Christian Unger

By: Rachel Namery, MS Nutrition Science

An Interesting Role of Vitamin D in Glucose Homeostasis
A recent study suggests that higher levels of vitamin D are associated with a decreased risk of glucose imbalance among non-diabetic Southwest Chinese adults.

Type II diabetes is a metabolic disease that is far too prevalent across the globe. For example, in 2013, half of the population in China was prediabetic; a condition in which fasting glucose levels are between 100 -125. Individuals with prediabetes are at a greater risk of developing type II diabetes. Unlike most diabetes, pre-diabetes is reversible if caught early and fixed with health lifestyle changes. Rates of type 2 diabetes have increased markedly since 1960 in parallel with obesity. As of 2015 there were approximately 392 million people diagnosed with the disease compared to around 30 million in 1985, a ten-fold increase in 30 years. Interestingly, those born in the summer have a lower risk of developing type II diabetes. Vitamin D status plays a crucial role in helping prevent many diseases including some cancers, multiple sclerosis, cardiovascular disease, osteoporosis and diabetes. Studies have shown a direct correlation between vitamin D deficiency and insufficiency with obesity and type II diabetes. Doctors and scientists theorize this relationship is because of vitamin D’s ability to help regulate pancreatic beta-cell function, insulin action and inflammation. With so much compelling research on vitamin D, it is becoming clearer that levels need to be monitored as a part of a proactive approach to one’s health.

Interesting research on vitamin D and glucose homeostasis
A recent large cross-sectional study examined whether a higher serum vitamin D level was
associated with better glucose homeostasis among 1,514 healthy adults between the ages of 25 and 65 (mean age of 48.74) without diabetes. The sample was broken down into three groups: one was the group of people who were deficient (25(OH)D<20 ng/ml) in vitamin D, two was the group that was insufficient (25(OH)D between 20-30 ng/ml) and group three were those with 25(OH)D >30 ng/ml. The researchers measured the participants 25(OH)D levels, fasting plasma glucose, hemoglobin A1C, (HbA1c), fasting insulin, the homeostatic model assessment 2-insulin resistance (HOMA2-IR) and odds of having prediabetes. The researchers used these measures to define glucose homeostasis. Other anthropometric measures and demographics were recorded as well.

What were the outcomes? This study suggests that adequate vitamin D levels (25(OH)D >30 ng/ml) were correlated with healthier glucose homeostasis. In addition, the researchers found a significant inverse association between 25(OH)D and fasting insulin (p = 0.016), insulin resistance (p = 0.016) and HBA1c (p =0.0003). That is, the higher one’s vitamin D, the less likely one has diabetic markers. The study also suggests lower levels of vitamin D are associated with prediabetes risk. Adults in with the highest 25(OH)D had a 12.4% lower fasting insulin (p = 0.0007), 12.3% lower HOMA2-IR (p = 0.0007) and 2.2% lower HbA1c (p = 0.0001) compared to those with the lowest vitamin D levels. Also, the researchers observed a 32% lower odds of prediabetes in the adults in the highest tertile of serum vitamin D compared to those in the lowest tertile.

The researchers concluded,
“Higher serum 25(OH)D level is associated with decreased risk of impairment of glucose
homeostasis among adults without diabetes in Southwest China. Further studies are
warranted to determine the role of vitamin D in glucose homeostasis.”
These findings support past studies on the topic in both non-diabetics and diabetics. For example, a meta-analysis including 71 studies that evaluated 25(OH)D status in both diabetic and non-diabetics found a significant inverse association between vitamin D status and type II diabetes. They also found a correlation between vitamin D deficiency and higher fasting plasma glucose in both diabetics and non-diabetics.

Possible Recommendations
After consulting with your doctor and determining your vitamin D status you could possibly implement more sun exposure or supplementation to bring your levels back to an optimal range which may help with glucose homeostasis.

Source
Danting.Li. et al. Higher Serum 25(OH)D level is associated with decreased risk of impairment of glucose homeostasis: data from SouthWest China. BMC Endocrine

By: Rachel Namery, MS Nutrition Science

What is Vitamin D and What Does it Do?

Vitamin D is a fat-soluble vitamin found in small amounts of some foods, added to some food, and available as a dietary supplement. It also produced by the body when UV rays from sunlight hit the skin and trigger vitamin D synthesis. Vitamin D that is obtained from the sun, food, and supplements is inert in the body and must undergo 2 hydoxylations within the body for activation. The first happens in the liver and converts Vit D into 25-hydroxyvitamin D, also known as calcidiol. Then the second step occurs primarily within the kidneys and forms the biologically active form of 1,25-dihydroxyvitamin D, known as calcitriol.

