High energy intake and insulin levels, as well as increased sugar and candy consumption, are associated with lower disease activity in acute intermittent porphyria, a small population-based study suggests.
The study, “Lifestyle factors including diet and biochemical biomarkers in acute intermittent porphyria: Results from a case-control study in northern Norway,” was published in the journal Molecular Genetics and Metabolism.
Acute intermittent porphyria (AIP) is a rare inherited metabolic disorder that typically presents no symptoms (asymptomatic). About 90% of those affected by AIP never experience symptoms linked to the disease.
However, many factors can contribute to trigger AIP symptoms, including mental or physical stress, alcohol, smoking, certain medications, fasting, fever, infections, or hormonal factors.
According to the American Porphyria Foundation (APF), patients should avoid prolonged fasting, and, of their total energy intake, 55% to 60% should be carbohydrates in order to avoid AIP attacks. However, a review study has suggested that there is no clear evidence on the benefit of a sustained high-carbohydrate diet, and that this dietary strategy may not prevent AIP attacks.
In the Norwegian study (NCT01617642), researchers compared dietary intake patterns and disease biomarker levels in 50 cases of AIP patients, and 50 age- and sex-matched healthy volunteers to understand the impact of lifestyle factors in AIP manifestations.
Among the AIP patients, 34 were symptomatic, of whom 15% had experienced one AIP attack, and 85% have had more than one porphyria attack.
The team found that both AIP and control groups consumed fewer slow-release carbohydrates — 40% of total energy intake for AIP patients, and 39% of total energy intake for the control group. They also consumed more sugar and saturated fatty acids than recommended for the Nordic countries. Also, vitamin D deficiency was common in both groups.
In general, no significant differences in mean values of dietary intake was detected between patients and controls, except for polyunsaturated fatty acids (PUFAs) intake, which was was significantly lower in AIP cases.
The intake of sugar and candies was found to be higher in AIP cases with reduced levels of U-delta aminolevulinic acid (ALA) — the precursor to porphyrins. A buildup of porphyrins leads to the development of porphyria.
Blood analysis revealed that insulin levels were higher in cases with low urine porphobilinogen (PBG) — one of the several types of porphyrins in the body. Also, plasma resistin levels (inflammation marker) were higher in symptomatic patients than the asymptomatic ones.
These finding suggest that “glucose should be administered together with insulin during porphyric attacks” as they could have an inhibitory effect.
Further analysis revealed that increasing total energy intake was negatively correlated with urine PBG levels in AIP cases, “suggesting that the total energy intake affects the biochemical disease activity,” the researchers wrote.
The intake of alcohol was found to be much higher than expected in AIP cases, and higher than the recommended upper limit of 1 alcohol unit (12 g) per day in a few cases. However, alcohol intake was significantly lower in symptomatic than in asymptomatic AIP patients.
“Since alcohol had triggered attacks in 32% of the AIP cases in line with a previous study, we speculate that the symptomatic cases reduced the intake to avoid attacks,” the researchers said.
According to patient reports, attacks were triggered by psychological stress (62%), physical strain (38%), food items (24%), alcohol (32%), and medications (29%).
“Several lifestyle factors, including total energy intake, alcohol, stress, and medications may affect the disease activity of AIP,” the researchers stated.
They noted, however, that the study “has several limitations that might have affected the results. First, most of the AIP cases had the same AIP mutation. Second, many different parameters were analyzed, implying that the risk of false positive results in the statistical analysis is high. Third, the number of AIP cases was limited to 50, mainly due to the rarity of the disease.”
Therefore, future studies should examine “the role of other related mutations and other epigenetic changes that could explain why only a few of those with an AIP mutation have symptoms of the disease, while most cases are asymptomatic,” the study noted.