Exposure to a chemical in tobacco smoke could make it more difficult for people to see in low-contrast conditions, such as low light, fog or glare, a new study suggests.
Researchers found that higher levels of cadmium in the blood were associated with diminished contrast sensitivity, they report in JAMA Ophthalmology.
“This particular aspect of vision is really important because it affects your ability to see the end of a curb or put a key into a lock in low light,” said lead author Adam Paulson of the University of Wisconsin, Madison, School of Medicine. “It’s something that at this point in time there’s no way to correct, unlike visual acuity, which you can easily correct with glasses or contact lenses.”
Smoking can raise cadmium levels, as can consumption of leafy green vegetables and shellfish, Paulson said. It may be possible to eat greens and avoid cadmium if you can find produce that has not been treated with pesticides, he added.
For a closer look at the impact of two heavy metals, cadmium and lead, Paulson and his colleagues analyzed data from a larger study dubbed the Beaver Dam Offspring Study, which was designed to look at the aging process. Volunteers enrolled in that study between 2005 and 2008.
Both lead and cadmium accumulate in the retina, Paulsen said.
The retina is the layer of nerve cells at the back of the eye that senses light and sends signals to the brain.
Volunteers’ contrast sensitivity was examined through an eye test. Instead of making letters smaller and smaller, researchers made successive reductions in the contrast between the letters and the background. Volunteers would start with black letters against a white background. Then, with each iteration, the letters would become more and more washed out.
At the beginning of the study, all 1,983 participants had no impairment. All were retested at five and 10 years after the study started. At the 10-year mark, nearly one quarter of the study volunteers had some impairment of their contrast sensitivity, and that impairment was associated with levels of cadmium, but not lead.
That doesn’t necessarily mean that lead won’t impact contrast sensitivity. “Levels of lead in our study population were actually quite low,” Paulsen said. “It could be that in our study there wasn’t enough exposure to lead. It’s possible that another study might find an association.”
The new study suggests “that certain trace chemicals that we are exposed to in small amounts could be harming our eyes in subtle, incremental ways over time,” said Dr. Mandeep S. Singh of the Wilmer Eye Institute at Johns Hopkins Medicine. “Here, the investigators implicate cadmium, which is present at relatively high levels in cigarette smoke, but there could be other culprits which we don’t know about. But it is another good reason to avoid smoking.”
Many people don’t realize they can have good visual acuity, 20-20, and still not feel like they can see well, Singh said in an email. “Even people who can read all the way down to the smallest letters on the eye chart can have deficits in contrast sensitivity that tells us their vision is not OK.”
Cadmium is a neurotoxin, and it could be damaging the nerve cells of the vision system, Singh said.
Even those with 20-20 vision can experience problems with daily living if their contrast sensitivity is impaired, said Dr. Nicholas J. Volpe, George and Edwina Tarry Professor and chairman of the department of ophthalmology at Northwestern University’s Feinberg School of Medicine in Chicago.
Contrast sensitivity declines as we age, Volpe said. But the new study suggests there might be other factors that can affect it.
Volpe cautioned that the study has found an association, but it can’t prove that cadmium actually causes contrast sensitivity to decline. It’s possible cadmium is a marker for some other factor.
Another issue is that the researchers weren’t able to say that cadmium, independent of smoking, was associated with contrast sensitivity declines, Volpe said. So, until there are more studies, “I don’t know that we’ll be checking cadmium levels,” he said. “More often I’ll be saying, don’t smoke.”
Coffee compounds may help fight prostate cancer
In a first, scientists have identified compounds found in coffee which may inhibit the growth of prostate cancer. The study, published in the journal The Prostate, was carried out on drug-resistant cancer cells in cell culture and in a mouse model. Coffee is a complex mixture of compounds which has been shown to influence human health in both positive and negative ways. There is increasing evidence that drinking certain types of coffee is associated with a reduction in incidence of some cancers, including prostate cancers.
Researchers from Kanazawa University in Japan have studied the effects of two compounds found in coffee, kahweol acetate and cafestol, on prostate cancer cells and in animals, where they were able to inhibit growth in cells which are resistant to common anti-cancer drugs such as Cabazitaxel. The researchers initially tested six compounds, naturally found in coffee, on the proliferation of human prostate cancers cells in a petri-dish. They found that cells treated with kahweol acetate and cafestol grew more slowly than controls. They then tested these compounds on prostate cancer cells which had been transplanted to 16 mice.
