Q: Can eating tomatoes lower my blood pressure?
A: It might. A lot of research has been performed on the health benefits of tomatoes, particularly around the carotenoid pigment lycopene. One cup (240 ml) of tomato juice provides about 20 mg to 25 mg of lycopene.
A recent study evaluated the effect of a tomato extract (250 mg) containing a standardized amount of lycopene (approximately 15 mg) on systolic and diastolic blood pressure. Thirty-one subjects took the extract for eight weeks followed by placebo for eight weeks. While taking the extract, systolic blood pressure decreased from 144 to 134 (mm Hg) and diastolic blood pressure decreased from 87.4 to 83.4.1
While this is a small, short-term trial, the results are quite positive. Plus, there is further evidence to suggest that other phytonutrients in tomatoes may help with blood pressure. The Dietary Approaches to Stop Hypertension study showed that dietary changes substantially lowered blood pressure. When the diet used in the DASH study was analyzed, researchers found it had higher levels of a variety of phytonutrients, including lycopene, beta-carotene and phytosterols.2 Tomatoes contain all these phytonutrients. So it may not be just the lycopene but the full complement of phytonutrients in the tomato extract. Thus, this data suggests tomatoes or a tomato extract, not just lycopene alone, may lower blood pressure.
Q: I've heard that just taking a prenatal vitamin may not provide enough vitamin D during pregnancy. Is this true?
A: That's correct. It appears that even regular use of prenatal multivitamin supplements may not prevent vitamin D deficiency. In a recent study of 200 white and 200 black pregnant women, more than 80 percent of the latter and nearly half of the former (tested at delivery) had levels of vitamin D that were deemed less then optimal, even though more than 90 percent of them used prenatal vitamins.3
This is critical because a newborn's vitamin D stores are completely reliant on the mother. We know that low levels of vitamin D are a risk factor for rickets, type 1 diabetes and schizophrenia.4,5 A newer study suggests that pregnant women with low levels of vitamin D are at increased risk for pre-eclampsia.6
Vitamin D is found naturally in fatty fish but in few other foods. Other dietary sources include fortified foods such as milk and some cereals. Vitamin D can also be made by your body after exposure to the sun.
These recent studies suggest that current vitamin D dietary-intake recommendations are not enough to meet the demands of pregnancy. I think all pregnant women should get their vitamin D levels checked.
Q: I have heard that stinging nettle can be used for urinary tract infections, but I was told it would also help with my seasonal allergies. Do I dare to hope?
A: Stinging nettle (Urtica dioica) is a traditional botanical medicine that has been used for urinary tract infections, as well as for benign prostatic hyper?plasia and joint problems. That said, I have actually used it most frequently for seasonal allergies. However, there isn't much data on this use. One older, placebo-controlled study does suggest stinging nettle works modestly. In this study, researchers took 98 people with allergic rhinitis and gave them a freeze-dried preparation of stinging nettles. From results, it appeared that the herb controlled symptoms better than placebo.7
Some researchers think that stinging nettle might be beneficial for allergic rhinitis because of its quercetin content—a bioflavonoid that is thought to have anti-inflammatory and mast-cell stabilizing effects and has been shown to decrease histamine release from inflammatory cells in the nose.8 I typically use 300 mg of freeze-dried stinging nettle extract three to four times per day, and I sometimes combine that with straight quercetin at 500 mg three times per day.
1. Engelhard YN, et al. Natural antioxidants from tomato extract reduce blood pressure in patients with grade-1 hypertension: a double-blind, placebo-controlled pilot study. Am Heart J Jan 2006;151(1):100.
2. Most MM. Estimated phytochemical content of the dietary approaches to stop hypertension (DASH) diet is higher than in the Control Study Diet. J Am Diet Assoc 2004;104(11):1725-7.
3. Bodnar LM, et al. High prevalence of vitamin D insufficiency in black and white pregnant women residing in the northern United States and their neonates. J Nutr 2007;137(2):447-52.
4. McGrath J. Hypothesis: is low prenatal vitamin D a risk-modifying factor for schizophrenia? Schizophr Res 1999;40(3):173-7.
5. Knip M, Akerblom HK. Early nutrition and later diabetes risk. Adv Exp Med Biol 2005;569:142-50.
6. Bodnar LM, et al. Maternal vitamin D deficiency increases the risk of pre-eclampsia. J Clin Endocrinol Metab May 29 2007. [Epub ahead of print]
7. Mittman P. Randomized, double-blind study of freeze-dried Urtica dioica in the treatment of allergic rhinitis. Planta Med 1990;56(1):44-7.
8. Otsuka H, et al. Histochemical and functional characteristics of metachromatic cells in the nasal epithelium in allergic rhinitis: studies of nasal scrapings and their dispersed cells. J Allergy Clin Immunol Oct 1995;96(4):528-36.
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