Long-term exposure to low-dose ionising radiation has been linked to the development of solid cancers and leukaemia. Consequently, workers in the healthcare sector and in the nuclear industry who are at risk for repeated radiation exposure have to be monitored. They are limited to an effective radiation dose of 100 mSv every 5 years, with a maximum of 50 mSv allowed in any given year. With the increasing use of radiological scanning in the general population, patients are not monitored for their overall exposure to ionising radiation and there is little information on the subject.

Researchers from Emory University recently conducted a study on 655,613 enrollees, aged 18 – 64 years, from 5 healthcare markets: Arizona; Dallas; Orlando, Florida; South Florida and Wisconsin (N Engl J Med 2009; 361: 849 – 857). The amount of radiation exposure to each patient over the period January 1 2005 to December 31 2007 was noted. The mean cumulative effective dose of radiation exposure from imaging procedures was 2.4 +/- 6.0 mSv per person per year. Women underwent significantly more imaging procedures than men; 78.7 % of women undergoing at least one procedure during the 3 year period as compared to 57.9% of men. The proportion of enrollees undergoing at least one procedure during the 3 year period increased with age as well: 49.5% aged 18 – 34 years versus 85.9% aged 60 – 64 years. While most of the patients studied had low exposure (≤ 3 mSv per year, equivalent to the background level of radiation from natural sources in the United States), not an insignificant number of enrollees were exposed to higher radiation doses. Moderate annual effective doses (> 3 – 20 mSv) were incurred at an annual rate of 193.8 / 1000 enrollees, while 18.6 / 1000 enrollees and 1.9 / 1000 enrollees had high (> 20 – 50 mSv) and very high (> 50 mSv) exposure, respectively. The top 5 imaging procedures with the largest contributions to the cumulative effective radiation dose were myocardial perfusion scanning (22.1%), CT of the abdomen (18.3%), CT of the pelvis (12.2%), CT of the chest (7.5%) and diagnostic cardiac catheterization (4.6%). From this study, it was estimated that approximately 4 million non-elderly adult Americans would be receiving > 20 mSv per year from imaging procedures.

Part of the reason why Joe Public requests various imaging procedures during health checks is the perception that, if the various scans are normal, he is safe and free of cancer. He is only safe at that point in time. There is no guarantee that a small cancer is already lurking somewhere in the body. The scan could not demonstrate it because it was too small for the machine to ‘see’. Furthermore, there is no stopping a new cancer from developing 3 months after the scanning procedures. Imaging procedures should be ordered and used judiciously. While the doctor looking after the patient has a duty not to over-investigate, the patient must also refrain from pressurizing the doctor into doing a scan just because the patient saw a health report on TV about how powerful XYZ scan is in detecting cancer of the little toe!

One of the dreaded complications of chronic hepatitis B and C viral infection is the development of liver cirrhosis. As the cirrhosis progress, the hardened liver would no longer be able to sustain life, thus, precipitating the need for a liver transplant. Will the fact that one is under-weight or over-weight at the time of liver transplantation influence patient outcome?

Researchers at the University of Washington examined the United Network for Organ Sharing (UNOS) database from 1987 to 2007 in order to determine the morbidity and mortality of patients undergoing liver transplantation at the extremes of the body mass index (BMI). The 73,538 recipients were stratified into 6 BMI categories: underweight (< 18.5 kg/m²), normal weight (18.5 - < 25 kg/m²), overweight (25 - < 30 kg/m²), obese (30 - < 35 kg/m²), severely obese (35 - < 40 kg/m²) and very severely obese (≥ 40 kg/m²). There were 1827 patients in the underweight group, 1447 patients in the very severely obese group and 68,172 patients in the other groups, which became the control (Liver Transpl 2009; 15: 968 – 977). Groups at the extreme ends of BMI (<18.5 and ≥ 40) were compared to control. The analysis showed that underweight patients are more likely to die from haemorrhagic complications and cerebrovascular accidents. The very severely obese patients were more likely to die from infectious complications and cancers. Thus, underweight and very severe obesity were significant predictors of death in those who had liver transplantation.

Is this poorer outcome also evident in other organ transplantation, such as kidney transplantation? Not much information is available for under-weight recipients. What about over-weight recipients? A study from University Hospital of Wales analysed the outcomes of 114 obese kidney recipients, allocated into Group A (BMI 30 – 34.9, moderate obesity) and Group B (BMI ≥ 35, morbid obesity). The 1 year and 5 year patient survival rates in Group A were 98.9% and 95.6% respectively, compared to 87.5% and 79.2% respectively in Group B patients. The degree of obesity also influenced kidney graft survival. The 5 year graft survival rate in Group A was 94.5% compared to only 63% in Group B (Transplant Proc 2008; 40: 3408 – 3412). Morbidly obese kidney recipients have a significantly poorer outcome.

It is easy to become over-weight. It is more difficult to become under-weight. Obesity has become a global health issue and will become a major health problem in the 21^st century. You have a big say in whether you become too fat or just right. Choose wisely!

Academics from the Harvard University recently published a meta-analysis and review of the available studies on the effects of walnut consumption on blood lipids and other cardiovascular risk factors (Am J Clin Nutr 2009; 90: 56 – 63). They analysed the results from 13 studies involving 365 subjects. The diets lasted 4 – 24 weeks with walnuts providing 10 – 24% of total calories. The study showed that walnuts supplemented diets, compared to control diets, resulted in a significantly greater decrease in total cholesterol and LDL-cholesterol concentrations. (LDL-cholesterol is normally referred to as the ‘bad’ cholesterol.) If larger and longer-term trials confirm these findings and show beneficial cardiovascular effects, then everyone would most likely want to have a high-walnut-enriched diet.

No doubt some people would embark on this walnut-enriched diet after reading just the article above. However if one then reads the article in GUT on linoleic acid and ulcerative colitis (GUT 2009; epub 23^rd July) one might hesitate to start the diet. (Sunflower, corn, wheat germ, soybean and walnuts oils are a rich source of linoleic acid. Linoleic acid is an unsaturated omega-6 fatty acid used in the synthesis of arachidonic acid which is a component of the cell membrane. Metabolites of arachidonic acid have pro-inflammatory properties and are increased in the mucosa of patients with ulcerative colitis (UC). UC is a condition where the lining of the colon suffers from chronic inflammation.) Researchers from the University of East Anglia analysed the dietary data from 203,193 men and women aged 30 – 74 years, resident in the UK, Sweden, Denmark, Germany and Italy and participating in the prospective cohort European Prospective Investigation into Caner and Nutrition (EPIC) study. They were followed up for a median of 4 years and 126 participants developed UC. The risk of developing UC among participants who had the highest quartile of linoleic acid intake was increased by 149%.

On the one hand we read that walnut enriched diet lowers total cholesterol and LDL-cholesterol concentrations in the body. On the other hand too much linoleic acid (walnuts oil is rich in linoleic acid) in the diet increases the risk of developing UC. Feeling frustrated and confused?

Until we can get clear and definitive data, it is difficult to be adamant on what food stuff you must eat and in what quantity. In the meantime, I myself would stick to the principles of eat healthily, eat in moderation and take regular exercise.