Trial of tyrosine and its effect on working memory in healthy elderly and young people

• Aged 18-35 years or aged 60-75 years

• Normal and stable weight (BMI 18.5-25 kg/m2 and weight 50-95 kg)

• Willing to abstain from blood donation during the study

• Willing to comply with study procedures

• Willing to accept use of all encoded data, including publication, and the confidential use and storage of all data for at least 15 years.

• Dutch-speaking

• Non-smoking

• Normal or corrected-to-normal vision

• Thyroid problems, such as hyperthyroidism, hypothyroidism, thyroid cancer

• Using medication that can interfere with tyrosine’s action; monoamine oxidase inhibitors and other antidepressants, sympathomimetic amines, and opioids

• Following a low-protein diet as prescribed by a dietician or physician

• Intestinal problems that affect nutrient absorption (such as coeliac disease)

• Parkinson’s Disease

• Depression

• Use of tyrosine supplements

• Being allergic or having a dislike to the product carrier (banana-flavored yoghurt)

• Bad venous access, as judged by the research nurse

• Personnel of Wageningen UR, Division of Human Nutrition, their partner and their first and second degree relatives

• Current participation in other scientific research

• Mini Mental State Examination (MMSE) score < 24 (to exclude cognitive impaired participants, only for elderly participants)

• Estimated IQ <85 (based on Nederlandse Leestest voor Volwassenen (NLV) -score)

• (History of) clinically significant psychiatric disorder

• (History of) clinically significant neurological disorder, such as brain infarct, chronic migraine, major depression

• Under treatment for cardiac or vascular diseases and use of medication for these conditions

• General medical conditions, such as repetitive strain injury (RSI) or sensori-motor handicaps, as judged by the investigator

• Alcohol consumption of more than 14 (women) or 21 (men) units per week