Technical note: Measurement of total estrone content in foods. Application to dairy products

Diet and fertility: a review

The literature on the relationship between diet and human fertility has greatly expanded over the last decade, resulting in the identification of a few clear patterns. Intake of supplemental folic acid, particularly at doses higher than those recommended for the prevention of neural tube defects, has been consistently related to lower frequency of infertility, lower risk of pregnancy loss, and greater success in infertility treatment. On the other hand and despite promising evidence from animal models, vitamin D does not appear to exert an important role in human fertility in the absence of deficiency. Antioxidant supplementation does not appear to offer any benefits to women undergoing infertility treatment, but it appears to be beneficial when it is the male partner who is supplemented. However, the available evidence does not allow discerning which specific antioxidants, or at which doses, are responsible for this benefit. Long-chain omega-3 fatty acids appear to improve female fertility, although it remains unclear to what extent contamination of shared food sources, such as fish with high levels of environmental toxicants, can dampen this benefit. Lastly, adherence to healthy diets favoring seafood, poultry, whole grains, fruits, and vegetables are related to better fertility in women and better semen quality in men. The cumulative evidence has also piled against popular hypotheses. Dairy and soy, once proposed as reproductive toxicants, have not been consistently related to poor fertility. In fact, soy and soy supplements appear to exert a beneficial effect among women undergoing infertility treatment. Similarly, because data from large, high-quality studies continue to accumulate, the evidence of a potentially deleterious effect of moderate alcohol and caffeine intake on the ability to become pregnant seems less solid than it once did. While a complete picture of the role of nutrition on fertility is far from complete, much progress has been made. The most salient gaps in the current evidence include jointly considering female and male diets and testing the most consistent findings in randomized trials.

In rats fed high-energy diets, taste, rather than fat content, is the key factor increasing food intake: a comparison of a cafeteria and a lipid-supplemented standard diet

Background

Food selection and ingestion both in humans and rodents, often is a critical factor in determining excess energy intake and its related disorders.

Methods

Two different concepts of high-fat diets were tested for their obesogenic effects in rats; in both cases, lipids constituted about 40% of their energy intake. The main difference with controls fed standard lab chow, was, precisely, the lipid content. Cafeteria diets (K) were self-selected diets devised to be desirable to the rats, mainly because of its diverse mix of tastes, particularly salty and sweet. This diet was compared with another, more classical high-fat (HF) diet, devised not to be as tasty as K, and prepared by supplementing standard chow pellets with fat. We also analysed the influence of sex on the effects of the diets.

Results

K rats grew faster because of a high lipid, sugar and protein intake, especially the males, while females showed lower weight but higher proportion of body lipid. In contrast, the weight of HF groups were not different from controls. Individual nutrient’s intake were analysed, and we found that K rats ingested large amounts of both disaccharides and salt, with scant differences of other nutrients’ proportion between the three groups. The results suggest that the key differential factor of the diet eliciting excess energy intake was the massive presence of sweet and salty tasting food.

Conclusions

The significant presence of sugar and salt appears as a powerful inducer of excess food intake, more effective than a simple (albeit large) increase in the diet’s lipid content. These effects appeared already after a relatively short treatment. The differential effects of sex agree with their different hedonic and obesogenic response to diet.

