Current recommendations: Higher reference values for the biofactors zinc and vitamin B6

Together with the Nutrition Societies of Austria and Switzerland, the German Nutrition Society (DGE) has revised the reference values for the supply of zinc and vitamin B6 and published them in July 2019.

New reference values for the biofactor zinc depending on the phytate content
Until now, the recommended daily intake of zinc was 7 mg for wom-en and 10 mg for men – irrespective of the amount of phytate in the diet. In the current intake recommendations of the German Nutrition Society (DGE), the daily intake of zinc for adults is set in relation to the phytate content of the food consumed. Phytate is particularly abundant in wholemeal products and legumes – according to nutri-tional guidelines of the DGE, these are foods that should represent the basis of wholefood nutrition. A high phytate intake can reduce the bioavailability of zinc by up to 45%. According to the new DGE recommendations, if the diet contains a high phytate content, the supply of zinc must therefore also be increased.

The reference values for zinc have been significantly increased
For this reason, the DGE has now set the reference values for the biofactor zinc in relation to a low, medium or high phytate content of the food:

Phytate Content of the FoodZinc Reference Values for WomenZinc Reference Values for Men
Low7 mg/day11 mg/day
Medium8 mg/day14 mg/day
High10 mg/day16 mg/day

All zinc reference values, with the exception of the value for women with a low-phytate diet, are higher than in the previous DGE recom-mendation. A wholefood diet according to the principles of the DGE is associated with a medium phytate intake. The corresponding ref-erence values have been increased to 8 mg/day for women and to as much as 14 mg/day for men – an increase of 14% for women and 40% for men compared to the previous reference values.

Biofactor zinc involved in the immune defence, skin metabolism and hormone synthesis
The biofactor zinc is involved in numerous metabolic processes in the body. Over 300 enzymes contain zinc or are activated by zinc. A sufficient supply of zinc is particularly important for an intact im-mune defence, protection against oxidative stress and stable skin health. As a component of the hormone insulin, the biofactor also plays a key role in the regulation of the blood sugar levels and the synthesis of other important hormones (glucagon, thyroid, sexual and growth hormones).

Current studies require adaptation of the reference values for vitamin B6
As the biofactor vitamin B6 plays an important role in the body's own amino acid metabolism, it was previously assumed that the vitamin B6 requirement was dependent on the protein content of the food. The German Nutrition Society (DGE) had therefore derived the ref-erence value for vitamin B6 on the basis of the reference value for the protein intake. Recent studies on this topic have not been able to confirm the previously suspected relationship between the vitamin B6 intake and the protein content.
The decisive aspect for the new vitamin B6 reference values is the biomarker pyridoxal-5`-phosphate, which is abbreviated to PLP. This biomarker is the most important form of storage for vitamin B6 in the musculature and blood plasma. In so-called “balance studies” it was determined at which vitamin B6 intake quantities the desirable blood plasma concentration of PLP was reached.

New reference values for the biofactor vitamin B6 are slightly higher
However, the balance studies have so far only been carried out on adult women. As there are no meaningful balance studies for chil-dren, adolescents or adult men, their vitamin B6 reference values have been derived from the women's data.
The current vitamin B6 reference values are 1.4 mg for women, 1.6 mg for men and, corresponding to their age, somewhat lower for children and adolescents – according to the opinion of the DGE. As a result of the changed study situation, the reference values are higher than before in most of the age groups; for pregnant and breastfeeding women they are slightly below the previous reference values.

According to the National Food Consumption Study II, the average daily intake of vitamin B6 is 1.2 mg for women and 1.6 mg for men. The current DGE recommendations regarding the vitamin B6 reference values – 1.4 mg for women and 1.6 mg for men – are therefore not fulfilled by some adults.

What does the body need vitamin B6 for?
The biofactor is involved in numerous metabolic processes. In addition to its involvement in the amino acid metabolism – as mentioned above – vitamin B6 also plays an important role in the carbohydrate metabolism and in the formation of the B vitamin niacin. Further-more, vitamin B6 regulates the homocysteine metabolism in conjunction with other B vitamins. The amino acid homocysteine can damage blood vessels and promote thrombus formation. Together with vitamin B12 and folic acid, vitamin B6 is involved in the breakdown of this vascular-damaging amino acid.

Zinc and vitamin B6 – official opinion of the German Society for Biofactors
The reference values of the biofactors zinc and vitamin B6 have been adjusted by the DGE on the basis of the latest available data. With a few exceptions, the new reference values for zinc and vitamin B6 are higher than the previous intake recommendations.

The German Society for Biofactors (GfB) points out that these reference values apply to healthy adults. They do not take into account any additional requirements in certain life situations or those resulting from factors such as illnesses, the taking of pharmaceuticals or absorption disorders.

"In the case of the biofactor zinc, for example, pregnancy, lactation and stress can increase the zinc requirement, while competitive sports and heavy sweating can promote zinc excretion and alcohol and nicotine abuse can inhibit the absorption of zinc," say the experts from the German Society for Biofactors (GfB). Furthermore, zinc absorption can be reduced in chronic intestinal diseases such as Crohn's disease, ulcerative colitis and celiac disease or after in-testinal resections. Diabetes mellitus and the intake of ACE inhibitors, diuretics or corticoids lead to the increased excretion of the biofactor via the kidneys.

According to information provided by the German Society for Biofactors, risk factors for vitamin B6 deficiency also include stress, high levels of physical activity or stimulants such as nicotine and alcohol. The vitamin B6 requirement and the risk of vitamin B6 deficiency increase after operations, frequent infections, liver or chronic intestinal diseases and after taking certain medicines (proton pump inhibitors, contraceptives, medicines used to treat epilepsy and asthma).

Significantly higher dosages may therefore be necessary for risk groups and for the treatment of a biofactor deficiency, according to the opinion of the German Society for Biofactors (GfB).

Presseinformation der Deutschen Gesellschaft für Ernährung
e. V. (DGE):DGE aktuell 15/2019 vom 09.07.2019