Exercise overcomes “fat” genes
Low-carb diet–vegetable protein safer
B vitamins prevent brain shrinkage
Weight loss – could it be harmful?
Fruit-veggie variety against cancer
Plasma B vitamins lower colon cancer
While there may be a genetic tendency toward obesity, this is not the main determinant of inadequate weight control. Obesity is a much greater problem in the United States than in other countries, many of which are the sources of the gene pool here. The children of immigrants, who have grown up with local eating and exercise habits, often develop the weight problems of their school friends and neighbors, rather than their parents. It is hard to explain this result with genetics, rather than lifestyle.
A new study of 20,430 individuals in the European Investigation of Cancer (EPIC)-Norfolk shows that physical activity changes the propensity to obesity. The researchers evaluated the genetic makeup of the subjects (those genes associated with body mass index (BMI), their physical activity, and the change in their BMI over time.
They followed the participants for 3.6 years, and found that the number of BMI-increasing genes related to obesity in the population as a whole, but the association was far greater in inactive individuals than in those with the highest levels of physical activity. They concluded from the data that physical activity is associated with a 40 percent reduction in the likelihood that the genes would lead to obesity. (Li S, et al., Physical activity attenuates the genetic predisposition to obesity in 20,000 men and women from EPIC-Norfolk Prospective Population Study. PLoS Med. 2010 Aug 31;7(8). pii: e1000332.)
This shows that you can modify genetic tendencies with lifestyle choices. How much physical activity do you need to achieve these results? Current recommendations are for at least two hours per week of moderate physical activity (for example, brisk walking), preferably spread out over the week. It is also advisable to do muscle strengthening activities at least twice per week (resistance training with weights or elastic exercise bands, or heavy gardening – digging or hoeing). These guidelines are valid at any age.
Most studies show that diets that are high in complex carbohydrates and low in refined carbohydrates (particularly sugar and white flour) lead to better outcomes in long-term health and mortality rates. However, many people still look for benefits from carbohydrate-restricted diets. This is especially true among those looking for a “simpler” answer to weight control. For those following a low-carb approach for whatever reason, new research shows that the kind of protein sources that they choose can make a difference in their disease and mortality risks.
Researchers followed 85,168 women (aged 34-59) from 1980 to 2006 and 44,548 men (aged 40-75)from 1986 to 2006. Using food-frequency questionnaires, subjects were evaluated for their carbohydrate intake, and whether their protein intake was mainly from animal or vegetable sources. A low-carb score was associated with a trend to a 12 percent increase in all-cause mortality.
When these data were further analyzed, it was found that mortality risk on the low-carb diet depended on the source of the dietary protein. For example, more animal protein was associated with 23 percent higher all-cause mortality, a 14 percent increase in heart deaths, and a trend to a 28 percent higher cancer mortality. (Fung TT, et al., Low-carbohydrate diets and all-cause and cause-specific mortality: two cohort studies. Ann Intern Med. 2010 Sep 7;153(5):289-98.)
Subjects on a low-carb diet whose proteins were mainly derived from vegetable sources had a 20 percent reduction in overall mortality, and a 23 percent reduction in cardiac mortality. This statistical conclusion suggests a value in terms of mortality risk from following a low-carb diet if the protein sources are vegetarian. It is not clear that this is the correct conclusion. In a large, free-living population, lower mortality from carb restriction is most likely due to the elimination of refined carbs, while high complex carbs (whole grains, legumes, root vegetables, and others) are not the problem, and they provide a wide range of nutrients that cannot be found in animal food sources alone.
Brain atrophy (shrinkage) is often seen in elderly people. It is even more likely to be seen in those with mild cognitive impairment (MCI), which is not dementia, but is often a precursor to more serious loss of brain function. A high blood level of homocysteine is a risk factor for the development of brain atrophy, MCI, and dementia. Certain B complex vitamins can lower homocysteine levels, and researchers set out to learn if B vitamin supplements might reduce brain atrophy and MCI.