Vitamin D promotes calcium absorption within the gut and helps to maintain proper levels of serum calcium and phosphate concentrations to help normal mineralization of bone and to prevent hypocalcemic tetany. It is also used for bone growth and bone remodeling by the osteoblasts and osteoclasts. Without the proper levels of vitamin D, the bones can become thin, brittle, or misshapen. Vitamin D sufficiency helps prevent rickets and osteomalacia in children and adults respectively. Together with calcium, vitamin D helps to protect older individuals form osteoporosis.

Vitamin D also has other roles within the body of which include modulation of cell growth, neuromuscular and immune function, and also the reduction of inflammation. Many genes that are responsible for encoding proteins that regulate cell proliferation, differentiation, and apoptosis are also modulated in part by vitamin D. This role of role of vitamin D is primarily what this article focuses on.

Vitamin D as a protective tool against colorectal cancer?
A new meta-analysis of 17 studies found vitamin D levels < 40 ng/ml and increased increased risk for colorectal cancer.

What is Colorectal Cancer?
Colorectal cancers are any cancers that start in the rectum or colon. These cancers usually start as polyps, or growths, on the innermost lining of the rectum or colon. Like many cancers, this type can spread very quickly and grow to all the other layers of the colon and rectum; other times it is indolent. The American Cancer Society predicted that 1 in 21 men and 1 in 23 women in the United States will develop some type of colorectal cancer throughout their lifespan and over 50,000 people die from this cancer every year. This is an alarming number. Once this cancer spreads it needs to be treated aggressively via chemotherapy, radiation or other invasive therapies. Some risk factors for colorectal cancer include, genetic predisposition, lifestyle (diet, smoking, inactivity), type II diabetes, obesity and a history of polyps. Thankfully, there is something you can do to help protect yourself against developing colorectal cancer, even if you are at an increased risk from other factors.

Vitamin D and Colorectal Cancer
Studies show​ a connection between vitamin D status and colorectal cancer. One ​meta analysis showed an inverse relationship between vitamin D levels and risk of colorectal cancer. They also found that patients who had colorectal cancer experienced improved survival rates if they had a higher vitamin D status.

A recent article pooled 17 cohort studies and evaluated the research on circulating vitamin D status and risk of colorectal cancer. The 17 cohort studies consisted of 5,706 participants with colorectal cancer case and 7,107 controls who all had varying levels of circulating 25(OH)D. They considered vitamin D deficiency as levels below 12 ng/mL (30 nmol/L), sufficiency as levels between 20-25 ng/mL (50-62.5 nmol/L), and optimal levels ranged between 30-40 ng/mL (75-100 nmol/L).

The Findings
● Vitamin D levels below 12 ng/mL was associated with a 31% increased colorectal cancer
risk (RR: 1.31; CI: 1.05-1.62).
● Those with vitamin D levels between 30 – 34.9 ng/mL experienced a 19% decreased risk
of developing colorectal cancer (RR: 0.81; CI: 0.67 to 0.99).
● Vitamin D levels between 35-40 ng/mL was associated with a 27% reduced risk of
colorectal cancer (RR: 0.73; CI: 0.59-0.91).
● They also found in women, for each 10 ng/mL (25 nmol/L) increase in circulating vitamin
D, there was a 19% decreased risk of colorectal cancer.
The researchers concluded,
“Optimal 25(OH)D concentrations for colorectal cancer risk reduction, 75-100 nmol/L (30-40 ng/ml), appear higher than current IOM recommendations.”

The findings showed that the inverse relationship of 25(OH)D and risk of colorectal cancer was statistically significant in women (p < 0.001) but not statistically significant in men (p = 0.20). This analysis suggests that colorectal cancer risk decreases as circulating 25(OH)D increases up to 40 ng/mL (100 nmol/L).

Vitamin D Council recommendations
Supplementing with 5,000-10,000 IU vitamin D3 per day may help reduce one’s risk of colorectal cancer. If levels > 40 ng/ml they are possibly more protective, however, like in breast cancer, no studies have addressed it.

Source
McCullough,M et al. Circulating vitamin D and colorectal cancer risk: an international pooling
project of 17 cohorts .Journal national cancer institute, 2018

These are just some general tips from literature and also anecdotal experience that I have noticed over the years as I prioritize sleep above my training. It is the one of the most important things in my life.

[Read more…] about Christian’s Tips for Sleep