Light at night (especially blue light)
It’s long been known that bright light during the night suppresses melatonin. More recently, the critical factor has been identified as blue light of around 480 nm wavelength, a big component of the white light emitted by LEDs and other lamps described as daylight or cool white. Now that this has been recognized, smartphone, tablet, and computer manufacturers have begun taking steps to reduce blue light emissions from their screens in the evening and during the night (on Apple devices, this feature is called “night shift”).
Why is this important? Because melatonin suppresses insulin secretion1, so when blue or white light at night suppresses melatonin, insulin levels will be higher, resulting in more inflammation.
Handling thermal paper (eg, receipts, tickets)
Bisphenol A (BPA) may no longer be used in Canada for the manufacture of baby bottles because it is known to disrupt hormones, especially estrogen. Perhaps less well known is that BPA stimulates insulin secretion2. BPA use has greatly increased since its commercial introduction in the 1950s, so that today it is ubiquitous in our environment. An environmentally important use is in the coating on paper used for receipts produced by thermal printers, whether at the grocery store, the gas pump, or anywhere one uses a credit card. Other thermally printed items include bus and train tickets, parking tickets, boarding passes, lottery slips and vegetable weight stickers. BPA has also been detected in paper products other than thermal paper including currency bills, food contact papers, food cartons, napkins, paper towels, and toilet paper. These products are typically made from recycled paper which includes thermal printer paper.
Handling any of these paper products can cause BPA to be absorbed through the skin. Greasy skin, including use of hand lotions, increases skin absorption. The alcohol found in many hand sanitizer products also increases absorption. Hand washing only removes some of the BPA from the skin. Both epidemiologic studies as well as laboratory studies with animals suggest that current environmental exposures to BPA may be contributing to the current worldwide epidemic of obesity and type 2 diabetes3.
Just as for blue light at night, there is reason to believe that this is due to increased insulin, suggesting that BPA stimulates inflammation.
Short sleep duration has been found to be associated with obesity and high BMI and experimental studies suggest the cause as increased appetite, particularly for carbohydrates, when sleep is restricted4.
Night-shift work exposure appears to increase risk for breast cancer as well as for cardiovascular mortality5. The effect may be from the increased light exposure which suppresses melatonin, in turn leading to higher insulin levels which promote cancer (and inflammation).
Most vitamins and supplements (including hidden vitamins in foods)
A 2011 paper in the Archives of Internal Medicine looked at the self-reported use of dietary supplements and mortality in over 38,000 older women, part of the ongoing Iowa Women’s Health Study6. It was found that vitamin B6 and folic acid supplements increased mortality, as did iron, zinc, magnesium, and copper supplements. Iron, in particular, showed a strong dose-response relationship to mortality. On the other hand, calcium supplements decreased mortality.
Now, we all know about how important folic acid is for reproductive success. Folic acid is so effective at preventing certain birth defects when taken by pregnant women, that starting in 1998 flour manufacturers have been required to add folic acid to flour to prevent these neural tube defects. Of course, this means that we might be getting more folic acid than is good for us when we’re older.
The decreased mortality in older women taking calcium supplements is interesting. The commentary which followed this article7 pointed out that other studies had shown risks from calcium. For example, a meta-analysis of randomized trials demonstrated an increased MI risk from calcium supplements, while an observational study identified a 24% increased CHD risk. Increased risk of prostate cancer has also been found. The same commentary also referenced meta-analyses of other anti-oxidants reporting increased cardiovascular and all-cause mortality from vitamins A and E, as well as beta-carotene.
An example is a study involving a total of more than 35,000 men from 427 study sites in the United States, Canada, and Puerto Rico, all over 50 years of age8. The men were randomized into one of 4 different groups: selenium supplement, vitamin E supplement, both selenium and vitamin E, or placebo. Over 10 years, the vitamin E group had a significantly elevated risk of developing prostate cancer, compared to placebo.
An intervention study involved over 29,000 people in China who received one of four different combinations of daily supplements over a period of 6 years9 with the intention to prevent gastric and esophageal cancer. Linxian is a province with high baseline rates of esophageal cancer. This paper reported on outcomes 10 years later. What they found was: vitamin A and zinc increased total and stroke mortality; vitamin C and molybdenum decreased stroke mortality; selenium, vitamin E, and beta-carotene decreased mortality (all causes, cancer overall, and gastric cancer).
