Q: What is the evidence that dietary cholesterol or other fat influences serum cholesterol?
A: Foods high in cholesterol, like eggs or cheese, can raise blood cholesterol levels, though the effect is relatively modest and varies from person to person. The best evidence available suggests that saturated fat, rather than dietary cholesterol per se, is the major contributor to serum cholesterol.
In 1991, The New England Journal of Medicine described the case of an 88-year-old man who ate 25 eggs a day for at least 15 years and had normal cholesterol levels and apparently normal arteries. This report challenged a central dogma of medicine: namely, that dietary cholesterol leads to elevated serum cholesterol and atherosclerosis. That belief arose in 1913, when Russian scientist Nikolai Anichkov observed that rabbits developed atherosclerosis after being fed a high-cholesterol diet.
Over the years, the association between diet and atherosclerotic plaque grew, but controversy grew as well. Critics noted that rabbits do not consume cholesterol in the wild, and humans do not consume cholesterol in isolation. The vast majority of foods that are high in cholesterol, like steak or butter, are also high in saturated fats. Notable exceptions to this rule are egg yolks and shellfish, such as shrimp, lobster and crab.
In 1965, a landmark Harvard study — one which could not be replicated today because of evolving ethical standards, as it was performed on schizophrenic patients confined to a mental hospital — showed that saturated fat exerted a greater effect on serum cholesterol than dietary cholesterol did. Subsequent studies supported this conclusion, including the 20-year Western Electric Study of 1,900 men from 1981 and an analysis of 395 experiments that appeared in the British Medical Journal in 1997.
Ultimately, the weight of the evidence led to changes in recommendations. In 2013, the American Heart Association stated, “There is insufficient evidence to determine whether lowering dietary cholesterol reduces LDL-C,” or “bad” cholesterol.” More recently, the Dietary Guidelines Advisory Committee, whose recommendations inform U.S. Department of Agriculture policy, dropped its previous recommendation to limit dietary cholesterol, advising that “cholesterol is not a nutrient of concern for overconsumption.”
It should be emphasized that there is great individual variation in the response to dietary cholesterol. Some people are like the 88-year-old man described above and are able to maintain a normal serum cholesterol despite a high intake of dietary cholesterol. Others are more like Anichkov’s rabbits, and their serum cholesterol levels rise in response to high levels of dietary cholesterol.
These 6 Foods Are All You Need To Improve Your Eyesight: Nutritionist Nmami Agarwal
Poor eyesight is primarily a sign of poor nutrition. Vision problems are quite common in the world. The World Health Organisation states that as many as 1.3 billion people across the world live with some form of vision impairment. It is thus important to get eye exams done regularly. However, to prevent having any eye problems, a healthy and nutritious diet can go a long way. Nutritionist Nmami Agarwal recently took to Instagram to talk about some foods that can promote a healthy eyesight. In her blog, she mentions that there are various reasons that can result in poor vision.
From mental and physical tension to overeating, malnutrition, intake of excessive sugar, meat, protein or fat, junk food; poor muscle tone, lack of physical activity and flexibility can all result in poor vision.
For healthy eyes, a healthy lifestyle is what you need. Along with regular exercise, following are the foods you must include in your diet for healthy vision.
Foods for a healthy vision as suggested by Nmami Agarwal:
1. Leafy green veggies: Leafy green veggies are rich in lutein and zeaxanthin which help in improving vision. Vitamin C rich leafy greens are great for your eye health. Spinach, collards and kale are some instances of healthy leafy green veggies.
2. Citrus fruits: Orange, grapefruit and lemons are citrus fruits good for your eyesight. Vitamin C in citrus fruits acts as antioxidants and help in preventing age-related eye damage.
3. Nuts: Nuts are rich in omega 3 fatty acids and Vitamin E, both of which help in fighting from age-related eye problems. Peanuts, brazil nuts and walnuts are instances of nuts good for your eyesight.
4. Fish: Salmon, trout, tuna and herring are all fish that are good for your eyesight. Oily fish is rich in omega 3 fatty acids that offer protection to eyes from macular degeneration and dry eye syndrome. Nmami informs in her blog that omega 3 fatty acids help in drainage of intraocular fluid from eyes, thus reducing risk of glaucoma or high eye pressure.
5. Carrots: Carrots are rich in Vitamin A and carotene. Both of these are important for a healthy vision. Vitamin A specifically is a component of rhodospin, a protein which helps the retina to absorb light.
