Sunday, January 24, 2010

Folic acid: an essential B vitamin with a warning on overdose

Folate is the naturally occurring form of vitamin B9, while folic acid is the synthesized form. This vitamin is essential in the synthesis and repair of DNA, in the production of red and white blood cells, in the synthesis of important amino acids, and in any period of rapid cell growth, such as childhood and pregnancy.

The urgent need for Folate in pregnancy Neural tube defects are among the most dreaded birth defects, affecting 1 in 1500 births in the US today. The baby is born without a major portion of its brain and skull (and dies shortly after birth) or with incomplete closure of the spinal cord in the back, leading to some degree of paralysis, pain, and problems with bowel and bladder function. Insufficient folate in the diet (along with genetic and unknown factors) plays a role in this problem, and supplementation of the mother’s diet can decrease the incidence of neural tube defects by more than 70%. The folic acid supplement, as well as adequate dietary intake of folate, should start even before the beginning of pregnancy, as the neural tube starts developing in the first month. It is extremely important for young women to take a multivitamin containing 400 micrograms (mcg) of folic acid on a regular basis; even if she does not plan to become pregnant (at least 50% of pregnancies are unplanned; in celibate or lesbian women the multi will also help with a possibly haphazard diet.) More folate is needed during pregnancy and lactation. Because not all girls and young women take vitamins, the FDA mandated the fortification of refined grain products (white flour, pasta, breakfast cereals) with folic acid in 1998. It is estimated that young women get about 100 mcg a day of folic acid from fortified cereal grains – which is an improvement, but insufficient. An excellent diet and/or a multivitamin is still important. Studies show an approximate 50% reduction in neural tube defects in the US since fortification in 1998. Similar programs of fortification have taken place in Costa Rica and many European countries. Other problems in pregnancy, such as fetal cleft lip, premature delivery and serious bleeding at delivery from placental detachment, have been associated with folate deficiency. See for Nicolas Kristof’s opinion page article on the benefits of micronutrient enrichment of foods in Honduras and elsewhere.

Homocysteine: Homocysteine is an amino acid that used to be associated with higher rates of heart disease amd stroke; it can be lowered by conversion into methionine (another amino acid) by folic acid, vitamins B6 and B12. However, studies from two Canadian Universities in 2006 showed that lowering homocysteine levels with these B vitamins did not decrease the risk of heart attack or death from heart disease, but did significantly decrease the risk of stroke. Studies also show that lowering homocysteine levels with B vitamins in people with former strokes lowers their risk of hip fractures.

Anemia: People with a low intake of folate from food, or with chronic alcoholism, can develop a kind of anemia characterized by large, malformed red blood cells. This anemia is akin to ‘pernicious anemia’ related to vitamin B12 deficiency, and can have serious consequences. Medical care is essential.

Cancer: There is growing controversy over the effects of giving high dose folic acid supplements to prevent cancer or other diseases, since recent clinical trials have shown an increase in lung cancer and polyps of the colon. Animal experiments show that small amounts of folic acid supplements can decrease cancer risk, and high amounts can increase it. However, no amount of folate in foods is dangerous and studies show a decreased cancer risk, including breast cancer, among those with the highest dietary intakes.

Foods containing folate: All forms of green leafy vegetables, broccoli, avocado, asparagus, peas, beans of all kinds, lentils, peanuts, wheat germ, oranges and other citrus fruits, and many other whole foods contain folate. You will benefit from folate by making vegetables and fruits the center of your diet. Cooking can destroy folate, so it is best to steam or stir fry vegetables lightly, or cook them in a microwave. Avoid boiling in abundant water.

What’s the bottom line with folate and folic acid supplements?
Keep eating as many vegetables and fruits as possible, and include raw salads in your daily fare. You will be ingesting plenty of folate, which is a very good thing. Young women who might become pregnant should take a daily multi with 400 mcg of folic acid and special vitamins during pregnancy. Adult multivitamins with 400 mcg of folic acid should be taken by people with high risk of stroke or a prior stroke, and by those dependent on alcohol. For other adults, a multi is probably safe, if it contains no more than 400 mcg of folic acid. Who said it would be simple?
Sadja Greenwood, MD, MPH past issues on this blog

Thursday, January 21, 2010

Selenium: Take a Supplement, or a Brazil Nut?

