Research Extracts: Dietary Effects On Sperm, Weight Loss And Breast Cancer Risk, And Other Research
Welcome to the February 2020 edition of Research Extracts. “The Extracts” is designed to keep busy practitioners and savvy consumers up-to-date on the latest research on diet, nutrients, botanicals, the microbiome, the environment, and lifestyle approaches to good health. Our medical team, which includes NDs, MDs, PhDs, RDs, an MS, and an LAc, has summarized the essence of several of the most interesting studies.
Research summaries in this issue include: (1) dietary effects on human sperm, (2) gender differences in blood pressure as we age, (3) weight loss and breast cancer risk, and (4) obesity and vitamin D deficiency.
Human sperm displays rapid responses to diet
Metabolic disease and obesity are on the rise worldwide. At the same time, there is a trend in the decline of sperm quality. Evidence indicates that the paternal diet can affect the metabolic health of offspring through a process involving sperm tsRNA.
Basically, sperm health holds a determinate for the future metabolic health of the progeny. This study evaluated whether acute changes in diet could produce measurable changes in sperm health. The study recruited 15 healthy men with a normal body mass index and instituted a personalized dietary program for each one. During a 2-week study period, the participants consumed meals provided by the research team.
In the first week, the participants ate a healthy diet, according to the Nordic nutrient recommendation, with a total caloric intake corresponding to their estimated total energy expenditure (TEE). In the second week, the healthy diet was supplemented with sugar equal to an additional 50 percent of their estimated TEE.
This was a daily average of 375 grams of sugar, or 3.5 liters of sugar-sweetened beverages. The caloric content of the first week was meant to maintain initial body weight; whereas, the caloric intake of the second week was meant to increase the initial weight by 1.5 kg (3.3 pounds). Semen samples were collected at three points: the first at the start of the intervention, the second after the healthy diet week, and the third after the high-sugar diet week. The total number of sperm varied among the participants, and total sperm count was not affected by diet.
Five of the 15 participants had a very low starting point for sperm motility, while the other 10 started with normal sperm motility. The five participants with low sperm motility had remarkable improvement that was apparent after the first week.
RNA was extracted from the sperm samples to evaluate for changes in tsRNA components in the sperm sample after dietary intervention. Specific subtypes of sperm RNA were acutely upregulated in response to diet. The changes in sperm RNA were associated with RNA subtypes that might increase the sperm’s transmission of metabolic programming to the next generation. The study demonstrated that human sperm is sensitive to nutritional changes, both in respect to sperm motility and the RNA pool.
Contributed by Amanda Frick, ND, LAc
- Nätt D, Kugelberg U, Casas E, et al. Human sperm displays rapid responses to diet. PLOS Biology 2019;17(12):e3000559. doi:10.1371/journal.pbio.3000559
Blood pressure patterns over time are not the same for men and women
In general, males and females experience cardiovascular disease differently. Many current models explaining this assume the underlying physiology is fundamentally the same. A recent study proposes this assumption warrants reconsideration.
The authors propose that evaluation in a gender-specific way could yield novel explanations for the different experiences men and women have relative to cardiovascular health.
The authors applied their hypothesis by compiling data from 32,833 individuals in four cohort studies spanning 43 years. They assessed the sex-specific course of blood pressure change from baseline over time.
Although blood pressure increases appear to begin at a younger age in males, the study found that women tend to experience a more rapid increase in blood pressure measures (systolic, diastolic, mean arterial, and pulse pressures) over their lifespan, even after adjusting for factors such as BMI, cholesterol, diabetes, and smoking – all known to influence blood pressure.
Despite this finding, the study found that incidence of cardiovascular disease events, such as heart attack, is higher in men. The authors suggest that an exploration of sexual dimorphism, rather than an assumption of fundamentally similar physiology, in the underlying cardiovascular landscape helps to uncover explanations for the discrepancies in experience that men and women have when it comes to cardiovascular disease.