6. Seeds: Some seeds like hemp seeds, sunflower seeds and chia seed can help in improving vision. Fatty acids in these seeds can improve dry eye conditions. These seeds are also rich in omega 3 fatty acids and are also a good source of Vitamin E.
Exercise may protect against Alzheimer’s: Study
Exercise produces a hormone that may improve memory and protect against Alzheimer’s disease, according to a study. Researchers have previously discovered a hormone called irisin that is released into the circulation during physical activity. Initial studies suggested that irisin mainly played a role in energy metabolism. The latest study, published in the journal Nature Medicine, found that the hormone may also promote neuronal growth in the brain’s hippocampus, a region critical for learning and memory.
“This raised the possibility that may help explain why physical activity improves memory and seems to play a protective role in brain disorders such as Alzheimer’s disease,” said Ottavio Arancio, a professor at Columbia University in the US.
Arancio and his colleagues at the Federal University of Rio de Janeiro in Brazil and Queens University in Canada first looked for a link between irisin and Alzheimer’s in people. Using tissue samples from brain banks, they found that irisin is present in the human hippocampus and that hippocampal levels of the hormone are reduced in individuals with Alzheimer’s.
To explore what irisin does in the brain, the team turned to mice. These experiments show that irisin, in mice, protects the brain’s synapses and the animals’ memory: When irisin was disabled in the hippocampus of healthy mice, synapses and memory weakened. Similarly, boosting brain levels of irisin improved both measures of brain health, researchers said.
The researchers then looked at the effect of exercise on irisin and the brain. They found that mice who swam nearly every day for five weeks did not develop memory impairment despite getting infusions of beta amyloid — the neuron-clogging, memory-robbing protein implicated in Alzheimer’s.
Blocking irisin with a drug completely eliminated the benefits of swimming, the researchers found.
Mice who swam and were treated with irisin-blocking substances performed no better on memory tests than sedentary animals after infusions with beta amyloid.
The findings suggest that irisin could be exploited to find a novel therapy for preventing or treating dementia in humans, Arancio said. The team is now searching for pharmaceutical compounds that can increase brain levels of the hormone or can mimic its action.
“In the meantime, I would certainly encourage everyone to exercise, to promote brain function and overall health,” he said. “But that’s not possible for many people, especially those with age-related conditions like heart disease, arthritis, or dementia. For those individuals, there is a particular need for drugs that can mimic the effects of irisin and protect synapses and prevent cognitive decline,” Arancio said.
Absence of gut bacteria might influence depression: Study
While gut bacteria can largely impact our physical wellbeing, a recent study suggests a significant link between gut bacteria and mental health.
Researchers from VIB-KU Leuven Center for Microbiology in Belgium conducted a study in which they gathered and analysed health data of a large group of people in an attempt to find out which gut bacteria may play a role in causing depression. The findings of this new study appeared in the journal Nature Microbiology.
Researchers involved in the study named the gut bacteria that are linked to mental wellbeing and also concluded that many bacteria can produce substances called neuroactive that can interact with the nervous system. For the study, researchers studied the fecal microbiome data in conjunction with diagnoses of depression in 1,054 people taking part in the Flemish Gut Flora Project.
“Through this analysis, the team revealed that two types of bacteria — those from the genera Coprococcus and Dialister — were absent from the guts of people with a diagnosis of depression. This even applied to those who took antidepressant medication”, according to a report in Medical News.
“The relationship between gut microbial metabolism and mental health,” says study co-author Prof. Jeroen Raes, “is a controversial topic in microbiome research. The notion that microbial metabolites can interact with our brain — and thus behavior and feelings — is intriguing, but gut microbiome-brain communication has mostly been explored in animal models, with human research lagging behind. In our population-level study we identified several groups of bacteria that co-varied with human depression and quality of life across populations.”
“This finding,” adds Prof. Raes, “adds more evidence pointing to the potentially dysbiotic nature of the Bacteroides2 enterotype we identified earlier. Apparently, microbial communities that can be linked to intestinal inflammation and reduced well-being share a set of common features.”
“The team also devised a special technique that allowed it to find out which bacteria might influence the nervous system. They looked at over 500 human gut bacteria, focusing on whether they could produce neuroactive compounds. In the end, the team came up with a list characterising the range of neuroactivity of different bacteria”, Medical News stated.