Dairy intake in relation to breast and pubertal development in Chilean girls

Background: Frequent dairy consumption in childhood has been related to higher growth-hormone concentrations that may affect mammary gland and pubertal development.Objective: We evaluated the relation of dairy intake to breast composition at Tanner stage 4 and age at menarche.Design: A total of 515 Chilean girls are included in the Growth and Obesity Cohort Study. The subjects have been followed longitudinally since they were 3-4 y old (from 2006 to the present). Starting in 2013, diet was assessed every 6 mo via a 24-h recall. The breast fibroglandular volume (FGV) was measured with the use of dual-energy X-ray absorptiometry at Tanner stage 4. The date of menarche was reported every 6 mo. Our analysis included 290 girls with data on prospective diet and breast composition and 324 girls with data on prospective diet and age at menarche.Results: The mean ± SD breast FGV and percentage of fibroglandular volume (%FGV) (i.e., FGV divided by total breast volume times 100) at Tanner stage 4 was 81.7 ± 32.2 cm³ and 42.0% ± 16.7%, respectively. Only sweetened, artificially flavored milk-based drinks were associated with the %FGV with girls who consumed >125 g/d having a %FGV that was 4.5% (95% CI: 0.9%, 8.1%) higher than that of girls who consumed none (P-trend = 0.007). Yogurt intake was associated with a lower FGV. Specifically, girls who consumed >125 g yogurt/d had -10.2 cm³ (95% CI: -20.2, -0.3 cm³) less FGV than did girls who consumed no yogurt (P-trend = 0.03). The majority (90.7%) of girls in our cohort attained menarche before the data analyses with a mean ± SD age at menarche of 11.9 ± 0.7 y. In multivariable models, low-fat dairy, low-fat milk, and yogurt intakes were associated with a later age at menarche. In particular, girls who consumed >125 g yogurt/d had menarche, on average, 4.6 mo (95% CI: 1.9, 7.4 mo) later than girls who consumed no yogurt (P-trend = 0.01).Conclusion: More-frequent consumption of sweetened, artificially-flavored milk-based drinks is associated with a higher %FGV, whereas higher yogurt intake is associated with a lower FGV and delayed age at menarche in Chilean girls.

Dairy intake in relation to in vitro fertilization outcomes among women from a fertility clinic

STUDY QUESTION

Is dairy food consumption associated with live birth among women undergoing infertility treatment?

SUMMARY ANSWER

There was a positive association between total dairy food consumption and live birth among women ≥35 years of age.

WHAT IS KNOWN ALREADY

Dairy food intake has been previously related to infertility risk and measures of fertility potential but its relation to infertility treatment outcomes are unknown.

STUDY DESIGN, SIZE, DURATION

Our study population comprised a total of 232 women undergoing 353 in vitro fertilization (IVF) treatment cycles between February 2007 and May 2013, from the Environment and Reproductive Health study, an ongoing prospective cohort.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Diet was assessed before assisted reproductive technology (ART) treatment using a validated food frequency questionnaire. Study outcomes included ovarian stimulation outcomes (endometrial thickness, estradiol levels and oocyte yield), fertilization rates, embryo quality measures and clinical outcomes (implantation, clinical pregnancy and live birth rates). We used generalized linear mixed models with random intercepts to account for multiple ART cycles per woman while simultaneously adjusting for age, caloric intake, BMI, race, smoking status, infertility diagnosis, protocol type, alcohol intake and dietary patterns.

MAIN RESULTS AND THE ROLE OF CHANCE

The age- and calorie-adjusted difference in live birth between women in the highest (>3.0 servings/day) and lowest (<1.34 servings/day) quartile of dairy intake was 21% (P = 0.02). However, after adjusting for additional covariates, this association was observed only among women ≥35 years (P, interaction = 0.04). The multivariable-adjusted live birth (95% CI) in increasing quartiles of total dairy intake was 23% (11, 42%), 39% (24, 56%), 29% (17, 47%) and 55% (39, 69%) (P, trend = 0.02) among women ≥35 years old, and ranged from 46 to 54% among women <35 years old (P, trend = 0.69). There was no association between dairy intake and any of the intermediate outcomes.

LIMITATIONS, REASONS FOR CAUTION

The lack of a known biological mechanism linking dairy intake to infertility treatment outcomes calls for caution when interpreting these results and for additional work to corroborate or refute them.

WIDER IMPLICATIONS OF THE FINDINGS

Dairy intake does not appear to harm IVF outcomes and, if anything, is associated with higher chances of live birth.

STUDY FUNDING/COMPETING INTERESTS

This work was supported by NIH grants R01-ES009718 and R01ES000002 from NIEHS, P30 DK046200 from NIDDK and T32HD060454 from NICHD. M.C.A. was supported by a Ruth L. Kirschstein National Research Service Award T32 DK 007703-16 from NIDDK. She is currently employed at the Nestlé Research Center, Switzerland and completed this work while at the Harvard School of Public Health. The other authors declare no conflicts of interest.

Dairy intake and semen quality among men attending a fertility clinic

OBJECTIVE

To examine the relationship between dairy food intake and semen parameters.

DESIGN

Longitudinal study.

SETTING

Academic medical center fertility clinic.

PATIENT(S)

One hundred fifty-five men.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Total sperm count, sperm concentration, progressive motility, morphology, and semen volume.

