Women's Health Research

[Guest guest]

The below excerpts may be of interest:

Women's Health Research Update

Len Kravitz, Ph.D.

http://www.drlenkravitz.com/Articles/womenshealth.html

Physical Activity and Breast Cancer: New Update

Friedenreich, C.M. & Cust, A.E. (2008). Physical activity and breast cancer

risk: impact of timing, type and dose of activity and population subgroup

effects. British Journal of Sports Medicine, 42, pp 636-647.

According to the American Cancer Society (2008), breast cancer is the most

common malignancy among women in the U.S. with 26% of the cancer cases totally

182,460 new cases in 2008. Lung and bronchus cancer (14%) are second followed by

colon and rectum cancer (10%) in women. The American Cancer Society advises that

to reduce the risk of developing breast cancer, women should adopt lifestyle

behaviors such as reducing alcohol use, engaging in physical activity,

maintaining a healthy weight, eating a balanced diet (with at least 5 servings

of fruits and vegetables a day) and breast feeding. Well over 80 studies now

convincingly suggest that there is an inverse relation with physical activity to

breast cancer (i.e., exercise reduces the risk of breast cancer) (Friedenreich

and Cust, 2008). In this recent review by Friedenreich and Cust, the authors

found a decrease in the risk of breast cancer by approximately 25% among the

most physically active women as compared to the least active females. Both

moderate and vigorous exercise exhibited nearly equal benefits for a decrease in

breast cancer risk. As well, physical activity through a woman's lifetime

conferred the highest risk prevention benefits. The authors note that physical

activity reduced the risk of breast cancer in all groups of females except obese

(as determined by BMI & Mac179; 30 kg/m2 {weight in kg/height in meter squared}).

The greatest risk reduction was with lean females who had a BMI of < 22 kg/m2.

The authors summarize that the positive influence of physical activity to

reduced cancer risk may be due to a modulation of inflammation and immune

function. It appears that exercise may favorably change the balance of pro- and

anti-inflammatory cytokines (signaling molecules that, like hormones and

neurotransmitters, are used extensively in cellular communication) thus

lessoning the negative effects of chronic inflammation in the circulatory

system.

TAKE AWAY MESSAGE: The evidence is very persuasive that moderate to vigorous

exercise reduces the risk of breast cancer. Those females who do regular

physical activity during their lifetime have an even lesser risk. These risks

are more noticeable in non-obese female populations..........

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Exercise Metabolism in Women: New Insights and Implications

Tarnopolosky, M.A. (2008). Sex differences in exercise metabolism and the role

of 17-beta estradiol. Medicine & Science in Sports & Exercise, 40(4), 648-654.

It has generally been assumed that men and women have similar muscle fiber types

and thus metabolize fats, carbohydrates and proteins similarly. Indeed, the

majority the studies on metabolism have been done with male populations,

assuming this similarity. However, in a review of all substrate (fat,

carbohydrate and protein breakdown for energy) oxidation (loss of a electrons

and thus the substrate is being broken apart) studies during endurance exercise

(>60 minutes), Tarnopolosky (2008) summarizes that it is clear that women have a

higher fat utilization and lower carbohydrate energy expenditure. This elevated

fat utilization during endurance exercise is seen with women before and after

training, thus suggesting that the underlying mechanism is due to a sex

difference between men and women, and not a training effect. As well,

Tarnopolosky notes that women have been shown to have a slightly higher percent

of Type I or slow twitch (oxidative) fiber type, which may partially contribute

to the increased fat metabolism during endurance-type activities. More

profoundly, it appears that higher levels of the major estrogen seen in women,

17-beta estradiol (which men also have in low levels in the body) is the

mediating hormone that enhances fat oxidation (thus sparing carbohydrates)

pathways during endurance exercise.

TAKE AWAY MESSAGE: Since women are metabolizing fat more effectively during

endurance exercise > 60 minutes, an exercise program that includes sustained

aerobic exercise bouts is encouraged for those female students and clients

wishing to optimize fat metabolism through exercise..............

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Carruthers

Wakefield, UK