Does soy protein affect circulating levels of unbound IGF-1?

The skeletal safety of milk-derived proteins: A meta-analysis of randomized controlled trials

PURPOSE

There has been a persistent claim that dairy products contain calcium-leaching proteins, although the soundness of such a claim has been challenged. A meta-analysis of randomized controlled trials (RCTs) on the effects of milk-derived protein supplementation on bone health indices in adults was performed to reconcile the controversy surrounding the potential skeletal safety concerns of proteins of dairy origin.

METHODS

The PubMed and Web of Science databases were searched for relevant RCTs. A random-effects model was used to generate pooled effect sizes and 95% confidence intervals.

RESULTS

Milk-derived protein supplementation did not significantly affect whole-body BMD (n = 7 RCTs) and BMD at the lumbar spine (n = 10), hip (n = 8), femoral neck (n = 9), trochanter (n = 5), intertrochanter (n = 2), and ultradistal radius (n = 2). The concentrations of bone formation markers (bone-specific alkaline phosphatase [n = 11], osteocalcin [n = 6], procollagen type 1 amino-terminal propeptide [n = 5]), bone resorption markers (N-terminal telopeptide of type 1 collagen [n = 7], C-terminal telopeptide of type 1 collagen [n = 7], deoxypyridinoline [n = 4]), and parathyroid hormone (n = 7) were not significantly affected. However, increased insulin-like growth factor-1 (IGF-1) concentrations (n = 13) were observed. Reduced IGF-1 concentrations were observed when soy protein was used as a comparator, and increased IGF-1 concentrations were observed when carbohydrate was used.

CONCLUSION

Our findings do not support the claim that proteins of dairy origin are detrimental to bone health.

The health effects of soy: A reference guide for health professionals

Soy is a hotly debated and widely discussed topic in the field of nutrition. However, health practitioners may be ill-equipped to counsel clients and patients about the use of soyfoods because of the enormous, and often contradictory, amount of research that has been published over the past 30 years. As interest in plant-based diets increases, there will be increased pressure for practitioners to gain a working knowledge of this area. The purpose of this review is to provide concise literature summaries (400-500 words) along with a short perspective on the current state of knowledge of a wide range of topics related to soy, from the cholesterol-lowering effects of soy protein to the impact of isoflavones on breast cancer risk. In addition to the literature summaries, general background information on soyfoods, soy protein, and isoflavones is provided. This analysis can serve as a tool for health professionals to be used when discussing soyfoods with their clients and patients.

Thiamine Demonstrates Bio-Preservative and Anti-Microbial Effects in Minced Beef Meat Storage and Lipopolysaccharide (LPS)-Stimulated RAW 264.7 Macrophages

This study assessed the anti-inflammatory effect of thiamine (TA) in lipopolysaccharide-stimulated RAW264.7 cells and also assessed the preservative properties of TA in minced beef. TA demonstrated a concentration-dependent antimicrobial effect on microbial contaminants. Inhibition zones and MIC from the effect of TA on the tested bacterial strains were respectively within the ranges 15−20 mm and 62.5−700 µg/mL. TA significantly (p < 0.05) decreased all the pro-inflammatory factors [(nitric oxide (NO), prostaglandin E2 (PGE2), TNF-α, IL-6, IL-1β, and nuclear factor-κB (NF-κB)] monitored relative to LPS-stimulated RAW264.7 cells. TA inhibited the expression of both iNOS and COX-2. In minced beef flesh, the growth of Listeria monocytogenes was inhibited by TA. TA improved physicochemical and microbiological parameters of stored minced beef meat compared to control. Principal component analyses and heat maps elucidate the quality of the tested meats.