RESULT(S)

Low-fat dairy intake was positively related to sperm concentration and progressive motility. On average, men in the highest quartile of intake (1.22-3.54 servings/d) had 33% (95% confidence interval [CI] 1, 55) higher sperm concentration and 9.3 percentage units (95% CI 1.4, 17.2) higher sperm motility than men in the lowest quartile of intake (≤0.28 servings/d). These associations were primarily explained by intake of low-fat milk. The corresponding results for low-fat milk were 30% (95% CI 1, 51) higher sperm concentration and 8.7 percentage units (95% CI 3.0, 14.4) higher sperm motility. Cheese intake was associated with lower sperm concentration among ever-smokers. In this group, men in the highest tertile of intake (0.82-2.43 servings/d) had 53.2% (95% CI 9.7, 75.7) lower sperm concentration than men in the lowest tertile of cheese intake (<0.43 servings/d).

CONCLUSION(S)

Our findings suggest that low-fat dairy intake, particularly low-fat milk, is related to higher sperm concentration and progressive motility, whereas cheese intake is related to lower sperm concentration among past or current smokers.

Estrone and estrone sulfate concentrations in milk and milk fractions

Dairy products naturally contain estrogens, and some consumer groups contend these estrogens cause adverse health effects. The objectives of this research were to characterize estrone (E(1)) and estrone sulfate (E(1)S) concentrations in milk from a large number of individual cows, in skim and fat fractions of milk, and in retail milk to provide food and nutrition practitioners with information to estimate potential consumption. Milk was from Holstein cows. Data are presented as means and standard deviations. Analysis of variance was used to determine differences in E(1) and E(1)S content of whole milk and its skim and fat fractions. Mean E(1) and E(1)S concentrations (n=173 cows) were 7.0±12.7 and 46.7±62.1 pg/mL (25.89±46.96 and 172.74±229.71 pmol/L), respectively. Analysis of milk fractions (n=50 samples) demonstrated that 55% of E(1) and 14% of E(1)S were associated with the fat fraction with the remainder associated with the skim fraction. Concentrations of E(1) and E(1)S in pasteurized-homogenized whole milk (n=8) averaged 10.3±0.6 and 85.9±7.3 pg/mL (38.09±2.22 and 317.74±27.00 pmol/L), respectively. Production rates of E(1) plus estradiol in human beings range from 54,000 to 630,000 ng/day. US Food and Drug administration guidelines state that no physiologic effects occur when consumption is ≤1% of the endogenous quantities produced by the segment of the population with the lowest daily production. This threshold value for intake would be 540 ng/day. Estimated total E(1) intake from three servings of whole milk was 68 ng/day, which represents 0.01% to 0.1% of daily production rates in human beings. These findings support levels below the current guidelines for safe consumption.

Oleoyl-estrone is a precursor of an estrone-derived ponderostat signal

Oleoyl-estrone (OE) is a powerful anti-obesity compound that decreases food intake, decreases insulin resistance and circulating cholesterol. OE stimulates a severe loss of body fat by decreasing adipose tissue lipid synthesis and maintaining lipolysis. Therefore, the body economy loses lipid energy because energy expenditure is maintained. This study analyses the discrepancy between OE effects and the distribution of labelled OE in plasma. Estrone radioimmunoassay of organic solvent plasma extracts of rats treated with OE showed the massive presence of acyl-estrone, but saponification did not release estrone, but containing similar unknown compound. Analysis of label distribution in plasma after oral gavages of (3)H-OE showed the presence of a more hydrophilic compound than OE or any estrogen as well as (3)H(2)O, formed from (3)H-OE in the acidic stomach medium. OE was not attached to a specific transporter in plasma. Through serum HPLC analysis we found W, a labelled derivative more hydrophilic than OE or estrone. The results were confirmed using (14)C-OE. HPLC-MS/MS studies showed that plasma OE levels were one order of magnitude lower than those of W. When liver cell cytosols from rats laden with (3)H-OE were incubated with nuclei from untreated rats, the OE-derived label (i.e., Ws) was found attached to nuclear DNA. Neither estradiol nor estrone interfered with its binding. W is a fairly hydrophilic compound of low molecular weight containing the estrone nucleus, but it is not an ester because saponification or esterases do not yield estrone as OE does. It is concluded that OE acts through its conversion to W, its active form; which binds to a nuclear receptor different from that of estrogen. The estimated W serum levels are proportional to the pharmacological OE effects in vivo. We postulate W as a new type of hormone that exerts the full range of in vivo effects thus far attributed to OE. The full identification of W is anticipated to open the way for the development of new OE-like anti-obesity drugs.

