OLDER adults with relatively low intakes of vitamins B6 and B12 may have a higher risk of developing depression than those, who get more of the nutrients, a new study suggests.
Researchers found that among 3,500 older adults they followed for up to a dozen years, the risk of developing depression symptoms declined by two per cent for every 10-milligramme (mg) increase in daily vitamin B6 from food and supplements. The same was true for every 10-microgramme (mcg) increase in vitamin B12 intake.
The findings, published in the American Journal of Clinical Nutrition, do not prove that the B vitamins themselves protect against depression. But the results do echo those of some previous studies tying the vitamins — as well as, folate, another B vitamin — to depression risk.
The prime shortcoming of most of those previous studies, however, was that they studied people at one point in time, rather than following them over years — making it unclear whether the lower B-vitamin intake came before or after the depression.
Lead researcher and an associate professor at Rush University Medical Center in Chicago, United States of America, Dr. Kimberly Skarupski said the main strength of the current study is that it followed a large group of people over 12 years, measuring depression symptoms at several time points.
That bolsters the case that relatively low intakes of the B vitamins might contribute to depression in some people. Still, Skarupski and her colleagues say their results should be interpreted with “caution,” because study participants’ consumption of the vitamins might be a proxy for other factors, like a generally healthy diet.
The study included 3,500 Chicago-area adults, who were at least 65 years old and depression-free at the outset. Participants’ consumption of folate and vitamins B6 and B12 was estimated based on their responses to a detailed dietary questionnaire. They were then assessed for depression periodically over the next dozen years.
The researchers found that anywhere from 11 per cent to 14 per cent of participants had symptoms indicative of clinical depression at some point during the follow-up.
When they looked at the relationship between B vitamins and depression, they found that the risk generally dipped as consumption of B6 or B12 increased. The link held when Skarupski’s team accounted for a number of other factors — such as race, education and income, antidepressant use and lifestyle habits like smoking and drinking.
While the results do not prove cause-and-effect, Skarupski said they do emphasise the importance of older adults’ being mindful of their diets.
“Older adults should eat well-balanced diets and talk with their healthcare providers about their nutritional intake and nutrient status,” she advised.
Vitamin B6 is found in a range of foods, including beans, potatoes, bananas, meat, chicken, peanut butter and certain fish, like salmon and tuna. The recommended intake for men older than 50 is 1.7 mg per day, while women are advised to get 1.5 mg, the upper limit is set at 100 mg daily, as too much B6 can cause nerve damage.
Foods naturally rich in B12 include beef, certain fish, like salmon and trout, and milk products, B12 is also added to some foods, such as fortified breakfast cereals.
The recommended dietary allowance for the vitamin in adults is 2.4 microgrammes per day, there is no established upper limit for B12 because of its low potential for harmful effects. Because older adults have difficulty absorbing the B12 naturally found in food, experts generally recommend that they try to get their daily allotment through fortified food or a multivitamin.
An analysis that included nearly 400,000 participants finds that those with higher blood levels of vitamin B6 and the essential amino acid methionine (found in most protein) had an associated lower risk of lung cancer, including participants who were current or former smokers, according to a study in the June 16 issue of JAMA.
Previous research has suggested that deficiencies in B vitamins may increase the probability of DNA damage and subsequent gene mutations. “Given their involvement in maintaining DNA integrity and gene expression, these nutrients have a potentially important role in inhibiting cancer development, and offer the possibility of modifying cancer risk through dietary changes,” the authors write. They add that deficiencies in nutrient levels of B vitamins have been shown to be high in many western populations.
Also, the June edition of the Journal of Thoracic Oncology features a study aimed at determining the optimal dose of the chemotherapy drug nab-paclitaxel with carboplatin as a first-line therapy in patients with non-small cell lung cancer (NSCLC). Results will provide researchers with a data needed to guide a phase 3 trial.
Dr. Paul Brennan, of the International Agency for Research on Cancer, Lyon, France, and colleagues conducted an investigation of B vitamins and methionine status based on serum samples from the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort study, which recruited 519,978 participants from 10 European countries between 1992 and 2000, of whom 385,747 donated blood.
By 2006, 899 lung cancer cases were identified and 1,770 control participants were individually matched by country, sex, date of birth, and date of blood collection.
After an analysis of the incidence rate of lung cancer within the entire EPIC cohort and adjusting for various factors, the researchers found a lower risk for lung cancer among participants with increasing levels of B6 (comparing the fourth vs. first quartile of B6 levels). A lower risk was also seen for increasing methionine levels.
“Similar and consistent decreases in risk were observed in never, former, and current smokers, indicating that results were not due to confounding (factors that can influence outcomes) by smoking. The magnitude of risk was also constant with increasing length of follow-up, indicating that the associations were not explained by pre-clinical disease,” the researchers write.
When participants were classified by median (midpoint) levels of serum methionine and B6, having above-median levels of both was associated with a lower lung cancer risk overall. A moderate lower risk was observed for increasing serum folate levels, although this association was restricted to former and current smokers, and was not apparent in never smokes.
“Our results suggest that above-median serum measures of both B6 and methionine, assessed on average five years prior to disease onset, are associated with a reduction of at least 50 per cent on the risk of developing lung cancer. An additional association for serum levels of folate was present, that when combined with B6 and methionine, was associated with a two-thirds lower risk of lung cancer,” the authors write.
The researchers add that if their observations regarding serum methionine, B6, or both are shown to be causal, identifying optimum levels for reducing future cancer risk would appear to be appropriate.