Different Effects of Soy and Whey on Linear Bone Growth and Growth Pattern in Young Male Sprague-Dawley Rats

The aim of this investigation was to determine the better protein for supporting optimal linear growth, as the exact composition and benefits of specific dietary proteins in supporting linear growth is unknown. In the current study, we compared the effect of soy and whey proteins, both proteins contain all essential amino acids and are considered the best proteins in their categories. Young male rats were subjected to multiple feeding protocols using iso-energetic diets containing soy or whey as the sole protein source. The rats were allowed to eat ad libitum for 11, 24, or 74 days in the first set of experiments, and the soy group was pair-fed to the whey group in the second set. The differences in weight gain, food consumption, and humeri length of the soy group that were greater at the beginning of the ad libitum experiments lessened over time. Pair-fed experiments revealed that the increased weight and humeri length resulted from the differences in food consumption. However, other parameters were protein specific. Bone quality, which was better in the soy group at 24 days, was matched by the whey group and even surpassed that of the soy group in the long-term experiment, with a significantly greater bone mineral density, cortical thickness, and growth plate. Although in the short term the levels of insulin like growth factor (IGF)-I were similar between the groups, IGF-I increased with age in the whey group, and the levels at the long-term experiment were significantly higher compared to the soy group. Furthermore, using the pair fed setup made it clear that when the difference in food consumption were no longer playing part, whey was more efficient in increasing IGF-I. There were no indications of metabolic sequelae. Although the use of soy is gaining in popularity as a sustainable protein, our findings indicate a better effect of whey on linear growth by leading to slower growth with better-organized epiphyseal growth plates and bone quality.

Naturally occurring hormones in foods and potential health effects

Hormones and hormone-like substances, for example, phytoestrogens, are food components that can be endogenously produced by a food source or occur secondary to farming practices. The hormone content of foods has been studied for decades, and safety evaluations in the United States and Europe indicate that naturally occurring hormones found in foods are safe for human consumption. More recent studies have focused on the role of certain hormones found in specific foods (e.g. dairy or soy) and their potential health effects. However, limited summaries exist on food content of hormones and hormone-like phytoestrogens in the context of a comprehensive US diet and implications, if any, of their daily consumption for overall health. This review provides an outline of hormone biosynthesis and functions in the body; discusses the more commonly studied, naturally occurring hormones in food and their biological role within food; estimates relative dietary contribution and when available, bioavailability, of naturally occurring food hormones; and summarizes the potential health associations of their intake in food. Based on the review of the scientific literature, the hormone content of typical serving sizes of commonly consumed foods is undetectable or in quantities that fall well within safety guidelines without any evidence for adverse effects on health.

The effect of soy intervention on insulin-like growth factor 1 levels: A meta-analysis of clinical trials

A low insulin-like growth factor 1 (IGF-1) level is known to be associated with many disorders. Several studies have shown that soy consumption may influence IGF-1, but the findings remain inconclusive. In this work, we conducted a systematic review and meta-analysis to provide a more accurate estimation of the effect of soy consumption on plasma IGF-1. A comprehensive systematic search was performed in Scopus, Embase, Web of Science, and PubMed/MEDLINE databases from inception until October 2019. Eight studies fulfilled the eligibility criteria. The pooled weighted mean difference (WMD) of the eligible studies was calculated with random-effects approach. Overall, a significant increment in plasma IGF-1 was observed following soy intervention (WMD: 13.5 ng/ml, 95% CI: 5.2, 21.8, I2 = 97%). Subgroup analyses demonstrated a significantly greater increase in IGF-1, when soy was administered at a dosage of ≤40 g/day (WMD: 11.7 ng/ml, 95% CI: 10.9 to 12.6, I2 = 98%), and when the intervention duration was <12 weeks (WMD: 26.6 ng/ml, 95% CI: 9.1 to 44.1, I2 = 0.0%). In addition, soy intervention resulted in a greater increase in IGF-1 among non-healthy subjects (WMD: 36 ng/ml, 95% CI: 32.7 to 39.4, I2 = 84%) than healthy subjects (WMD: 9.8 ng/ml, 95% CI: 8.9 to 10.7, I2 = 90%). In conclusion, this study provided the first meta-analytical evidence that soy intake may increase IGF-1 levels, but the magnitude of the increase is dependent on the intervention dosage, duration, and health status of the participants.