Gießener Vollwert-Ernährungs-Studie Teil II: Einfluß der Kostform auf den Vitamin-B₁₂- und Folatstatus in der Schwangerschaft

Abstract

Giessen Wholesome Nutrition Study, part II: the effect of diet on vitamin B12 and folate status during pregnancy

Wholesome Nutrition meets international recommendations on food consumption regarding a healthy diet and is characterised by a high consumption of foods of plant origin and a high consumption of raw food as well as whole grain products. At the same time the consumption of meat and eggs is reduce significantly compared to the average diet. The question is, whether Wholesome Nutrition ensures an adequate nutrient supply for persons with a high nutrient requirement such as pregnant women. The supply of vitamin B₁₂ and folate is of special interest because of the association with the occurrence of neural tube defects, low birth weight, intrauterine growth retardation, delayed maturation of the nervous system and anaemia.
The study conducted was a prospective longitudinal cohort study in which a questionnaire, an estimated food record and a pregnancy diary were used as instruments. In addition blood samples were analysed. Women were admitted to the study, when adhering to a Wholesome Nutrition (WN; n = 76) for a minimum of 2 years, or eating an average German diet (CG; n = 43). WN group was subdivided into ovo-lacto vegetarians (OLV; n = 30) and low-meat eaters (LME; n = 46).
Dietary and nutrient intake was assessed in every trimester of pregnancy (9.-12., 20.-22. and 36.-38. gestational week) by an estimated 4-day food record. Nutrient intake was calculated based on the German food code and nutrient data base (BLS Version II.2, BGVV 1996). Folate intake was calculated as free folate equivalents (FFE) as well as dietary foalte equivalents (DFE).
The food record was linked to blood samples to assess biochemical parameters throughout pregnancy. Serum and red blood cell (RBC) vitamin B₁₂ concentrations, vitamin B₁₂ bound transcobalamin II (holo-TC II) and vitamin B₁₂ bound haptocorrin (holo-Hap) were analysed. Additionally the unsaturated vitamin B₁₂ binding capacity (UBBC) and trans-cobalamins (apo-TC II and apo-TC I/III) were determined to calculate the percentage saturation of the transcobalamins. Folate status was assessed by the measurement of plasma and RBC folate.
The food consumption of WN group and CG differed significantly. WN group consumed more whole grain products, vegetables and fruits than the CG. A high amount of vegetables and fruits were eaten unheated. LME ate less meat and fish than the CG; OLV avoid meat and fish totally.
The preference of foods of plant origin and the low consumption of foods of animal origin lead to a lower dietary intake of cobalamin in OLV and LME than in the CG. The mean dietary intake of cobalamin was 2.5 µg/d for OLV, 3.8 µg/d for LME and 5.3 µg/d for the CG. Only half of the OLV met the recommendations for vitamin B12 of the Institute of Medicine (1998) and only 1/3 of OLV met the recommendations of the German Nutrition Society (1991). About ¼ of OLV showed a dietary cobalamin intake below the recommendations for pregnant women of the WHO.
The WN group showed a higher dietary intake of folate than the CG. The mean folate intake was 350 µg DFE/d (173 µg FFE/d) for OLV, 347 µg DFE/d (166 µg FFE/d) for LME and CG 319 µg DFE/d (140 µg FFE/d) for the CG.
The Vitamin B₁₂ status was significantly affected by the diet. OLV, LME and the CG showed significant differences in most biochemical parameters of vitamin B₁₂ status. Low cobalamin intake of OLV was reflected in low vitamin B12 concentrations in serum as well as low percentage saturation of transcobalamins. The lowest vitamin B₁₂ concentrations in serum showed the OLV followed by the LME. Additionally the absolute saturation of haptocorrin as well as the total saturation was lower in OLV than in LME and the CG. The apo-Hap concentrations were highest in OLV, followed by LME and the CG. Holo TC II as well as RBC vitamin B₁₂ concentrations were not affected by the diet. The unsaturated trans-cobalamin concentrations were strongly affected by pregnancy and were not ideal for the assessment of vitamin B₁₂ status during pregnancy. A vitamin B₁₂ deficiency showed 44% of OLV, 16 % of LME and 8 % of the CG. The risk of vitamin B₁₂ deficiency during pregnancy was higher in OLV (9.2) and LME (2.3) compared to the CG.
The different diets and the different dietary folate intakes also affected folate status. The diet groups differed significantly in plasma as well as RBC folate concentrations. The mean folate concentrations in plasma and RBCs were highest in OLV, followed by LME. In the total course of pregnancy folate deficiency was observed in 7.5 % of OLV, in 20.3 % of LME and 29.0 % of the CG.
The diet also significantly affected homocysteine concentrations. Especially in the first trimester of pregnancy homocysteine concentrations were highest in OLV, followed by LME and the CG. At the end of pregnancy homocysteine concentrations hardly differered between the diet groups. Homocysteine concentrations above normal range were mostly observed in OLV. The risk for raised homocysteine concentrations was higher for OLV (4.6) and for LME (2.2) than for the CG. Homocysteine concentrations were negatively affected by vitamin B12 deficiency as well as folate deficiency. Highest homocysteine concentrations were observed in participants with vitamin B₁₂ and folate deficiency.
The results suggest that Wholesome Nutrition characterised by a high intake of folate-rich vegetables and a high amount of raw food optimises folate status and reduces the risk of folate deficiency during pregnancy. The data also suggest an optimum in folate intake at 300 µg FFE/d, which is similar to the international recommendation for folate intake during pregnancy. On the other hand a vegetarian variant of Wholesome Nutrition may also be a risk for vitamin B₁₂ deficiency during pregnancy and may lead to a functional folate deficiency as well as raised homocysteine concentrations. Vegetarians should assure an adequate cobalamin intake and a sufficient consumption of dairy products and, if acceptable, fish. The data also suggest an optimum in cobalamin intake at 4 µg/d. A cobalamin intake of 4 µg/d should be met by all vegetarians during pregnancy to compensate low vitamin B₁₂ storage. In the first weeks of pregnancy and in persons with a low consumption of dairy products a vitamin B₁₂ supplementation for vegetarian women should be considered.