Four mice were controls, four were treated with kahweol acetate, four with cafestol, with the remaining mice being treated with a combination of kahweol acetate and cafestol. “We found that kahweol acetate and cafestol inhibited the growth of the cancer cells in mice, but the combination seemed to work synergistically, leading to a significantly slower tumour growth than in untreated mice,” said Hiroaki Iwamoto from Kanazawa University.
“After 11 days, the untreated tumours had grown by around three and a half times the original volume, whereas the tumours in the mice treated with both compounds had grown by around just over one and a half times the original size,” said Iwamoto. This is a pilot study, so this work shows that the use of these compounds is scientifically feasible, but needs further investigation, researchers said. It does not mean that the findings can yet be applied to humans.
“What it does show is that these compounds appear to have an effect on drug resistant cells prostate cancer cells in the right circumstances, and that they too need further investigation,” said Iwamoto. “We are currently considering how we might test these findings in a larger sample, and then in humans,” he said.
Kahweol acetate and cafestol are hydrocarbons, naturally found in Arabica coffee. The coffee-making process has been found to affect whether these compounds remain in coffee after brewing (as with espresso), or whether they are stripped out (as when filtered). “These are promising findings, but they should not make people change their coffee consumption. However, if we can confirm these results, we may have candidates to treat drug-resistant prostate cancer,” said Atsushi Mizokami, professor at Kanazawa University.
Strength training may reduce fatty liver disease
Besides being beneficial for heart, strength training can also reduce accumulation of fat in liver and improve blood glucose regulation, says a study on mice. The study, led by a team from the University of Campinas in Brazil, showed strength training can reduce fat stored in liver and improve blood glucose control in obese mice, even without overall loss of body weight.
The findings suggest strength training may be a fast and effective strategy for reducing the risk of fatty liver disease and diabetes in obese people.
“That these improvements in metabolism occurred over a short time even though the overall amount of body fat was unchanged, it suggests strength training can have positive effects on health and directly affect liver’s function and metabolism,” said Pereira de Moura from the varsity.
“It may be a more effective, non-drug and low-cost strategy for improving health,” she said. During the research, published in the Journal of Endocrinology, the team investigated effects of strength-based exercise on liver fat accumulation, blood glucose regulation and markers of inflammation in obese mice.
Obese mice performed strength training over a short time, the equivalent of which in humans would not be enough to change their body fat composition.
After this short-term training, the mice had less fatty livers, reduced levels of inflammatory markers and their blood glucose regulation improved, despite no change in their overall body weight.
These health benefits would be even more effective if accompanied by reduction of body fat, she added. Based on these findings, obese individuals could be directed to increase their activities through strength training, but should always first consult their primary care physician.
More investigation is required in both animals and people to understand how liver metabolism is affected by strength training. Obesity, a growing health epidemic globally, leads to inflammation in liver and impairs its ability to regulate blood glucose. It increases the risk of Type-2 diabetes and its associated complications, including nerve and kidney damage.
Do Eggs Increase Your Cholesterol Levels? Here’s What You Should Know
Do you savour cheese omelettes? If so, think again as consuming more eggs and dietary cholesterol may up the risk of cardiovascular disease (CVD) and death from any cause, researchers have warned.
The study suggests that egg yolks are one of the richest sources of dietary cholesterol among all commonly consumed foods. One large egg has 186 milligrams of dietary cholesterol in the yolk.
“The take-home message is really about cholesterol, which happens to be high in eggs and specifically yolks,” said co-author Norrina Allen, Associate Professor at the Northwestern University.
“As part of a healthy diet, people need to consume lower amounts of cholesterol. People who consume less cholesterol have a lower risk of heart disease,” Allen added.
For the study, which will be published in the journal JAMA, the team involved 29,615 adults from six prospective cohort studies for up to 31 years of follow up.
They found eating 300 mg of dietary cholesterol per day was associated with 17 per cent higher risk of incident cardiovascular disease and 18 per cent higher risk of all-cause deaths.
The cholesterol was the driving factor independent of saturated fat consumption and other dietary fat, the team said.
Eating three to four eggs per week was associated with 6 per cent higher risk of CVD and 8 per cent higher risk of any cause of death, they added.
The researchers say that eating less than 300 milligrams of dietary cholesterol per day was the guideline recommendation before 2015. However, the most recent dietary guidelines omitted a daily limit for dietary cholesterol.
The guidelines also include weekly egg consumption as part of a healthy diet. An adult in the US gets an average of 300 milligrams per day of cholesterol and eats about three or four eggs per week.
Other animal products such as red meat, processed meat and high-fat dairy products (butter or whipped cream) also have high cholesterol content, said lead author Wenze Zhong from the varsity.
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