hydroxyvitamin D?, ranging from 10 to 32 ng/mL.

All of the women participated in a 12-month diet and exercise program that included 45 minutes of moderate to vigorous exercise 5 days a week. Half the women were randomly assigned to receive vitamin D? 2000 IU/day, and the other half were assigned to identical-looking placebo pills.

The researchers measured serum levels of adiponectin, leptin, tumor necrosis factor (TNF)-alpha, IL-6, IL-1b, IL-8, and IL-10, and calculated a composite inflammatory biomarker score.

At 12 months, there were no significant between-group differences in analyte changes.

However, in stratified analyses of women in the vitamin D? group, reductions in IL-6 levels were significantly larger in those who lost 5% to 10% of their baseline body weight than in those women who lost no weight or who gained weight (37.3% vs 17.2%; P = .004).

In women in the vitamin D? group who lost 10% or more of their baseline weight, there were similar, although attenuated, IL-6 reductions (17.3% vs 13.6%; P = .02).

The effects of vitamin D? supplementation on levels of IL-1b were "inconsistent" when stratified by weight loss, and there were no intervention effects on TNF-alpha, IL-10, IL-8, a composite inflammatory biomarker score, adiponectin, or leptin.

The study was funded by the Breast Cancer Research Foundation, Susan G. Komen for the Cure, the National Institutes of Health, the Seattle Cancer Consortium Breast Cancer Specialized Program in Research Excellence, the Fred Hutchinson/University of Washington Cancer Consortium, and the Safeway Foundation. The authors have disclosed no relevant financial relationships.

Cancer Prev Res (Phila). Published online April 23, 2015.

    
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