Selenium is an element that is essential in the human diet in small amounts, but toxic at high levels. All animals require selenium, since we evolved from the sea where it is abundant. Plants do not appear to require selenium for survival, but incorporate it into their structures. Edible plants contain differing amounts of selenium, as the element is found in varying amounts in rocks and soil throughout the world. The element is found in higher amounts where there were inland seas.

Thyroid hormone: While iodine is essential for the synthesis of thyroid hormone, a selenium dependent enzyme must be present to activate this hormone, which in turn regulates normal growth, development and metabolism.

Sperm development: a recent study from Vanderbilt University showed that a protein containing selenium is essential for normal sperm development and male fertility.

Viral Infection: selenium deficiency appears to enhance the virulence of some viral infections, by inducing mutations in the expression of some viral genes. In a region of China where soils are very low in selenium, young women and children develop a disease of the heart muscle; this seems to be worsened by a change in a common virus that affects the heart. Selenium supplementation can protect against this, but cannot reverse the damage to the heart muscle.

Cancer – a mixed picture: Chronic infection with viral hepatitis B or C increases the risk of liver cancer; selenium supplements given in China in an area with a high incidence of hepatitis B and liver cancer reduced the incidence of this cancer. Similar findings were seen in Taiwan. A study in Finland showed that low selenium status in creased the risk of lung cancer: the association was more pronounced in smokers. On the other hand, a prospective study of more than 60,000 female nurses in the US found no association between selenium levels and total cancer risk. The data on prostate cancer are confusing – several studies have shown lower selenium levels in men with prostate cancer, but a recent large study from the National Cancer Institute, following 295,344 men who were cancer free on enrollment, found that excessive multivitamin use (more than 7 times per week) increased the risk of fatal prostate cancer compared with never users. The positive association with prostate cancer and excessive multivitamin use was strongest in men with a family history of prostate cancer or in men who took supplemental selenium, zinc, or beta-carotene. Further studies are needed to understand whether selenium levels in the body are linked to prostate cancer, and several are underway. Selenium supplements (200 micrograms daily) increased the risk of squamous cell skin cancer in a study from Memorial Sloan-Kettering, and did not alter the incidence of basal cell skin cancers.

HIV/AIDS: Declining selenium levels are found in HIV infected people and are markers of disease progression and severity. A randomized control trial of HIV positive men and women from the University of Miami found that selenium supplements (200 micrograms a day) taken for 2 years significantly decreased the rates of hospitalization. A further study showed a decreased viral load and more CD4 cells with the same dose of selenium.. Proteins containing selenium negatively affect the replication of the AIDS virus. Many AIDS patients in the US take selenium supplements, and it is also used in some African countries/
Who needs selenium supplements? Based on the information currently available, it is wise for most people to get this trace element in their diet, and not from supplements. Supplemental selenium should be considered by people with HIV infections, and by those with severe gastrointestinal problems such as Crohn’s disease or surgical removal of part of the stomach or intestines.

Food Sources of Selenium: Organ meats, shellfish and other healthy (non-endangered) fish are the important sources of selenium in our diets. Whole grains are also important sources (avoid white flour and white rice), as are sunflower seeds, and other nuts. Whole grains grown in Nebraska and the Dakotas have high levels (but who knows the origin of the wheat in our daily bread?) Brazil nuts grown in areas of Brazil with selenium-rich soil may provide 50 to 100 mcg in one nut, which is an excellent daily amount for adults. However, Brazil nuts grown on selenium-poor soil may provide 10 times less – another ‘who knows?’ conundrum. Studies from New Zealand have shown that the selenium in Brazil nuts improves serum selenium levels as effectively as supplements. My final conclusion from all this is that adults can benefit from a daily Brazil nut! You can give a few Brazil nuts a week to children over age 9. Good news - it seems that the cultivation of Brazil nuts will improve conditions in the rainforests of Brazil; the nut is not suitable for growth in plantations and can only grow in the rainforest itself.
Sadja Greenwood, MD back issues

Wednesday, January 13, 2010

Is there a Supreme Bean?