An interesting finding showed up when results were separated by age. In the group who received selenium, vitamin E, and beta-carotene, there was 17% less death from esophageal cancer in the under-55 group, but 14% increased deaths in the over-55 group. So age may play an important role.
Why would vitamin or other supplements be bad for us? As with most things in life that we need, too little is bad, but too much is bad also. It’s clear that we need food, water, small amounts of vitamins and minerals, sunshine, oxygen, and so on. But too much food leads to obesity, diabetes, high blood pressure, heart disease, etc. Drinking too much water can cause seizures. Too much oxygen in premature infants causes blindness. Too much sun causes cataracts and skin cancer. And too much of certain vitamins is dangerous, as we saw above.
It may also be that separating out a particular compound from the plant-based food in which it is found, modifies its arbsorption or its functioning. Plants have multiple ways of influencing our physiology, including the effects of non-digestible fibre on our gut microbiome, plant microRNA acting on the microbiome, and maybe even plant microRNA being absorbed and acting directly inside our cells. This mechanism, called cross-kingdom microRNA, is explored in more depth in this paper.
Smoothies and juices
When the fibre content of plant-based foods is mechanically disrupted by blending or juicing, the food will be more rapidly absorbed and stimulate higher levels of insulin10.
Whew! Who knew?
In the next instalment of my DIY: Inflammation essay, I’ll be focusing on dietary supplements which may be beneficial, and why, in contrast to this instalment’s message which was to avoid most dietary supplements.
- Li Y, Xu Z. Effects of Melatonin Supplementation on Insulin Levels and Insulin Resistance: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Horm Metab Res. 2021;53:616-624. PMID 34496412
Wajid F, Poolacherla R, Mim FK, Bangash A, Rutkofsky IH. Therapeutic potential of melatonin as a chronobiotic and cytoprotective agent in diabetes mellitus. J Diabetes Metab Disord. 2020;19:1797-1825. PMID 33520862 ↩
- Soriano S, Alonso-Magdalena P, Garcia-Arevalo M et al. Rapid insulinotropic action of low doses of bisphenol-A on mouse and human islets of Langerhans: role of estrogen receptor beta. PLoS One. 2012;7:e31109. PMID 22347437 ↩
- Akash MSH, Sabir S, Rehman K. Bisphenol A-induced metabolic disorders: From exposure to mechanism of action. Environ Toxicol Pharmacol. 2020;77:103373. PMID 32200274 ↩
- Van Cauter E, Spiegel K, Tasali E, Leproult R. Metabolic consequences of sleep and sleep loss. Sleep Med. 2008;9 Suppl 1:S23-8. PMID 18929315 ↩
- Wei F, Chen W, Lin X. Night-shift work, breast cancer incidence, and all-cause mortality: an updated meta-analysis of prospective cohort studies. Sleep Breath. 2021PMID 34775538 ↩
- Mursu J, Robien K, Harnack LJ, Park K, Jacobs DR. Dietary supplements and mortality rate in older women: the Iowa Women’s Health Study. Arch Intern Med. 2011;171:1625-1633. PMID 21987192 ↩
- Bjelakovic G, Gluud C. Vitamin and mineral supplement use in relation to all-cause mortality in the Iowa Women’s Health Study. Arch Intern Med. 2011;171:1633-1634. PMID 21987193 ↩
- Klein EA, Thompson IMJ, Tangen CM et al. Vitamin E and the risk of prostate cancer: the Selenium and Vitamin E Cancer Prevention Trial (SELECT). JAMA. 2011;306:1549-1556. PMID 21990298 ↩
- Qiao YL, Dawsey SM, Kamangar F et al. Total and cancer mortality after supplementation with vitamins and minerals: follow-up of the Linxian General Population Nutrition Intervention Trial. J Natl Cancer Inst. 2009;101:507-518. PMID 19318634 ↩
- Bolton RP, Heaton KW, Burroughs LF. The role of dietary fiber in satiety, glucose, and insulin: studies with fruit and fruit juice. Am J Clin Nutr. 1981;34:211-217. PMID 6259919
Haber GB, Heaton KW, Murphy D, Burroughs LF. Depletion and disruption of dietary fibre. Effects on satiety, plasma-glucose, and serum-insulin. Lancet. 1977;2:679-682. PMID 71495 ↩
- Instalment 5: behaviours that reduce inflammation
- instalment 7: dietary supplements that may be helpful