Wednesday, August 31, 2011
You may be confused, and skeptical, about the importance of a high fiber diet. The connection between dietary fiber and a reduced risk of colon cancer has been disputed because of conflicting studies and differing measurements of dietary fiber. However, according to the American Institute for Cancer Research (AICR – a non-profit that fosters research on diet and cancer), a diet high in whole grains, fruits, legumes and vegetables is valuable to reduce both overweight and several cancers. AICR looked at over 7,000 studies worldwide, finding evidence that whole grains in the diet do lower the risk of colorectal cancer. In a large prospective cohort study, subjects who ate the most whole grains had a 20% lower risk of colorectal cancer than those who ate the least.
As readers know – whole grains include minimally processed wheat, spelt (an ancient variety of wheat) oats, rye, corn, barley, millet, quinoa and amaranth. When buying these grains as bread, crackers or pasta, it is important to read the label, and make sure that your product does not contain a deceptive sprinkle of whole grain but is 100% what you are looking for - the whole grain.
Foods high in fiber are relatively low in energy density; they contribute to a feeling of fullness and reduce the risk of overweight. Here is another way that whole grains prevent disease. Overweight is related to an increased risk of several cancers, including colon, uterine, breast (in women post menopause), esophagus, pancreas, gall bladder, liver, and kidney.
A study from Tufts University showed that the distribution of body fat varied with whole and refined grain intake. Subjects with the highest intake of whole grains had the lowest amount of deep abdominal fat – known as visceral adipose tissue. Around our waists and in our buttocks and thighs, fat lies under our skins, which we can feel by pinching ourselves gently. This fat poses less of a problem in normal-weight people. However, visceral fat lies inside the abdominal cavity, packed in between the stomach, liver, intestines and kidneys. This visceral fat has been shown to be a risk factor for insulin resistance, type 2 diabetes, cardiovascular disease and a shorter life. Visceral fat is associated with chronic inflammation in the body, and higher insulin levels – both linked to an increased risk of cancer. It is also linked to higher total and LDL cholesterol, and lower HDL (good) cholesterol.
Obviously, fat in the diet is essential – for the absorption of vitamins A, D, E and K from foods, for essential fatty acids like omega-3s, for taste, satiety and maintenance of stored energy reserves. Healthy fat intake is good, but having excess amounts of visceral fat is dangerous.
Here’s advice from Harvard Medical School on how to reduce visceral fat.
*Regular moderate intensity physical exercise – 30 to 60 minutes a day. This would include brisk walking, biking, and gym workouts. Check with your MD or NP before beginning a program if you have not been active.
*Reduce portion size and emphasize whole grains and lean protein over white flour, rich desserts, sugary food and drinks, and alcohol.
It’s that simple – in theory at least – and such a program will work. Many people welcome the help of a program such as Weight Watchers or Overeaters Anonymous to get started and keep going.
Marion Nestle, a professor in the Department of Nutrition at New York University and the author of many books on food and food policy, has a daily blog which you may enjoy: www.foodpolitics.com. She has short, humorous and cogent posts on the latest in food science, how to eat, and how to improve our food system.
Sadja Greenwood, MD, MPH – back issues on this blog
Saturday, August 13, 2011
Garlic has been used by humans for over 4000 years; it originated as a wild plant in Central Asia and spread all over the world. It has been found in the tombs of Egyptian pharaohs dating back to 3200 B.C.E. Garlic is a rich source of organosulfur compounds, which are thought to be responsible for its aroma and flavor as well as its potential health benefits. Garlic has been found to inhibit bacteria, viruses and some types of fungus in the laboratory, but this has not been reliably shown in humans. Nevertheless, garlic supplements are among the best selling in the US today; I will try to explain the evidence behind its popularity as an herbal medicine. Its use in enhancing the flavor of food must be experienced: “and there was a cut of some roast…which was borne on Pegasus-wings of garlic beyond mundane speculation” C.S. Forester.
Heart Disease: Many randomized controlled trials have looked at the effect of garlic and garlic supplements on people with elevated cholesterol, LDL cholesterol and triglycerides. Some trials showed an improvement in 3 months, but no lasting effects by 6 months. However, most studies have shown that garlic supplements significantly decrease platelet clumping, which is a first step in the formation of blood clots. Because of this effect, people on blood thinners should talk to their doctors before taking garlic supplements. There is no solid evidence so far that garlic supplements reduce blood pressure or prevent the progression of plaque in the arteries, leading to heart attack or stroke. However, some studies do show benefits in these areas, and research continues.
Cancer of the stomach and colon: Studies from China, other Asian countries and Europe show that people eating raw or cooked garlic have a lower rate of cancers of the stomach, colon and rectum. However, the amount of garlic eaten, either raw or cooked, and the variable amount of vegetables also eaten made it difficult to be precise about rates of reduction, which were 30 to 50%. Aged garlic extract in high doses was also found to decrease the number of precancerous polyps in the colon. These are important benefits.
Effects of cooking: the organosulfur compounds that give garlic its beneficial effects can be inactivated by heat. The protective effects of garlic can be partially conserved by crushing or chopping garlic and letting it stand for 10 minutes before cooking. Powdered or dehydrated garlic is made from garlic cloves dried at low temperatures to prevent inactivation; the dried garlic is pulverized and made into tablets. The beneficial compounds vary greatly among commercial products – enteric coated tablets that pass the USP ‘allicin release test’ are likely to be the best. Garlic supplements are also made from fluid extracts, garlic oil and aged garlic extracts. In my opinion, the most beneficial way to use garlic for health and pleasure is to eat it raw in salad and cooked in many dishes. Follow the 10 minute rule for cooking – crush or chop garlic and let it stand for 10 minutes before cooking, to preserve its benefits.
Adverse Effects: Some people report gastrointestinal symptoms after eating garlic, some have allergic responses such as asthma, and some have skin rashes. Occasional cases of serious bleeding have been reported. However, these reactions are rare. For most of us, garlic is a strong, or subtle, delight.
There are many miracles in the world to be celebrated and, for me, garlic is the most deserving. Leo Buscaglia (the love doctor)
Sadja Greenwood, MD, MPH