In a double-blind study with supplements of what they called “high dose” folic acid, B6, and B12, researchers evaluated 271 individuals over 70 years old with MCI at the start of the study. One group was given daily doses of 800 mcg of folate, 500 mcg of B12, and 20 mg of B6 (pyridoxine) and the other group received placebos. A subset of 168 participants received sequential MRI scans to evaluate the size of the brain.
The treatment was for two years. Among those with high homocysteine levels at the start of the study, those on the supplements, had an atrophy rate of 0.76 percent while those on placebo had a 1.08 percent atrophy rate (a 45 percent difference). For those with the very highest levels of homocysteine, brain shrinkage was half as much in the vitamin group as in the placebo group. (Smith AD, et al., Homocysteine-lowering by B vitamins slows the rate of accelerated brain atrophy in mild cognitive impairment: a randomized controlled trial. PLoS One. 2010 Sep 8;5(9). pii: e12244.)
Those with the highest rate of atrophy had lower test scores on cognitive tests at the end of the study. Why the researchers insisted on calling the vitamins “drugs” because of the dose is unclear. These doses are about what you find in a good quality multivitamin, and there is no evidence of risk from any of them at these doses (and for folate and B12, no risk at virtually any dose). These are safe and inexpensive treatments that have a wide range of benefits (see below).
Persistent organic pollutants (POP) are those toxic industrial chemicals that are extremely difficult to break down, accumulate in the environment and in fatty tissue, and stay in the body for years. They include PCBs, DDT, dioxin, tributyltin (TBT, a flame retardant), and the pesticides dieldrin and chlordane, among many others. Because of their bioaccumulation, levels in the fatty tissues increase with age, and total body exposure is higher with increased body fat.
These chemicals are increasingly being shown to be related to the development of arthritis, heart disease, strokes, diabetes and insulin resistance, mitochondrial dysfunction, cancer, immune disorders, and endocrine disruption (including thyroid disease). Exposure comes from waste dumping, leaching into water supplies, pesticides in foods, and breast milk.
Because these accumulate in fatty tissue, they are released into the bloodstream during weight loss. Higher blood levels lead to greater exposure to sensitive vital organs (kidneys, liver, heart, and others) and deleterious effects on health. A study of 1099 adults over 40 years old showed that serum concentrations of POPs were higher in those with long-term weight loss. They were lower in those subjects with long-term weight gain. (Lim JS, et al., Inverse associations between long-term weight change and serum concentrations of persistent organic pollutants. Int J Obes (Lond). 2010 Sep 7.)
This is not really an argument for the value of weight gain. These pollutants are, as noted, persistent, and even without weight loss, they leach gradually into tissues and harm organs. Ideally, it would be good to avoid them (and avoid accumulating excessive weight), but it is almost impossible to avoid them in today’s environment (even doing your best to eat organic foods). Over the long term, losing the weight has far more benefits than keeping it on. Once it is gone, the burden of POPs is lower.
In a European study of 452,187 participants, dietary choices played a role in reducing lung cancer risk in smokers (but not as large a role as stopping smoking). Over 8.7 years, those in the quarter of subjects who ate the widest variety of fruits and vegetables (23 to 40 different varieties) had a 27 percent lower risk of getting squamous cell cancer than those in the lowest quarter. (Büchner FL, et al., Variety in fruit and vegetable consumption and the risk of lung cancer in the European prospective investigation into cancer and nutrition. Cancer Epidemiol Biomarkers Prev. 2010 Sep;19(9):2278-86.)
Colorectal cancer (CRC) is one of the most common tumors. In a case-control study, 1365 CRC cases were matched to 2319 controls. Researchers measured plasma level of vitamins B2, B6, and B12 to determine if they were related to the risk of CRC.
Those subjects with the highest level of vitamin B2 had a 29 percent lower risk of CRC, and those with the highest level of B6 had a 32 percent lower risk compared to those with the lowest plasma levels of the nutrients. Vitamin B12 was not associated with any change in risk. (Eussen SJ, et al., Plasma vitamins B2, B6, B12, and related genetic variants as predictors of colorectal cancer risk. Cancer Epidemiol Biomarkers Prev. 2010 Sep 2.) Any good multivitamin should raise plasma levels of these nutrients.
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