Oleoyl-estrone

Oleoyl-estrone (OE) is a powerful slimming agent that is also present in plasma and adipose tissue, where it is synthesized. It acts through the formation of a derivative W. OE effects (and W levels) are proportional to the dose. OE reduces food intake but maintains energy expenditure (thermogenesis). The energy gap is fulfilled with adipose tissue fat, sparing body protein and maintaining glycemia (and glycogen) with lower insulin and leptin levels. OE (in fact W) acts through specific receptors, different from those of estrogen. OE increases cholesterol catabolism, reducing hypercholesterolemia in obese rats. The main metabolic effect on adipose tissue is lowering of lipid synthesis, maintaining unchanged the intracellular lipolytic processes; the imbalance favors the progressive loss of fat, which is largely used by the muscle. OE administration induces additive effects with other antiobesity agents, such as β(3)-adrenergic agonists, forcing a massive loss of lipid. Corticosteroids markedly limit OE action by altering the liver control of lipogenesis. OE also inhibits the action of 17β-hydroxysteroid dehydrogenase, decreasing the synthesis of β-estradiol and testosterone. Discontinuous treatment allows for maximal efficacy both in rats and humans. OE has the advantage that the loss of fat is maintained and does not require additional dietary limitations.

Intestinal oleoyl-estrone esterase activity in the Wistar rat

Low-dose oral oleoyl-estrone (OE) (i.e. in dairy products) is hydrolysed to estrone, which promotes growth and fat deposition. However, pharmacological doses of OE are absorbed largely intact and elicit fat losses. Thus, in order to find out how the intestine handles OE, esterase activity (at pH 5, 7 or 8) was measured in rat stomach, duodenum, jejunum, ileum, cecum, large intestine, and liver using OE as substrate. There were no sex-related differences. Pure pancreatic cholesterol-ester esterase hydrolysed OE even in the absence of taurocholate. The differences in the pH-related activity distribution pattern and selective inhibition and taurocholate dependence show that, in addition to the luminal (i.e. pancreatic) cholesterol-ester esterase, other esterases hydrolyse OE; these combined activities may be sufficient to rapidly dispose of pharmacological doses of OE. Female rats received a tritium-labeled OE gavage; the luminal and tissue label content were measured up to 24 h. The high retention of label in the stomach suggest that this may be a significant site of absorption. The rapid decrease of label in intestinal lumen (and rat tissues) shortly after the administration, hint at rapid absorption and disposal. In conclusion, the high OE-esterase activity and early absorption of OE are indicative of upper gastro-intestinal tract absorption skipping most of the medium-tract esterases.

In the rat, estrone sulphate is the main serum metabolite of oral oleoyl-estrone

Two different oral doses of oleoyl-estrone: 1 and 10 nmol/g a day were given once to male Wistar rats. The serum levels of free estrone, estrone sulphate, estradiol, and acyl-estrone were measured at intervals up to 72 h after the gavage. Oleoyl-estrone was rapidly absorbed; with the 1 nmol/g dose no changes were observed in plasma acyl-estrone but levels increased dramatically with 10 nmol/g, peaking at 6 h; high acyl-estrone levels were maintained up to 24 h, returning to normalcy at 48 h. With the 10 nmol/g dose, free estrone at most doubled its levels but estrone sulphate concentrations rose by one order of magnitude; in both cases, the increases soon (2 h) reached a plateau that was maintained for almost two days. Estradiol levels remained unchanged except for a transient peak at 2 h at the 10 nmol/g dose. The relationship between free estrone and its sulphate was linear, and those of estrone and estrone sulphate versus acyl-estrone showed the existence of an upper serum concentration limit for both molecules. The results hint at estrone sulphate being an important metabolite of oleoyl-estrone disposal, confirm the limited estrogenic response to oleoyl-estrone administration and agree with a rapid absorption and disposal of oleoyl-estrone, nevertheless maintaining high circulating levels of the ester for a time after its oral administration.