Go to Health: Is there a Supreme Bean?
Some insist that it’s coffee, but for many it’s the soybean, which nourishes hungry people throughout the world; its balance of essential amino acids makes soy a plant protein as valuable as eggs or meat.  Soy has been grown in China for some 5000 years, to enrich the soil (like other beans it has bacteria on its roots that fix nitrogen), and for human consumption.
Heart Disease Prevention:  Following studies showing significant decreases in serum cholesterol, LDL cholesterol (the ‘bad’ kind) and triglycerides, the FDA granted a health claim for soy in 1999: “25 grams of soy protein a day, as part of a diet low in saturated fat and cholesterol, may reduce the risk of heart disease.”  HDL, (‘good cholesterol’) did not increase.  Recently, new studies have challenged the ‘heart healthy’ claim for soy protein per se, but concede that soy milk, tofu, soy nuts and some soy burgers should be beneficial to heart health because of their polyunsaturated fats, fiber, vitamins and low content of saturated fat.  The American Heart Association said: “Using these soy foods to replace foods high in animal protein that contain saturated fat and cholesterol may confer benefits to cardiovascular health.” 
Breast Cancer:  Genistein and daidzein (so called phytoestrogens,  or plant estrogens) are substances in soy that are similar structurally to human estrogen but act differently in the human body.  They have much lower biologic activity than human estrogens and in some cases may function as anti-estrogens.  A recent study on breast cancer and soy from Vanderbilt University was encouraging.   The researchers looked at 5000 Chinese women in Shanghai, ages 20 -75, who were breast cancer survivors. They found those who ate the most soy (15 grams or more of soy protein daily) had a 29% lower risk of dying than those who consumed the least (5 grams or less).  A similar benefit appeared for breast cancer recurrence risk regardless of tamoxifen use.  The benefits of soy increased up to 11 grams of soy protein daily, and then leveled off or reversed, so more was not necessarily better.  The women ate mainly tofu and whole soy beans. The researchers warned that similar benefits can not be extrapolated to dietary supplements containing soy (pills, bars or foods containing isolated soy protein). The associations did not vary with menopausal status, cancer stage, or estrogen receptor status of a woman’s cancer.
Vitamin K2 & Hip Fracture: a recent study from the University of Tokyo School of Medicine showed that natto, a Japanese fermented soybean food, contains large amounts of Vitamin K2; there is increasing evidence that Vitamin K plays a positive role in bone strength and osteoporosis prevention.  Serum concentrations of vitamin K2 were significantly higher in frequent natto eaters, and the incidence of hip fracture was correspondingly lower, in every prefecture of Japan.
Soybean foods in the US: Today about 90% of soybeans grown in the US are genetically modified to make the plant resistant to the herbicide Roundup. Ninety percent of these beans are turned into soy oil and defatted soy meal that is fed to chickens, turkeys and pigs.  The abundance of soy meal, as well as corn, makes possible the new and very problematic industrial farming of these animals.  The US, Brazil and Argentina are major growers and exporters of soybeans, and the Brazilian crop has been responsible for a considerable loss of rainforest. Some soybeans, including organic soybeans, made into human foods in the US are imported from Brazil and China, where organic standards may differ from ours. Most Silk soymilk is no longer organic; the company was bought over by Dean Foods and switched many of their products to “natural” rather than organic. Edensoy products are made from organic soybeans grown in the US; Westsoy, Wildwood and others also have organic soy products.  If you care about this issue, read labels!   To get the benefits of soy, nutritionists advise people to eat whole soy products, such as tofu, tempeh, soy milk and soy nuts, rather than manufactured foods containing isolated soy protein.   Happy New Year, dear readers, and let us all appreciate the natural foods stores and organic farmers in West Marin.
Sadja Greenwood, MD, back issues at