Contributed by Sheena Smith, MS MA
- Ji H, Kim A, Ebinger J, et al. Sex differences in blood pressure trajectories over the life course. JAMA Cardiol January 2020. doi:10.1001/jamacardio.2019.5306
Does weight loss decrease breast cancer risk?
Excess body weight has long been tied to many serious health risks, including diabetes, hypertension, and some forms of cancer. For women, in particular, excess weight is a known increased risk factor for developing breast cancer.
According to the Susan G. Komen Foundation, being overweight or obese after menopause increases the risk of developing estrogen-receptor positive breast cancer by 30-60 perecent.1 This is thought to be in part due to women with excess body fat tending to have higher levels of circulating estrogens.2 You can test your own estrogen levels with a simple home test if you are interested in how they compare to other women your age.
One question that has not been clearly answered is whether weight loss in women of menopausal age would lower breast cancer risk. This is an important question because overweight and obesity are at near epidemic levels, and because breast cancer is the most common cancer affecting women.
A recent paper3 that analyzed the data from 10 studies and 180,000+ women older than 50 suggests that sustained weight loss is beneficial and could be a very important part of cancer prevention in menopausal and postmenopausal women.
The analysis clearly shows that virtually any sustained weight loss is of benefit. Women who lost and regained weight (if they did not regain all of it), women who lost weight and maintained stable weight, and women who gained but then lost weight, all had lower breast cancer risk compared to women who remained overweight during the years the data was collected.
The authors expressed hope that this knowledge will help motivate at-risk women to lose weight and thereby reduce their risk of developing breast cancer later in life.
Contributed by Jacqueline Jacques, ND
- Overweight, obesity, and breast cancer. http://ww5.komen.org/BreastCancer/OverweightWeightGain.html. [Accessed January 31, 2020.]
- Cleary M, Grossmann M. Obesity and breast cancer: the estrogen connection. Endocrinology 2009;150(6):2537-2542.
- Teras L, Patel A, Wang M, et al. Sustained weight loss and risk of breast cancer in women ≥50 years: a pooled analysis of prospective data. JNCI J Natl Cancer Inst doi:10.1093/jnci/djz226
More evidence that being overweight increases the risk for vitamin D deficiency
Obesity is linked to low vitamin D levels, and potential mechanisms have been elucidated, including an obesity-related sedentary lifestyle resulting in less outdoor activity and sun exposure, sequestration of fat-soluble vitamin D in fat tissue, and dilution of vitamin D in the larger fat mass associated with obesity.
A current study adds to this growing body of evidence for obesity-related low vitamin D levels. The epidemiological study looked at 3,623 Korean adolescent girls and young women (ages 12-29).
As part of the Korea National Health and Nutrition Examination Survey (KNHANES), in addition to a lifestyle and demographics questionnaire, vitamin D levels (serum 25-hydroxyvitamin D), body mass index (BMI), and percent body fat were tested during health examinations between 2008-2014. Overweight/obese was defined in women as a BMI of 25 or greater; in adolescent girls it was defined as a BMI above the 95th percentile for their age group.
Obesity was also defined as 30 percent or more body fat. In the study, vitamin D insufficiency was defined as below 20 ng/mL, although most nutrition-oriented practitioners consider 30 ng/mL to be the minimum serum vitamin D level needed for a definition of sufficiency.
Both increased BMI and higher percent body fat were associated with increased risk for low vitamin D levels. An elevated BMI was associated with a 49-percent increased risk of low vitamin D status; whereas, 30 percent or greater body fat was associated with a 50-percent increased risk for insufficient vitamin D. The study is consistent with previous epidemiological studies of adolescent girls and young women, including a study conducted in southeastern United States.
Contributed by Kathi Head, ND
- Jang H, Lee Y, Park K. Obesity and vitamin D insufficiency among adolescent girls and young adult women from Korea. Nutrients 2019 Dec 13;11(12). pii: E3049. doi: 10.3390/nu11123049.
Whether you are underweight, normal weight, or overweight, do you know what your vitamin D status is? Find out with this simple at-home test.